Abstract

THE EFFECT OF BCG IMMUNIZATION IN MICE CHALLENGED WITH MYCOBACTERIUM TUBERCULOSIS

Jamal Bayed S. and Abdelbagi El Fadil*

Abstract

Background: Tuberculosis (TB) is one of the most prevalent cause of death due to a single pathogen. Bacillus Calmette Guérin (BCG) is the only vaccine available for clinical use that protects against miliary TB; however, this vaccine has shown variable levels of efficacy against pulmonary TB. In Sudan, a single dose of BCG vaccine is given.The incidence of TB in Sudan is very high in spite of primary vaccination in neonatal period and therefore requires consideration for repeated immunization. Objective: To investigate the effect of BCG immunization in Mice challenged with M. tuberculosis. Materials and Methods: A total number of 160 mice were examined for their immunopotency and protective efficacy of BCG against challenge dose of M. tuberculosis as single dose. In experiment contains two groups of mice each of ten mice n = 10 (20mice). The first group(A) were immunized with BCG (0.2ml) first dose (I.P) for 21 days. The second group(B) were not immunized with BCG. All mice with BCG were tested for tuberculin skin test (TST) so as to determine susceptibility and resistance against tuberculosis. All the groups were challenged with (0.5ml)virulent M. tuberculosis H37Rv strain (American Type Culture Collection, ATCC 35718). M tuberculosis. 107(CFU). Another group of mice n=6 for the study of humoral response by immunization of mice with immune serum and challenged with M. tuberculosis Following by two groups of mice n=10 for each group A and B for the susceptibility and resistance of the strains of mice by immunization of mice with BCG for 21 days and testing by tuberculin skin test (TST). The efficacy was based on a survival rate of challenged mice, mortality rate and bacterial load of M. tuberculosis in the lungs of infected mice. Result: After three weeks of observations Tuberculin skin test reaction for the BCG immunized mice were positive, hence the mice strain of BALB/c were susceptible and Swiss white mice were resistant for BCG. Survival mice in group (A) were 50%, and group(B) 0%.The mortality rates for (A) 50%, and (B) 100%. The immunopotency and protective efficacy of BCG first dose was (50%). Humoral immunity response against M. tuberculosis showed negative reaction hence mortality rate was 100%. Conclusions: The incidence of TB is high in spite of primary vaccination in neonatal period and therefore requires consideration for repeated immunization of BCG.

Keywords: BCG, M. tuberculosis, BALB/c Mice, Swiss white mice, tuberculin skin test (TST).