ABSTRACT
Background: The novel coronavirus SARS-CoV- 2 has caused far-reaching consequences world-wide. Lack of immunity in human, severe airway disease based on a high virulence and its airborne transmission pointed to a significant role of the airways. To investigate immune responses and antibody seroconversion in nasal lining fluid and in serum we examined a cohort of health professionals at the university hospital Klinikum rechts der Isar in Munich. By long-term follow-up of infected and non-infected participants, we were able to investigate the development of local and systemic immunity against SARS-CoV- 2. Method(s): To learn about nasal antibody production we reached out for hospital staff with estimated high risk of a possible Covid19 infection due to their working conditions and staff members suffering from symptoms like fever, cough, loss of smell and taste or sore throat. To detect current infections, we performed SARS-CoV- 2 PCR testing at visit one (V1) and asked our participants to rate possible Covid19 symptoms by filling a questionnaire before every sampling. We eventually included participants, who had been tested positive for SARS-CoV- 2 before (n = 22), as well as people without detected infection, including high-risk contact persons of Covid19 patients and individuals with no Covid-19 infection so far (n = 85). The cohort included 107 hospital staff members, who were sampled six times overall between March and September 2020. Each of the six visits V1 -V6 contained the sampling of serum and nasal fluid to measure IgG, IgM, and IgA rates using immunoassay technique. Result(s): We were able to show the increase of IgA and IgG in the nasal mucosa after recent Covid19 infection. In infected individuals the levels of SARS-CoV- 2 specific nasal IgA increased until V2 with a mean of 4,81 +/- 1,92 mug/l compared to a mean of 0,13 mug/l in non-infected participants, followed by a plateau until V4 and decreased again until V6. Nasal IgG showed a similar trend, apart from a steeper decline after reaching a peak on V2 with a mean of 7,39 +/- 1,63 mug/l, which correlated to the antibody responses in serum. Non-infected individuals showed a mean level of 0,03 mug/l nasal IgG on V2. Serum IgA declined from V1 onwards and hereby showed a quicker drop of systemic antibody levels compared to the nasal lining fluid. Nasal antibody rates reached peaks of 40,00 mug/l (nasal IgA) and 25,74 mug/l (nasal IgG). However, these counts will need further confirmation by a vaccinated control group. Conclusion(s): Nasal measurement of SARS-CoV- 2 specific antibodies provides deeper understanding of mucosal processes while facing inflammation, which may pave the way to less invasive diagnostic possibilities in the future. Furthermore, nasal antibodies built-up after an infection with Covid19 may be protective features concerning a possible re-infection with the virus.