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Microvirus of chlamydia psittaci strain guinea pig inclusion conjunctivitis: isolation and molecular characterization.

The authors report the isolation and molecular characterization of a bacteriophage, φCPG1, which infects CHLAMYDIA: psittaci strain Guinea pig Inclusion Conjunctivitis. Purified virion preparations contained isometric particles of 25 nm diameter, superficially similar to spike-less members of the φX174 family of bacteriophages. The single-stranded circular DNA genome of φCPG1 included five large ORFs, which were similar to ORFs in the genome of a previously described CHLAMYDIA: bacteriophage (Chp1) that infects avian C. psittaci. Three of the ORFs encoded polypeptides that were similar to those in a phage infecting the mollicute Spiroplasma melliferum, a pathogen of honeybees. Lesser sequence similarities were seen between two ORF products and the major capsid protein of the φX174 coliphage family and proteins mediating rolling circle replication initiation in phages, phagemids and plasmids. Phage φCPG1 is the second member of the genus CHLAMYDIAMICROVIRUS:, the first to infect a member of a CHLAMYDIA: species infecting mammals. Similarity searches of the nucleotide sequence further revealed a highly conserved (75% identity) 375 base sequence integrated into the genome of the human pathogen Chlamydia pneumoniae. This genomic segment encodes a truncated 113 residue polypeptide, the sequence of which is 72% identical to the amino-terminal end of the putative replication initiation protein of φCPG1. This finding suggests that C. pneumoniae has been infected by a phage related to φCPG1 and that infection resulted in integration of some of the phage genome into the C. pneumoniae genome.

Amino Acid Sequence↗

Cell-mediated and humoral immune responses to chlamydial antigens in guinea pigs infected ocularly with the agent of guinea pig inclusion conjunctivitis.

Cell-mediated immune response and humoral response to chlamydial antigens were investigated in guinea pigs infected with the agent of guinea pig inclusion conjunctivitis (GPIC). Pronounced cell-mediated immune response to the homologous antigen, as well as to two other chlamydial antigens, 6BC (Chlamydia psittaci) and LB-1 (C. trachomatis), occurred in all infected animals. Cell-mediated immune response to GPIC, and to a lesser extent to 6BC and LB-1 as well, was enhanced with time after infection even without the re-inoculation of the infectious agent. Extensive cross-reactions among the three chlamydial antigens during the cell-mediated immune response appeared to be due to shared species-specific and group-reactive antigens. Serum antibody response was pronounced and uniform to GPIC; it was less marked to 6BC and LB-1, with fewer cross-reactions than seen in tests for cell-mediated immunity.

Animals↗

Infection of genital tract and transmission of ocular infection to newborns by the agent of guinea pig inclusion conjunctivitis.

Female guinea pigs were inoculated intravaginally with the agent of guinea pig inclusion conjunctivitis (Gp-ic). Evidence for infection was obtained by demonstration of Gp-ic inclusions in epithelial cells of genital tract smears, histopathology, recovery of Gp-ic during infection, and antibody response. Infection of the genital tract was produced with low doses (20-200 median egg lethal doses) of the agent. The infection lasted about 3 weeks, and there was no marked clinical response. Ocular infection that could be detected as early as 3 days after birth in offspring of infected mothers was also demonstrated.

Animals↗

Infectivity titration of guinea-pig inclusion conjunctivitis agent in irradiated McCoy cells.

Estimation of the infectivity of the agent of guinea-pig inclusion conjunctivitis for irradiated McCoy cells, assayed as inclusion-forming units, was influenced by the age of cells after irradiation, the maturation time of the inclusions, the centrifugal force and the centrifugation temperature. Agent passaged through irradiated McCoy cells or guinea-pig conjunctivae showed a greater capacity to infect irradiated McCoy cells without centrifuging than agent grown in a chick embryo. The nature of the change and the mechanism of infectivity enhancement by centrifuging are discussed.

