Effect of Chlamydiaphage phiCPG1 on the course of conjunctival infection with "Chlamydia caviae" in guinea pigs

Abstract

Over the last several years, four different phages of chlamydiae, in addition to a phage associated with Chlamydia psittaci isolated from an ornithosis infection in ducks over 25 years ago, have been described and characterized. While these phages and their chlamydial host specificities have been characterized in vitro, there is virtually nothing known about the interaction of the phage with chlamydiae in their natural animal host. phiCPG1 is a lytic phage specific for "Chlamydia caviae," which is a natural parasite of the guinea pig. In this study, guinea pigs were inoculated in the conjunctiva with suspensions of phiCPG1 and C. caviae and the effect on the development of pathology and on the course of chlamydial infection in the conjunctiva was determined. The presence of phage delayed the appearance of the peak level of chlamydiae in the animal and decreased the pathological response. Evidence for replication of the phage in C. caviae in the conjunctival tissue was observed. Modifying the ratio of phage to chlamydiae altered the course of infection and affected phage replication. There was no evidence for the phage increasing the virulence of C. caviae infection.

FIG. 1.

Kinetics of C. caviae infection in the guinea pig conjunctiva and the effect of the presence of ϕCPG1 on (A) the gross pathological response in the conjunctiva and (B) the course of C. caviae infection with and without phage. The inoculum was the original C. caviae/phage culture lysate containing 10⁶ IFU of C. caviae and 51.44 μg/ml of VP1 DNA. Each group contains five animals each, and the data points represent the means of each group except for the pathology scores, which are the means of both conjunctivas from each animal. The error bars for the phage DNA represent 1 standard deviation.

FIG. 2.

Kinetics of C. caviae infection in the guinea pig conjunctiva and the effect of the presence of ϕCPG1 on (A) the gross pathological response in the conjunctiva and (B) the course of C. caviae infection with and without phage. The inoculum was prepared by adding 10⁶ IFU of C. caviae to purified phage. Each group contains five animals each, and the data points represent the means of each group except for the pathology scores, which are the means of both conjunctivas from each animal. The error bars for the phage DNA represent 1 standard deviation.

FIG. 3.

Effect of different ratios of chlamydiae and phage on chlamydial infection in the conjunctiva. (A) C. caviae (10⁶ IFU) and purified phage from the original C. caviae/phage culture lysate or a 1:10 dilution of the purified phage from the lysate were inoculated into the conjunctiva. (B) C. caviae (10⁵ IFU) and purified phage from the original phage stock were inoculated into the conjunctiva. Each group contains five animals each, and the data points represent the means for each group. The error bars for the phage DNA represent 1 standard deviation.