Experimental Trachoma Research Articles

Effect of bacterial secondary infection in an animal model of trachoma.

In trachoma the interaction between chronic chlamydial and acute bacterial conjuntivitis has been suggested as important in determining the severity of disease and, therefore, blindness. We investigated the effect of acute conjunctival infection with each of three common human pathogens, Haemophilus influenzae, Haemophilus aegyptius , and Streptococcus pneumoniae, in a model of trachoma established in cynomolgus monkeys. Although acute conjunctivitis developed, animals with trachoma were not more susceptible to infection than other monkeys, nor did they develop more severe disease as a result of the bacterial conjunctivitis. The failure of bacterial conjunctivitis to exacerbate the experimental trachoma indicates that, in this model at least, chronically maintained chlamydial infection alone is sufficient to produce the changes characteristic of trachoma.

Criteria for measuring the efficacy of trachoma vaccines in baboons.

Trachoma vaccines are usually assayed by testing their ability to protect monkeys or baboons against subsequent challenge of the conjunctiva with a pathogenic strain of trachoma/inclusion conjunctivitis (TRIC) agent. In such experiments the course of infection in vaccinated baboons was compared in terms of arbitrary scores assigned to a range of clinical signs, and of counts of TRIC inclusions in conjunctival scrapings. Analysis of many such scores indicated that after a large challenge dose of strain MRC-4s, the scores for signs of inflammation reached their maximum earlier than the follicle score; the inflammation score was closely related to the number of inclusions, whereas the follicle score was not. With this system, the optimum periods for eliciting differences between vaccinated and control measures varied according to the sign used; it was later for follicles than for inflammation or inclusions. For assessing the influence of vaccination, the mean of the inflammation scores read weekly for the first 3 weeks after challenge and the mean inclusion score over the same period were equally satisfactory, and either was rather better than the mean of three follicle scores taken over the period 3-6 weeks.For assessing the influence of vaccines or therapeutic agents on experimental trachoma it is important to determine which signs discriminate best between treated and control animals, and the optimum times for measuring them.

Experimental trachoma in owl monkeys.

Experimental trachoma in nonhuman primates has been handicapped because trachoma (as opposed to inclusion conjunctivitis) produces very mild clinical disease and minimal microbiologic changes. In a direct comparison between the Old World Taiwan monkey, Macaca cyclopis, and the New World owl monkey, Aotus trivirgatus, the latter was found to be much more susceptible. Owl monkeys manifested severe disease for a period of 2 or more weeks, while none was observed in Taiwan monkeys during the same period of time. Given identical inoculations of 2,000 EID50 in the left eye and 20 EID50 in the right eye, six Taiwan monkeys on the 7th day averaged 21 inclusions in the left eye and one in the right. Comparable figures for six owl monkeys were 641 and 1,396, respectively.

Pannus with Experimental Trachoma and Inclusion Conjunctivitis Agent Infection of Taiwan Monkeys

It has been established by previous inves­ tigators that common laboratory animals are refractory to trachoma and that only pri­ mates contract the disease. After the etiologic agent became available through cultiva­ tion in yolk sacs of embryonated eggs, ex­ perimental trachoma in monkeys with the organisms propagated in eggs was reported by Thygeson and associates. They reported that the experimental disease was not ac­ companied by pannus, cicatrization or major involvement of the upper tarsus and, in these respects, it differed sharply from human trachoma. Inclusion conjunctivitis in man has been considered to be different from trachoma clinically, in that it affects mainly the lower conjunctivas, does not cause pannus or con.junctival scars and has a tendency to run a more acute but shorter course. In addition, it is epidemiologically different from tracho­ ma in that it is associated with genital infec­ tion. The organisms of inclusion conjunctiv­ itis can be cultivated by similar egg tech­ niques. Again, experimental eye disease can be produced only in primates and is report­ ed to be generally more severe than trachoma. As in the case of experimental trachoma, no pannus or scars have been re­ ported.