Animals↗

Animal model studies of genital chlamydial infections. Immunity to re-infection with guinea-pig inclusion conjunctivitis agent in the urethra and eye of male guinea-pigs.

A previous report demonstrated that male guinea-pigs could be infected in the urethra with guinea-pig inclusion conjunctivitis (GPIC) agent and that the infection was transmitted during mating from infected males to females. In the experiments reported here, inoculation of male guinea-pigs in the urethra with GPIC organisms resulted in infection which subsided spontaneously in about 2 weeks. Males were demonstrated to be completely resistant to urethral challenge with 10(3)ID50 when tested 6 weeks after urethral infection. These guinea-pigs, immune to re-infection of the urethra, remained susceptible to infection of the eye, but this ocular infection was shorter in duration than that in previously uninfected control animals. Infection in the eye resulted in immunity to both ocular and urethral infection when animals were challenged 6 weeks after the ocular infection.

Animals↗

Experimental chlamydial salpingitis in immunosuppressed guinea pigs infected in the genital tract with the agent of guinea pig inclusion conjunctivitis.

At necropsy indication of spread of infection to fallopian tubes was found in 25 of 41 (60%) female guinea pigs infected in the genital tract with the chlamydial agent of guinea pig inclusion conjunctivitis and immunosuppressed with cyclophosphamide. Eighteen were examined histologically, and the diagnosis of acute salpingitis was confirmed in 10, based on inflammatory reaction, detection of guinea pig inclusion conjunctivitis in tissue, and formation of cysts (pyosalpinx and hydrosalpinx). Infection of fallopian tube tissue was confirmed by indirect immunofluorescence and electron microscopy. Infection of endometrial tissue and peritoneum was also recognized. Data suggested that the immunosuppression mediated by cyclophosphamide resulted in a prolonged genital tract infection and concomitant ascending infection leading to salpingitis.

Animals↗

Immunity to vaginal reinfection in female guinea pigs infected sexually with Chlamydia of guinea pig inclusion conjunctivitis.

Guinea pig boars were inoculated intraurethrally with the chlamydial agent of guinea pig inclusion conjunctivitis (GPIC). At the heights of their urethral infections, they were caged with sows in estrus. Whereas some of the sows had not been previously exposed to GPIC agent, others had received an intravaginal inoculation 5 to 8 weeks earlier. Those sows for which infected boars provided the first exposure were challenged by intravaginal inoculation 5 to 8 weeks later. Vaginal and conjunctival scrapings were taken regularly and stained for chlamydial inclusions. Titers of serum anti-GPIC antibodies and of vaginal secretory IgA anti-GPIC antibodies were determined by immunofluorescence. Our results show for the first time that a sexually acquired vaginal GPIC infection induces immunity to manual reinfection of the vagina. Because of the high incidence of secondary conjunctival infections among the vaginally infected sows, we could not provide a sound statistical basis for our tentative conclusion that manual infection of the vagina induces immunity to sexual reinfection. The results of our antibody titrations confirm previous work showing that vaginal GPIC infection induces formation of both serum antibody and vaginal secretory immunoglobulin A antibody.

Animals↗

Electron microscopic observations concerning the in vivo uptake and release of the agent of guinea-pig inclusion conjunctivitis (Chlamydia psittaci) in guinea-pig exocervix.

This report details electron-microscopical observations concerning C. psittaci infection in vivo. The model employed was that of the guinea-pig infected at the exocervical region with the agent of guinea-pig inclusion conjunctivitis (GPIC). Our observations indicate that chlamydial particles gain access to their target cells by the mechanism of endocytosis. Single GPIC elementary bodies were seen to be positioned within individual endosomes. The observations reported here provide evidence that chlamydial particles that had undergone their developmental cycle within the exocervical epithelial cells may leave the epithelium in 2 ways; within entire infected cells that had been shed into the lumen of the cervix and by means of the liberation of chlamydial particles from disrupted cells. The mechanism of cell disruption and shedding is thought to involve the large number of PMNs observed to be present within the enlarged intercellular spaces of the infected epithelium.

