ABSTRACT
Objectives and Study: SARS-CoV-2, a novel coronavirus causing the pandemic clinical disease COVID-19, is generally associated with mild disease in most young patients with inflammatory bowel disease (IBD) despite their receiving immunosuppressive therapy. The aim of this study was to longitudinally evaluate characteristics of clinical and serologic response to SARS-CoV-2 infection in a cohort of young patients with IBD receiving biologics. Methods: Starting May 2020 we obtained serum on patients with IBD at the time of infusion with either infliximab or vedolizumab, along with baseline demographic and clinical data, as well possible SARSCoV2 exposure history (patient, family member). To measure antibodies to SARS-CoV-2, we used a fluorescent bead-based immunoassay that takes advantage of the high dynamic range of fluorescent molecules using flow cytometry. We immobilized biotinylated SARS-CoV-2 Spike protein receptor binding domain (S-RBD) or Nucleocapsid protein of SARS-CoV-2 (N) to detect specific IgG antibodies to the virus in patient serum. Spike protein-RBD-specific antibodies were detectable in serial dilutions up to 100,000-fold of serum samples. Titration curves from COVID-19 convalescent and healthy controls were used to normalize the area under the curve (AUC) values to quantitate the antibody levels. Antibody isotypes were measured using anti-Ig (IgG, IgA, IgM, IgG1-4) specific secondary antibodies conjugated to a fluorescent tag. We used a sensitive and high throughput SARS-CoV-2 neutralization assay using a lentivirus that expresses Spike protein to assess specific inhibition of viral entry. The results shown reflect the first serum sample obtained from unique patients. Results: 410 subjects were studied (mean age 17 years, 59% male, 305 (74%) Crohn's disease, 105 (25%) ulcerative colitis/IBD-U, 341 (83%) on infliximab, 69 (17%) vedolizumab, 13% concomitant methotrexate. 27/410 (6.6%) were positive for S-RBD and Nucleocapsid specific IgG. AUC values varied from 3150 to 285724 (Fig 1). S-RBD specific IgA+ 4/27 (15%) and IgG1+ 20/27 (74%) were found. Other isotypes undetectable. Patients' serum efficiently neutralized the virus at up to 10,000-fold serial dilution in only 10/27 (37%). (Fig 2). No differences in age, gender, diagnosis, or specific therapies were noted for (+) vs (-) anti-SARS-CoV-2 antibody status. 13/27 (48%) patients were asymptomatic. Non-exclusive symptoms were rhinorrhea 9 (33%), headache 8 (30%), sore throat 4 (15%). cough 4 (15%), diarrhea 4 (15%), chills 3 (11%), loss of smell/taste 2 (7%), fever 1 (4%). No patient was hospitalized. 4 (15%) had a family member with PCR+ COVID-19. Conclusions: We found a significant prevalence of anti SARS-CoV-2 antibody in our IBD population with the majority of + patients having non-neutralizing antibody. The role of biologics in mitigating clinical and serologic response to SARS-CoV-2 requires exploration.
ABSTRACT
Development of antibody protection during SARS-CoV-2 infection is a pressing question for public health and for vaccine development. We developed highly sensitive SARS-CoV-2-specific antibody and neutralization assays. SARS-CoV-2 Spike protein or Nucleocapsid protein specific IgG antibodies at titers more than 1:100,000 were detectable in all PCR+ subjects (n=115) and were absent in the negative controls. Other isotype antibodies (IgA, IgG1-4) were also detected. SARS-CoV-2 neutralization was determined in COVID-19 and convalescent plasma at up to 10,000-fold dilution, using Spike protein pseudotyped lentiviruses, which were also blocked by neutralizing antibodies (NAbs). Hospitalized patients had up to 3000-fold higher antibody and neutralization titers compared to outpatients or convalescent plasma donors. Interestingly, some COVID-19 patients also possessed NAbs against SARS-CoV Spike protein pseudovirus. Together these results demonstrate the high specificity and sensitivity of our assays, which may impact understanding the quality or duration of the antibody response during COVID-19 and in determining the effectiveness of potential vaccines.