# Clinical Significance of Respiratory Torque Teno Virus in Immunocompromised Patients with Acute Respiratory Failure

Alexis Maillard, Linda Feghoul, Virginie Lemiale, Séverine Mercier-Delarue, Alexandre Demoule, Samir Jaber, Kada Klouche, Achille Kouatchet, Laurent Argaud, Francois Barbier, et al.

► To cite this version:

Alexis Maillard, Linda Feghoul, Virginie Lemiale, Séverine Mercier-Delarue, Alexandre Demoule, et al. Clinical Significance of Respiratory Torque Teno Virus in Immunocompromised Patients with Acute Respiratory Failure. Clinical Microbiology and Infection, 2025, 31 (12), pp.2073-2081. 10.1016/j.cmi.2025.07.035. hal-05223677

HAL Id: hal-05223677

https://hal.science/hal-05223677v1

Submitted on 16 Feb 2026

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons CC BY 4.0 - Attribution - International License
Clinical significance of respiratory torque teno virus in
immunocompromised patients with acute respiratory
failure

Alexis Maillard ¹, Linda Feghoul ², Virginie Lemiale ³, Séverine Mercier-Delarue ², Alexandre Demoule ⁴, Samir Jaber ⁵, Kada Klouche ⁶, Achille Kouatchet ⁷, Laurent Argaud ⁸, Francois Barbier ⁹, Naike Bigé ¹⁰, Anne-Sophie Moreau ¹¹, Emmanuel Canet ¹², Frédéric Pène ¹³, Maud Salmona ¹⁴, Djamel Mokart ¹⁵, Elie Azoulay ³, Jérôme LeGoff ¹⁴

¹ Service de médecine intensive et réanimation, Hôpital Saint-Louis, Assistance Publique des Hôpitaux de Paris, Paris, France. Electronic address: alexis.maillard@aphp.fr.

² Service de Virologie, Hôpital Saint-Louis, Assistance Publique des Hôpitaux de Paris, Paris, France.

³ Service de médecine intensive et réanimation, Hôpital Saint-Louis, Assistance Publique des Hôpitaux de Paris, Paris, France.

⁴ Service de Médecine Intensive - Réanimation (Département R3S), Sorbonne Université, Institut pour la Recherche Médicale (INSERM), UMRS1158, Paris, France; Neurophysiologie Respiratoire Expérimentale et Clinique, and Assistance Publique Hôpitaux de Paris (AP-HP), Groupe Hospitalier Universitaire AP-HP-Sorbonne Université, Site Pitié-Salpêtrière, Paris, France.

⁵ Département Anesthésie et Réanimation B, Centre Hospitalier Universitaire de Montpellier, Hôpital Saint-Eloi, Montpellier, France.

⁶ Département de médecine intensive et réanimation, Hôpital Lapeyronie, Montpellier, France.

⁷ Médecine intensive et réanimation, Centre Hospitalo-Universitaire (CHU) d'Angers, Angers, France.

⁸ Médecine Intensive-Réanimation, Hospices Civils de Lyon, Hôpital Edouard Herriot, Lyon, France.

⁹ Unité de Soins Intensifs Médicaux, La Source Hospital, Centre Hospitalier Régional d'Orléans, Orléans, France.

¹⁰ Service de médecine intensive et réanimation, Hôpital Saint-Antoine, Assistance Publique des Hôpitaux de Paris, Paris, France.

¹¹ Pôle de médecine intensive-Réanimation, Hôpital Roger Salengro, CHU Lille, Lille, France.

¹² Service de Médecine Intensive-Réanimation, Centre Hospitalier Universitaire Hôtel-Dieu, Nantes, France.
¹³ Service de Médecine Intensive-réanimation, Hôpital Cochin, Assistance Publique des Hôpitaux de Paris, Paris, France.

¹⁴ Service de Virologie, Hôpital Saint-Louis, Assistance Publique des Hôpitaux de Paris, Paris, France; Université Paris Cité, Institut pour la Recherche Médicale (INSERM), Insight Team, Paris, France.

¹⁵ Département d'Anesthésie-Réanimation, Institut Paoli-Calmettes, Marseille, France.

**Keywords:**

Acute respiratory failure; Critical care; Immunocompromised host; Torque teno virus.
# Abstract

**Objectives:**

Among immunocompromised patients with acute respiratory failure, identification of those at higher risk for opportunistic infections is crucial to optimize management. The torque teno virus (TTV) DNA burden in the blood has been identified as a surrogate marker of functional immunity in solid organ transplant recipients. This study investigates the clinical relevance of the presence of TTV DNA in nasopharyngeal swabs of immunocompromised patients with acute respiratory failure (ARF).

**Methods:**

We enrolled immunocompromised patients with ARF admitted to 32 intensive care units. Nasopharyngeal swabs collected on admission were tested for TTV DNA. Causes of ARF were reviewed by three expert investigators blinded to TTV results, with specific attention to the presence of opportunistic infections. The primary endpoint was the association between TTV DNA burden in nasopharyngeal swabs and the rate of opportunistic infections causing the ARF.

**Results:**

Of the 505 patients, respiratory TTV DNA was detected in 304 of 505 (60%), with TTV burden $\ge2.9 \log_{10}$ copies/mL in 184 of 305 (36%). TTV burden $\ge2.9 \log_{10}$ copies/mL was significantly associated with a higher prevalence of opportunistic infections (20% [36/178] vs. 11% [33/307]; adjusted odds ratio, 2.41; 95% CI, 1.35-4.28; p 0.002). High TTV burden $\ge2.9 \log_{10}$ copies/mL was also associated with a higher rate of all cause pulmonary infections (67% [119/178] vs. 56% [108/192] when not detected), microbiologically documented bacterial infections (35% [62/178] vs. 23% [45/192]), and with a higher rate of influenza-like respiratory virus detection in nasopharyngeal swabs (15% [27/184] vs. 6% [12/201] when not detected). Furthermore, TTV detection was associated with a higher rate of mechanical ventilation or death at day 28 (59% [179/304] vs. 48% [97/201] when not detected).

**Discussion:**

In immunocompromised patients with ARF, high TTV burden in the respiratory tract is associated with higher rates of pulmonary infections due to opportunistic pathogens and with adverse outcomes.
# INTRODUCTION

Advances in oncology, hematology, and solid organ transplantation (SOT), along with the increased use of immunosuppressive drugs, have made immunodeficiency increasingly common. In immunocompromised patients, acute respiratory failure (ARF) is the leading cause of intensive care unit (ICU) admission[1], requires invasive mechanical ventilation (IMV) in more than half of patients, and is associated with a high mortality rate[2-4]. ARF causes include bacterial or viral infections, other opportunist pathogens, and non-infectious causes. Identifying the ARF cause is crucial[2-4], as ARF of undetermined cause is linked to higher mortality[4]. Noninvasive diagnostic tests on sputum, nasopharyngeal samples, or blood must be performed systematically, whereas the indication for fiberoptic bronchoscopy with bronchoalveolar lavage should be carefully evaluated, as this procedure may increase the risk of IMV and death[5]. In this setting, improving clinician's ability to identify patients having an opportunistic infection would help optimize management and guide diagnostic testing.

