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

Ocular anti-inflammatory activity of prednisolone acetate loaded chitosan-deoxycholate self-assembled nanoparticles

Background and purpose: Conventional topical ophthalmic aqueous solutions and suspensions are often associated with low bioavailability and high administration frequency, pulsatile dose and poor exposure to certain ocular parts. The aim of this study was to develop an ophthalmic nanoparticles loaded gel, for delivering prednisolone acetate (PA), to increase dosing accuracy, bioavailability, and accordingly, efficiency of PA in treating inflammatory ocular diseases. Methods: A novel formulation of self-assembled nanoparticles was prepared by the complexation of chitosan (CS) and, the counter-ion, sodium deoxycholate (SD), loaded with the poorly-water-soluble PA. Particle size, zeta potential, encapsulation efficiency (EE) and drug loading content (LC) of prepared nanoparticles were assessed. Moreover, the nanoparticles were characterized using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Drug release and eye anti-inflammatory potential of the prepared novel formulation was investigated. Results: Mean particle size of the nanoparticles have dropped from 976 nm ±43 (PDI 1.285) to 480 nm ±28 (PDI 1.396) when the ratio of CS-SD was decreased. The incorporation of 0.1-0.3% of polyvinyl alcohol (PVA), in the preparation stages, resulted in smaller nanoparticles: 462 nm ±19 (PDI 0.942) and 321 nm ±22 (PDI 0.454) respectively. DSC and FTIR results demonstrated the interaction between CS and SD, however, no interactions were detected between PA and CS or SD. Drug release of PA as received, in simulated tears fluid (pH 7.4), showed a twofold increase (reaching an average of 98.6% in 24 hours) when incorporated into an optimized nanoparticle gel formulation (1:5 CS-SD). Conclusion: The anti-inflammatory effect of PA nanoparticles loaded gel on female guinea pig eyes was significantly superior to that of the micronized drug loaded gel (P < 0.05).

A Review on Chlamydial Diseases in Animals: Still a Challenge for Pathologists?

Chlamydiae have a worldwide distribution causing a wide range of diseases in human hosts, livestock, and companion animals as well as in wildlife and exotic species. Moreover, they can persist in their hosts as asymptomatic infections for extended periods of time. The introduction of molecular techniques has revolutionized the Chlamydia field by expanding the host range of known chlamydial species but also by discovering new species and even new families of bacteria in the broader order Chlamydiales. The wide range of hosts, diseases, and tissues affected by chlamydiae complicate the diagnosis such that standard diagnostic approaches for these bacteria are rare. Bacteria of the Chlamydiales order are small and their inclusions are difficult to detect by standard microscopy. With the exception of avian and ovine chlamydiosis, macroscopic and/or histologic changes might not be pathognomic or indicative for a chlamydial infection or even not present at all. Moreover, detection of chlamydial DNA in specimens in the absence of other methods or related pathological lesions questions the significance of such findings. The pathogenic potential of the majority of recently identified Chlamydia-related bacteria remains largely unknown and awaits investigation through experimental or natural infection models including histomorphological characterization of associated lesions. This review aims to summarize the historical background and the most important developments in the field of animal chlamydial research in the past 5 years with a special focus on pathology. It will summarize the current nomenclature, present critical thoughts about diagnostics, and give an update on chlamydial infections in domesticated animals such as livestock, companion animals and birds, as well as free-ranging and captive wild animals such as reptiles, fish, and marsupials.

The effect of infectious dose on humoral and cellular immune responses in Chlamydophila caviae primary ocular infection

Following infection, the balance between protective immunity and immunopathology often depends on the initial infectious load. Several studies have investigated the effect of infectious dose; however, the mechanism by which infectious dose affects disease outcomes and the development of a protective immune response is not known. The aim of this study was to investigate how the infectious dose modulates the local and systemic humoral and the cellular immune responses during primary ocular chlamydial infection in the guinea pig animal model. Guinea pigs were infected by ocular instillation of a Chlamydophila caviae-containing eye solution in the conjunctival sac in three different doses: 1×10², 1×10⁴, and 1×10⁶ inclusion forming units (IFUs). Ocular pathology, chlamydial clearance, local and systemic C. caviae-specific humoral and cellular immune responses were assessed. All inocula of C. caviae significantly enhanced the local production of C. caviae-specific IgA in tears, but only guinea pigs infected with the higher doses showed significant changes in C. caviae-specific IgA levels in vaginal washes and serum. On complete resolution of infection, the low dose of C. caviae did not alter the ratio of CD4⁺ and CD8⁺ cells within guinea pigs’ submandibular lymph node (SMLN) lymphocytes while the higher doses increased the percentages of CD4⁺ and CD8⁺ cells within the SMLN lymphocytes. A significant negative correlation between pathology intensity and the percentage of CD4⁺ and CD8⁺ cells within SMLN lymphocyte pool at selected time points post-infection was recorded for both 1×10⁴, and 1×10⁶ IFU infected guinea pigs. The relevance of the observed dose-dependent differences on the immune response should be further investigated in repeated ocular chlamydial infections.