Animals↗

Immunity to reinfection and immunization of male guinea pigs against urethral infection with the agent of guinea pig inclusion conjunctivitis.

BACKGROUND AND OBJECTIVES: There is little information available on immunity of males to chlamydial infection after recovering from a primary urethral infection or after immunization with chlamydial antigen. The guinea pig model of genital infection using the chlamydial agent of guinea pig inclusion conjunctivitis was utilized to evaluate the protective immune response in these circumstances. GOAL: To determine whether immunity to reinfection develops after a primary urethral infection and whether immunity develops as a result of immunization with inactivated chlamydiae. STUDY DESIGN: Groups of five male guinea pigs each in two separate experiments were infected in the urethra with chlamydiae and challenged with a fresh inoculum at either 30, 75, or 150 days after infection. The course of the challenge infection was then determined. Similarly, guinea pigs were immunized subcutaneously with ultraviolet-inactivated chlamydial elementary bodies and the course of urethral infection was determined when inoculated 2 weeks after immunization. RESULTS: Male guinea pigs were highly resistant to reinfection after a primary urethral infection. Animals that were immunized with inactivated chlamydiae generally became infected upon challenge, but the intensity of the infection was markedly reduced. CONCLUSIONS: Male guinea pigs possess protective mechanisms that make them more resistant to repeat chlamydial genital infection for a longer period of time than is seen in female guinea pigs. In addition, immunization of males with inactivated chlamydial antigen by a parenteral route is able to elicit a protective response to urethral infection with chlamydiae.

Animals↗

Ocular and dermal delayed hypersensitivity reactions in guinea-pigs following infection with guinea-pig inclusion conjunctivitis agent (Chlamydia psittaci).

Guinea-pigs which had been sensitized to guinea-pig inclusion conjunctivitis agent by ocular infection, were given ocular and dermal challenges with a range of doses of agent. Ocular delayed-type hypersensitivity responses were elicited by a wide range of doses. Such responses were associated with the presence of chlamydial inclusions and inflammatory cells. The EID50 for ocular reinfection was only slightly higher than that for primary ocular infection. Dermal delayed-type hypersensitivity reactions were produced only when high doses of agent were used. The relevance of these observations to human chlamydial eye disease is discussed.

Animals↗

Evaluation of the Kodak Surecell Chlamydia test for the laboratory diagnosis of adult inclusion conjunctivitis.

PURPOSE: The Kodak Surecell Chlamydia test, a rapid enzyme immunoassay, has been reported to be highly sensitive (93%) and specific (96%) for detecting chlamydial lipopolysaccharide antigen in conjunctival specimens from infants, but has not been evaluated previously in adult conjunctival specimens. This study was designed to determine the efficacy of the Kodak Surecell Chlamydia test for the laboratory diagnosis of adult inclusion conjunctivitis. METHODS: Twenty Chlamydia culture-positive conjunctival specimens from adults (true-positives) and 20 true-negative specimens were tested with the Kodak Surecell Chlamydia test. RESULTS: The Kodak Surecell Chlamydia test was 40% (8/20) sensitive, 100% (20/20) specific, and 70% (28/40) efficient. CONCLUSIONS: This study indicates that the Kodak Surecell Chlamydia test, though highly specific, is less sensitive in its ability to diagnose chlamydial conjunctivitis in adults than has been reported previously in infants.

Adult↗

Limited survey of genital infection by guinea pig inclusion conjunctivitis agent.

Cervical or urethral scrapings were collected from 245 guinea pigs that had clinical signs of guinea pig inclusion conjunctivitis (GPIC) or were parents of newborn young having clinical signs of GPIC. Giemsa-stained smears were examined for cytoplasmic inclusion bodies, and samples were passaged in 6-day-old embryonating eggs. Complement-fixation tests were performed on 44 samples passaged through eggs in an effort to detect the presence of GPIC antigen. Unequivocal evidence of chlamydial infection of the genital tract was not found.