Immunogenicity of experimental trachoma vaccines in baboons: III. Experiments with inactivated vaccines

Heating at 37° C. for 5 days completely abolished the capacity of a trachoma/inclusion conjunctivitis (TRIC) vaccine to protect baboons against conjunctival infection. Treatment with formalin also impaired or abolished immunogenicity.The rate of inactivation of TRIC agent by ultraviolet light was exponential, and was about 7 times faster than that of a suspension of vaccinia virus of comparable turbidity. By contrast with vaccinia, irradiation of TRIC agent with twice the dose of ultraviolet light needed to destroy infectivity resulted in loss of immunogenicity.The deleterious action of these inactivation procedures on the potency of TRIC vaccines may be explained in terms of damage to a protective antigen; alternatively, live vaccines may be more immunogenic because TRIC agents are capable of multiplying within primate hosts after parenteral injection.Unlike the same type of variant of another strain of inclusion conjunctivitis, the ‘fast-killing’ variant of MRC-4 was still pathogenic for the baboon conjunctiva.

Immunogenicity of experimental trachoma vaccines in baboons: I. Experimental methods, and preliminary tests with vaccines prepared in chick embryos and in HeLa cells

Parallel titrations of a strain of trachoma (MRC–221) and one of inclusion conjunctivitis (MRC–4) in the baboon conjunctiva and in chick embryos suggest that ten to twenty 50% egg infective doses are equivalent to one 50% baboon infective dose; but that at least 1000 egg infective doses are needed to induce moderate or severe infections in all of a given number of baboons.For vaccine experiments in baboons, a system of scoring physical signs and presence of inclusion bodies was devised; the significance of differences in vaccinated and control animals in their response to conjunctival challenge was determined by analysis of variance. An aqueous suspension of live MRC–4 grown in the yolk sac was given as two subcutaneous doses and one intravenous dose at weekly intervals, and protected all of six baboons challenged with the homologous strain; three similarly spaced subcutaneous doses were less effective. The immunity induced by this vaccine waned considerably during the ensuing 15 months. Vaccine prepared from a live ‘fast-killing’ variant of MRC–4 grown in HeLa cells was less effective than MRC–4 itself in protecting baboons against infection with the parent strain.Although both yolk sac and HeLa cell vaccines induced the formation of antibody fixing complement with trachoma group antigen, the serum titres in individual animals at the time of challenge were unrelated to the degree of protection; during a 15 month observation period there were pronounced falls in the titres of antibody induced either by vaccination or by challenge with egg-grown TRIC agent.We wish to thank Dr I. Sutherland (M.R.C. Statistical Research Unit) for his helpful advice during the early stages of this work. We are also greatly indebted to Mr P. Avis (Pfizer Ltd.) for his advice and for undertaking the statistical computations; and to Miss Anne Smith and Miss Pay Storey (M.R.C. Trachoma Research Unit) for doing the complement fixation tests.

Immunogenicity of experimental trachoma vaccines in baboons. II. Experiments with adjuvants, and tests of cross-protection.

A mineral oil adjuvant failed to enhance or to prolong the somewhat shortlived immunity induced in baboons by trachoma/inclusion conjunctivitis (TRIC) vaccines, and was of little or no value in increasing or prolonging the formation of group complement-fixing (CF) antibody. Vaccines prepared with protamine sulphate or with calcium phosphate were no more immunogenic than the untreated parent suspensions.Cross tests with aqueous vaccines revealed antigenic differences in the TRIC agents examined, in terms of their ability to protect against conjunctival challenge. Strain MRC–1/OT differed from MRC–17 and from MRC–4, and MRC–187 from MRC–4f.The four Gambian trachoma agents tested were much less effective than the MRC–4 strain of inclusion conjunctivitis in inducing group CF antibody in baboons. The titre of circulating antibody bore no relation to the state of immunity to conjunctival challenge.In three baboons given mineral oil adjuvant vaccine and in one given aqueous vaccine the conjunctival responses to subsequent challenge were significantly enhanced. This reaction may be an expression of a hypersensitive state induced by relatively ineffective vaccines; like immunity, it is unrelated to the titre of CF antibody in the serum.

Field studies of protection from infection by experimental trachoma virus vaccine in preschool-aged children on Taiwan.

