COVID-19 Infection Does Not Alter HLA Antibody Reactivity (2022)

IntroductionThe requirement for immunosuppression in organ transplant recipients, particularly suppression of the T cell response, has made this population especially vulnerable to prolonged and severe infections during the ongoing SARS-CoV-2 pandemic.1Cholankeril G. Podboy A. Alshuwaykh O.S. et al.Early impact of COVID-19 on solid organ transplantation in the United States.Transplantation. 2020; 104: 2221-2224https://doi.org/10.1097/TP.0000000000003391Crossref PubMed Scopus (46) Google Scholar Acknowledgment of this increased risk led to the reduction of deceased-donor organ transplantation, and for many programs, complete cessation of living-donor operations during the early periods of the COVID-19 pandemic.2Aubert O. Yoo D. Zielinski D. et al.COVID-19 pandemic and worldwide organ transplantation: a population-based study.Lancet Public Health. 2021; 6: e709-e719https://doi.org/10.1016/S2468-2667(21)00200-0Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar,3Boyarsky B.J. Chiang P.-Y. Werbel W.A. et al.Early impact of COVID-19 on transplant center practices and policies in the United States.Am J Transplant Published online. May 10. 2020; 20: 1809-1818https://doi.org/10.1111/ajt.15915Crossref PubMed Scopus (187) Google Scholar Nevertheless, for transplant recipients, the risk of contracting viral disease does not exist in a vacuum. Solid organ transplant candidates have a number of characteristics that increase their morbidity and mortality risk above that of the general population. Delineating the presentation and effects of SARS-CoV-2 in this cohort is critical to understanding the new landscape of organ transplantation in the context of an ongoing pandemic.4Hilbrands L.B. Duivenvoorden R. Vart P. et al.COVID-19-related mortality in kidney transplant and dialysis patients: results of the ERACODA collaboration.Nephrol Dial Transplant. 2020; 35: 1973-1983https://doi.org/10.1093/ndt/gfaa261Crossref PubMed Scopus (177) Google Scholar, 5Thaunat O. Legeai C. Anglicheau D. et al.IMPact of the COVID-19 epidemic on the moRTAlity of kidney transplant recipients and candidates in a French Nationwide registry sTudy (IMPORTANT).Kidney Int. 2020; 98: 1568-1577https://doi.org/10.1016/j.kint.2020.10.008Abstract Full Text Full Text PDF PubMed Scopus (49) Google Scholar, 6Craig-Schapiro R. Salinas T. Lubetzky M. et al.COVID-19 outcomes in patients waitlisted for kidney transplantation and kidney transplant recipients.Am J Transplant Published online November 8. 2020; 21: 1576-1585https://doi.org/10.1111/ajt.16351Crossref PubMed Scopus (40) Google ScholarOf particular concern in both transplant recipients and candidates is the possibility of heterologous immunity after infection, with cross-reactive T cell receptor specificity leading to unanticipated allosensitization. Virus-specific T cells that harbor cross-reactivity to human leukocyte antigen (HLA) antigens have been identified for Epstein-Barr virus, cytomegalovirus, varicella zoster virus, HIV, herpes simplex virus 2, and Influenza.S5-S11 Whereas T cell cross-reactivity is not easily determined, HLA antibodies are routinely tested in this population and provide a useful surrogate endpoint. A recent report describes the presence of HLA antibodies in the convalescent serum of male patients without any known allosensitizing events.7Juskewitch J.E. Stubbs J.R. Gandhi M.J. Elevated rate of HLA antibodies in male COVID-19 convalescent plasma donors: A risk factor for transfusion-related acute lung injury.Mayo Clin Proc. 2021; 96: 500-502https://doi.org/10.1016/j.mayocp.2020.11.007Abstract Full Text Full Text PDF PubMed Scopus (6) Google Scholar In response to this, the HLA antibody profile among a small series of waitlist candidates who developed symptomatic COVID-19 was assessed.8Roll G.R. Lunow-Luke T. Braun H.J. et al.COVID-19 does not impact HLA antibody profile in a series of waitlisted renal transplant candidates.Hum Immunol. 