Mucosal response of Inactivated and Recombinant COVID-19 vaccines in
Congolese individuals
Abstract
Background: The efficacy of immunization against an airborne pathogen
depends in part on its ability to induce antibodies at the major entry
site of the virus, the mucosa. Recent studies have revealed that mucosal
immunity is poorly activated after vaccination with mRNA vaccines, thus
failing in blocking virus acquisition upon its site of initial exposure.
Little information is available about the induction of mucosal immunity
by inactivated and recombinant COVID-19 vaccines. This study aims to
investigate this topic. Methods: Saliva and plasma samples from 440
healthy Congolese were collected including (1) fully vaccinated two
month post vaccination with either an inactivated or a recombinant
COVID-19 vaccine and (2) non-vaccinated control group. Total
anti-SARS-COV-2 RBD IgG and IgA antibodies were assessed using in-house
ELISAs for both specimens. Findings: Altogether, the positivity of IgG
was significantly higher in plasma than in saliva samples both in
vaccinated and non-vaccinated control groups. Inversely, IgA positivity
was slightly higher in saliva than in plasma of vaccinated group. The
overall IgG and IgA levels were respectively over 103 and 14 times lower
in saliva than in plasma samples. We found a strong positive correlation
between IgG in saliva and plasma also between IgA in both specimens (r =
0.70 for IgG and r = 052 for IgA). Interestingly, contrary to IgG, the
level of salivary IgA was not different between seropositive control
group and seropositive vaccinated group. No significant difference was
observed between recombinant and Inactivated COVID-19 vaccines in total
IgG and IgA antibody concentration release 2 months post vaccination
both in plasma and saliva. Conclusion: Inactivated and recombinant
COVID-19 vaccines in use in the Republic of Congo poorly activated
mucosal IgA mediated antibody response two months post-vaccination.