|ROLE OF NON TUBERCULOUS MYCOBACTERIAL INFECTION
IN IMMUNIZATION AGAINST TUBERCULOSIS
|VK Challu, Sujatha Chandrasekaran, TR Sreenivas, MM
Chauhan, Bharathi Jones, R Rajalakshmi, B Mahadev, VH Balasangameshwara
& K Chaudhuri: Indian J TB, 1992, 39, 165-70.
One of the hypothesis put forth for the failure
of BCG vaccine to show protection against bacillary pulmonary tuberculosis
in Chingleput trial was the interference from non-tuberculous mycobacteria
that were prevalent in the trial area. In order to test this, a
study was conducted with the following objectives: to investigate
(1) Protection given by BCG and M.avium intracellulare (MAI) which
is the most prevalent species, against the challenge with high and
low virulent strains of M.tuberculosis in sensitised guineapigs.
(2) Whether M.avium Intracellulare (MAI) interferes with the protective
effect of BCG against challenge with both high and low virulent
strains of M.tuberculosis. Sensitization was done with MAI in guineapigs
using both oral and intradermal routes. Groups of species were immunized
with BCG/Placebo and later challenged with high/low virulent strains
of M.tuberculosis. Colony counts of M.tuberculosis bacilli from
spleens of the animals were done to measure the protective effect.
The findings were: (1) BCG showed protection against both high and
low virulent challenges. (2) MAI in both oral and intradermal routes
had no effect against low virulent challenge. (3) There was no significant
interaction between BCG and MAI against low virulent challenge.
(4) MAI when given orally, showed a significant protection against
high virulent challenge. The same was not seen with intradermal
route. (5) MAI orally, interfered with the protective effect of
BCG against high virulent strains of M.tuberculosis.
|KEY WORDS: BCG, PROTECTIVE EFFECT, NTM, M. AVIUM,