Field trials of experimental egg-grown trachoma virus vaccine have been carried out in preschool-aged children in 2 rural areas on Taiwan. Four hundred and five children randomly divided between a placebo and trachoma vaccine groups have been followed for 2 1/2 years during which 4 injections of vaccine have been given. Eighteen per cent of the placebo group have converted to trachoma compared to 8% of those receiving vaccine. An average of 2.98 months of trachoma have been observed in the placebo group compared to 1.22 months in the vaccine group. Both these measures suggested that the vaccine was approximately 60% effective in reducing trachoma. A third study in an urban area with 89 children showed similar vaccine effectiveness.

Cell cultures for detection of trachoma virus from experimental simian infections.

SummaryOcular specimens, taken repeatedly from experimental trachoma in 2 rhesus monkeys, were cultured in parallel in McCoy cell cultures and in yolk sacs of embryonated eggs, to explore the feasibility of using the cell culture method of demonstrating virus as an aid in recognizing the infection. The results indicate a potential usefulness of the cell culture method in which the test can be read in 48 hours. When washing of the conjunctival sacs was compared with swabbing with dry cotton as a method of obtaining material for culture, the former procedure yielded a slightly greater number of positive tests. Bacteriologic studies on the specimens showed that the levels of streptomycin and ristocetin used in the cell cultures and yolk sacs satisfactorily protected against contamination by a variety of bacterial types.

The effect of trachoma virus vaccine on the course of experimental trachoma infection in blind human volunteers.

The TRIC-Taiwan-1-1958 strain of elementary body virus isolated from a trachoma patient on Taiwan has been proven capable of reproducing trachoma by experimental inoculation of six human volunteers. Virus material derived from the seventh passage in embryonated hen eggs caused the clinical picture of trachoma in every inoculation, even at the dilution of 10(-4) of infected yolk sacs (approximately 1 EID(50)). There was a similar clinical picture with each inoculation beginning with an acute follicular conjunctivitis which progressed for 4 months and then persisted with chronic changes until 9 months when treatment was begun. The illness was generally more acute than would be expected in natural trachoma. That trachoma was reproduced was shown by the involvement of the cornea with epithelial keratitis and pannus, and by the occurrence of gelatinous follicles and eventual cicatrization of the conjunctiva. These clinical findings were supported by repeated demonstrations of typical inclusion bodies of Halberstaedter-Prowazek from conjunctival and even corneal cells, by repeated reisolation of elementary body virus in egg yolk sacs, and by the development of complement-fixing antibody with a "specific" trachoma antigen in each volunteer. Control inoculations with adenovirus type 4 and normal yolk sac showed different clinical and laboratory findings. Experimental trachoma vaccine was given to three of the volunteers to study its effect on the course of illness. An antibody response to the vaccine was demonstrated and there was a modification of disease in the volunteers receiving vaccine. While the three volunteers who received placebo each developed cross-infection of their uninoculated eye and had an acute reactivation of the bilateral disease after 1 to 2 months of antibiotic eye ointment therapy, the vaccinated volunteers remained free of infection in uninoculated eyes and showed no relapse after ointment therapy. Treatment with sulfamethoxypyridazine, a sulfa drug with prolonged action, proved to be an effective and relatively simple method of therapy for experimental trachoma.

EXPERIMENTAL TRACHOMA PRODUCED BY A WESTERN AUSTRALIAN VIRUS

Medical Journal of AustraliaVolume 1, Issue 16 p. 597-597 Current Comment EXPERIMENTAL TRACHOMA PRODUCED BY A WESTERN AUSTRALIAN VIRUS First published: 01 April 1961 https://doi.org/10.5694/j.1326-5377.1961.tb68954.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume1, Issue16April 1961Pages 597-597 RelatedInformation

Observations on Experimental Trachoma in Monkeys Produced by Strains of Virus Propagated in Yolk Sac

Observations on Experimental Trachoma in Monkeys Produced by Strains of Virus Propagated in Yolk Sac

Experimental trachoma produced by a West Australian virus.