Infectious dose and repeated infections are key factors influencing immune response characteristics in guinea pig ocular chlamydial infection

The aim of this study was to determine whether infectious dose of Chlamydia caviae after repeated infections influences the immunological responses and subsequent clearance of pathogen at the ocular surface of guinea pigs. Animals were infected three times via the conjunctiva at six- and twelve-week intervals by applying either 1 × 10(4) or 1 × 10(6) inclusion-forming units (IFUs) of C. caviae. Ocular pathology, infection course, C. caviae-specific serum IgG levels and their capacity to bind and neutralize infection ex vivo were assessed. Animals infected with 1 × 10(4) IFUs had completely diminished ocular infection and pathology after the 2nd infection with increased levels of C. caviae-specific serum IgG and their effective capacity to bind and neutralize C. caviae. Only partial protection was observed in animals infected with 1 × 10(6) IFUs after the 2nd and 3rd infections. Our findings show that full protection was observed in animals repeatedly infected with the lower dose. The lower dose appeared not to compromise the host immune system, thereby enabling fast clearance of the pathogen and the establishment of competent neutralizing antibodies.

Essential role for neutrophils in pathogenesis and adaptive immunity in Chlamydia caviae ocular infections

Trachoma, the world's leading cause of preventable blindness, is produced by chronic ocular infection with Chlamydia trachomatis, an obligate intracellular bacterium. While many studies have focused on immune mechanisms for trachoma during chronic stages of infection, less research has targeted immune mechanisms in primary ocular infections, events that could impact chronic responses. The goal of this study was to investigate the function of neutrophils during primary chlamydial ocular infection by using the guinea pig model of Chlamydia caviae inclusion conjunctivitis. We hypothesized that neutrophils help modulate the adaptive response and promote host tissue damage. To test these hypotheses, guinea pigs with primary C. caviae ocular infections were depleted of neutrophils by using rabbit antineutrophil antiserum, and immune responses and immunopathology were evaluated during the first 7 days of infection. Results showed that neutrophil depletion dramatically decreased ocular pathology, both clinically and histologically. The adaptive response was also altered, with increased C. caviae-specific IgA titers in tears and serum and decreased numbers of CD4(+) and CD8(+) T cells in infected conjunctivae. Additionally, there were changes in conjunctival chemokines and cytokines, such as increased expression of IgA-promoting interleukin-5 and anti-inflammatory transforming growth factor β, along with decreased expression of T cell-recruiting CCL5 (RANTES). This study, the first to investigate the role of neutrophils in primary chlamydial ocular infection, indicates a previously unappreciated role for neutrophils in modulating the adaptive response and suggests a prominent role for neutrophils in chlamydia-associated ocular pathology.

Clinical examination and laboratory tests for estimation of trachoma prevalence in a remote setting: what are they really telling us?

Worldwide, an estimated 84 million people have active trachoma and 7.6 million people have trachomatous trichiasis. WHO's SAFE strategy is an effective tool in the worldwide effort to eliminate blinding trachoma, but its institution and monitoring requires a simple, reliable, and cost-effective method to detect disease. To date, clinical examination has provided the main method of diagnosis. Detection of Chlamydia trachomatis with nucleic acid amplification tests does not always correlate well with clinical findings, which has prompted the suggestion that these methods should replace clinical examination. However, a review of the research carried out in animals and human beings suggests the relation between laboratory tests and clinical examination is due to the kinetics of trachoma and not to an inherent problem in either detection system. Given the increased difficulties of using laboratory tests in parts of the world where trachoma is endemic, we should not abandon clinical grading as a tool to assess the need for, and the effectiveness of, trachoma intervention programmes.

Experimental infection of the conjunctival sac of lambs with Mycoplasma conjunctivae

Ovine keratoconjunctivitis (OKC) identical to that seen in field cases was produced experimentally with 10(6) colony forming units of an isolate of Mycoplasma conjunctivae which had been passaged three times in vitro. Cytological studies showed that the peak neutrophil count in conjunctival exudate occurred 8 days after inoculation of the conjunctival sac. Rapid onset of clinical signs in the uninoculated eye showed the ease with which the organism could be transferred from affected to unaffected eyes.

