Role of B Cells in Mucosal Vaccine–Induced Protective CD8+ T Cell Immunity against Pulmonary Tuberculosis
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AbstractEmerging evidence suggests a role of B cells in host defense against primary pulmonary tuberculosis (TB). However, the role of B cells in TB vaccine–induced protective T cell immunity still remains unknown. Using a viral-vectored model TB vaccine and a number of experimental approaches, we have investigated the role of B cells in respiratory mucosal vaccine–induced T cell responses and protection against pulmonary TB. We found that respiratory mucosal vaccination activated Ag-specific B cell responses. Whereas respiratory mucosal vaccination elicited Ag-specific T cell responses in the airway and lung interstitium of genetic B cell–deficient (Jh−/− knockout [KO]) mice, the levels of airway T cell responses were lower than in wild-type hosts, which were associated with suboptimal protection against pulmonary Mycobacterium tuberculosis challenge. However, mucosal vaccination induced T cell responses in the airway and lung interstitium and protection in B cell–depleted wild-type mice to a similar extent as in B cell–competent hosts. Furthermore, by using an adoptive cell transfer approach, reconstitution of B cells in vaccinated Jh−/− KO mice did not enhance anti-TB protection. Moreover, respiratory mucosal vaccine–activated T cells alone were able to enhance anti-TB protection in SCID mice, and the transfer of vaccine-primed B cells alongside T cells did not further enhance such protection. Alternatively, adoptively transferring vaccine-primed T cells from Jh−/− KO mice into SCID mice only provided suboptimal protection. These data together suggest that B cells play a minimal role, and highlight a central role by T cells, in respiratory mucosal vaccine–induced protective immunity against M. tuberculosis.
