Dissemination and immunogenicity of live TRIC agent in baboons after parenteral injection: II. Experiments with a ‘slow-killing’ strain

Abstract

SUMMARYAfter a single subcutaneous injection into baboons the MRC-4 strain of trachoma/inclusion conjunctivitis (TRIC) agent underwent limited multiplication at the injection site, but was then eliminated rapidly from the skin and regional lymph nodes. Forty-eight hours after a single intravenous injection, but not thereafter, it appeared in the peripheral lymph nodes and spleen. The single parenteral injections failed to immunize baboons against conjunctival challenge with the homologous strain. These findings contrasted with those previously reported for the more virulent mutant, MRC-4 f, which multiplied readily in the skin, lymph nodes and spleen, persisted in these tissues up to 3 weeks after injection, and conferred good immunity to conjunctival challenge with MRC-4. The difference in behaviour of MRC-4 and MRC-4 f might be accounted for, at least in part, by the use of a smaller inoculum of live MRC-4; but similar findings in guinea-pigs, reported elsewhere, suggest that the differences observed are real. In conjunction with previous work, the present study suggests that the immunogenicity of TRIC agent is closely related to the mass of antigen that can be administered to or propagated within the recipient.We are grateful to Mr D. Venters for his able technical assistance.