Chlamydia trachomatis infections in infants

In recent years considerable progress has been made in understanding chlamydial infections. The spectrum of pediatric Chlamydia trachomatis infection includes neonatal inclusion conjunctivitis, infantile pneumonia, occasional respiratory or genital tract infections in older children and sexually transmitted diseases in adolescents. The role of maternal chlamydial infection in prematurity and in perinatal death is currently an area of active study. We outline the current knowledge of the biologic characteristics of C. trachomatis, the epidemiologic features of chlamydial infection, and the clinical aspects, diagnosis and treatment of neonatal chlamydial infections.

Management and prevention of ocular viral and chlamydial infections

A majority of cases of preventable and/or curable ocular morbidity and blindness are caused by ocular infections. They may account for 70 to 90% of all ocular morbidity seen by family doctors, general practitioners, health centers, and local ophthalmologists in both developed and developing countries. Unfortunately, most health authorities and doctors, including ophthalmologists, consider these diseases to be of little or no importance because they are not fully aware of the high prevalence of these infections and the blinding sequelae which may occur following incorrect diagnosis and treatment. Also, they are not aware of the social and economic impact of these infections in the absence of proper management and implementation of preventive measures. In this review, we examine present knowledge of chlamydial and common viral ocular infections. We discuss the problems of diagnosis, management, and prevention and propose solutions relevant to developed and developing countries.

Responses to tuberculin in the guinea-pig eye as a model of cell mediated immune responses in the external eye

The clinical and histological findings in an animal model of ocular cell mediated immune responses are described. These were evoked in sensitised guinea-pigs by dropping tuberculin into the conjunctival sac or injecting it under the palpebral conjunctiva. When tuberculin was dropped into the conjunctival sac, higher doses were required to evoke a strong response than when it was injected subconjunctivally. When high doses of antigen were used for challenge, a mild response was observed in unchallenged contralateral eyes. The cellular response at low doses of tuberculin consisted predominantly of mononuclear cells. At higher doses the cellular infiltrate was more pronounced, and polymorphonuclear cells tended to predominate 24 hours after challenge, while at 48 hours mononuclear cells predominated.

Chlamydial pelvic infection in cats: a model for the study of human pelvic inflammatory disease

The inoculation of feline keratoconjunctivitis agent (Chlamydia psittaci) directly into the oviducts of eight cats produced an acute disease that was characterised by hyperaemia of the tissue and pronounced polymorphonuclear leucocyte infiltration of the epithelium and subepithelial stroma. The lumens of the tubes contained exudates of desquamated epithelial cells and polymorphonuclear leucocytes. After about 30 days the disease subsided leaving chronic inflammation with the tissue infiltrated with both polymorphonuclear and mononuclear cells. Fimbrial scarring and formation of adhesions were apparent by 40 to 50 days after inoculation. Chlamydiae were isolated in McCoy cell cultures from most cats, in one for as long as 51 days after inoculation. Inclusions were seen in histological sections or smears of cells from the fimbriae of four of the eight cats. Six of the eight cats developed antibodies to feline keratoconjunctivitis agent, which were detectable as early as 12 days after inoculation. To facilitate repeated examinations of the cats' fallopian tubes, techniques for laparoscopy in cats and for the collection of specimens while under laparoscopic examination were developed. The latter technique has since been applied successfully in man.

A study of inclusion conjunctivitis in newborn and young adults. Clinical picture, culture, conjunctival scrapings and cytology of the tear fluid in 12 cases

Chlamydia trachomatis were cultured from the conjunctiva of 8 newborn babies and 4 young adults' (age 20-30 years) affected with acute or therapy-resistant chronic conjunctivitis. The newborn had acute purulent conjunctivitis noticed 4 to 12 days after birth. Five of them had been treated with topical chloramphenicol without effect before the diagnosis was made. They responded well to topical tetracycline ointment, but 3 relapsed. Two developed chronic conjunctivitis and respiratory tract infection, one under long time topical chloramphenicol treatment. The adults had a chronic, in 3 unilateral, conjunctivitis with pronounced follicularly (3) or papillary (1) conjunctival hypertrophy. Different degrees of pseudoptosis, micropannus and corneal infiltrates (in 3) were noticed. In the tear fluid, the quantitative pipette method revealed inflammation shown by neutrophilic granulocytes and lymphocytes with an appreciable predominance of the former in the newborn, while less so in the adults. In the newborn the diagnosis was easily made by culture and by demonstrating inclusions bodies in Giemsa-stained conjunctival scrapings. In the adults the methods were less sensitive. A negative response to one culture does not preclude chlamydial infection.

