Immune responses to chlamydial antigens in humans

Chlamydial infections

Chlamydia trachomatis is a unique intracellular parasite that causes a number of common sexually transmitted disease syndromes, including nongonococcal urethritis in both men and women, epididymitis in men, and pelvic inflammatory disease in women. Infants exposed at delivery are at risk for the development of conjunctivitis and pneumonia. There is strong evidence that Chlamydia is a cause of obstructive infertility and ectopic pregnancy in women. It appears that these complications result from the chronic inflammatory response and secondary scarring that are elicited by long-term asymptomatic or nearly asymptomatic fallopian tube infections. Because treatment with tetracycline, doxycycline, or erythromycin is simple, effective, and inexpensive, major efforts should be put into identifying asymptomatic young women through screening of the subpopulations at highest risk. These include sexually active adolescent women and older women who are not monogamous. Blacks are at higher risk than other ethnic groups for infection. The cost of diagnosing chlamydial infection has decreased with the introduction of new nonculture diagnostic tests. This should increase the availability of testing for screening purposes. It is critical to remember that male sex partners of infected women must be treated; otherwise all efforts to prevent long-term complications by identifying and treating asymptomatic women are doomed to failure.

Role of cell-mediated immunity in the resolution of secondary chlamydial genital infection in guinea pigs infected with the agent of guinea pig inclusion conjunctivitis

Guinea pigs which have recovered from a genital infection with the agent of guinea pig inclusion conjunctivitis demonstrate strong immunity to reinfection for a short period of time but then become susceptible to reinfection. The secondary infection is markedly shortened in duration and decreased in intensity. Previous studies have indicated an important role for humoral immunity in resistance to and in recovery from reinfection. However, the contribution of cell-mediated immunity to immunity toward or recovery from a secondary infection is not clear. Guinea pigs were infected in the genital tract with guinea pig inclusion conjunctivitis and were challenged at either 30 or 75 days after the primary infection. Prior to challenge, one group of animals were injected with rabbit anti-guinea pig thymocyte serum (ATS) while control groups received either normal rabbit serum or no treatment. Treatment was continued daily for the course of the experiment. On day 30, ATS-treated guinea pigs had a slightly higher rate of reinfection, and generally the infection persisted longer than in controls. On day 75, all animals became reinfected upon challenge, but control animals resolved their infections in 3 to 9 days. In contrast, most ATS-treated animals remained infected throughout the course of the experiment. Although the animals became reinfected, the levels of chlamydiae were much lower than those observed during the primary infection. ATS treatment abrogated T-cell responses, but serum and secretory antibody responses remained normal. Histopathological examination revealed some decrease in mononuclear infiltration of endocervical and uterine tissues in ATS-treated animals. These data indicate that previously infected guinea pigs require both cell-mediated immunity and humoral immunity for resolution of a challenge infection.

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.

Susceptibility to reinfection after a primary chlamydial genital infection

Female guinea pigs which had been infected genitally with the agent of guinea pig inclusion conjunctivitis were challenged at various times after infection with fresh inocula to determine the duration of immunity resulting from the primary infection. At 30 days after infection, most guinea pigs were resistant to reinfection, as indicated by the inability to isolate chlamydiae from cervical swabs. However, at 77, 155, and 294 days, all animals became reinfected, although the course of the infection was abbreviated and of lower intensity. When various immune parameters were examined, a decrease in antibodies in both serum (immunoglobulin G [( IgG]) and genital secretions (IgA, IgG) was observed after 30 days. A decrease in antibodies to the major outer membrane protein and an 84K component was noted in serum. In genital secretions, IgA antibodies to all major chlamydial components declined markedly after 30 days. Cell-mediated immunity as measured by proliferation of peripheral blood lymphocytes to guinea pig inclusion conjunctivitis antigen also was at a peak response 30 days after infection and decreased thereafter. Thus, loss of complete immunity could not be associated with a particular immune parameter. When genital secretions were examined 14 days after the challenge infection, IgA antibody levels to the lipopolysaccharide and 61K protein components had increased in intensity, whereas other antibodies were relatively low. In addition, complete immunity to a third infection was not increased in duration when animals had recovered from two previous genital infections.

Pelvic inflammatory disease in patients infected with Chlamydia trachomatis: in vitro cell mediated immune response to chlamydial antigens

Blood samples were obtained from 11 women with laparoscopically confirmed acute salpingitis who yielded positive cultures of Chlamydia trachomatis from the cervix. Four patients also had perihepatitis. Lymphocyte transformation assays, using C trachomatis serovars I and L2 as antigens, showed that the patients' lymphocytes responded to antigenic stimulation more strongly than the lymphocytes of age matched controls. Responses to the I and L2 antigens correlated strongly, but greater responses were obtained to the L2 antigen. No correlation was found between the response in the lymphocyte transformation assay and the degree of the inflammatory changes of the fallopian tubes, the presence of perihepatitis, or the titres of humoral antibodies to C trachomatis as measured by microimmunofluorescence. Sequential transformation assays, however, showed that patients with perihepatitis tended to have a more sustained response.

Long-term clinical, microbiological, and immunological observations of a volunteer repeatedly infected with Chlamydia trachomatis

A blind volunteer was inoculated in one eye with an isolate of Chlamydia trachomatis in 1961 and followed for 20 years. During this time, many observations were made of his clinical responses to the first inoculation and several subsequent inoculations with the same and other strains, chlamydial shedding, and antibody and cell-mediated immune responses. Evidence is presented that partial resistance to chlamydial eye infection developed during repeated infections and that antibodies, cell-mediated immune reactions, and specific antigen in conjunctival cells persisted for many years after the last infection. The antibody response was directed mainly against the original infecting immunotype, regardless of whether the response was restimulated by infection with the same immunotype or with other immunotypes. The lymphocyte stimulation response appeared to be species specific.