Background
Rapid RNA vaccine development during the SARS-CoV-2 pandemic has increased study into the antibody response to both the virus and vaccine targets. We compared the antigen specificity of antibody types in a vaccinated University cohort, UniCOV-UCC, which had been participating in University SARS-CoV-2 screening project, UniCoV.
Methods
454 participants, already in a university yearlong SARS-CoV-2 screening study, were enlisted and consented over a 3 month period and asked to declare exposure to SARS-CoV-2 in the past 6 months. Serum & Saliva samples were subsequently obtained and serum screened on site using rapid point of care (POC) tests to antibodies to viral nucleocapsid and spike antigens. Subsequent ELISA analysis was used to confirm results characterise serum and salivary IgG and IgA.
Results
The survey revealed 54 % (245) of participants believed they had been exposed to SARS-CoV-2 in the past 6 months. However, nucleocapsid antibody POC results revealed that 95% (431) had exposure to SARS-CoV-2 in the past 6 months. Vaccine derived neutralising anti- Spike levels were also assessed revealing varying levels of protection. Anti-Spike antibody POC images were digitally scored and compared to titrated antibody levels in competitive binding neutralisation assay ELISA revealing a detection level of 62.5 ng/ml equating to 55% competitive binding
A subset of volunteers (16) whom became infected during the trial, June 2021, had low initial anti-Spike antibodies on POC demonstrated significantly elevated serum and saliva IgG and serum IgG (P<0.05) following SARS-CoV-2 infection but not salivary IgA.
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