| dc.description.abstract | Background: Tuberculosis (TB) is a global disease which infects approximately one-quarter of the world’s population. However, only 5-10% develop clinical TB, suggesting the presence of immune protection. To date, the protective role of antibodies in respiratory mucosal lining is not well documented. Understanding the role of mucosal immunity against TB is important to replace currently used Bacillus Calmette-Guerin (BCG) and develop a new vaccine. The project aims to compare the induction and protective role of secretory IgA and IgG in serum and saliva against the Mycobacterium tuberculosis (Mtb) antigens lipoarabinomannon (LAM) and heparin-binding hemagglutinin adhesin (HBHA) among pulmonary TB patients (PTB), household contracts (HHC) to TB patients, and community controls (CC). Methods: In this cross-sectional study, we included a total of 90 participants within three study groups (PTB, HHC, CC), each with 30 participants. Structured interviews with close-ended questionnaires sample collection were conducted in Addis Ababa, Ethiopia. Sera and saliva samples were collected and assayed by enzyme-linked immunosorbent assay (ELISA). Sputum smear microscopy and gene- Xpert test were used to identify pulmonary TB patients and QuantiFERON-TB GOLD in-tube (QFT-GFT) was done to screen TB infection. Data analyses were performed using IBM SPSS (version 28) and GraphPad Prism version 8.0.0 for windows. Results: Our results showed that IgA responses to HBHA in HHC were significantly higher than PTB patients in both saliva and serum (P<0.05). QFT-negative groups had higher anti-HBHA IgA responses than PTB patients (P<0.05), and HBHA-stimulated IgA responses were higher in HHC compared to HBHA-unstimulated IgA levels in HHC and CC in serum (P<0.05). In comparison to PTB patients, both HHC and CC as well as QFT-positive and QFT-negative had higher IgA responses to HBHA (P<0.05, P<0.01, P<0.05, P<0.01, respectively) and LAM (<0.05, P<0.01, P<0.01, P<0.01, respectively). Anti-LAM and anti-HBHA IgA levels were significantly higher in the saliva of the study participants compared to their levels in serum (P<0.0001). Conclusion: The findings of this study suggest the presence of protective immunity and role of IgA and IgG in preventing the development of active and latent TB. In addition, for the first time, our study reports the protective role of secretory IgA (mucosal immunity) against HBHA in saliva, which may have significant implications for future TB vaccine development. | eng |