2021; 82: 568-573https://doi.org/10.1016/j.humimm.2021.04.002Crossref PubMed Scopus (7) Google Scholar The study was encouraging for the following reasons: none of the patients developed de novo HLA antibodies, and pre-existing HLA antibodies in highly sensitized candidates did not increase. Nevertheless, larger numbers are needed to determine whether repeat HLA antibody testing prior to kidney transplantation is necessary after COVID-19 infection.The kidney transplant waitlist at our institution, Emory University Hospital, consists of approximately 2000 patients across southeastern United States. Patients send in monthly serum samples for panel reactive antibody (PRA) testing to maintain updated data on sensitization status. We aimed to use historical serum samples from these patients to determine the prevalence of SARS-CoV-2 seropositivity among our kidney transplant waitlist population, across the state of Georgia, during the summer of 2020. In addition, we aimed to monitor the duration of humoral immunity in the waitlist population, and to evaluate SARS-CoV-2 seropositive patients for changes in HLA alloreactivity.ResultsPatient DemographicsThe Emory kidney transplant waitlist consisted of 2010 candidates overall with 1188 hemodialysis patients, 390 peritoneal dialysis patients, 234 candidates not on dialysis, and 198 on home hemodialysis (Supplementary Figure S1a). Four hundred dialysis-dependent candidates were selected from high-risk counties, defined as having a case rate above the average (2229/100,000 residents, August 2020). Of the 400 patients tested, 28 (7%) were positive (Supplementary Methods, Supplementary Figure S1b). Patients who tested positive had a lower mean age compared to those who tested negative (44 years vs. 55 years, P < 0.01, Table 1). This was the only significant difference between groups, who were majority male (65%), Black (62%), and approximately 4 years from their initial referral. There was a similar distribution of hemodialysis and peritoneal dialysis between groups. Spatial analysis of these cases did not demonstrate any evidence of geographic clustering (Supplementary Results).Table 1Demographic analysis of the tested waitlist candidatesPatient demographics by SARS-CoV-2 serologyCharacteristicNegative, n = 374aStatistics presented: mean (SD), n (%).Positive, n = 28aStatistics presented: mean (SD), n (%).P-valuebStatistical tests performed: Wilcoxon rank-sum test, χ2 test of independence, Fisher's exact test.Age, mean (SD)55 (13)44 (10)< 0.001Sex, n (%)0.085Female114 (36%)4 (17%)Male200 (64%)20 (83%)Race, n (%)0.8African-American192 (61%)16 (67%)Caucasian76 (24%)4 (17%)Other46 (15%)4 (17%)Time since referral (yrs), mean (SD)4.05 (2.23)3.84 (2.27)0.6Dialysis method0.8Hemodialysis270 (72%)19 (68%)Peritoneal dialysis104 (28%)9 (32%)Clinical and demographic variables were compared between waitlist candidates who tested positive and those who tested negative.a Statistics presented: mean (SD), n (%).b Statistical tests performed: Wilcoxon rank-sum test, χ2 test of independence, Fisher's exact test. Open table in a new tab Patients who tested positive were interviewed by phone, and 19 of 28 patients responded. Ten of the seropositive patients who responded were aware of prior COVID infection, and most of them endorsed a symptom history (9/10) along with a positive test (10/10). As of April 2021, 9 of 19 patients were vaccinated, and the rest expressed interest in future vaccination.Serologic ResponseCOVID SerologyAntibodies to full-spike were nearly ubiquitous in patients who tested positive, with corresponding bimodal distribution of S1 and S2 antibodies. Trimmed mean fluorescent intensity was compared between positive patients who were symptomatic and asymptomatic (Supplementary Figure S2b). Across all SARS-CoV-2 proteins tested, symptomatic patients appeared to have a higher average trimmed mean fluorescent intensity than asymptomatic patients, however this difference was not statistically significant for any individual protein.Follow-up testing was performed in April 2021. All patients maintained seropositivity over the course of available