Torque teno viruses (TTV) are part of the physiological human virome in healthy individuals [6]. In SOT recipients, high TTV burden in blood predicts a higher risk for opportunistic infections [7-9]. High TTV burden in the respiratory tract, has been associated with respiratory dysbiosis in lung transplant recipients[10], and with more severe respiratory infections[11-13].

In this study performed in immunocompromised patients with hypoxemic ARF, we investigated the clinical relevance of TTV replication in the upper respiratory tract. We hypothesized that TTV burden in nasopharyngeal swabs might correlate with the risk of opportunistic infections in these patients.

# METHODS

## Patients

We performed a *post-hoc* analysis of the HIGH randomized clinical trial[14] that enrolled 776 adult immunocompromised patients with hypoxemic ARF in 32 ICUs in France between May 19, 2016, and December 31, 2017. As described in the original trial[14], patients were randomized to high-flow or standard oxygen, with no effect on day-28 mortality or intubation. All patients had known immunosuppression: long-term (>3 months) or high-dose (>0.5 mg/kg/day) steroids, use of other immunosuppressant drugs, SOT, solid tumor requiring chemotherapy in the last 5 years, hematologic malignancy regardless of time since diagnosis, hematopoietic stem cell transplantation, or primary immune deficiency. Hypoxemic ARF was defined as PaO2 <60 mmHg or SpO2 <90% on room air, or tachypnea >30/min or labored breathing or respiratory distress and need for oxygen ≥6L/min. The original study protocol was approved by the CPP Ile de France IV St-Louis ethics committee (March 3, 2016, #NIRB00003835/2016/08) and French health authorities, including post-hoc analyses of collected data and samples.

## ARF etiologies

The final etiologic diagnoses for the cause of ARF were made by managing physicians using either invasive (fiberoptic bronchoscopy and bronchoalveolar lavage) and/or noninvasive tests
according to clinician's decisions. As detailed in supplemental materials, all etiological diagnoses were independently reviewed by four expert investigators. Opportunistic infections included *Pneumocystis jirovecii* pneumonia, invasive fungal infections, and CMV or HSV pneumonia.

## Nasopharyngeal swabs collection

At enrollment, clinicians were asked to collect a nasopharyngeal swab for each included patient. Nasopharyngeal swabs were collected in 3 ml of Universal Transport Medium (Copan Diagnostics Inc.) and stored at -80°C until testing.

## Torque teno virus quantification

Nucleic acids from nasopharyngeal samples were extracted from 200 µL of Universal Transport Medium using the QiaSymphony instrument (Qiagen). TTV was quantified by real-time PCR (TTV R-Gene, bioMérieux) on an ABI 7500 instrument (ThermoFisher). As the assay was not initially designed for respiratory samples, we evaluated intra- and inter-assay reproducibility on 22 nasopharyngeal samples with TTV loads ranging from 2 to 6 log copies/mL. As detailed in **Tables S1-S3**, mean intra-assay coefficients of variation (CVs) were 1.9%, 2.6%, and 1.3% for TTV loads of 2.5-3.5, 3.5-4.5, and >4.5 log copies/mL, respectively; inter-assay CVs were 5.2%, 3.5%, and 2.5% for the same ranges. For blood quantification, serum samples were stored at -80 °C until testing. Nucleic acids were extracted with the MagNAPure 96 system, and quantification was performed using the same assay according to the manufacturer's instructions.

## Study endpoints

The primary endpoint was the association between TTV DNA burden in nasopharyngeal swabs and the rate of opportunistic infections causing the ARF that led to the patient's admission to intensive care. TTV DNA results were not available at the time of diagnosis or adjudication. A threshold of 2.9 log10copies/mL was used to define a high TTV burden as it has been shown to be an independent predictor of ICU admission in COVID-19 in a previous study [11]. As detailed in the results section, this threshold was also validated as the optimal cut-off to predict opportunistic infections in the present study. Secondary endpoints included the association between TTV detection and respiratory viruses in nasopharyngeal swabs and the association with adverse clinical outcomes: 28-day mortality or invasive mechanical ventilation (IMV), and 28-day days without organ life support (DAWOLS, including use of mechanical ventilation, vasopressors/inotropes, or renal replacement therapy). Because chemotherapy has previously been associated with a subsequent decrease in blood TTV burden [15-17], we performed a subgroup sensitivity analysis according to recent chemotherapy (<30 days). Further subgroup analyses were performed according to the main cause of immunosuppression.
**Statistical Analysis**

Categorical variables were described as 1 numbers (percentages) and quantitative variables as medians [interquartile range (IQR)]. Between-group comparisons were performed using Fisher's exact test or chi-square tests for categorical variables, as appropriate, and the Wilcoxon rank-sum test for quantitative variables. Linear trends were examined through Cochrane Armitage tests for categorical variables and Spearman correlation for quantitative variables. All tests were two-sided with α = .05. Analyses were performed using the R Statistical Software (version 4.1.1).

***Association between TTV detection and opportunistic infections:***

A restricted cubic spline analysis was used to explore potential nonlinear relationships
between TTV DNA levels in nasopharyngeal swabs and the incidence of diagnosed
opportunistic infections. The association between TTV burden (≥2.9 log10/mL versus <2.9
log10/mL) in nasopharyngeal swabs and the diagnosis of opportunistic infection was assessed
using a binomial logistic regression model. Multivariable models included all baseline factors
associated with outcomes in the univariable analysis as well as clinically relevant predefined
variables (see Table 3). Missing data were handled using multivariate imputation by chained
equations (MICE package), with 20 imputed datasets used in all multivariable models.

***Association between TTV detection and adverse outcomes:***

The association between TTV detection in nasopharyngeal swabs and the occurrence of death or IMV by day 28 was assessed using a Cox regression survival model (detailed in supplemental material).

RESULTS

Of the 776 enrolled immunocompromised patients with ARF, 505 underwent nasopharyngeal swab

testing for DNA TTV and were included in the analysis (Figure 1). Baseline characteristics
were similar between tested and untested patients (Tables S4-S5). No patients were lost to
follow-up at Day 30. As shown in Table 1 main causes of immunosuppression included
hematologic malignancies (221, 42.0%), allogeneic stem cell transplantation (SCT) (37,
7.3%), solid tumor (176, 35.5%) or solid organ
transplantation (55, 11.1%).

TTV DNA in nasopharyngeal swabs

As shown in **Figure 2**, TTV DNA was detected in 304/505 nasopharyngeal swabs (60.2%), with TTV burden ≥2.9 log10copies/mL in 184/505 patients (36.4%). Detection varied by immunosuppression type, highest in SOT (46/55, 83.6%) and SCT (29/37, 78.4%), lowest in myeloid malignancies (17/72, 23.6%) Within immunosuppressive therapy, the use of corticosteroids, calcineurin inhibitors, and mycophenolate mofetil was associated with a
higher TTV burden. In contrast, recent chemotherapy (< 30 days) and leucopenia <1 G/L were negatively associated with TTV detection. To explore the association between TTV burden in respiratory samples and blood, we analyzed 471/505 patients with an available serum collected at enrollment (93.2%). TTV DNA was detected in serum in 388/471 patients (82.4%) and showed a strong correlation with nasopharyngeal burden (r²=0.701; p<0.001) (Figures S1,S2).

