Histopathologic and humoral study of Balb/c mice inoculated with BCG by different routes

With the aim of determining the distribution and humoral immunogenicity of the bacillus Calmette-Guérin (BCG) administered by the oral (O), intravenous (IV) and subcutaneous (SC) routes, we studied 54 male Balb/c mice weighing 17-22 g that had been inoculated with BCG (10(6) CFU) by the O (n = 18), IV (n = 18) and SC (n = 18) routes. At weekly intervals we determined the distribution of the microorganism using histopathological techniques including Ziehl-Neelsen staining. Serum samples of the same animals were analyzed by ELISA and Western blot to determine the antibody response to the microorganism. In all groups, distinctive histopathologic lesions harboring the microorganism were found. Using the SC route the lesions were located at the inoculation site, whereas there was systemic dissemination with the O and IV routes, being more prominent with the latter. Anti-BCG antibodies were detected by ELISA in all groups; this response was more intense in the IV group, followed by the SC and O groups. In the Western blot analysis, reactivity against multiple bands and the predominant recognition of a 65 kd band in all groups was observed.