BCG vaccine-induced mucosal humoral immunity in human nasal associated lymphoid tissue

Abstract

ObjectivesMycobacterium tuberculosis (Mtb) is the causative pathogen of tuberculosis (TB). TB vaccine studies have long been conducted. Since the discovery of the successful intradermally administered Mycobacterium bovis Bacillus Calmette–Guérin (BCG) vaccine against TB, no licensed TB mucosal vaccine has yet been approved. Our research aims to investigate the suitability of human NALT-derived MNCs as an in vitro human cell culture model to explore the mucosal humoral immune responses to the BCG vaccine. Moreover, to assure that BCG vaccine able to induce the different antibody isotypes including IgG, IgM and IgA. MethodsTonsils from 20 patients who underwent elective tonsillectomies at Madinah Germany Hospital were recruited. Tonsillar mononuclear cells (MNCs) were separated and co-cultured in the presence and absence of the BCG vaccine. ELISA was used to measure BCG-induced IgG, IgM and IgA antibodies in the cell culture supernatants following stimulation and culture. ResultsNasal-associated lymphoid tissue (NALT) cell culture as an in vitro model was successfully used to evaluate the BCG-induced humoral immune response. Significant (p = 0.001, n = 20) levels of specific, anti-TB IgG, IgM, and IgA antibody responses were detected in MNCs stimulated with the BCG vaccine compared with unstimulated MNCs. Significant differences were found between anti-TB antibody classes. Anti-TB IgG antibody was significantly higher (mean = 2.33) than anti-TB IgM (mean = 1.37) antibody (p = 0.0001, n = 20). Anti-TB IgM antibody was significantly higher than IgA (mean = 0.93) antibody (p = 0.0018, n = 20). ConclusionsThe current human model will be beneficial for the future comprehensive study of other immune components such as cellular immune responses to the BCG vaccine. The model would be ideal to design, improve and study the possible intranasal use of the BCG vaccine.