Dear Vini!

Please You look at this article:

Article Pulmonary Mycobacterium bovis BCG Vaccination Confers Dose-D...

C57/BL6 mice

Based on the hypothesis that BCG delivered parenterally induces weak immune responses in the lungs and leads to poor protection, we compared the protective efficacy conferred by intratracheal (i.t.) and s.c. BCG strain Danish 1331 vaccination of mice against a low-dose (100 CFU) Mycobacterium tuberculosis strain H37Rv i.t. challenge. A broad range of doses of the BCG vaccine (from 101 to 107 CFU) was tested to study the dose-response effect for each route of administration. The s.c. route was selected, as it is routinely used in vaccine studies using a mouse model, and the i.t. route was used because it is the only respiratory route that allows for the accurate delivery of defined vaccine doses in the range used here. The data obtained from s.c. vaccination confirmed a lack of association between vaccine dose and protection, with approximately a 1-log reduction in M. tuberculosis growth in the lungs in all groups of mice vaccinated with BCG subcutaneously, compared to that of nonvaccinated controls, apart from the lowest vaccine dose group (101 CFU) (Fig. 1A). In contrast, a strong dose-response effect was observed in mice vaccinated by the i.t. route. The 107 BCG CFU vaccination by the i.t. route reduced the pulmonary bacterial counts up to 3 logs compared with the nonvaccinated group (Fig. 1B). In previous studies that have shown no differences in terms of protection between the s.c. and aerosol routes of BCG vaccination, the BCG dose used was 103 CFU (12). Consistent with this, we also failed to see a statistically significant difference between the s.c. and i.t. delivery routes using 103 CFU of BCG (Fig. 1A).

Dear Alexander Chernov , thankyou very much for your answer