ABSTRACT
BackgroundMucosal antibodies can prevent virus entry and replication in mucosal epithelial cells and hence virus shedding. Preclinical and clinical studies have shown that a parenteral booster injection of a vaccine against a mucosal pathogen promotes stronger mucosal immune responses following prior infection compared to two injections of a parenteral vaccine. We investigated whether this was also the case for a COVID-19 mRNA vaccine. MethodsTwenty-three COVID-19 convalescent patients and 20 SARS-CoV-2-naive subjects were vaccinated with respectively one and two doses of the Pfizer-BioNTech COVID-19 RNA vaccine. Nasal Epithelial Lining Fluid (NELF) and plasma were collected before and after vaccination and assessed for Immunoglobulin (Ig)G and IgA to Spike and for their ability to inhibit the binding of Spike to its ACE-2 receptor. Blood was analyzed one week after vaccination for the number of Spike-specific Antibody Secreting Cells (ASCs) with a mucosal tropism. ResultsIn COVID-19 convalescent patients, a single dose of vaccine amplified pre-existing Spike-specific IgG and IgA antibody responses in both NELF and blood against both vaccine homologous and variant strains, including delta. These responses were associated with Spike-specific IgG and IgA ASCs with a mucosal tropism in blood. Nasal IgA and IgG antibody responses were lower in magnitude in SARS-CoV-2-naive subjects after two vaccine doses ConclusionThis study showed that a parenteral booster injection of a COVID-19 RNA vaccine promoted stronger mucosal immune responses in COVID-19 convalescent patients compared to SARS-CoV-2 naive subjects who had received a first vaccine dose.
ABSTRACT
BackgroundThe current standard for coronavirus 2019 disease (COVID-19) diagnosis is reverse transcriptase-polymerase chain reaction (RT-PCR) testing of naso-pharyngeal swabs (NPS), Sampling with NPS is invasive and requires specialized and trained personnel, which limits rapid and repeated screening for the disease. A less invasive and possibly self-administered sampling method may increase the capacity for testing and be more effective in identifying, isolating, and filtering out currently infected persons. MethodsOver a period of three months, we included volunteers presenting with recent symptoms suggestive of a SARS-CoV-2 infection at a free COVID-19 screening center in the city of Nice, France. NPS as well as nasal and oral sponges were collected in parallel and analyzed by RT-PCR for SARS-CoV-2. ResultsOne hundred and forty-seven subjects were included, of whom, 41.5% were diagnosed with COVID-19 using NPS RT-PCR. RT-PCR on nasal and oral sponges showed a sensitivity of 87 to 98% and 72 to 87%, respectively for diagnosis of COVID-19 in symptomatic subjects, depending on the type of RT-PCR technique used. The specificity was 100% whatever the RT-PCR test. The viral load determined with the oral samples was significantly lower than with NPS. ConclusionTaken together, these results demonstrated that the oral sponge sampling method can be standardized, is easy to use and cheap. The acceptability makes it a repeatable test, notably for elderly people or children. It may become a high-frequency - low analytical sensitive testing strategy. Summary of the "take home" messageOral sponge sampling for SARS-CoV2 RT-PCR, is easy to use, can be self-administered with a sensitivity of up to 87 % in symptomatic patients.
