Oropharyngeal (OPG) vaccination activates head and neck lymphoid tissues required for immune protection against mucosal Brucella infection

Abstract

Abstract Human brucellosis remains a global health problem with no human vaccines existing. Most human infections occur mucosally with eventual systemic brucellae dissemination. Current interventions primarily focus on the systemic disease, rather than considering neutralizing the infection at its source. A number of studies show that the OPG mucosa is the principal site of brucellae uptake following oral or inhalational exposures. We have devised an OPG infection method using an attenuated Brucella mutant by allowing the mice to drink (ad bibitum) from a pipette tip. BALB/c mice were fed once daily for 3 days with 108 CFUs. Individual head and neck lymph nodes (HNLNs), and spleens were examined at 2 weeks post-infection for bacterial colonization and proinflamatory cytokine responses. Elevated colonization was observed in submandibular LNs (SmLNs) and deep cervical LNs (CLNs). Modest colonization was detected in the parotid LNs (PrLNs) and spleens. Splenic and individual HNLN lymphocytes were analyzed for IFN-g, TNF-a, granzyme B, and perforin production by flow cytometry. SmLN, CLN, and PrLN IFN-g-producing CD8+ T cells significantly exceeded IFN-g-producing CD4+ T cells by 2.5-, 2.5-, and 1.5-fold, respectively. Increased numbers of CD4+ and CD8+ T cells expressing TNF-a, granzyme B, and perforin were also observed. All activated lymphocytes were predominantly of effector-memory phenotype, CD44+CD62LlowCCR7low. These studies demonstrate that ad bibitum vaccination against brucellosis results in colonization and activation of the HNLNs, mimicking natural human infection, enabling future inquiry into the immune mechanisms responsible for protection to mucosal Brucella infections. Work supported by NIH AI-125546.