SUMMARY Guinea-pigs were repeatedly infected with guinea-pig inclusion conjunctivitis agent. Reinfection caused severe conjunctival inflammation, and repeated reinfection led to chronic inflammation lasting for many months. This was followed by the development of pannus, follicles on the palpebral conjunctivae, scarring of the lower palpebral conjunctiva, and deformities of the lower lid. Reinfection was accompanied by small numbers of inclusion-bearing cells, small numbers of polymorphonuclear cells, and high numbers of mononuclear cells. There was no increase in the level of serum antibodies. The chronic conjunctivitis was associated with high numbers of mononuclear cells and no inclusions or polymorphonuclear cells. The response to reinfection appears to be a delayed-type hypersensitivity reaction, and we suggest that the chronic inflammation, pannus, scarring, and lid deformities associated with hyperendemic trachoma may be due to repeated reinfection combined with delayed-type hypersensitivity.Primary ocular infection with guinea-pig inclusion conjunctivitis (GPIC) agent produces acute conjunctivitis, with no pannus or scarring, which resolves spontaneously in 30 to 40 days.1-3 It has not therefore been considered a good model for trachoma.In this study we have looked at the ocular responses of guinea-pigs to reinfection with GPIC agent, and compared them with the responses to primary infection. We have found that repeated reinfection produces chronic conjunctivitis with scarring and pannus, similar to trachoma. Materials and methodsAnimals, organisms, methods for clinical assessment, conjunctival scrapings and serology are described in the previous paper.3 EXPERIMENTAL DESIGN Animals were infected and reinfected in the left eye, with 1 drop of inoculum (containing 106 E1Dr0 of GPIC agent strain A10) as described in the previous paper.3The first experiment was carried out on 5 fullygrown animals, which were examined, photographed Correspondence to Dr M. A. Monnickendam. and scraped immediately before infection and at intervals after infection and reinfection. These animals were infected 7 times.The second experiment was carried out on 128 young guinea-pigs. Fresh groups of 4 animals were taken immediately before infection and at various intervals after infection and reinfection; eyes were examined, photographed and scraped, and blood collected for serology. These animals were infected 5 times.

SUMMARY Clinical and histological studies of the outer eyes of newborn and adult female guineapigs were carried out together with histological studies of fetal eyes. Fine superficial corneal vessels, extending from the limbus, were seen in most newborn and adult eyes and were also present in histological preparations of fetal eyes. These vessels were therefore considered to be features of the normal guinea-pig eye. Masses of tissue composed of lymphoid cells, which were often organised into germinal centres, were found in the fornices of newborn and adult eyes. Smaller accumulations of lymphoid cells were found in fetal eyes, and this lymphoid tissue was therefore also considered to be a normal feature of the guinea-pig eye. In adult eyes mild but short-lived oedema or hyperaemia of the palpebral conjunctiva was quite common. There were no differences in the amounts of conjunctival cellular infiltration in these eyes compared with normal eyes, and these inflammatory changes were therefore not considered to be significant.

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