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Intracerebral infection of mice with ovine strains of Chlamydia psittaci: an animal screening test for the assay of vaccines.

Intracerebral inoculation of mice with the A22 strain of ovine C. psittaci gave a reproducible non-lethal infection; multiplication of the inoculum could be quantitated by titration of mouse brain extracts in tissue culture. Mice which had recovered from infection, or which had been inoculated subcutaneously with living organisms of A22 strain, showed solid resistance to intracerebral challenge infection. However, subcutaneous inoculation of formalin-inactivated chlamydia showed little protective effect unless given in very high dosage. Inactivated vaccines of the heterologous ZC113 strain gave better, but still incomplete, protection against A22 challenge infection than did the homologous inactivated vaccine. The implication of these findings is discussed. The mouse intracerebral protection test appears to be a suitable laboratory procedure for assessing the potency of vaccines against enzootic ewe abortion and for comparing the immunological cross-protection between the various strains of C. psittaci currently found in the natural disease in sheep.

Animals↗

An enzyme immunoassay to detect specific antibodies to protein and lipopolysaccharide antigens of Chlamydia trachomatis.

We have developed an enzyme immunoassay to measure antibodies to the proteins and lipopolysaccharide (LPS) of Chlamydia trachomatis. Antibodies to proteins could be differentiated from antibodies to lipopolysaccharide (LPS) by treatment of the antigen with periodate or Triton X-100. Some important parameters of the oxidation by periodate were studied by comparing the response of several monoclonal antibodies. Four types of response could be observed: type I, a reduced response after mild or strong oxidation; type II, a normal response after mild oxidation, but reduced after strong oxidation; type III, not affected; type IV, an increased response after oxidation. Treatment with Triton X-100 had the same effect as mild oxidation and confirmed the response types I, III, and IV. Treatment of antigen with periodate reduced the IgG response measured in sera from patients with evidence of Chlamydia psittaci infection.

Antibodies, Bacterial↗

A complement-fixation, enzyme-linked immunosorbent assay as an aid in the serological investigation of enzootic abortion in ewes.

An enzyme-linked immunosorbent assay which detects complement fixed in an antigen/antibody complex (CFELISA) was used to examine sera previously examined by the complement fixation test (CFT) in an investigation of enzootic abortion in ewes (EAE). The CFELISA was easy to perform and did not suffer from the many drawbacks of the CFT. Accepting a CFT titre of > or = 32 to indicate infection, the CFELISA had a sensitivity of 98 per cent and a specificity of 100 per cent; the predictive value of a positive result was 100 per cent and that of a negative result was 98 per cent.

Abortion, Veterinary↗

Experimental chlamydial pneumonia in pigs.

Naturally occurring disease in pigs associated with chlamydial infections has not been reported in Britain, though evidence of chlamydial challenge has been demonstrated in two separate serological surveys. An isolate of Chlamydia psittaci (28/68) from an ovine pneumonia produced pneumonia in pigs following intratracheal inoculation. Transient pyrexia at 24 hr was followed by increased respiratory rates and inappetance which lasted for a further 48 hr in challenged pigs. Histologically acute exudative reactions were present in the lungs by 24 hr with proliferative changes predominating after 10 days. While variations in the concentrations of inocula were reflected by corresponding increases and/or decreases in gross lung damage, clinical signs and histological reactions were unaltered. Chlamydial organisms were recovered only from lung tissues.

Animals↗

Ocular chlamydial zoonosis: an experimental study in monkeys.

Two locally isolated strains of Chlamydia psittaci from faeces of apparently healthy sheep and conjunctiva of Holstein heifers suffering from conjunctivitis and pneumonia were used for ocular experimental studies in 7 Rhesus monkeys. Titrated (ELD50 10(3.6)/0.2 ml and 10(4.5)/0.2 ml) partially purified yolk sac suspension of each strain was instilled onto conjunctiva of each animal. The clinical and laboratory studies were followed till 8 weeks post-infection. Both the strains produced trachoma like follicles (0.3-0.5 mm dia) preferably on lower conjunctiva between 2-4 weeks of post-infection. Pannus was not observed in any of the experimental eye. Laboratory studies revealed a good correlation between reisolation, fluorescent antibody test and cytology between 2-4 weeks of post-infection. Highest complement fixing antibody titre 1:32 was recorded in 4 out of 7 animals. The studies indicated that both the animal strains had no barrier across ocular tissues in monkeys, vis-à-vis human conjunctiva.