<figure><img src="image_2.png" /><figcaption>**Figure 1.** Flow chart of the study.</figcaption></figure>

Further details are provided in the original manuscript of the HIGH randomized controlled trial.[13] TTV is for Torque Teno Virus. In the case of multiple diagnosed causes of ARF, patients with a diagnosed opportunistic infection were classified as "opportunistic infection", patients with a diagnosed other infection without an opportunistic infection were classified as "other infection".

## Association between TTV detection and clinical/radiological presentation

We found no clinically significant association between TTV detection in nasopharyngeal swabs and either comorbidities, severity (Table 1), clinical presentation or CT scan patterns (Table 2). To account for the global clinical and radiologic presentation, we performed an exploratory unsupervised hierarchical clustering analysis to isolate 6 clusters based on a set of variables from the background, clinical signs and radiologic pattern (detailed in supplemental materials, Figure S3, Table S6). The TTV burden in nasopharyngeal swabs varied significantly between clusters and paralleled the rate of opportunistic infections.
<table><caption>Table 1 - Characteristics at inclusion</caption><thead><tr><th></th><th>Overall</th><th>Negative PCR</th><th>TTV &lt; 2.9 log<sub>10</sub><sup>a</sup><br>copies/mL</th><th>TTV ≥ 2.9 log<sub>10</sub><sup>a</sup><br>copies/mL</th><th>p-value</th></tr></thead><tbody><tr><td>n</td><td>505</td><td>201</td><td>120</td><td>184</td><td></td></tr><tr><td>Demographics</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Age (year)</td><td>64.0 [56.6, 71.2]</td><td>64.4 [57.0, 71.6]</td><td>63.7 [55.3, 71.0]</td><td>63.8 [57.3, 70.7]</td><td>0.632</td></tr><tr><td>Sex (female)</td><td>164 (32.5)</td><td>73 (36.3)</td><td>42 (35.0)</td><td>49 (26.6)</td><td>0.102</td></tr><tr><td>Underlying conditions</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Charlson comorbidity index<sup>a</sup></td><td>5.0 [3.0, 7.0]</td><td>5.0 [4.0, 6.0]</td><td>5.0 [3.0, 7.0]</td><td>5.0 [3.0, 7.0]</td><td>0.627</td></tr><tr><td>Poor performance status (3 or 4)<sup>b</sup></td><td>196 (42.1)</td><td>81 (43.1)</td><td>47 (41.6)</td><td>70 (41.4)</td><td>0.942</td></tr><tr><td>Chronic<sup>c</sup></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Respiratory (restrictive or<br>obstructive disease)</td><td>156 (31.5)</td><td>62 (31.5)</td><td>39 (32.8)</td><td>55 (30.6)</td><td>0.922</td></tr><tr><td>Heart failure</td><td>29 (5.9)</td><td>11 (5.6)</td><td>6 (5.1)</td><td>12 (6.7)</td><td>0.832</td></tr><tr><td>Liver disease</td><td>64 (12.9)</td><td>24 (12.2)</td><td>9 (7.6)</td><td>31 (17.2)</td><td>0.047</td></tr><tr><td>Kidney disease</td><td>101 (20.4)</td><td>34 (17.3)</td><td>27 (22.7)</td><td>40 (22.2)</td><td>0.377</td></tr><tr><td>Clinical severity at inclusion</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Time between ICU admission and<br>randomization</td><td>0.0 [0.0, 1.0]</td><td>0.0 [0.0, 1.0]</td><td>0.0 [0.0, 1.0]</td><td>0.0 [0.0, 1.0]</td><td>0.294</td></tr><tr><td>> 2 days</td><td>84 (10.6)</td><td>53 (11.2)</td><td>13 (10.8)</td><td>18 (9.8)</td><td>0.874</td></tr><tr><td>SOFAscore<sup>a</sup></td><td>4.0 [1.0, 6.0]</td><td>4.0 [2.0, 6.0]</td><td>4.0 [2.0, 6.0]</td><td>3.0 [1.0, 6.0]</td><td>0.231</td></tr><tr><td>SOFAscore > 7<sup>a</sup></td><td>71 (16.5)</td><td>28 (16.3)</td><td>20 (20.2)</td><td>23 (14.5)</td><td>0.480</td></tr><tr><td>Haemodynamic status</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Vasopressors</td><td>51 (10.1)</td><td>18 (9.0)</td><td>14 (11.7)</td><td>19 (10.3)</td><td>0.732</td></tr><tr><td>Systolic blood pressure<sup>f</sup></td><td>104.0 [85.2, 138.0]</td><td>105.0 [86.0, 134.0]</td><td>103.0 [88.8, 133.2]</td><td>105.0 [84.0, 144.5]</td><td>0.839</td></tr><tr><td>Heart rate<sup>a</sup></td><td>115.0 [90.0, 135.0]</td><td>116.0 [94.0, 135.0]</td><td>111.0 [87.0, 136.2]</td><td>113.0 [89.0, 132.8]</td><td>0.516</td></tr><tr><td>Respiratory status</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Respiratory rate (/min)<sup>b</sup></td><td>32.0 [38.0, 38.0]</td><td>32.0 [27.0, 37.0]</td><td>32.0 [27.0, 37.0]</td><td>33.0 [28.0, 38.0]</td><td>0.141</td></tr><tr><td>Oxygen flow (L/min)<sup>c</sup></td><td>10.0 [6.0, 15.0]</td><td>12.0 [6.0, 15.0]</td><td>10.0 [6.0, 15.0]</td><td>9.0 [6.0, 15.0]</td><td>0.454</td></tr><tr><td>Pco2/FiO2 ratio<sup>j</sup></td><td>118.0 [84.0, 166.0]</td><td>121.0 [88.0, 173.0]</td><td>115.0 [80.0, 159.0]</td><td>118.0 [81.5, 158.5]</td><td>0.544</td></tr><tr><td>Neurological status</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Glasgow score<sup>b</sup></td><td>15.0 [15.0, 15.0]</td><td>15.0 [15.0, 15.0]</td><td>15.0 [15.0, 15.0]</td><td>15.0 [15.0, 15.0]</td><td>0.325</td></tr><tr><td>Lactate (mmol/L)<sup>l</sup></td><td>1.7 [1.0, 2.9]</td><td>1.8 [1.1, 2.3]</td><td>1.9 [1.0, 3.0]</td><td>1.5 [1.0, 3.0]</td><td>0.807</td></tr><tr><td>Causes of immunosuppression<sup>a</sup></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Hematologic malignancies</td><td></td><td></td><td></td><td></td><td>&lt;0.001</td></tr><tr><td>None</td><td>293 (58.0)</td><td>104 (51.7)</td><td>74 (61.7)</td><td>115 (62.5)</td><td></td></tr><tr><td>Myeloid malignancy</td><td>72 (14.3)</td><td>55 (27.4)</td><td>14 (11.7)</td><td>3 (1.6)</td><td></td></tr><tr><td>Lymphoid malignancy</td><td>103 (20.4)</td><td>34 (16.9)</td><td>26 (21.7)</td><td>43 (23.4)</td><td></td></tr><tr><td>Allogeneic stem cell<br>transplantation</td><td>37 (7.3)</td><td>8 (4.0)</td><td>6 (5.0)</td><td>23 (12.5)</td><td></td></tr><tr><td>Solid tumors<sup>g</sup></td><td>176 (35.5)</td><td>71 (36.2)</td><td>44 (36.7)</td><td>61 (33.9)</td><td>0.641</td></tr><tr><td>Chemotherapy &lt; 1 month<sup>a</sup></td><td>175 (36.6)</td><td>89 (46.8)</td><td>35 (30.4)</td><td>51 (29.5)</td><td>0.001</td></tr><tr><td>Solid organ transplantation<sup>a</sup></td><td>55 (11.1)</td><td>9 (4.6)</td><td>14 (11.7)</td><td>32 (17.8)</td><td>&lt;0.001</td></tr><tr><td>Immunosuppressive drugs for non-<br>transplant-related reasons<sup>a</sup></td><td>135 (27.3)</td><td>43 (22.2)</td><td>35 (29.2)</td><td>57 (31.7)</td><td>0.039</td></tr><tr><td>Leucocyte count &lt; 1 G/L<sup>g</sup></td><td>78 (16.2)</td><td>41 (21.1)</td><td>22 (20.0)</td><td>15 (8.4)</td><td>0.001</td></tr><tr><td>Immunosuppressive therapy<sup>a</sup></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Corticosteroid</td><td>121 (24.6)</td><td>31 (16.0)</td><td>32 (27.1)</td><td>58 (32.4)</td><td>&lt;0.001</td></tr><tr><td>Calcineurin inhibitors</td><td>41 (8.1)</td><td>7 (3.5)</td><td>9 (7.5)</td><td>25 (13.6)</td><td>&lt;0.001</td></tr><tr><td>Mycophenolate mofetil</td><td>25 (5.0)</td><td>3 (1.5)</td><td>7 (5.8)</td><td>15 (8.2)</td><td>0.003</td></tr><tr><td>Others</td><td>36 (7.3)</td><td>15 (7.7)</td><td>8 (6.8)</td><td>13 (7.3)</td><td>0.858</td></tr><tr><td>≥ 2 immunosuppressive drugs</td><td>127 (25.9)</td><td>32 (16.5)</td><td>33 (28.0)</td><td>62 (34.6)</td><td>&lt;0.001</td></tr></tbody></table>

