529 - COVID-19 Antibody Responses in Solid Organ Transplant Recipients

Background: Studies to date indicate that most adults develop IgG antibody to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) within 6 weeks of COVID-19 symptom onset. The seroconversion rate of solid organ transplant recipients (SOTR) following COVID-19 is unknown. Elucidation of humoral immune responses following COVID-19 in SOTR may inform risk of reinfection and the development of safe and effective vaccines for immunocompromised hosts.
 
 

Methods: We assessed the frequency of SARS-CoV-2 IgG detection among adult SOTR diagnosed with COVID-19 by nasopharyngeal PCR assays between 3/1/2020 and 6/5/2020. SARS-CoV-2 IgG was detected in serum using the Abbott IgG assay at the manufacturer's recommended cut-off. Our primary objective was the frequency of SARS-CoV-2 IgG seropositivity after COVID-19. A secondary objective was to identify clinical factors associated with seroconversion.  The mean age and nadir absolute lymphocyte count (ALC) were calculated between seropositive and negative SOTR and compared by Student’s t-test.
 
 

Results: Among 93 SOTR diagnosed with COVID-19, 19 died before SARS-CoV-2 IgG testing could be performed, and 18 had testing pending as of abstract submission. 56 SOTR (44 kidney, 5 heart, 4 liver, 1 lung, and 1 heart-kidney recipients) completed testing and were included in the analysis. Median age was 58 years (IQR 49.5-67), and all received maintenance immunosuppression at the time of COVID-19 diagnosis with median nadir ALC during illness of 400 (IQR 200-600). SARS-CoV-2 IgG testing was performed at a median of 60 days (IQR 50-70) from symptom onset, the shortest interval being 16 days. 47 out of 56 SOTR tested positive for SARS-CoV-2 IgG.  The likelihood of seroconversion was not different between those who were tested at < or ≥ 60 days from symptom onset (p=0.26), nor did it vary significantly by age (p =0.59), gender (p=0.53) or nadir ALC (p =0.28).
 
 

Conclusion: 83% of evaluated SOTR with COVID-19 disease had detectable SARS-CoV-2 IgG in serum at a median of 60 days after symptom onset. Studies are ongoing to identify variables associated with poor antibody response among the nearly 20% of SOTR in this cohort who failed to seroconvert. The significance of seroconversion on risk of reinfection and vaccine immunogenicity remains to be determined.