Animals↗

Phage infection of the obligate intracellular bacterium, Chlamydia psittaci strain guinea pig inclusion conjunctivitis.

The infectious cycle of phiCPG1, a bacteriophage that infects the obligate intracellular pathogen, Chlamydia psittaci strain Guinea Pig Inclusion Conjunctivitis, was observed using transmission electron microscopy of phage-hyperinfected, Chlamydia-infected HeLa cells. Phage attachment to extracellular, metabolically dormant, infectious elementary bodies and cointernalisation are demonstrated. Following entry, phage infection takes place as soon as elementary bodies differentiate into metabolically active reticulate bodies. Phage-infected bacteria follow an altered developmental path whereby cell division is inhibited, producing abnormally large reticulate bodies, termed maxi-reticulate bodies, which do not mature to elementary bodies. These forms eventually lyse late in the chlamydial developmental cycle, releasing abundant phage progeny in the inclusion and, upon lysis of the inclusion membrane, into the cytosol of the host cell. Structural integrity of the hyperinfected HeLa cell is markedly compromised at late stages. Released phage particles attach avidly to the outer leaflet of the outer membranes of lysed and unlysed Chlamydiae at different stages of development, suggesting the presence of specific phage receptors in the outer membrane uniformly during the chlamydial developmental cycle. A mechanism for phage infection is proposed, whereby phage gains access to replicating chlamydiae by attaching to the infectious elementary body, subsequently subverting the chlamydial developmental cycle to its own replicative needs. The implications of phage infection in the context of chlamydial infection and disease are discussed.

Animals↗

Resistance to reinfection with a chlamydial agent (guinea pig inclusion conjunctivitis agent).

Although most chlamydial infections are chronic or recurrent, infection of the guinea pig's eye with guinea pig inclusion conjunctivitis (GPIC) agent induces a marked resistance to reinfection. To characterize this resistance to GPIC agent, we compared the disease and infection in previously infected guinea pigs with that in animals infected for the first time. In animals experiencing primary infection, even the lowest dose (10 egg-lethal doses [ELD50]) produced the disease and chlamydial inclusions in conjunctival smears, but the incubation period became progressively shorter with the highest inocula (10(4) and 10(5) ELD50). In animals with previous infection only these two highest inocula produced disease and infection, but the disease was short-lived, and replication of the agent was severely limited. The mechanism of this resistance may be due to secretory antibody in the tears, cellular immunity, or other local factors.

Animals↗

Target tissues associated with genital infection of female guinea pigs by the chlamydial agent of guinea pig inclusion conjunctivitis.

Female guinea pigs were experimentally infected in the genital tract with the strain of Chlamydia psittaci that causes guinea pig inclusion conjunctivitis. Chlamydiae were found frequently in superficial squamous epithelial cells of the exocervix, along with heavy involvement at the squamocolumnar junction. In this zone chlamydiae were observed in columnar cells, but inflammation and chlamydial inclusions were not observed in true endocervical epithelium. These observations were supported by results of immunofluorescence microscopy. Electron micrographs revealed typical chlamydiae within surface epithelial cells at the squamocolumnar junction; various stages of the growth cycle (elementary, reticulate, and intermediate bodies) were also present. Cytopathologic features were not remarkable, but peripheral distribution of organelles, rarefaction of the cytoplasm, and loss of microvilli were observed.

Animals↗

Azithromycin vs doxycycline in the treatment of inclusion conjunctivitis.

