The influence of dietary protein on the protective effect of BCG in guinea pigs.

Specific pathogen-free, Hartley guinea pigs were vaccinated with viable Bacille Calmette-Guerin (BCG) and given isocaloric diets identical in every nutrient except protein (control = 30%; low protein = 10%). A non-vaccinated group was maintained on the control diet. Five weeks later, all animals were infected with an aerosol containing virulent M. tuberculosis H37Rv. On the same day, half of the protein-deficient guinea pigs were transferred to the control diet, while the remainder were maintained on the low protein (10%) diet. Animals from each diet treatment were tuberculin tested and sacrificed 1,2,3 and 4 weeks post-challenge. Protein-deficient guinea pigs exhibited diminished tuberculin reactions and loss of BCG-induced protection against virulent challenge as measured by the number of viable M. tuberculosis recovered from the lung and spleen. Renourished animals expressed normal levels of delayed hypersensitivity within 1 week of initiating the normal diet and were protected as well as vaccinated control guinea pigs against virulent respiratory challenge.