Animals↗

Studies on experimental chlamydial mastitis in goat histoenzymology.

Two strains of Chlamydia psittaci (one isolated from aborted goat foetus and the other from brain of a buffalo calf that had died of meningoencephalitis) were injected intracisternally into six goats to produce experimental mastitis. Cryostat sections of 7-8 microns thickness, obtained from udder, teat, liver and kidney of infected and control animals were incubated for histoenzymic demonstration of alkaline-(AKPase), acid-(ACPase) and adenosine-tri-(ATPase) phosphatases; lactate-(LDH) and succinate-(SDH) dehydrogenases and for reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-D). Results demonstrated that AKPase and NADPH-D declined while ACPase accumulated in acinar cells of udder while both NADPH-D and ACPase decreased in teat sinus epithelium. Hepatic canaliculi in perilobular areas of liver lobules registered complete absence of AKPase and ATPase. Hepatocytes and renal tubules accumulated LDH, SDH and NADPH-D. The interstitial connective tissue of udder and kidney presented higher levels of AKPase. Comparison of results with biochemical alterations in the level of these enzymes revealed striking discrepancies which seem to arise because of failure of biochemical procedures to discriminate between functional cells of tissue and inflammatory cells. The functional significance of histoenzymic alterations has been discussed.

Animals↗

Pneumonia due to Legionella bozemanii and Chlamydia psittaci/TWAR following renal transplantation.

Chlamydia and Legionella are recognized causes of atypical pneumonia. A case of pneumonia due to Chlamydia psittaci/TWAR and Legionella bozemanii following renal transplantation is described. Legionella bozemanii infection was diagnosed by a rise in antibodies and by isolation of the organism from bronchoscopy specimens. It is unusual to find pneumonia caused concomitantly by two such agents. This case, despite the fatal outcome, emphasises the necessity for a comprehensive approach to the diagnosis of atypical pneumonia, including culture for Legionella, especially in immunocompromised patients.

Female↗

Dominance of Chlamydia psittaci-specific IgG2 subclass in the humoral immune responses of naturally and experimentally infected cattle.

Indirect enzyme-linked immunosorbent assays were applied to differentiate Chlamydia (C.) psittaci-specific IgG1 and IgG2 levels in 143 individual serum samples from cattle with naturally occurring chlamydial infections and in 190 sequential serum samples from 26 experimentally infected pregnant cows, calves, and a bull. The mean IgG1:IgG2 ratio of naturally infected cattle was 1:4 indicating a significant (p less than 0.001) IgG2 dominance. Similar ratios were detected in the experimentally infected cattle. The dominance of IgG2 was independent of breed, sex, and age. Twenty-nine cattle had significant immunoglobulin levels to both C. psittaci and Coxiella (C.) burnetii simultaneously. The predominance of C. psittaci-specific IgG2, in contrast to the predominance of C. burnetti-specific IgG1 detected in these same individual serum samples under identical conditions, indicates that the ability to preferentially produce either IgG1 or IgG2 was not limited in these individual cattle. A transient yet significant IgG1 response was also developed in cows following chlamydia-induced abortions (immunotype 1) or in cattle infected with the polyarthritis-serositis-encephalomyelitis agents (immunotype 2). IgG1 levels decreased faster than IgG2 levels. These findings have diagnostic implications and identify the need for determining the immunoglobulin classes and subclasses of the humoral immune responses of animals and man to chlamydial infections.

Abortion, Veterinary↗

The development of proliferative responses of ovine peripheral blood mononuclear cells to Chlamydia psittaci during pregnancy.

In vitro lymphoproliferative responses to Chlamydia psittaci elementary bodies were detected in the peripheral blood mononuclear cells of pregnant sheep infected with C. psittaci. These responses were suppressed in cells collected in the immediate peri-parturient period, but returned to levels significantly above background within 14 days. Infection also suppressed the lymphoproliferative response to the T-cell mitogen Con A until abortion or lambing, but did not affect the proliferative response to the B-cell mitogen LPS.

Abortion, Veterinary↗

Immunological specificity of monoclonal antibodies to Chlamydia psittaci ovine abortion strain.

