Salmonella enterica Induces Joint Inflammation and Expression of Interleukin-17 in Draining Lymph Nodes Early after Onset of Enterocolitis in Mice

Abstract

ABSTRACT In developing countries, one-third of reactive arthritis (ReA) cases are associated with Salmonella enterocolitis; nevertheless, there is no animal model for studying this pathology. Here we induced a self-limiting Salmonella enterica serovar Enteritidis enterocolitis in mice to analyze the onset of ReA. BALB/c mice received orally 20 μg of streptomycin 24 h before intragastric inoculation of a low dose (3 × 10 3 to 4 × 10 3 CFU) of S . Enteritidis. In response to Salmonella infection, a 30-fold increase in the expression of interleukin-17 (IL-17), measured by quantitative PCR, was observed in mesenteric lymph nodes 5 days postinfection. At this time synovitis was already evident, and concomitantly, a significant increase in joint tumor necrosis factor alpha (TNF-α) was detected by enzyme-linked immunosorbent assay (ELISA). The early development of joint lesions was accompanied by an increased expression of IL-17 in inguinal and popliteal lymph nodes. Infection with 10 7 CFU of an isogenic Δ invG mutant bearing a defective type III secretion system of Salmonella encoded in the pathogenicity island 1 apparatus (TTSS-1) induced enterocolitis histologically similar to that triggered by the wild-type strain. Interestingly, despite the higher infective dose used, the mutant did not trigger intestinal IL-17. Moreover, no synovitis was observed in mice suffering Δ invG enterocolitis. Neutralization of IL-17 in mice infected with S . Enteritidis prevented both synovitis and the increment of TNF-α in the joints, suggesting that IL-17 participates in the generation of Salmonella -induced ReA through the induction of TNF-α in the joints.