Protective efficacy of recombinant BCG Tokyo (Ag85A) in rhesus monkeys (Macaca mulatta) infected intratracheally with H37Rv Mycobacterium tuberculosis.

We have reported previously that recombinant BCG Tokyo (Ag85A) (rBCG-Ag85A[Tokyo]) shows promise as a tuberculosis vaccine, demonstrating protective efficacy in cynomolgus monkeys. As a next step, rhesus monkeys were utilized because they are also susceptible to Mycobacterium tuberculosis and show a continuous course of infection resembling human tuberculosis. The recombinant BCG vaccine (5x10(5) CFU per monkey) was administered once intradermally into the back skin to three groups of rhesus monkeys, and its protective efficacy was compared for 4months with that of its parental BCG Tokyo strain. Eight week vaccination of the monkeys with rBCG-Ag85A[Tokyo] resulted in a reduction of tubercle bacilli CFU (p<0.01) and lung pathology in animals infected intratracheally with 3000 CFU H37Rv M. tuberculosis. Vaccination prevented an increase in the old tuberculin test after challenge with M. tuberculosis and reaction of M. tuberculosis-derived antigen. Thus, it was shown that even in rhesus monkeys rBCG-Ag85A[Tokyo] induced higher protective efficacy than BCG Tokyo.