PURPOSE: The aim of the study was to compare the efficacy and safety of azithromycin and doxycycline in the treatment of chlamydial conjunctivitis in adults. DESIGN: An open, randomized clinical trial. METHODS: Seventy-eight adult patients with incluson conjunctivitis were enrolled in this multicenter clinical study. Patients with chlamydial conjunctivitis as indicated by a positive direct fluorescent antibody (DFA) test or cell culture were randomized to receive a single 1-g dose of azithromycin or doxycycline, 100 mg twice daily for 10 days. A conjuctival swab for cell culture was obtained from all patients immediately before the treatment for subsequent confirmation of the presence of chlamydial infection in the central laboratory. Control examinations were performed 10 to 12 days and 4 to 6 weeks after the treatment initiation. Clinical and bacteriological responses to the treatment were evaluated at the last visit. The occurrence and frequency of adverse events were analyzed as well. RESULTS: Of 78 patients enrolled, 51 completed the study and were evaluated for efficacy. The main reasons for withdrawal were lack of confirmation of the presence of chlamydial infection by the central laboratory and failure to attend the follow-up visit. Eradication of C. trachomatis was achieved in 23 of 25 (92%) patients treated with azithromycin and in 25 of 26 (96%) patients treated with doxycycline. Clinical cure was observed in 15 (60%) and 18 (69%) patients treated with azithromycin and doxycycline, respectively. Both drugs were equally well tolerated. CONCLUSIONS: A single 1-g azithromycin therapy was as effective as standard 10-day treatment with doxycycline (100 mg twice daily) in the treatment of adult inclusion conjunctivitis.

Adolescent↗

Guinea-pig inclusion conjunctivitis as a model for the study of trachoma: clinical, microbiological, serological, and cytological studies of primary infection.

The course of primary ocular infection with guinea-pig inclusion conjunctivitis agent was followed in 2 groups of animals. One group of fully grown animals was repeatedly scraped; the other of small animals was used on 1 occasion only and scraped after clinical examination. The intensity of conjunctival inflammation was measured, conjunctival scrapings were taken, and the numbers of polymorphonuclear cells, mononuclear cells, and epithelial cells containing chlamydial inclusions were counted, and the level of antibodies in serum was measured. It was found that inflammation of the conjunctiva lasted for about 30 to 40 days, and the clinical features (oedema, hyperaemia, papillary reaction) were very similar in the 2 groups. Inclusions and polymorphonuclear cells were found for up to 21 days, and mononuclear cells were found on days 7 to 25. Serum antibodies were first detected on day 10 and reached a peak on day 21. The intensity of inflammation was significantly higher on day 2 in the animals which had been scraped. After this the severity of the inflammation and the course of disease were similar in the 2 groups.

Animals↗

Partial protection against genital reinfection by immunization of guinea-pigs with isolated outer-membrane proteins of the chlamydial agent of guinea-pig inclusion conjunctivitis.

Because partial protection against reinfection is induced by experimental infection in the guinea-pig model of genital chlamydial infection, we sought to induce immunity by immunization. Female guinea-pigs were immunized subcutaneously with the major outer-membrane protein (MOMP) and the 61 kDa cysteine-rich outer-membrane protein (61 kDa) of the agent of guinea-pig inclusion conjunctivitis (GPIC) eluted from SDS-polyacrylamide gels (SDS-MOMP, SDS-61 kDa). Post-immunization sera and secretions contained antibodies to the SDS-purified proteins at high titre as measured by immunoblotting, whereas enzyme immunoassays (EIA) using whole elementary bodies as antigen showed significantly lower titres (P < 0.001). Likewise, blastogenic responses of peripheral mononuclear cells to GPIC elementary bodies were weak. Animals immunized with SDS-MOMP and SDS-61 kDa were fully susceptible to intravaginal challenge, as were control animals immunized with buffer without protein. Another group of animals were immunized with material prepared by extraction of chlamydial outer-membrane complexes with octyl beta-D-glucopyranoside (OGP) and dithiothreitol, which consisted largely of MOMP (OGP-MOMP). In contrast to the SDS-MOMP group, sera and secretions in the OGP-MOMP group showed high titres in EIA, and high titre antibodies to MOMP by immunoblot; however, most animals also had antibodies to 61 kDa, 72 kDa and ca. 84 kDa outer-membrane proteins. OGP-MOMP animals were partially protected against genital challenge as evidenced by low inclusion scores compared to control animals, although duration of infection measured by culture isolation was similar to controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