samples, which is a mean of 220 days follow-up (Supplementary Figure S2c). Only samples prior to patient vaccination were tested.Panel Reactive AntibodiesTransplant waitlist candidates who tested positive for SARS-CoV-2 antibodies were examined for changes in PRA at the time of seroconversion. Each SARS-CoV-2 positive sample was compared to the sample immediately prior to seroconversion. Details of prior sensitization exposures along with individual demographics and calculated PRA levels were compiled (Supplementary Table S1). Paired sample t-test demonstrated no significant increase in FlowPRA values before and after seroconversion (Figure 1). Across highly sensitized candidates, there was no consistent change in HLA antibody specificity as evaluated by single antigen bead testing. Patients were examined on an individual level, and there was no sustained change in antibody specificity associated with seroconversion.DiscussionThe COVID-19 pandemic has disproportionately impacted immunosuppressed or immunocompromised populations, including solid organ transplant recipients.1Cholankeril G. Podboy A. Alshuwaykh O.S. et al.Early impact of COVID-19 on solid organ transplantation in the United States.Transplantation. 2020; 104: 2221-2224https://doi.org/10.1097/TP.0000000000003391Crossref PubMed Scopus (46) Google Scholar, 2Aubert O. Yoo D. Zielinski D. et al.COVID-19 pandemic and worldwide organ transplantation: a population-based study.Lancet Public Health. 2021; 6: e709-e719https://doi.org/10.1016/S2468-2667(21)00200-0Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar, 3Boyarsky B.J. Chiang P.-Y. Werbel W.A. et al.Early impact of COVID-19 on transplant center practices and policies in the United States.Am J Transplant Published online. May 10. 2020; 20: 1809-1818https://doi.org/10.1111/ajt.15915Crossref PubMed Scopus (187) Google Scholar, 4Hilbrands L.B. Duivenvoorden R. Vart P. et al.COVID-19-related mortality in kidney transplant and dialysis patients: results of the ERACODA collaboration.Nephrol Dial Transplant. 2020; 35: 1973-1983https://doi.org/10.1093/ndt/gfaa261Crossref PubMed Scopus (177) Google Scholar, 5Thaunat O. Legeai C. Anglicheau D. et al.IMPact of the COVID-19 epidemic on the moRTAlity of kidney transplant recipients and candidates in a French Nationwide registry sTudy (IMPORTANT).Kidney Int. 2020; 98: 1568-1577https://doi.org/10.1016/j.kint.2020.10.008Abstract Full Text Full Text PDF PubMed Scopus (49) Google Scholar, 6Craig-Schapiro R. Salinas T. Lubetzky M. et al.COVID-19 outcomes in patients waitlisted for kidney transplantation and kidney transplant recipients.Am J Transplant Published online November 8. 2020; 21: 1576-1585https://doi.org/10.1111/ajt.16351Crossref PubMed Scopus (40) Google Scholar Though most transplant programs have instituted vaccination requirements for waitlist candidates, the sequelae of natural infection is still relevant. We aimed to add to the current literature surrounding the duration of the humoral response in the immune-dysregulated chronic kidney disease population and to examine HLA antibody positive patients for evidence of heterologous immunity related to SARS-CoV-2 infection.Of the 400 waitlist candidates tested, 28 tested positive for antibodies against SARS-CoV-2. Testing of serum samples immediately preceding and following SARS-CoV-2 seroconversion failed to detect a significant increase in PRA values subsequent to SARS-CoV-2 infection. In addition, individual antibody specificities did not demonstrate any consistent or sustained changes after infection. Seroconversion does not appear to be a significant risk factor for development of donor specific antibodies in this cohort of patients. Whereas larger sample sizes are needed to fully understand the effects of SARS-CoV-2 on the alloimmune response, these results are reassuring and add to the prior literature that has, to date, only examined calculated PRA values in nonsensitized and a small number (n = 4) of highly sensitized patients.7Juskewitch J.E. Stubbs J.R. Gandhi M.J. Elevated rate of HLA