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Isolation of Chlamydia trachomatis by use of 5-iodo-2-deoxyuridine-treated cells.

Irradiated McCoy cells have provided a useful technique for the isolation of Chlamydia trachomatis strains, among which are found the etiological agents of trachoma, inclusion conjunctivitis, and lymphogranuloma venereum. Because irradiation is not always readily available, 5-iodo-2-deoxyuridine (IUDR) treatment of cells was investigated as a substitute procedure. IUDR-treated cells were found to be as sensitive to C. trachomatis infection as were irradiated McCoy cells. Stock chlamydial strains gave similar titers of iodine-stained inclusions in either system. When cells treated with IUDR were compared with irradiated cells for the isolation of C. trachomatis from clinical specimens, 5 of 138 specimens yielded isolates in IUDR-treated cells not found in irradiated ones, and one isolate was obtained from irradiated but not from IUDR-treated cells. In those 56 cases where inclusions were seen in both systems, there were significantly more inclusions in IUDR-treated than in irradiated cells. Although this series of cultures is too small to determine whether IUDR-treated cells are superior to irradiated ones for the isolation of C. trachomatis, the data indicate that IUDR treatment is at least equally effective.

Animals↗

The developmental cycle of Chlamydia trachomatis in McCoy cells treated with cytochalasin B.

The growth of a genital trachoma-inclusion conjunctivitis agent strain of Chlamydia trachomatis in McCoy cells treated with cytochalasin B was studied by quantitative infectivity estimations and by light and electron microscopy. Provided that infection of the monolayer was initiated by centrifuging the infectious particles on to the cells before incubation, this chlamydial strain grew as fast and to as high a titre [approximately 10(7) inclusion-forming units (i.f.u.) per culture] as those chlamydiae which infect cell cultures in vitro without centrifugation. Each i.f.u. inoculated yielded approximately 600 i.f.u., and extracellular infectivity was detected soon after intracellular infectivity appeared. Inclusions were recognized by fluorescent antibody staining techniques early in the developmental cycle when cultures were not infectious and when only reticulate bodies were seen by electron microscopy. Inclusions were recognized in Giemsa-stained preparations examined by dark ground microscopy only when elementary bodies appeared in the inclusions. Iodine staining was not a reliable indicator either of the number of inclusions present or of their infectivity.

Cell Line↗

Characterization of chlamydial genital infection resulting from sexual transmission from male to female guinea pigs and determination of infectious dose.

A major problem in the study of chlamydial genital infections in animal models has been the use of varied doses of chlamydiae for infection in different laboratories. It is clearly desirable to use a dose which approximates that of natural sexual infection, but that dose to date has not been determined because of the inability of researchers to quantify chlamydiae in semen. Fortunately, sexual transmission of chlamydiae has been described for the guinea pig model of infection with the chlamydial agent of guinea pig inclusion conjunctivitis (GPIC). In this study, we undertook to determine the approximate infection dose in actual sexual transmission by comparing the kinetics of infection in female guinea pigs acquired via sexual contact to those of genital infections induced artificially with known quantities of chlamydiae. Groups of guinea pigs were infected intravaginally with 10(4), 10(3), 10(2), and 10(1) inclusion-forming units (IFU) of GPIC, and the kinetics of the infection were determined. Infection with 10(2) IFU produced infections with lower peak levels than those in animals receiving 10(4) or 10(3) IFU. Seventy percent of animals receiving 10(2) IFU became infected, while 100 and 79% of animals receiving 10(4) and 10(3) IFU, respectively, became infected. Animals receiving 10(2) IFU also had a longer incubation period. Of 19 animals that mated with infected males, 63.2% became infected, with an infection course which was not significantly different than that of the 10(2)-IFU-infected group. The data suggest that female guinea pigs received approximately 10(2) IFU by sexual transmission. Of interest was the observation that the guinea pigs infected by sexual transmission shed organisms for a significantly shorter time period than that of any group that was artificially infected. This result suggests that there may be factors associated with semen which passively transfer antimicrobial activity to the female or enhance the innate host response in the female. Immunization of females with an inactivated vaccine was also found to elicit a protective immune response against sexual challenge, demonstrating that the model can be used in the evaluation of possible vaccine candidates and/or methodologies. There is currently no other animal model available for any sexually transmitted disease in which the disease or the ability to prevent the disease may be studied in animals infected by the natural means.

