Humoral response to sars-cov-2 infection among liver transplant recipients

Background: There is still a lack of knowledge on host immune response and risk of reinfection, particularly in special groups, such as liver transplant recipients. Immunosuppressive agents are known to interfere with T- and/or B-lymphocytes, which are required to mount an adequate serologic response. Therefore, we aim to investigate the antibody response to SARS-CoV-2 in liver transplant (LT) recipients after COVID-19. Methods: We conducted a prospective multicenter casecontrol study analyzing antibodies against the nucleocapsidprotein and spike protein of SARS-CoV-2 in LT recipients with confirmed SARS-CoV-2 infection (COVID-LT) compared to immunocompetent patients (COVID-immunocompetent) and liver transplant patients without COVID-19 symptoms (non-COVID LT). Serum samples were collected from all the participants included in the study. In the COVID-LT cohort, as well as in the COVID-immunocompetent cohort, the samples were drawn between 4-8 weeks after the detection of the SARS-CoV-2 infection. Results: Overall, 35 LT recipients were included in the COVID-LT cohort. Male gender was most prevalent (25 recipients, 71.4%) and mean age was 56.7±13.9 years. 35 and 70 subjects fulfilling the matching criteria were assigned to the COVID-immunocompetent and non-COVID LT cohort, respectively. We showed that LT recipients, despite the use of immunosuppressive drugs and less symptoms, mounted a detectable anti-nucleocapsid antibody titer in 80% of the cases, although the level was significantly lower in comparison to the level detected in the COVID-immunocompetent cohort (3.73 vs. 7.36, p<0.001). When analyzing the anti-spike-protein antibody response, no difference in positivity rates was found between the COVIDLT and the COVID-immunocompetent cohorts (97.1% vs. 100%, p=0.314). Considering the non-COVID LT group, we found that cross-reactivity with other coronavirus species is irrelevant for these assays (only one positivity for the antinucleocapsid and two for the anti-spike). Conclusion: Our findings suggest that the humoral response of LT recipients is only slightly lower than expected compared with that of COVID-19 immunocompetent controls. Anti-nucleocapsid antibodies, although specific for SARS-CoV-2 when tested alone, may erroneously lead to an underestimation of the immune response in this population. Testing for anti-spike antibodies adds sensitivity. Altogether, routine antibody testing against separate SARS-CoV-2 antigens shows that LT patients are capable of mounting an adequate antibody response against SARS-CoV-2.