The results are presented as n (%) for categorical variables and median [IQR] for quantitative variables. Unless otherwise noted, p-value is for comparison between the three groups using chi-squared tests. * p-value for tests for linear trends (Cochran Armitage test for categorical variables) except for Hematologic malignancies (chi-square test). a data missing for 12 patients; b data missing for 35 patients; c data missing for 9 patients; d data missing for 27 patients; e data missing for 75 patients; f data missing for 19 patients; g data missing for 20 patients; h data missing for 38 patients; i data missing for 30 patients; j data missing for 54 patients; k data missing for 16 patients; l data missing for 84 patients; m data missing for 9 patients; n data missing or 27 patients; o data missing for 10 patients; p data missing for 11 patients; q data missing for 23 patients; r data missing for 14 patients.
<table><caption>Table 2 - Clinical and radiological presentation, causes of acute respiratory failure and clinical outcomes.</caption><thead><tr><th></th><th>Overall</th><th>Negative PCR</th><th>TTV &lt; 2.9 log<sub>8</sub><br>copies/mL</th><th>TTV ≥ 2.9 log<sub>8</sub><br>copies/mL</th><th>p-value</th></tr></thead><tbody><tr><td>n</td><td>505</td><td>201</td><td>120</td><td>184</td><td></td></tr><tr><td>Clinical presentation</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Fever (≥ 38.3°C) *</td><td>202 (41.9)</td><td>90 (46.4)</td><td>44 (39.3)</td><td>68 (38.6)</td><td>0.260</td></tr><tr><td>Cough <sup>b</sup></td><td>224 (45.6)</td><td>75 (38.9)</td><td>59 (49.2)</td><td>90 (50.6)</td><td>0.052</td></tr><tr><td>Purulent sputum <sup>b</sup></td><td>69 (14.1)</td><td>23 (11.8)</td><td>12 (10.2)</td><td>34 (19.1)</td><td>0.049</td></tr><tr><td>Localized crackles on auscultation</td><td>165 (32.7)</td><td>58 (28.9)</td><td>40 (33.3)</td><td>67 (36.4)</td><td>0.283</td></tr><tr><td>Days since respiratory signs onset <sup>a</sup></td><td>1.0 [0.0, 3.0]</td><td>1.0 [0.0, 2.0]</td><td>1.0 [0.0, 3.2]</td><td>1.0 [0.0, 4.0]</td><td>0.021</td></tr><tr><td>Blood tests</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Lymphocytes count (G/L) <sup>a</sup></td><td>9.3 [2.8, 16.1]</td><td>10.1 [2.8, 17.3]</td><td>9.4 [2.2, 15.1]</td><td>8.4 [3.3, 14.8]</td><td>0.698</td></tr><tr><td>Total bilirubin (µmol/L) <sup>a</sup></td><td>12.0 [7.0, 22.6]</td><td>12.0 [8.0, 23.4]</td><td>12.0 [7.0, 21.0]</td><td>10.0 [7.0, 22.0]</td><td>0.289</td></tr><tr><td>Computed tomography (333 patients)</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Normal</td><td>16 (4.7)</td><td>8 (6.3)</td><td>3 (4.1)</td><td>5 (3.6)</td><td>0.560</td></tr><tr><td>Localized ground-glass opacities</td><td>69 (20.5)</td><td>22 (17.5)</td><td>17 (23.0)</td><td>30 (21.9)</td><td>0.561</td></tr><tr><td>Diffuse ground-glass opacities</td><td>85 (25.2)</td><td>28 (22.2)</td><td>20 (27.0)</td><td>37 (27.0)</td><td>0.619</td></tr><tr><td>Centrilobular nodular opacities</td><td>25 (7.4)</td><td>9 (7.1)</td><td>7 (9.5)</td><td>9 (6.6)</td><td>0.738</td></tr><tr><td>Pari-bronchovascular nodular opacities</td><td>15 (4.5)</td><td>4 (3.2)</td><td>4 (5.4)</td><td>7 (5.1)</td><td>0.677</td></tr><tr><td>Subpleural nodular opacities</td><td>17 (5.0)</td><td>9 (7.1)</td><td>3 (4.1)</td><td>5 (3.6)</td><td>0.393</td></tr><tr><td>Other patterns nodular opacities</td><td>29 (8.6)</td><td>11 (8.7)</td><td>5 (6.8)</td><td>13 (9.5)</td><td>0.795</td></tr><tr><td>Localized alveolar consolidation</td><td>103 (30.6)</td><td>36 (28.6)</td><td>22 (29.7)</td><td>45 (32.8)</td><td>0.742</td></tr><tr><td>Diffuse alveolar consolidation</td><td>48 (14.2)</td><td>21 (16.7)</td><td>10 (13.5)</td><td>17 (12.4)</td><td>0.602</td></tr><tr><td>Interlobular septal thickening</td><td>38 (17.2)</td><td>24 (19.0)</td><td>3 (4.1)</td><td>31 (22.6)</td><td>0.002</td></tr><tr><td>Pleural effusion</td><td>148 (43.9)</td><td>64 (30.8)</td><td>28 (37.8)</td><td>56 (40.9)</td><td>0.132</td></tr><tr><td>Bronchial wall thickening</td><td>41 (12.2)</td><td>12 (9.5)</td><td>11 (14.9)</td><td>18 (13.1)</td><td>0.485</td></tr><tr><td>Mediastinal lymph node enlargement</td><td>48 (14.2)</td><td>16 (12.7)</td><td>11 (14.9)</td><td>21 (15.3)</td><td>0.818</td></tr><tr><td>Causes of hypoxemic acute respiratory failure (485 patients) <sup>a</sup></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Pulmonary infections</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>All cause pulmonary infection</td><td>299 (61.6)</td><td>108 (56.2)</td><td>72 (62.6)</td><td>119 (66.9)</td><td>0.036</td></tr><tr><td>Bacterial pneumonia</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Microbiologically documented</td><td>139 (28.7)</td><td>45 (23.4)</td><td>32 (27.8)</td><td>62 (34.8)</td><td>0.016</td></tr><tr><td>Clinically documented</td><td>92 (19.0)</td><td>41 (21.4)</td><td>24 (20.9)</td><td>27 (15.2)</td><td>0.132</td></tr><tr><td>Viral pneumonia</td><td>39 (8.0)</td><td>12 (6.2)</td><td>12 (10.4)</td><td>15 (8.4)</td><td>0.430</td></tr><tr><td>Opportunistic infections (OI)</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>All cause opportunistic infection</td><td>69 (14.2)</td><td>21 (10.9)</td><td>12 (10.4)</td><td>36 (20.2)</td><td>0.011</td></tr><tr><td>HSV/CMV pneumonia</td><td>7 (1.4)</td><td>1 (0.5)</td><td>1 (0.8)</td><td>5 (2.7)</td><td>-</td></tr><tr><td>Pneumocystis (proventriculus) pneumonia</td><td>44 (9.1)</td><td>15 (7.8)</td><td>6 (5.2)</td><td>23 (12.9)</td><td>0.093</td></tr><tr><td>Invasive aspergillosis</td><td>16 (3.3)</td><td>4 (2.1)</td><td>5 (4.3)</td><td>7 (3.9)</td><td>0.313</td></tr><tr><td>Other OIs</td><td>5 (1.0)</td><td>3 (1.6)</td><td>0 (0.0)</td><td>2 (1.1)</td><td>-</td></tr><tr><td>Noninfected lung involvement</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Specific infiltrative pneumonitis</td><td>56 (11.5)</td><td>27 (14.1)</td><td>9 (7.8)</td><td>20 (11.2)</td><td>0.381</td></tr><tr><td>Drug related pneumonitis</td><td>8 (1.6)</td><td>7 (3.6)</td><td>1 (0.9)</td><td>0 (0.0)</td><td>-</td></tr><tr><td>Cardiogenic pulmonary edema</td><td>23 (4.7)</td><td>8 (4.2)</td><td>5 (4.3)</td><td>10 (5.6)</td><td>0.467</td></tr><tr><td>Pulmonary embolism</td><td>11 (2.3)</td><td>3 (1.6)</td><td>6 (5.2)</td><td>2 (1.1)</td><td>0.847</td></tr><tr><td>Extra-respiratory sepsis</td><td>47 (9.7)</td><td>20 (10.4)</td><td>11 (9.6)</td><td>16 (9.0)</td><td>0.642</td></tr><tr><td>Undetermined</td><td>65 (13.4)</td><td>25 (13.0)</td><td>16 (13.9)</td><td>24 (13.5)</td><td>0.894</td></tr><tr><td>Outcomes <sup>a</sup></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Life-supporting interventions (until day 28)</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Invasive mechanical ventilation (IMV)</td><td>205 (40.8)</td><td>76 (38.0)</td><td>51 (42.9)</td><td>78 (42.6)</td><td>0.352</td></tr><tr><td>Noninvasive ventilation <sup>a</sup></td><td>67 (13.4)</td><td>22 (11.0)</td><td>18 (15.3)</td><td>27 (14.8)</td><td>0.275</td></tr><tr><td>Renal-replacement therapy <sup>f</sup></td><td>80 (16.7)</td><td>29 (15.4)</td><td>17 (15.0)</td><td>34 (19.0)</td><td>0.362</td></tr><tr><td>Death at day 28</td><td>174 (34.3)</td><td>57 (28.4)</td><td>43 (35.8)</td><td>74 (40.2)</td><td>0.014</td></tr><tr><td>Death or IMV at day 28</td><td>276 (54.7)</td><td>97 (48.3)</td><td>69 (57.5)</td><td>110 (59.8)</td><td>0.022</td></tr><tr><td>ICU mortality <sup>a</sup></td><td>149 (29.6)</td><td>49 (24.4)</td><td>44 (36.7)</td><td>56 (30.6)</td><td>0.168</td></tr><tr><td>Hospital mortality <sup>b</sup></td><td>198 (39.4)</td><td>71 (35.5)</td><td>51 (42.9)</td><td>76 (41.5)</td><td>0.221</td></tr><tr><td>DAWLOS</td><td>22.0 [3.0, 28.0]</td><td>25.0 [6.0, 28.0]</td><td>21.5 [2.0, 28.0]</td><td>17.0 [3.0, 28.0]</td><td>0.025</td></tr></tbody></table>