Animals↗

Protein antigens of Chlamydia psittaci present in infected cells but not detected in the infectious elementary body.

Ocular infection of guinea pigs with the guinea pig inclusion conjunctivitis (GPIC) strain of Chlamydia psittaci produces a clinical condition representative of acute chlamydial conjunctivitis in humans. Guinea pigs which had recovered from two challenges with GPIC were used as a source of sera for the identification of antigens present in GPIC-infected tissue culture cells but absent in the infectious elementary body (EB). Immunoblots of lysates of infected HeLa cells probed with the convalescent-phase sera identified protein antigens of 22, 34, and 52 kDa (p22, p34, and p52, respectively) that were not detected in lysates of purified EB or in uninfected HeLa cells. Protein p22 was also not detected in lysates of purified reticulate bodies. Immunoblotting of lysates of HeLa cells infected with other chlamydiae demonstrated that the antigenicity of p22 and p34 was subspecies specific. Immunoblotting was also used to detect p22 and p34 in lysates of the conjunctivae of infected guinea pigs. Adsorption of convalescent-phase sera with GPIC EB produced a reagent with dominant reactivity toward p22, p34, and a 28-kDa EB protein. Immunofluorescent staining of GPIC-infected HeLa cells demonstrated that these adsorbed sera labeled the inclusion and inclusion membrane, with no apparent reactivity toward EB or reticulate bodies. Collectively, these data identify non-EB chlamydial components which may be released into the inclusion during intracellular growth.

Animals↗

Chlamydial infection of subcutaneous conjunctival transplants in guinea pigs.

The development and testing of candidate vaccines for trachoma are constrained because only humans and nonhuman primates are susceptible to conjunctival infection with Chlamydia trachomatis. Guinea pig inclusion conjunctivitis (GPIC), an analogous disease of guinea pigs, provides a useful, less expensive model to study ocular chlamydial infections. GPIC is caused by a Chlamydia psittaci strain whose external constituents are very similar to those of C. trachomatis. To develop a better model for studying GPIC immunity, conjunctival pockets were established under the abdominal skin of guinea pigs by subcutaneous implantation. Up to six implants could be produced in each animal. The success rate of implantation was 79.0% (n = 148). These pockets were then infected with GPIC. The organism was recovered from the autografts indicating local replication, and tests for serum antibody by microimmunofluorescence showed production of GPIC-specific antibody of IgG and IgM classes after infection. There was minimal antibody response after moderate inoculating doses to the implants, and the titers increased more slowly than after eye infection with GPIC; with higher concentration of the inoculum, however, the antibody response increased to the same levels as with the ocular challenge but more slowly. Inoculation of pockets with GPIC also produced acute inflammatory changes in infected autografts (n = 101). Histologic examination of infected grafts showed chlamydial inclusions in epithelial cells and significant infiltration with lymphocytes and polymorphonuclear cells. Subcutaneous autografts may provide a useful model for chronologic studies of chlamydial infection. The delayed immunologic response, however, suggests that these pockets of implanted epithelium do not have full access to the immune system.

Abdomen↗

Interaction of chlamydiae with host cells and mucous surfaces.