antibodies in male COVID-19 convalescent plasma donors: A risk factor for transfusion-related acute lung injury.Mayo Clin Proc. 2021; 96: 500-502https://doi.org/10.1016/j.mayocp.2020.11.007Abstract Full Text Full Text PDF PubMed Scopus (6) Google ScholarThis study has a number of limitations, because it is a single-institution, retrospective study with relatively small sample size. The study only included patients with natural immunity to SARS-CoV-2 acquired prior to vaccine release and did not examine the effects of subsequent vaccination on antibody profiles. The intermittent nature of PRA testing among waitlist candidates also allows the possibility that a transient increase in alloreactivity may occur without being captured by this dataset.9Katerinis I. Hadaya K. Duquesnoy R. et al.De novo anti-HLA antibody after pandemic H1N1 and seasonal influenza immunization in kidney transplant recipients.Am J Transplant. 2011; 11: 1727-1733https://doi.org/10.1111/j.1600-6143.2011.03604.xCrossref PubMed Scopus (108) Google Scholar In addition, patients were not followed up post-transplant to monitor the effects of immunosuppression. Finally, the immune response to SARS-CoV-2 was quantified one-dimensionally, without consideration for cell-mediated immunity, and without assessment of the neutralizing capability of antibodies that were detected.Although this was a small sample size and retrospective study, the results add to the developing body of knowledge surrounding transplant candidates and recipients during the ongoing COVID-19 pandemic. Hemodialysis patients were at no greater risk than peritoneal dialysis patients of seroconversion. Rather, younger age was the only significant difference between cohorts. Seroconversion was not associated with any increase in PRA. Waitlist candidates demonstrated a sustained natural humoral immune response over a mean of 220 days follow-up. These findings reinforce the importance of vaccination in the waitlist population, in whom a more robust immune response is possible. More research is needed to understand the effect of SARS-CoV-2 infection on the alloimmune response of transplant candidates in order to guide their calculated PRA and SARS-CoV-2 monitoring. Whereas testing for active SARS-CoV-2 infection by polymerase cahin reaction test upon receipt of an organ offer remains necessary to avoid infection in the setting of compromised protective immunity, the current data does not suggest any increased risk of allosensitization in these individuals. Therefore, we recommend continuing with standard calculated PRA testing for candidates on the kidney transplant waitlist, without any increase in frequency in the setting of SARS-CoV-2 infection.DisclosureCPL received funding from the James M. Cox Foundation and NIH/NCI (awards 5U19 AI051731-18, R01 MD011682-03, R01 AI126322-04, U01 AI138909-01). ACJ received funding from the ASTS Jon Fryer Resident Research Scholarship and James O. Robbins Foundation. Reagents were provided by OneLambda, Inc.All the other authors declared no competing interests. IntroductionThe requirement for immunosuppression in organ transplant recipients, particularly suppression of the T cell response, has made this population especially vulnerable to prolonged and severe infections during the ongoing SARS-CoV-2 pandemic.1Cholankeril G. Podboy A. Alshuwaykh O.S. et al.Early impact of COVID-19 on solid organ transplantation in the United States.Transplantation. 2020; 104: 2221-2224https://doi.org/10.1097/TP.0000000000003391Crossref PubMed Scopus (46) Google Scholar Acknowledgment of this increased risk led to the reduction of deceased-donor organ transplantation, and for many programs, complete cessation of living-donor operations during the early periods of the COVID-19 pandemic.2Aubert O. Yoo D. Zielinski D. et al.COVID-19 pandemic and worldwide organ transplantation: a population-based study.Lancet Public Health. 2021; 6: e709-e719https://doi.org/10.1016/S2468-2667(21)00200-0Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar,3Boyarsky B.J. Chiang P.