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

BALB/c mice were inoculated with Bartonella henselae by both systemic and m ucosal routes. Culture analysis of tissues from mice infected intraperitone ally with a high dose of B. henselae yielded positive results 24 hr after i nfection. However, culture analysis of blood taken between 6 hr and 7 days after infection from groups receiving live B. henselae were negative. Follo wing intraperitoneal infection, B. henselae was detected by polymerase chai n reaction in liver and mesenteric lymph nodes by 6 hr and up to 7 days aft er infection in liver, kidney and spleen tissue. Enzyme-linked immunosorben t assay (ELISA) of serum samples collected as early as 13 days after infect ion indicated humoral immune responses to B. henselae. Specific humoral res ponses remained through week 6. Analysis of faecal samples revealed inducti on of B. henselae-specific immunoglobulin A by day 28 after infection. In a ddition, B, henselac-specific cellular responses were indicated by a positi ve delayed-type hypersensitivity and a T helper 1 (Th1) (CD4(+) T cell)-typ e cytokine response following in vitro stimulation of splenocytes. The sign ificance and implications of these data in relation to B. henselae infectio ns are discussed.