For chlamydiae, as obligate intracellular parasites, attachment to and ingestion by host cells are essential steps in reproduction. Their attachment site appears to be heat-sensitive; it has not been correlated with any morphological entity. Antibody blocks chlamydial attachment to cells and, for certain chlamydia psittaci and chlamydia trachomatis strains which are highly infective for cell cultures, N-acetylglucosamine appears to contribute to cell receptor specificity. Sialic acid residues have been suggested as receptors for other C. trachomatis strains. The guinea-pig inclusion conjunctivitis strain of C. psittaci becomes associated with the conjunctiva during incubation of inoculated tissue fragments in vitro. However, although antibody from tears neutralizes infectivity of this strain in vivo, association of the organism with tissue fragments is not inhibited, suggesting that antibody neutralization in vivo is not mediated by prevention of attachment to cells. Chlamydial infectivity for cell monolayers is greatly increased by centrifugation. The process is temperature-dependent and involves cooperative interactions between direction force and the pressure generated during centrifugation. Enhanced infectivity appears to result from changes induced in the cell surface. These changes may favour nonspecific interactions in attachment, since antibody inhibition of infectivity on static cell monolayers is overcome by centrifugation.

Acetylglucosamine↗

[Occurrence and diagnosis of Chlamydia trachomatis infections in newborns and young infants (author's transl)].

Chlamydia trachomatis was assayed using McCoy cell culture on vaginal swabs from pregnant women and on conjunctival and nasopharyngeal swabs from newborns. C. trachomatis was found in 23 of 168 pregnant women (8%) and in 15 of 298 newborns (5%). Six newborns developed a typical inclusion conjunctivitis, whereas three infants developed pneumonia caused by C. trachomatis. Of a total of 50 children with conjunctivitis, C. trachomatis was found in six of 22 newborns, in four of 22 infants (2-3 months old) and in none of the older infants and children. Specific antibodies in serum could be demonstrated in most patients by the microimmunofluorescence technique, whereas antibodies against C. trachomatis were only found in a small percentage of the healthy children of various ages. Recommendations are given for the diagnosis of infections caused by C. trachomatis in newborns and infants.

Adolescent↗

Experimental genital tract infection with Chlamydia psittaci (GPIC agent) in male rats.

The course of experimental chlamydial infection of the male genital tract was studied. Inoculation of the Chlamydia psittaci agent of guinea pig inclusion conjunctivitis (GPIC agent) into the vas deferens of rats resulted in chlamydial infection of the epididymis, testis and the prostate gland. The inflammatory response was most prominent at 14 days after infection. Chlamydiae were recovered from the epididymides and the prostate glands for up to 90 and 60 days post inoculation, respectively. Histopathological changes associated with chlamydial infection of the epididymis or prostate gland were characterized by intratubular and interstitial purulent inflammation. Chlamydia-specific IgM- and IgG-antibodies were found in sera of nearly all infected animals. Results of this study indicate that this animal model may be useful to study the pathogenesis, immune responses and sequelae of chlamydial infections of the male genital tract.

Animals↗

Chlamydial infection in women with cervical dysplasia.

The prevalence of antibodies to chlamydiae, particularly to TRIC (trachoma-inclusion conjunctivitis) agents, was studied in women with cervical dysplasia and in women attending selected clinics (obstetrics, cancer-screening, and gynecology). In addition, attempts were made to isolate TRIC agents and herpesviruses from the cervices of these women. TRIC agent recovery rates 4.1 per cent for women with dysplasia, 5.4 per cent for pregnant women, 7.8 per cent in the women's clinic, and 0.8 per cent in the cancer-screening clinic. Herpesvirus recovery rates were lower, on the order of 1 per cent or less in each clinic. Complement-fixing antibodies to chlamydial group antigen were detected in 21.5 per cent of women with dysplasia. With a more sensitive fluorescent antibody method, 77.6 per cent of the women with dysplasia or cervical cancer were shown to have antibodies to chlamydiae. In general, antichlamydial antibodies were less prevalent in the other clinic populations. The results of this study indicate that women with cervical dysplasia or cancer may have a high prevalence of antibodies to sexually transmitted agents other than herpesvirus type 2.

Adolescent↗

Estimation of endpoints in biological systems.

A program, written in BASIC, has been developed to estimate rapidly endpoints from a small number of experimental data. The computational method is based on the work of Reed and Muench (Am. J. Hyg. 27, 493 1938). Several endpoints may be estimated in the same run. A subroutine allows the saving of experimental data in disk file and a printout subroutine permits different types of printout (tabular or graphical). Estimation of several infectious doses (ID) of a guinea-pig inclusion conjunctivitis (GPIC) Chlamydia psittaci strain is given as sample run.