The results are presented as n (%) for categorical variables and median [IQR] for quantitative variables. Unless otherwise noted, p-value is for comparison between the three groups using chi-squared tests. a data missing for 23 patients; b data missing for 14 patients; c data missing for 26 patients; d data missing for 83 patients; e data missing for 4 patients; f data missing for 25 patients; g data missing for 1 patient; h data missing for 3 patients.
*p-value for tests for linear trends for etiological diagnoses and clinical outcomes (Cochran Armitage test for categorical variables and Spearman correlation for quantitative variables), tests were not performed for sample < 10. DAWLOS is for days alive without life organ support
Figure 2. TTV detection in nasopharyngeal swabs in immunocompromised patients with ARF

<figure><img src="image_3.png" /></figure>

Panel A) Detection of torque teno virus (TTV) DNA in nasopharyngeal swabs from immunocompromised patients with acute respiratory failure (ARF). Panel B) Histogram of TTV DNA load detected in nasopharyngeal swabs from patients with confirmed TTV. Panel C) Detection of TTV in nasopharyngeal swabs according to the cause of immunosuppression and immunosuppressive therapy.

Association between TTV detection and the rate of opportunistic infections

As shown in **Table 2**, across the whole cohort TTV burden was significantly associated with the rate of opportunistic infections and the cubic spline showed a non-linearity of the association with a drop-off around 3 log10/mL (**Figure 3**). The area under the ROC curve was 0.58 (95%CI 0.51-0.66) and the optimal threshold was found to be 2.9 with a sensibility of 0.66 and a specificity of 0.52 (**Figure S4- S5**). When TTV burden was ≥2.9 log10/mL, the proportion of opportunistic infections was significantly higher (20.2% (36/178) vs. 10.7% (33/307), OR = 2.10, 95%CI 1.26-3.52; p=0.006), especially for *Pneumocystis jirovecii* pneumonia (12.9% (26/178) vs. 6.8% (21/307), p=0.023) (**Figure 3**, **Table 2** and **S7**). In multivariable analyses, a high TTV burden in nasopharyngeal swabs (≥ 2.9 log10/mL) was significantly associated with a higher rate of opportunistic infection (adjusted OR (aOR) = 2.41, 95%CI 1.35 to 4.28; p-value = 0.002), along with immunosuppressive therapies, and a poor-performance status (**Table 3**). No significant interaction was found between TTV burden and age, performance status, or immunosuppressive therapy.
<figure><img src="image_4.png" /><figcaption>Figure 3. TTV in nasopharyngeal swabs and opportunistic infections</figcaption></figure>

Analysis for the entire enrolled population in the upper panels (A-C) and restricted to the 303 patients without recent chemotherapy in the lower panels (D-E). Panel A and D) Cubic spline of the rate of opportunistic infections according to DNA TTV load in nasopharyngeal swabs for the whole population (A) or patients without recent chemotherapy (D). Panel B-C and E-F) Rate of diagnosed opportunistic infections (B, E) and *Pneumocystis jirovecii* pneumonia (C, F) in patients with no or < 2.9 log/mL TTV detected in nasopharyngeal swabs vs. TTV DNA ≥ 2.9 log/mL. Numbers in the box plots are the denominator.
<table><caption>Table 3. Risk factors for opportunistic infections as cause of ARF in multivariable analysis</caption><thead><tr><th rowspan="2">Variable</th><th colspan="2">Univariate model</th><th colspan="2">Full multivariable model</th></tr><tr><th>OR (95%CI)</th><th>p-value</th><th>OR (95%CI)</th><th>p-value</th></tr></thead><tbody><tr><td>Age (per 10 years increase)</td><td>0.99 (0.97 to 1.01)</td><td>0.399</td><td>0.9 (0.73 to 1.11)</td><td>0.315</td></tr><tr><td>3-4 ECOG</td><td>1.11 (1.04 to 1.18)</td><td>0.003</td><td>2.61 (1.44 to 4.76)</td><td>0.002</td></tr><tr><td>Hematologic malignancy</td><td></td><td></td><td></td><td></td></tr><tr><td>None</td><td>1 (reference)</td><td>-</td><td>1 (reference)</td><td>-</td></tr><tr><td>Myeloid malignancy</td><td>0.92 (0.84 to 1.01)</td><td>0.069</td><td>0.66 (0.24 to 1.84)</td><td>0.433</td></tr><tr><td>Lymphoid malignancy</td><td>0.96 (0.89 to 1.04)</td><td>0.297</td><td>0.69 (0.33 to 1.46)</td><td>0.338</td></tr><tr><td>Allogeneic SCT</td><td>0.86 (0.77 to 0.98)</td><td>0.018</td><td>0.08 (0.01 to 0.59)</td><td>0.014</td></tr><tr><td>Immunosuppressive therapy</td><td>1.09 (1.02 to 1.16)</td><td>0.011</td><td>2.04 (1.14 to 3.66)</td><td>0.017</td></tr><tr><td>Leucocytes count</td><td></td><td></td><td></td><td></td></tr><tr><td>0.5-20 G/L</td><td>1 (reference)</td><td>-</td><td>1 (reference)</td><td>-</td></tr><tr><td>&lt; 0.5 G/L</td><td>1.05 (0.96 to 1.16)</td><td>0.293</td><td>2.18 (0.92 to 5.2)</td><td>0.079</td></tr><tr><td>&gt; 20 G/L</td><td>0.92 (0.84 to 1)</td><td>0.045</td><td>0.4 (0.15 to 1.1)</td><td>0.077</td></tr><tr><td>Chemotherapy &lt; 1 month</td><td>1.02 (0.96 to 1.09)</td><td>0.555</td><td>1.15 (0.61 to 2.17)</td><td>0.669</td></tr><tr><td>TTV in nasopharyngeal swabs &gt; 2.9 log<sub>10</sub>/mL</td><td>1.1 (1.03 to 1.17)</td><td>0.004</td><td>2.41 (1.35 to 4.28)</td><td>0.003</td></tr></tbody></table>

All baseline variables that were found to be associated with opportunistic infections in the univariate analysis were included in the multivariate model as well as age, cause of immunosuppression (hematological malignancy, immunosuppressive therapy, recent chemotherapy). All variables included in the multivariable model are shown in this table. Missing data were imputed using multivariate imputation by chained equations (MICE library, R) with 20 imputed datasets. In total, 485 patients were included in the multivariate model (69 with an opportunistic infection).

<figure><img src="image_5.png" /><figcaption>Figure 4. Association of TTV in nasopharyngeal swabs with opportunistic infections and clinical outcomes</figcaption></figure>

Each dot represents a patient according to detection of TTV in nasopharyngeal swabs, diagnosis of opportunistic infection, and outcome at day 28 (death or invasive mechanical ventilation (IMV)). Translucent spheres have a diameter logarithmically proportional to the number of patients. Detection of TTV and viral burden (<2.9 log<sub>10</sub>/mL; ≥2.9 log<sub>10</sub>/mL) was associated to both day-28 IMV or death (see Table 2, p=0.022) and the diagnosis of opportunistic infections (see Figure 3 and Table 2, p=0.011).

As shown in **Figure 3**, the association between TTV burden in nasopharyngeal swabs and opportunistic infections was importantly strengthened in patients without recent chemotherapy: 23.9% (28/117) when TTV burden was ≥2.9 log<sub>10</sub>/mL vs. 6.9% (12/173) when <2.9 log<sub>10</sub>/mL (p<0.001) (sensibility=0.64, specificity=0.70; **Figure S4-S6**) with an OR of 5.4 (95%CI 2.39 to 12.18) in a multivariable analysis (**Table S8**). In other subgroup sensitivity analyses by cause of immunosuppression, this association was statistically significant in patients on immunosuppressive therapy, SOT recipients, and solid tumors without recent chemotherapy (<30 days) (**Figure S7-S8**). Of note, cubic spline analyses also suggested an association between serum TTV burden and the rate of opportunistic infections (**Figure S9**).
TTV in nasopharyngeal swabs was also associated with the rate of all-cause pulmonary infections, microbiologically documented bacterial infections (Table 2) and detection of respiratory viruses in nasopharyngeal swabs (Table S8, Figure S10).

DISCUSSION

The aim of this study was to evaluate the detection of TTV DNA in the respiratory tract of adult immunocompromised patients with acute hypoxemic respiratory failure. TTV was present in 60% of patients and correlated with higher rates of opportunistic infections and worse clinical outcomes. This finding provides a novel opportunity to potentially refine the management strategies for these high-risk patients.

