Clinical and Immunological Responses After SARS-CoV-2 Infection Causing COVID-19

There are very few long-term studies that analyze the immune responses in patients recovered from COVID-19 caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

The main aim of this study is to analyze the clinical profile and immune responses of recovered COVID-19 patients in a representative cohort of people in the Umbria region of Italy. The participants had a history of testing positive for SARS-CoV-2 in March 2020 by Reverse Transcriptase- Quantitative Polymerase Chain Reaction (RT-qPCR). The participants were invited for voluntary participation in a seroprevalence study. This study analyzes longitudinally the presence of antibodies against SARS-CoV-2 by sequential serological tests at different time points using two FDA-approved Immunoassays. At the first serum sample collection, the participants were asked to provide information about their COVID-19 clinical history including clinical profile, co-morbidities, and treatment undertaken using a standardized questionnaire. Successive sequential serological assessments were conducted to understand the immune responses in these recovered patients.

Moreover, stage two of the study involves, analysis of antibody titers in recovered vaccinated individuals and their follow-up.

Study design: A monocentric pilot longitudinal observational study

Study subjects: patients recovered from SARS-CoV-2 infection in March 2020 (detected by RT-PCR)

Study method: The study was conducted after written informed consent for voluntary participation. The antibody titers were longitudinally analyzed by sequential serological tests at different time points (TPs) using two FDA-approved Immunoassays. At the first serum sample collection, the participants were asked to provide information about their COVID-19 clinical history including clinical profile, co-morbidities, and the treatment undertaken using a standardized questionnaire.

From May 2020 to January 2021:

Anti-Nucleocapsid (NCP) antibodies were analyzed using FDA-approved CLIA immunoassay through sequential serum samples.

Time was treated as a factor and six different time points (TPs) were defined (T0-T5). The first blood sample was collected in the month of May 2020, 2 months after the month of infection (March), and was defined as T0. Consecutive serological samples were analyzed at different TPs; three months (T1), five months (T2), seven months (T3), eight months (T4), and ten months (T5) post-infection in June, August, October, November of 2020 and January 2021 respectively.

At this point, a more specific immunoassay was adopted to detect neutralizing antibodies against the Spike-Receptor binding domain for future assessments.

From late February 2021:

an additional n=12 patients (8 female and 4 male), who met the eligibility criteria for participation, were enrolled in the study and added to the original cohort (n=30). These patients (n=12), similar to the original cohort, had a history of testing positive for SARS-CoV-2 by RT-qPCR in March 2020, updating the sample size to n=42.

Since the legal provisions adopted by the Italian Ministry of Health advised mandatory vaccination for all Healthcare Workers, irrespective of previous disease status, n=10 patients (4 female and 6 male) were gradually vaccinated from mid-March 2021 and hence excluded from the original cohort, making the revised final sample size as n=32.

The presence of antibodies was analyzed The study continues to actively enroll patients for future analysis.

with vaccination in progress, the antibody titers of the recovered and then vaccinated patients will also be analysed separately.

Eligibility Criteria:
Inclusion Criteria:

1. Individuals who tested positive for SARS-CoV-2 in March 2020. These patients will be divided into two groups and followed up over time. The first group will include patients who have recovered and have not received the vaccine. The second group will include patients who have recovered and have received the vaccine.
2. No acute respiratory infection or active SARS-CoV-2 infection.
3. Informed consent of the adult participant.

Exclusion Criteria:

1. Individuals \<18 years or \>80 years.
2. No informed consent by the adult participant.
3. Suspicion of acute COVID-19 infection