Characterization of Bartonella henselae-specific immunity in BALB/c mice

BALB/c mice were inoculated with Bartonella henselae by both systemic and mucosal routes. Culture analysis of tissues from mice infected intraperitoneally with a high dose of B. henselae yielded positive results 24 hr after infection. However, culture analysis of blood taken between 6 hr and 7 days after infection from groups receiving live B. henselae were negative. Following intraperitoneal infection, B. henselae was detected by polymerase chain reaction in liver and mesenteric lymph nodes by 6 hr and up to 7 days after infection in liver, kidney and spleen tissue. Enzyme-linked immunosorbent assay (ELISA) of serum samples collected as early as 13 days after infection indicated humoral immune responses to B. henselae. Specific humoral responses remained through week 6. Analysis of faecal samples revealed induction of B. henselae-specific immunoglobulin A by day 28 after infection. In addition, B. henselae-specific cellular responses were indicated by a positive delayed-type hypersensitivity and a T helper 1 (Th1) (CD4+ T cell)-type cytokine response following in vitro stimulation of splenocytes. The significance and implications of these data in relation to B. henselae infections are discussed.