Torque teno viruses are part of the physiological virome and can be detected in the blood in up to 90% of healthy individuals[6]. To date, they have not been linked to any human disease role[18]. The current literature supports a correlation between the degree of adaptive immune suppression and TTV burden across immunocompromised conditions[19]. In SOT recipients, blood TTV burden aligns with the intensity of the immunosuppressive therapy[7] and has been described as a surrogate for impaired immunity: high TTV burden is associated with an increased risk for infection [8,20], as opposed to graft rejection[8,21,22], and with a poorer humoral and cellular responses to COVID-19 vaccines [23]. After HSCT, elevated blood TTV burden has been associated with more aggressive conditioning regimens, and higher doses of anti-thymocyte globulin[24]. A study of anti-CD19 CAR T-cell recipients also reported an association between elevated TTV levels and fewer immune-related adverse events, along with poorer haematological responses[17]. Preliminary data also suggest that high blood TTV burden may predict a heightened risk of severe relapse in patients with ANCA-associated vasculitis[25]. Finally, in rheumatoid arthritis patients undergoing disease-modifying antirheumatic drug therapy, elevated blood TTV levels were associated with better clinical response[26].

In patient with COVID-19, TTV burden was associated with more severe pneumonia [13,27], and nasopharyngeal TTV burden >2.9 log10 copies/mL has been shown to be an independent predictor of ICU admission[11]. In the present study, which included a wide range of immunocompromised patients, the rate and quantity of respiratory TTV varied significantly with the type of immunosuppression, the clinical/radiologic presentation, and the cause of ARF. Patients with TTV burden higher than 2.9 log10copies/mL were those at highest risk of opportunistic infections. TTV burden in nasopharyngeal swabs was highly correlated with serum levels, suggesting 1 that nasopharyngeal TTV might also reflect the global immunological status in these patients.

From a clinical standpoint, stratification of patients at higher risk for opportunistic infections is crucial[1]: despite diagnostic investigations, the cause of ARF remains unknown in up to 30% of cases[2], which is associated with an increased risk of death[3,4]. Opportunistic infections are causing ARF in up to 20% and remain associated with higher mortality[4] and are difficult to diagnose without bronchoscopy[28], while invasive procedures have been associated with worse outcomes[5]. TTV PCR in nasopharyngeal swabs could complement other markers (e.g. lymphocyte count, immunosuppressive therapy) to stratify those at higher risk for opportunistic infections. These patients may benefit most from invasive diagnostic procedures and/or empiric antimicrobial therapy. However, its predictive value remains
limited, particularly in certain subgroups (e.g. after recent chemotherapy) and further studies
are warranted to confirm and refine our findings.

This study has several limitations. First, it is a *post hoc* study of a clinical trial that was not primarily designed to investigate the clinical significance of TTV. Second, 264 (34%) were not sampled, and five others were not tested for TTV. Therefore, although their baseline characteristics and outcomes were similar, we cannot exclude a selection bias. Third, the causes of immunosuppression were heterogeneous in our population. One caveat is that recent chemotherapy may decrease TTV levels, as previously observed after chemotherapy for allogeneic HSCT or CAR T-cell infusion [15–17], possibly by depleting its cellular reservoirs [29]. In our study, patients who had received recent chemotherapy had significantly lower TTV levels (median 0.0 log₁₀/mL [0.0–4.0] vs. 2.3 log₁₀/mL [0.0–4.0], p < 0.001). Notably, the association between TTV load and opportunistic infections was observed only in patients without recent chemotherapy. Fourth, the observational design precludes conclusions regarding causality. Fifth, we did not evaluate of TTV DNA in deep respiratory specimens (e.g., bronchiolo-alveolar lavage) or in blood. Finally, this study was not designed to properly evaluate the clinical use of respiratory TTV quantification, and a dedicated study should replicate these preliminary results before implementation in clinical practice.

## FUNDING

Funded by the French Ministry of Health and French Intensive Care Society (P150912 HIGH). The authors thank QIAGEN or their donation of all QIAstat-Dx Respiratory SARS-CoV-2 Panel cartridges and the provision of a QIAstat-Dx Rise instrument.

## TRANSPARENCY DECLARATION

### Conflict of Interest Disclosures:

J.L.G. reported receiving personal fees from Qiagen (2022) and Abbott Rapid Diagnostics SAS (2021). E.A. has received fees for lectures from MSD, Pfizer, and Alexion; his institution and research group have received support from Baxter, Jazz Pharmaceuticals, Fisher & Paykel, Gilead, Alexion, and Ablynx; and he received support for article research from Assistance Publique - Hôpitaux de Paris. VL received support for article research from Assistance Publique - Hôpitaux de Paris and is treasurer of the GRRR-OH research group who received fees from Pfizer, Fisher-Paykel, Gilead, Astellas, Sanofi and, Alexion. F.B. reported personal fees from Merck Sharp and Dohme and BioMérieux outside the submitted work. A.D. reported grants from the French Ministry of Health; grants and personal fees from Philips, Fisher & Paykel, Respinor, and Lungpacer; personal fees from Baxter, Getinge, Gilead, and Lowenstein; and nonfinancial support from Fisher & Paykel outside the submitted work. A.M., L.F., S.MD., S.J., K.K., A.K., L.A., N.B., AS.M., E.C., F.P., M.S. and D.M. declare no competing interests.

### Role of the Funder/Sponsor:
The funders/sponsors had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

**Disclaimer:**

This study was performed on behalf of the Groupe de Recherche Respiratoire en Réanimation Onco-Hématologique (GRRR-OH).

**REFERENCES**

[1] Azoulay E, Russell L, Van de Louw A, Metaxa V, Bauer P, Povoa P, et al. Diagnosis of severe respiratory infections in immunocompromised patients. Intensive Care Med 2020;46:298–314. https://doi.org/10.1007/s00134-019-05906-5.

[2] Azoulay E, Mokart D, Kouatchet A, Demoule A, Lemiale V. Acute respiratory failure in immunocompromised adults. Lancet Respir Med 2019;7:173–86. https://doi.org/10.1016/S2213-2600(18)30345-X.

[3] Maillard A, Le Goff J, Barry M, Lemiale V, Mercier-Delarue S, Demoule A, et al. Multiplex Polymerase Chain Reaction Assay to Detect Nasopharyngeal Viruses in Immunocompromised Patients With Acute Respiratory Failure. Chest 2023:S0012-3692(23)05262-5. https://doi.org/10.1016/j.chest.2023.07.4222.

[4] Azoulay E, Pickkers P, Soares M, Perner A, Rello J, Bauer PR, et al. Acute hypoxemic respiratory failure in immunocompromised patients: the Efraim multinational prospective cohort study. Intensive Care Med 2017;43:1808–19. https://doi.org/10.1007/s00134-017-4947-1.

[5] Bauer PR, Chevret S, Yadav H, Mehta S, Pickkers P, Bukan RB, et al. Diagnosis and outcome of acute respiratory failure in immunocompromised patients after bronchoscopy. Eur Respir J 2019;54:1802442. https://doi.org/10.1183/13993003.02442-2018.

[6] Moustafa A, Xie C, Kirkness E, Biggs W, Wong E, Turpaz Y, et al. The blood DNA virome in 8,000 humans. PLOS Pathogens 2017;13:e1006292. https://doi.org/10.1371/journal.ppat.1006292.

[7] De Vlaminck I, Khush KK, Strehl C, Kohli B, Luikart H, Neff NF, et al. Temporal response of the human virome to immunosuppression and antiviral therapy. Cell 2013;155:1178–87. https://doi.org/10.1016/j.cell.2013.10.034.

