Immunogenicity and protective capacity of Mycobacterium bovis BCG after oral or intragastric administration in mice

After oral or intragastric administration of BCG to mice, comparable number s of IFN gamma and TNF gamma producing cells were detected in both local (P eyer's patches) and central (spleen) lymphoid organs. Similar levels of pre cursors of CD8+ cytotoxic T lymphocytes specific for mycobacterial antigens were also found in the spleen and the mesenteric lymph nodes. These immune responses remained high over the course of 3 months, the duration of obser vation. Oral administration of BCG led to an enlargement of the cervical ly mph nodes, which contained high levels of viable bacteria. In contrast, no adverse effects were observed in mice given the BCG via the intragastric ro ute. These two routes of immunization induced similar levels of protective immunity to those observed in mice immunized via the subcutaneous route aga inst a challenge with a virulent Mycobacterium tuberculosis strain (H37Rv). (C) 2000 Elsevier Science Ltd. All rights reserved.