Experimental trachoma produced by a West Australian virus.

Experimental trachoma produced by cultured virus. Part II.

Experimental trachoma produced by cultured virus. Part II.

The Treatment of Trachoma with Sulfanilamide: A Report of 31 Cases

In February 1938 Dr. Fred Loe, of Rosebud, S. D., notified us of his successful treatment of trachoma in Indian subjects with sulfanilamide, the details of which he has recently published. 1 Favorable results were also reported by Lian. 2 After obtaining marked improvement with this treatment in certain isolated cases and rapid cure in 2 cases of experimental trachoma in baboons, we decided to test the drug on a series of persons with previously untreated active follicular trachoma in whom corneal progress could be followed by means of the slit lamp and the corneal microscope. Accordingly, we selected 14 Apache Indian children with active follicular trachoma, 12 to be treated and 2 to be kept untreated as controls. All children had pannus and exhibited corneal activity, as evidenced by dilated pannus vessels, subepithelial infiltrates and fluorescein-staining punctate epithelial lesions. Typical epithelial cell inclusions, characteristic of active trachoma, were demonstrated

Treatment of Trachoma with Sulfanilamide

In February 1938 Dr. Fred Loe, of Rosebud, S. D., notified us of his successful treatment of trachoma in Indian subjects with sulfanilamide, the details of which he has recently published. 1 Favorable results were also reported by Lian. 2 After obtaining marked improvement with this treatment in certain isolated cases and rapid cure in 2 cases of experimental trachoma in baboons, we decided to test the drug on a series of persons with previously untreated active follicular trachoma in whom corneal progress could be followed by means of the slit lamp and the corneal microscope. Accordingly, we selected 14 Apache Indian children with active follicular trachoma, 12 to be treated and 2 to be kept untreated as controls. All children had pannus and exhibited corneal activity, as evidenced by dilated pannus vessels, subepithelial infiltrates and fluorescein-staining punctate epithelial lesions. Typical epithelial cell inclusions, characteristic of active trachoma, were demonstrated

Possible Relation of the Inclusion Body of Trachoma to Pathoenesis.

Among other reasons for regarding the causative agent of trachoma as a virus is the cytoplasmic inclusion of the epithelial cells of the conjunctiva, and occasionally even of the cornea. Marshalling together evidence that is essentially morphological, a number of investigators beginning with Halberstaedter and Prowazek have attempted to prove that the inclusion represents a mass or “colony” of infectious units. While conducting a broader study on the inclusion of trachoma and clinically allied diseases in this laboratory, observations have been made by indirect approach which are sufficiently interesting on this phase of the subject to merit their publication. In testing out the infective capacity of conjunctival tissues from different patients with trachoma, monkeys in one group were inoculated with individual tissues, all of which were found to contain inclusions. In a second group, monkeys were inoculated in a similar manner with tissues lacking inclusions. In a third group, monkeys were inoculated with pooled tissues, some of which were inclusion-bearing and others inclusion-deficient. A study of the data pertinent to these experiments reveals several interesting and suggestive results. Thus, 70 monkeys (Macacus rhesus) were inoculated with individual tissues from 37 patients, all containing inclusions. Typical experimental trachoma occurred in 35, or 50%, of the animals tested. On the other hand, 158 monkeys were inoculated with separate tissues from 112 patients in whom inclusions were not demonstrated. Of these animals 35, or 22%, were specifically infected. The pooled tissues which were derived from 89 patients, 44 with and 45 without inclusions, were inoculated into 106 monkeys and of these, 41, or 38%, were infected. If the figures for monkeys infected in each group are plotted in the form of a curve, the result is practically a straight line, with inclusion-bearing tissues inducing most infections, the inclusion-lacking tissues inducing least or approximately half as many infections, and the tissues pooled as indicated occupying an almost mathematically half-way position between the two extremes.