-Y. Werbel W.A. et al.Early impact of COVID-19 on transplant center practices and policies in the United States.Am J Transplant Published online. May 10. 2020; 20: 1809-1818https://doi.org/10.1111/ajt.15915Crossref PubMed Scopus (187) Google Scholar Nevertheless, for transplant recipients, the risk of contracting viral disease does not exist in a vacuum. Solid organ transplant candidates have a number of characteristics that increase their morbidity and mortality risk above that of the general population. Delineating the presentation and effects of SARS-CoV-2 in this cohort is critical to understanding the new landscape of organ transplantation in the context of an ongoing pandemic.4Hilbrands L.B. Duivenvoorden R. Vart P. et al.COVID-19-related mortality in kidney transplant and dialysis patients: results of the ERACODA collaboration.Nephrol Dial Transplant. 2020; 35: 1973-1983https://doi.org/10.1093/ndt/gfaa261Crossref PubMed Scopus (177) Google Scholar, 5Thaunat O. Legeai C. Anglicheau D. et al.IMPact of the COVID-19 epidemic on the moRTAlity of kidney transplant recipients and candidates in a French Nationwide registry sTudy (IMPORTANT).Kidney Int. 2020; 98: 1568-1577https://doi.org/10.1016/j.kint.2020.10.008Abstract Full Text Full Text PDF PubMed Scopus (49) Google Scholar, 6Craig-Schapiro R. Salinas T. Lubetzky M. et al.COVID-19 outcomes in patients waitlisted for kidney transplantation and kidney transplant recipients.Am J Transplant Published online November 8. 2020; 21: 1576-1585https://doi.org/10.1111/ajt.16351Crossref PubMed Scopus (40) Google ScholarOf particular concern in both transplant recipients and candidates is the possibility of heterologous immunity after infection, with cross-reactive T cell receptor specificity leading to unanticipated allosensitization. Virus-specific T cells that harbor cross-reactivity to human leukocyte antigen (HLA) antigens have been identified for Epstein-Barr virus, cytomegalovirus, varicella zoster virus, HIV, herpes simplex virus 2, and Influenza.S5-S11 Whereas T cell cross-reactivity is not easily determined, HLA antibodies are routinely tested in this population and provide a useful surrogate endpoint. A recent report describes the presence of HLA antibodies in the convalescent serum of male patients without any known allosensitizing events.7Juskewitch J.E. Stubbs J.R. Gandhi M.J. Elevated rate of HLA antibodies in male COVID-19 convalescent plasma donors: A risk factor for transfusion-related acute lung injury.Mayo Clin Proc. 2021; 96: 500-502https://doi.org/10.1016/j.mayocp.2020.11.007Abstract Full Text Full Text PDF PubMed Scopus (6) Google Scholar In response to this, the HLA antibody profile among a small series of waitlist candidates who developed symptomatic COVID-19 was assessed.8Roll G.R. Lunow-Luke T. Braun H.J. et al.COVID-19 does not impact HLA antibody profile in a series of waitlisted renal transplant candidates.Hum Immunol. 2021; 82: 568-573https://doi.org/10.1016/j.humimm.2021.04.002Crossref PubMed Scopus (7) Google Scholar The study was encouraging for the following reasons: none of the patients developed de novo HLA antibodies, and pre-existing HLA antibodies in highly sensitized candidates did not increase. Nevertheless, larger numbers are needed to determine whether repeat HLA antibody testing prior to kidney transplantation is necessary after COVID-19 infection.The kidney transplant waitlist at our institution, Emory University Hospital, consists of approximately 2000 patients across southeastern United States. Patients send in monthly serum samples for panel reactive antibody (PRA) testing to maintain updated data on sensitization status. We aimed to use historical serum samples from these patients to determine the prevalence of SARS-CoV-2 seropositivity among our kidney transplant waitlist population, across the state of Georgia, during the summer of 2020. In addition, we aimed to monitor the duration of humoral immunity in the waitlist population, and to evaluate SARS-CoV-2 seropositive patients for changes in HLA alloreactivity.