Effects of buprenorphine on immunogenicity and protective efficacy in the guinea pig keratoconjunctivitis model (Sereny test).

Shigellosis is a disease of global proportions, with an estimated 164.7 million episodes annually throughout the world as well as an estimated 1.1 million associated mortalities in developing countries. Due to increasing incidence, and continued emergence of multi-drug resistant strains, Shigella vaccine development is considered a top public health priority. The guinea pig keratoconjunctivitis model, the basis for the Sereny test, remains the most reliable in vivo indicator of virulence of Shigella strains and immunogenicity and protective efficacy of Shigella vaccine candidates. The model is effective in evaluating the ability of Shigella strains to invade the corneal epithelia of guinea pigs and spread to contiguous cells, with the more virulent strains causing ulcerative keratoconjunctivitis. However, analgesia is not routinely used to relieve this painful condition because of potential immunomodulation and confounding of experimental results. The objective of the study reported here was to evaluate use of buprenorphine hydrochloride as an analgesic during the Sereny test. Local and systemic immune responses were measured in guinea pigs given buprenorphine versus those responses in controls. Results of this study suggest that buprenorphine, administered at an analgesic dose of 0.05 mg/kg of body weight twice daily, can be successfully used with the model without significantly affecting immunologic evaluation of Shigella vaccine candidates. However, in buprenorphine-treated animals, there was a significant increase in the amount of mucopurulent ocular discharge, requiring frequent cleaning of the affected eyes. Additionally, animals treated with buprenorphine had significant reduction in body weight, in comparison with saline controls.