Fifty-one monoclonal antibodies were prepared by two different techniques against Chlamydia psittaci strain A22 isolated from an ovine abortion. These antibodies were tested for reactivity by the indirect immunofluorescent antibody technique with eleven reference Chlamydia strains (nine C. psittaci, one Chlamydia trachomatis and one Chlamydia pneumoniae). Four classes of specificity were recognized for monoclonal antibodies: genus, species, subspecies and type specificity. The type-specific monoclonal antibodies were non-reactive with ovine arthritis isolates. Twenty monoclonal antibodies were specific for two mammalian strains: ovine abortion A22 and K mouse. Some monoclonal antibodies were reactive with C. pneumoniae strains and non-reactive with C. trachomatis strains. All these monoclonal antibodies were very useful for improving the diagnosis of chlamydial infection, the antigenic analysis and the serotyping of C. psittaci.

Abortion, Veterinary↗

Simultaneous vaccination by three living attenuated strains of Brucella, Salmonella and Chlamydia in mice.

Associations of vaccines for simultaneous administration were successfully developed long ago, in particular in human medicine, although there have been very few attempts to associate living bacterial vaccines. Unfortunately, living vaccines can interact with one another resulting in either a virulent infection or an exclusion of one by the other. Having developed two new low virulence vaccinal strains of Chlamydia psittaci var. ovis and Salmonella abortus ovis for use in veterinary medicine, we studied associations of both and with the Brucella melitensis Rev1 vaccine in mice. There was no interaction between the Chlamydia and the Salmonella vaccines and between the Salmonella and the Brucella vaccines from the point of view of immunogenicity. In contrast, anti-Chlamydia immunity was decreased by about 15-19% when the Chlamydia vaccine was associated with the Brucella vaccine in double or triple association. Surprisingly, the Chlamydia vaccinal strain infection was slightly extended when administered in association. The simultaneous vaccination we tested could be of great interest in veterinary medicine, but special attention must be devoted to anti-Chlamydia immunity and would have to be studied in a ewe model.

Animals↗

Sequence analysis of the major outer membrane protein gene of an ovine abortion strain of Chlamydia psittaci.

The major outer membrane protein (MOMP) gene from an ovine abortion strain of Chlamydia psittaci (S26/3) has been cloned and sequenced. The gene shows the features of other chlamydial MOMPs but comparison with the previously reported sequence for the ovine abortion isolate A22/M has revealed substantial sequence divergence which is clustered into the same four intramolecular regions as the sequence variation found between C. trachomatis serovars. Subsequent restriction enzyme analysis of A22/M DNA has shown that it has an avian-type genomic profile and thus the comparison is between types rather than between strains.

Abortion, Veterinary↗

Efficacy of a bacterin prepared from Chlamydia psittaci grown in cell culture for experimental immunization of ewes.

The efficacy of a bacterin prepared from Chlamydia psittaci grown in mouse L-cells was compared to a similar bacterin prepared from C. psittaci grown in chicken embryos (CE). Both bacterins significantly reduced (P less than 0.03) incidence of abortion and weak lambs compared to non-vaccinated control ewes. The L-cell bacterin elicited a greater antibody response than the CE bacterin (P less than 0.03).

Abortion, Veterinary↗

Rapid detection of Chlamydia psittaci in vaginal swabs of aborted ewes and goats by enzyme linked immunosorbent assay (ELISA).

An enzyme linked immunosorbent assay (ELISA) for the detection of Chlamydia psittaci in vaginal swabs of aborted ewes and goats has been developed using microtiter plates coated with sheep anti-Chlamydia immunoglobulin G. This technique was compared to the direct isolation of the agent by plaque assay on McCoy cells. Among 89 specimens from animals in infected flocks, 58 were positive by both methods, seven were only positive by ELISA, and nine others were only positive by direct isolation (plaque assay). None of the 75 specimens from animals in healthy flocks gave a positive response in ELISA or the plaque assay. Unlike direct isolation in cell culture, the ELISA technique permitted the detection of Chlamydia even in the absence of special care in sampling and conservation of specimens.

Abortion, Veterinary↗

Comparison of the virulence in mice of some ovine isolates of Chlamydia psittaci.

Virulence associated with five ovine isolates of Chlamydia psittaci was compared using a mouse model. Comparable doses of each isolate were inoculated via the footpad into separate groups of 6-week-old mice. Four isolates from abortion were judged more virulent than an isolate from arthritis because of their ability to migrate from the site of infection to the spleen. Similar results were obtained using three different mouse strains. Re-isolation of C. psittaci indicated variation in susceptibility to infection between different mouse strains.

Animals↗