Growth and immunogenicity of TRIC agents in mice

Antibody type specificity to trachoma in eye secretions of saudi arab children

The presence of trachoma antibody in eye secretions of Saudi Arab children appears to be a direct response to the infecting organism. In 35 of 36 cases, the trachoma antibody type found in eye secretions was identical to the strain type isolated concurrently. Strain types were identified by use of donkey hyperimmune sera prepared against types 1, 1b, and 2. The specificity of the sera was enhanced by absorption with trachoma antigens of heterologous type. Similarly, antibody types were determined by absorbing samples of eye secretions with types 1, 1b, and 2. Complete absorption of trachoma antibody activity was achieved only by the antigen type homologous to the patient's own strain. In one instance, antibody could not be typed. No change in antibody or strain type was seen in four children examined twice during a 3- to 6-month period. Typing of trachoma antibody from eye secretions has potential as an immunological and epidemiological tool.

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.

Preparation of complement fixation antigen of Chlamydia psittaci grown in tissue culture by treatment with beta-propiolactone

A new method of preparing a chlamydial complement fixation (CF) antigen by treatment with beta-propiolactone (BPL) is presented. Chlamydia psittaci strains Pigeon-1041 and Budgerigar-No. 1, and Chlamydia trachomatis strain L2/434/BU, propagated in L-929 cell monolayers, were inactivated with BPL. This BPL-treated antigen was useful for detecting CF antibodies in both human and pigeon sera, and it did not cause false-positive reactions, as are sometimes observed between some human sera and phenol-treated antigen derived from eggs. When this CF antigen was treated with potassium periodate and tested for reactivity with mouse immune ascitic fluid, it was found that the antigen contained type- or strain specificity as well as genus specificity. Immunization with the BPL-treated antigen elicited type- or strain-specific neutralizing antibody.

Trachoma vaccine field trials in The Gambia

The ability of two live trachoma vaccines to protect against naturally acquired infection was tested in young Gambian children. With a mineral oil adjuvant vaccine prepared from a Gambian strain of trachoma (MRC–187) a barely significant measure of protection was demonstrable 6 months after the first dose, but not at 1 year, despite a reinforcing dose given 6 months after the first. In a later trial an aqueous vaccine prepared from the ‘fast-killing’ variants of strains ‘SA–2’ and ‘ASGH’ failed to induce immunity. Two years after vaccination, the proportion of vaccinated children progressing to cicatricial trachoma was less than in the controls, and the average severity of the disease in terms of clinical score was greater; vaccine-induced hypersensitivity may have contributed to this result.

Irrespective of whether they had received trachoma vaccine, children with completely normal eyes at the outset were less likely to acquire trachoma than those with slight conjunctival folliculosis or papillary hyperplasia. In children acquiring trachoma, there was a highly significant positive correlation between severity of the disease and the presence of conjunctival inclusions. The pattern of trachoma differed significantly in the two villages used in both trials; the prev alence, severity and proportion of inclusion-positive subjects were all higher in the village with the greater population density.

An efficient follow-up organization, use of a slit-lamp for clinical observations, and a scoring system for recording physical signs are all desirable for trachoma vaccine field trials.

We are highly indebted to Dr G. Turner (Lister Institute, Elstree, Herts) for his assistance in making the vaccine used for Trial II; to Dr N. M. Lam (Pfizer Ltd.) and Dr C. H. Smith (Evans Medical Ltd.) for making the Trial III vaccine; to Dr I. A. Sutherland (M.R.C. Statistical Unit) for his advice and help with the statistical aspects; to the Pennsylvania Refinery Co. Inc. for a generous gift of Drakeol 6 VR; and to Mr M. Race for his invaluable technical assistance in The Gambia. We are also grateful to the Director and staff of the M.R.C. Laboratories, The Gambia, for various facilities; and to The Gambian Government for per mission to undertake these trials.