RESUMEN
Background: Humoral immunity after SARS-CoV-2 vaccination has been extensively investigated in blood. Far less is known, however, about the potentially induced mucosal immunity. Aim of this study was to develop an ELISA method in order to determine the prevalence of IgG and IgA SARS-CoV-2 spike-protein-specific antibodies (Abs) in buccal and nasal surfaces of vaccinees after full vaccination with BNT162b2, mRNA-1273, ChAdOx1 or combination. Method(s): To this end, we prospectively analyzed 69 adult individuals after signed written consent who received their first vaccine dose between February and July 2021. Detection of IgG and IgA Abs was performed using the semi-quantitative ELISA assay from EUROIMMUN for both blood and swab samples after protocol modification for the latter. The eluates of the nasal and buccal swabs were analyzed undiluted while the same cut-off was set as for the serum assay. The samples were taken at regular intervals to ensure systematic recording of Ab course before and after each vaccination dose. Result(s): After second dose all study subjects developed IgG anti spike Abs in serum, yet 5.9% of them remained negative for IgA. In buccal swabs, positivity rates were 81.2% and 53.1% and in nasal swabs 84.1% and 90.6% for IgG and IgA, respectively. The IgG Abs in buccal swabs correlated more consistently with the respective measurements in blood with a correlation coefficient of r=0.74 while the IgA assay gave less concordant results. It is of note that IgA Abs appeared to be significantly more prevalent in the nasal compared to the buccal mucosa. Adjustment of the assay cut-off as to IgG antibody detection in buccal swabs from 1.1 to 0.2 conferred a sensitivity of 91.8% and a specificity of 100% in a total of 520 comparison measurements. Conclusion(s): In conclusion, our findings confirm a weaker yet clear prevalence of Abs in mucosal surfaces after full vaccination against SARSCoV- 2 with IgA anti-spike Abs being significantly more prevalent in the nasal cavity. Our method for IgG Ab detection in buccal swabs could be expanded to other pathogens of interest and serve as a reliable alternative to standard serum assays especially in the context of immunity screening of large populations.
RESUMEN
Background: Among the greatest challenges of the current pandemic with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is its ongoing evolution, resulting in variants of interest (VOI) and variants of concern (VOC) with an enhanced capacity for immune escape. The likelihood for the emergence of such variants exponentially rises with the time a host is infected with the virus and the virus is reproduced without being properly controlled by the immune system. Method(s): In this prospective observational cohort study we analyzed cellular and serological immune response parameters against SARS-CoV-2 and current variants of concern (VOC) in 147 COVID-19-convalescent and 39 COVID-19-naive individuals before and after BNT162b2 booster vaccination. End points included anti-SARS-CoV-2 IgG and IgA titers, neutralization capacities against wild type SARS-CoV-2 and the VOCs B.1.1.529 and B.1.617.2 as well as SARS-CoV-2-specific T cell IFN-gamma responses. Result(s): No significant differences regarding immunological response parameters were observed between younger and older individuals. Booster vaccination induced full recovery of both cellular and serological response parameters including IFN-g secretion and anti-spike antibody titers with strong neutralization capacities against wild type SARS-COV-2 and Delta. Surprisingly, even serological neutralization capacity against Omicron was detectable one month after second vaccination and four months before it had been first observed in South Africa. As a result, more than 90% of convalescent individuals exhibited detectable and 75% strong Omicron neutralization capacity after booster vaccination, compared with 72% and 46% of COVID-19-naive individuals. Conclusion(s): Broad and cross-reactive immune memory against SARSCoV- 2 including currently known VOCs can be established by booster vaccination with spike-based mRNA vaccines like BNT162b2, particularly in COVID-19-convalescent individuals of all ages. Nevertheless, especially in COVID-19-naive individuals future variants escaping the memory immune response may require vaccine approaches such as inactivated whole virus vaccines, which include all antigenic components of the virus. (Figure Presented).