Serum and tear antibodies to Chlamydia after reinfection with guinea pig inclusion conjunctivitis agent.

Repeated inoculation of th eyes of guinea pigs with the naturally occurring Chlamydia psittaci agent, guinea pig inclusion conjunctivitis (GPIC), showed that animals gradually become susceptible to reinfection with the passage of time after primary infection. Higher levels of serum IgG antibody had a significant association with resistance to challenge inoculation only with a high dose (250 ELD50) but not with a low dose (25 ELD50) inoculum. With each inoculum, however, some animals with high serum antibody were susceptible. the presence of antibodies in tears did not correlate with resistance to the first low-dose challenge inoculation, but both tear IgG and secretory antibody did have a significant association with resistance on the second rechallenge with a high-dose inoculum. Topical treatment of the eye with immune serum or tears during primary infection reduced the amount of agent in the conjunctiva only during the period of application. Local treatment of the eye with heat-killed vaccine prior to primary infection did not produce detectable antibody or protect animals against challenge inoculation; this local immunization did "prime" the animals, however, so that they had an accelerated antibody response after infection. Although there is abundant evidence that local immunity has an important role in resistance to challenge inoculation with GPIC, serum and tear antibody levels correlate equally well with resistance to repeated ocular challenge inoculation. Effective immunization procedures for this chlamydial infection then would involve stimulation of both local and systemic immune responses.