Development of a rectal sexually transmitted infection (STI) Model in Rhesus macaques using Chlamydia trachomatis serovars E and L2

Background: Rectal STI coinfection models enhance the understanding of rectal HIV transmission risk factors. Materials and Methods: Rhesus macaques (n=9) were exposed to one of three rectal Chlamydia trachomatis (CT) challenges: C. trachomatis L-2 (CT-L-2); C. trachomatis serovar E (CT-E), followed by CT-L-2; or CT-E, treatment/clearance, then CT-L-2. Infections were monitored by PCR. Weekly blood and rectal secretion/lavage samples were collected for cytokine analyzes and/or epithelial sloughing, occult, and overt blood determinations. Results: Chlamydial infections were successfully established in each animal, with varying degrees of persistence. Mucosal IL-1beta was upregulated in animals consecutively infected with CT-E then CT-L-2 (P=.05). Epithelial sloughing was also significantly increased post-infection in this group (P=.0003). Conclusions: This study demonstrates successful rectal infection of rhesus macaques with CT-E and CT-L-2 and describes measures of assessing rectal inflammation and pathology. Different infection strategies yield varying inflammatory and pathologic outcomes, providing well-described models for future SIV/SHIV susceptibility studies.