Unusual features in the conjunctiva and cornea of the normal guinea-pig: clinical and histological studies

Clinical and histological studies of the outer eyes of newborn and adult female guinea-pigs were carried out together with histological studies of fetal eyes. Fine superficial corneal vessels, extending from the limbus, were seen in most newborn and adult eyes and were also present in histological preparations of fetal eyes. These vessels were therefore considered to be features of the normal guinea-pig eye. Masses of tissue composed of lymphoid cells, which were often organised into germinal centres, were found in the fornices of newborn and adult eyes. Smaller accumulations of lymphoid cells were found in fetal eyes, and this lymphoid tissue was therefore also considered to be a normal feature of the guinea-pig eye. In adult eyes mild but short-lived oedema or hyperaemia of the palpebral conjunctiva was quite common. There were no differences in the amounts of conjunctival cellular infiltration in these eyes c found in fetal eyes, and this lymphoid tissue was therefore also considered to be a normal feature of the guinea-pig eye. In adult eyes mild but short-lived oedema or hyperaemia of the palpebral conjunctiva was quite common. There were no differences in the amounts of conjunctival cellular infiltration in these eyes c found in fetal eyes, and this lymphoid tissue was therefore also considered to be a normal feature of the guinea-pig eye. In adult eyes mild but short-lived oedema or hyperaemia of the palpebral conjunctiva was quite common. There were no differences in the amounts of conjunctival cellular infiltration in these eyes compared with normal eyes, and these inflammatory changes were therefore not considered to be significant.

Chlamydial genital infection in prostitutes in Iran

The prevalence of chlamydial genital infection was studied in 177 prostitutes in Iran; 100 in Teheran and 77 in the port of Bandar Abbas. Chlamydia trachomatis was isolated in eight (6.9%) of 116 patients with valid cultures. Type-specific antibodies were found against C trachomatis serotypes D to K (genital serotypes) in 94.2% and against serotypes A to C (trachoma serotypes) in 2% of the prostitutes. Type-specific IgM at a titre of greater than or equal to 8, indicating current infection, was found in 29.2%, whereas type-specific IgG at a titre greater than or equal to 64, suggesting a current or recent infection, was present in 71.5%. The lower chlamydial isolation rate in these women may have been due to previous treatment with antichlamydial drugs and because of immune responses resulting from repeated reinfection with chlamydiae. The results indicate that in Iran prostitutes are commonly infected with C trachomatis and are probably a major reservoir of chlamydial genital infection.

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.

Transmission of chlamydiae by the housefly

The ability of the housefly to carry viable Chlamydia trachomatis and to transmit a chlamydial ocular infection was studied under laboratory conditions. After feeding flies (Musca domestica) on suspensions of egg yolk sac infected with C. trachomatis serotypes A or B (responsible for hyperendemic trachoma) the agents were reisolated from flies' intestines for up to 6 hours and from their legs and/or proboscises for up to 2 hours. It was found that the viability of chlamydiae is dependent on the protective effect of yolk concentration in the original inoculum. Results of experiments with guinea-pig inclusion conjunctivitis as an animal model show that under laboratory conditions flies can readily transmit this chlamydial ocular infection from one animal to another. These results suggest that under field conditions flies can play an important role in the transmission of trachoma, particularly in areas with favourable conditions such as a large reservoir of infection among children with severe trachoma, copious eye discharge caused by trachoma and associated bacterial infections, a large fly population, and close proximity of children in large family groups.

Development of chronic conjunctivitis with scarring and pannus, resembling trachoma, in guinea-pigs

Guinea-pigs were repeatedly infected with guinea-pig inclusion conjunctivitis agent. Reinfection caused severe conjunctival inflammation, and repeated reinfection led to chronic inflammation lasting for many months. This was followed by the development of pannus, follicles on the palpebral conjunctivae, scarring of the lower palpebral conjunctiva, and deformities of the lower lid. Reinfection was accompanied by small numbers of inclusion-bearing cells, small numbers of polymorphonuclear cells, and high numbers of mononuclear cells. There was no increase in the level of serum antibodies. The chronic conjunctivitis was associated with high numbers of mononuclear cells and no inclusions or polymorphonuclear cells. The response to reinfection appears to be a delayed-type hypersensitivity reaction, and we suggest that the chronic inflammation, pannus, scarring, and lid deformities associated with hyperendemic trachoma may be due to repeated reinfection combined with delayed-type hypersensitivity.