TREATMENT OF TRACHOMA WITH SULFANILAMIDE

In February 1938 Dr. Fred Loe, of Rosebud, S. D., notified us of his successful treatment of trachoma in Indian subjects with sulfanilamide, the details of which he has recently published. 1 Favorable results were also reported by Lian. 2 After obtaining marked improvement with this treatment in certain isolated cases and rapid cure in 2 cases of experimental trachoma in baboons, we decided to test the drug on a series of persons with previously untreated active follicular trachoma in whom corneal progress could be followed by means of the slit lamp and the corneal microscope. Accordingly, we selected 14 Apache Indian children with active follicular trachoma, 12 to be treated and 2 to be kept untreated as controls. All children had pannus and exhibited corneal activity, as evidenced by dilated pannus vessels, subepithelial infiltrates and fluorescein-staining punctate epithelial lesions. Typical epithelial cell inclusions, characteristic of active trachoma, were demonstrated

NATURE OF THE FILTRABLE AGENT OF TRACHOMA

It is now generally agreed that none of the bacteria which have been found on the trachomatous conjunctiva are concerned etiologically in the disease. In 1912 Nicolle, Blaizot and Cuenod1concluded, on the basis of two filtration experiments in which they had employed modified Berkefeld V filters, that the agent of trachoma was filtrable. In the first experiment a bacteria-free filtrate of trachomatous material produced a disease typical of experimental trachoma in a Macacus inuus (Barbary ape) which was proved to be trachoma by transfer to a blind human eye. In the second experiment a bacteria-free filtrate proved infectious for a chimpanzee. Confirmation of the filtrability of the agent of trachoma has come from the experiments of Thygeson and Proctor2with baboons, Thygeson, Proctor and Richards3with a human volunteer and Julianelle, Morris and Harrison4with Macacus rhesus monkeys. These investi- gators have found

Studies On the Infectivity of Trachoma: IV. on the Bacteria Cultivable from Trachoma and Clinically Similar Conditions

An investigation of the bacterial flora in 243 cases of uncomplicated trachoma has been made. For comparative purposes cultures were obtained also from the conjunctivae of (1) a group of normal persons, (2) 50 cases of spontaneous folliculosis in children. (3) 10 cases of inclusion blennorrhea, and (4) a variety of acute conjunctivitides of uncertain diagnosis. No organism cultivated was typical of trachoma. The flora did not vary with severity or clinical stages of the disease or with presence or absence of epithelial-cell inclusions. All bacteria encountered in trachoma were isolated with similar frequency in other eye conditions. The same bacteria were also found in normal eyes, although less often. Individually or pooled, each variety of organism isolated was inoculated a number of times into the conjunctivae of monkeys. Experimental trachoma was never induced even though the tissues from which the cultures were isolated did produce this condition. Filtrates of infectious trachomatous material when inoculated together with cultures supplied no supplementary factors capable of rendering the organisms specifically infectious. It is concluded that none of the bacteria cultivable from trachoma is able to induce the experimental disease in monkeys. From the Oscar Johnson Institute, Washington University School of Medicine. Conducted under a grant from the Commonwealth Fund of New York, N.Y. An investigation of the bacterial flora in 243 cases of uncomplicated trachoma has been made. For comparative purposes cultures were obtained also from the conjunctivae of (1) a group of normal persons, (2) 50 cases of spontaneous folliculosis in children. (3) 10 cases of inclusion blennorrhea, and (4) a variety of acute conjunctivitides of uncertain diagnosis. No organism cultivated was typical of trachoma. The flora did not vary with severity or clinical stages of the disease or with presence or absence of epithelial-cell inclusions. All bacteria encountered in trachoma were isolated with similar frequency in other eye conditions. The same bacteria were also found in normal eyes, although less often. Individually or pooled, each variety of organism isolated was inoculated a number of times into the conjunctivae of monkeys. Experimental trachoma was never induced even though the tissues from which the cultures were isolated did produce this condition. Filtrates of infectious trachomatous material when inoculated together with cultures supplied no supplementary factors capable of rendering the organisms specifically infectious. It is concluded that none of the bacteria cultivable from trachoma is able to induce the experimental disease in monkeys. From the Oscar Johnson Institute, Washington University School of Medicine. Conducted under a grant from the Commonwealth Fund of New York, N.Y.