Sex influences murine T cell responses to vaccination with BCG or BCG∆BCG1419 grown as biofilms

Background It is known that host sex can influence the immune response to administration of Mycobacterium bovis Bacillus Calmette-Guérin (BCG). However, the effect of BCG or BCG-derived vaccines cultured as biofilms on development of T cell responses in both sexes remains unclear. Objectives To compare the influence of sex and vaccine strain (BCG Pasteur vs. BCGΔBCG1419c) on ex vivo T cell responses against mycobacterial purified protein derivative (PPD) stimulation in lung and spleen cells of mice vaccinated with bacteria grown as biofilms. Methods Male and female BALB/c mice were subcutaneously vaccinated with disaggregated, biofilm-derived BCG Pasteur or BCGΔBCG1419c. Sixty days later, lung and spleen cells were collected and stimulated ex vivo with PPD. Flow cytometry was used to quantify frequencies of mono- and bi-functional CD4⁺ and CD8a⁺ T cells expressing interferon gamma (IFN-γ) and tumour necrosis factor alpha (TNF-α) or interleukin-2 (IL-2), as well as frequencies of tissue-resident memory CD4⁺ T cells. Findings Sex influenced T cell responses in both organs. Lungs of female mice vaccinated with BCGΔBCG1419c showed reduced frequencies of CD8a⁺ IFN-γ⁺, and reduced frequency of CD4⁺ IFN-γ⁺ in spleen, compared with males. On the other hand, female mice vaccinated with BCG produced higher IL-2+ and IL-2+TNF-α+ T cells in spleen than paired males. Vaccine strain alone had limited effects, but sex-strain interactions shaped distinct immune profiles. Main conclusions Sex modulates the immunogenicity of BCG-based vaccines grown as biofilms. Our results underscore the importance of considering host sex and vaccine preparation in tuberculosis preclinical research.