Bacillus Calmette-Guérin Vaccination Promotes Efficient and Comprehensive Immune Modulation in Guinea Pig Models

Abstract

Background/Objectives: Tuberculosis (TB), caused by Mycobacterium tuberculosis H37Rv (M. tuberculosis), primarily affects the lungs. The Bacillus Calmette-Gu & eacute;rin (BCG) vaccine is the only available TB vaccine. Guinea pigs serve as an excellent preclinical model due to the similarity to human Tuberculosis pathology. However, the lack of a standardized vaccination protocol in guinea pigs causes inconsistencies in efficacy assessments, limiting precise evaluation and its application in vaccine studies. This study aims to address this gap by establishing a consistent and reliable protocol for evaluating the immunological efficacy of BCG vaccination. Methods: Guinea pigs were divided into control, M. tuberculosis-infected, and BCG-vaccinated groups. Four weeks post-vaccination, the infected and vaccinated groups were challenged with M. tuberculosis. The bacterial burden in the lungs and spleen was measured, histopathological changes were analyzed using hematoxylin and eosin (H&E) staining, and the infection levels of M. tuberculosis, as well as the presence of interleukin-2 (IL-2), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma) positive cells, were evaluated through immunohistochemical (IHC) staining. Results: BCG vaccination reduced the bacterial load to 3.60 x 104 CFU/lung and 5.52 x 103 CFU/spleen compared to 3.78 x 105 CFU/lung and 1.54 x 104 CFU/spleen in the infected group. The mean histopathological score for lungs was 1.67 compared to 2.67 in the infected group. Similarly, the mean histopathological score for the spleen was 1.33 compared to 2.33 in the infected group. IHC analysis showed a notable reduction in M. tuberculosis and inflammatory cytokine-positive cells in the vaccinated group. The TNF-alpha, IL-2, and IFN-gamma staining intensity decreased by 9.3, 4.8, and 11, respectively, compared to the infected group. Conclusions: This protocol enhances consistency in vaccine assessments, providing a reliable benchmark for the development of safer, more effective, and accessible TB vaccines.