Computers↗

An enzyme-linked immunosorbent assay (ELISA) for anti-chlamydial secretory immunoglobulin A in guinea pig tears.

A method is described which permits the assay of specific secretory immunoglobulin A (sIgA) antibodies produced by guinea pigs in response to ocular infection with the guinea pig inclusion conjunctivitis strain of Chlamydia psittaci (GPIC agent). The enzyme-linked immunosorbent assay (ELISA) developed was shown to be more sensitive and less subjective than the micro-immunofluorescence assay as a means of assaying specific antibody.

Animals↗

Homogeneity of the major outer membrane protein gene of feline Chlamydia psittaci.

Thirteen feline Chlamydia psittaci strains isolated in various countries over a 50-year period were examined by restriction mapping of the major outer membrane protein (MOMP) gene obtained after DNA amplification by the polymerase chain reaction and compared with avian, ovine and guinea pig inclusion conjunctivitis (GPIC) C psittaci strains. All the feline isolates produced a unique AluI pattern distinct from the other C psittaci strains and were characterised by a typical fragment doublet of 185/180 base pairs. Such a homogeneity argues for their genetic relatedness and suggests their clonal origin. These data demonstrate the usefulness of MOMP-gene restriction mapping in C psittaci typing.

Animals↗

Oculogenital disease.

This review comprises brief discussions of the epidemiology, clinical manifestations, laboratory features, and treatment of the oculogenital diseases as they appear typically in the newborn infant, the child, and the adult. Inclusion conjunctivitis is the most frequently occurring oculogenital infection in all three categories of patient. Oculogenital diseases are becoming increasingly important in both frequency and severity. They can be extremely serious and may thus require the immediate attention of the physician.

Adult↗

Molecular cloning of a gene encoding a Chlamydia psittaci 57-kDa protein that shares antigenic determinants with ca. 60-kDa proteins present in many gram-negative bacteria.

In order to develop reagents to study the immune response of guinea pigs to infection by Chlamydia psittaci guinea pig inclusion conjunctivitis strain (GPIC), we constructed a plasmid clone bank with C. psittaci DNA. One of the recombinant clones isolated produced large amounts of a 57-kilodalton (kDa) protein that was immunoreactive with sera from GPIC infected guinea pigs. While investigating this recombinant protein, we discovered that all the Gram-negative bacteria analyzed so far have immunoreactive proteins of similar size. This protein seems to be a 'common antigen' already described in various Gram-negative bacteria.

Antigens, Bacterial↗

Usefulness of omp1 restriction mapping for avian Chlamydia psittaci isolate differentiation.

Sixty-five avian Chlamydia psittaci isolates collected worldwide, including 27 previously characterized reference strains, were analysed by restriction mapping of the major outer membrane protein gene (omp1) obtained after DNA amplification by PCR. They were compared to 2 ruminant isolates, a feline pneumonitis and a guinea pig inclusion conjunctivitis (GPIC) isolate. According to their omp1 restriction patterns, avian strains were heterogeneous in that they exhibited 6 and 4 distinct patterns using AluI and MboII restriction enzymes, respectively, thus defining 7 groups. However, 84% of the studied strains belonged to groups 1 to 4, which share a specific fragment triplet of 411, 282 and 102 base pairs in their AluI digestion patterns. Comparisons with serological classifications showed a strict correlation and allowed further intraserovar differentiation. Furthermore, this classification based upon a single gene (omp1) roughly correlated with the data obtained by RFLP of native DNA and DNA/DNA hybridization studies. There was no host or geographic specificity in the pattern exhibited by these strains. The ruminant, feline pneumonitis and GPIC C. psittaci isolates were clearly distinguished from each other and the avian strains. Moreover, this method was clearly able to identify dubiously designated strains as well as mixtures of isolates within a single sample. In conclusion, this PCR approach based upon omp1 restriction mapping enables the differentiation of avian C. psittaci isolates and can be proposed as a taxonomic and epidemiologic tool.

Animals↗