[8] Doberer K, Schiemann M, Strassl R, Haupenthal F, Dermuth F, Görzer I, et al. Torque teno virus for risk stratification of graft rejection and infection in kidney transplant recipients- A prospective observational trial. Am J Transplant 2020;20:2081–90. https://doi.org/10.1111/ajt.15810.

[9] Haupenthal F, Rahn J, Maggi F, Gelas F, Bourgeois P, Hugo C, et al. A multicentre, patient- and assessor-blinded, non-inferiority, randomised and controlled phase II trial to
compare standard and torque teno virus-guided immunosuppression in kidney transplant recipients in the first year after transplantation: TTVguideIT. Trials 2023;24:213. https://doi.org/10.1186/s13063-023-07216-0.

[10] Megremis S, Constantinides B, Xepapadaki P, Yap CF, Sotiropoulos AG, Bachert C, et al. Respiratory eukaryotic virome expansion and bacteriophage deficiency characterize childhood asthma. Sci Rep 2023;13:8319. https://doi.org/10.1038/s41598-023-34730-7.

[11] Feghoul L, Caillault A, Peyrony O, Salmona M, Nere M-L, Delaugerre C, et al. Respiratory torque teno virus load at emergency department visit predicts intensive care unit admission of SARS-CoV-2 infected patients. J Med Virol 2023;95:e29319. https://doi.org/10.1002/jmv.29319.

[12] Maggi F, Pifferi M, Fornai C, Andreoli E, Tempestini E, Vatteroni M, et al. TT virus in the nasal secretions of children with acute respiratory diseases: relations to viremia and disease severity. J Virol 2003;77:2418-25. https://doi.org/10.1128/jvi.77.4.2418-2425.2003.

[13] Merenstein C, Liang G, Whiteside SA, Cobián-Güemes AG, Merlino MS, Taylor LJ, et al. Signatures of COVID-19 Severity and Immune Response in the Respiratory Tract Microbiome. mBio 2021;12:e0177721. https://doi.org/10.1128/mBio.01777-21.

[14] Azoulay E, Lemiale V, Mokart D, Nseir S, Argaud L, Pène F, et al. Effect of High-Flow Nasal Oxygen vs Standard Oxygen on 28-Day Mortality in Immunocompromised Patients With Acute Respiratory Failure: The HIGH Randomized Clinical Trial. JAMA 2018;320:2099-107. https://doi.org/10.1001/jama.2018.14282.

[15] Albert E, Solano C, Pascual T, Torres I, Macera L, Focosi D, et al. Dynamics of Torque Teno virus plasma DNAemia in allogeneic stem cell transplant recipients. J Clin Virol 2017;94:22-8. https://doi.org/10.1016/j.jcv.2017.07.001.

[16] Forqué L, Albert E, Piñana JL, Pérez A, Hernani R, Solano C, et al. Monitoring of plasma Torque teno virus, total Anelloviridae and Human Pegivirus 1 viral load for the prediction of infectious events and acute graft versus host disease in the allogeneic hematopoietic stem cell transplantation setting. J Med Virol 2023;95:e29107. https://doi.org/10.1002/jmv.29107.

[17] Benzaquén A, Giménez E, Iacoboni G, Guerreiro M, Hernani R, Albert E, et al. Torque Teno Virus plasma DNA load: a novel prognostic biomarker in CAR-T therapy. Bone Marrow Transplant 2023. https://doi.org/10.1038/s41409-023-02114-0.

[18] Taylor LJ, Keeler EL, Bushman FD, Collman RG. The enigmatic roles of Anelloviridae and Redondoviridae in humans. Curr Opin Virol 2022;55:101248. https://doi.org/10.1016/j.coviro.2022.101248.

[19] Kapps S, Haupenthal F, Bond G. Torque Teno virus-guided monitoring of immunosuppressive therapy. Nephrol Dial Transplant 2024:gfae149. https://doi.org/10.1093/ndt/gfae149.
[20] Fernández-Ruiz M, Albert E, Giménez E, Ruiz-Merlo T, Parra P, López-Medrano F, et al. Monitoring of alphatorquevirus DNA levels for the prediction of immunosuppression-related complications after kidney transplantation. American Journal of Transplantation 2019;19:1139-49. https://doi.org/10.1111/ajt.15145.

[21] Reyes NS, Laham G, Boccia N, García G, Jara R, Hermida E, et al. Prospective cohort study of Torque Teno Virus (TTV) viral load kinetics and the association with graft rejection in renal transplant patients. J Clin Virol 2023;165:105501. https://doi.org/10.1016/j.jcv.2023.105501.

[22] Solis M, Velay A, Gantner P, Bausson J, Filipputtu A, Freitag R, et al. Torquetenovirus viremia for early prediction of graft rejection after kidney transplantation. J Infect 2019;79:56-60. https://doi.org/10.1016/j.jinf.2019.05.010.

[23] Graninger M, Stumpf J, Bond G, Görzer I, Springer DN, Kessel F, et al. Prediction of humoral and cellular immune response to COVID-19 mRNA vaccination by TTV load in kidney transplant recipients and hemodialysis patients. J Clin Virol 2023;162:105428. https://doi.org/10.1016/j.jcv.2023.105428.

[24] Schmitz J, Kobbe G, Kondakci M, Schuler E, Magorsch M, Adams O. The Value of Torque Teno Virus (TTV) as a Marker for the Degree of Immunosuppression in Adult Patients after Hematopoietic Stem Cell Transplantation (HSCT). Biol Blood Marrow Transplant 2020;26:643-50. https://doi.org/10.1016/j.bbm.t.2019.11.002.

[25] Odler B, Riedl R, Lee J, Cooney L, Merkel P, St.Clair W, et al. Torque Teno Virus as a Potential Biomarker for Assessment of Immunocompetence in Patients with ANCA-associated Vasculitis. ACR Meeting Abstracts n.d.

[26] Studenic P, Bond G, Kerschbaumer A, Bécède M, Pavelka K, Karateev D, et al. Torque Teno Virus quantification for monitoring of immunomodulation with biologic compounds in the treatment of rheumatoid arthritis. Rheumatology (Oxford) 2022;61:2815-25. https://doi.org/10.1093/rheumatology/keab839.

[27] Emmel V, Gama B, de Paula A, Ferreira G, Binato R, Abdelhay E. Can torque teno virus be a predictor of SARS-CoV-2 disease progression in cancer patients? Journal of Infection and Chemotherapy 2022;28:1623-7. https://doi.org/10.1016/j.jiac.2022.08.015.

[28] Alanio A, Hauser PM, Lagrou K, Melchers WJG, Helweg-Larsen J, Matos O, et al. ECIL guidelines for the diagnosis of Pneumocystis jirovecii pneumonia in patients with haematological malignancies and stem cell transplant recipients. J Antimicrob Chemother 2016;71:2386-96. https://doi.org/10.1093/jac/dkw156.

[29] Kosulin K, Kernbichler S, Pichler H, Lawitschka A, Geyeregger R, Witt V, et al. Post-transplant Replication of Torque Teno Virus in Granulocytes. Front Microbiol 2018;9:2956. https://doi.org/10.3389/fmicb.2018.02956.
<figure><img src="image_6.png" /></figure>