DNA immunization with pgp3 gene of Chlamydia trachomatis inhibits the spread of chlamydial infection from the lower to the upper genital tract in C3H/HeN mice

doi:10.1016/S0264-410X(02)00631-X

Vaccine

Volume 21, Issues 11–12, 7 March 2003, Pages 1089-1093

https://doi.org/10.1016/S0264-410X(02)00631-X Get rights and content

Abstract

Chlamydia trachomatis pgp3 DNA immunized (no. 300) and non-immunized (no. 300) C3H/HeN mice were infected by vaginal inoculation with infectious C. trachomatis serotype D elementary bodies (EBs) and the spread of infection to the salpinges was assessed by cell culture isolation from tissue homogenates 7, 14, 21, 28, 35 and 42 days post-infection (p.i.). Overall, the pgp3-DNA immunization prevented salpinx infection in 94 (56%) mice, if compared with the 168 positive animals found among the non-immunized animals (P<0.001).

A group of negative control animals (i.e. mice immunized with plasmid DNA containing an irrelevant insert) was not protected, whereas all the mice of a positive immune control group (mice that had resolved a primary genital C. trachomatis infection) were resistant to re-infection. Pgp3 DNA immunization induced both humoral and mucosal anti-pgp3 antibodies.

Introduction

Chlamydia trachomatis is one of the world’s major causes of sexually transmitted diseases of the cervix and urethra and it is a major agent of pelvic inflammatory disease [1].

Recent attempts at chlamydial vaccine development have been based on a subunit design using the chlamydial major outer membrane protein (MOMP) or derived peptides [2], [3]. These subunit vaccines have generally failed, possibly because these antigens did not induce adequate cellular and humoral immune responses, both currently considered essential for an effective anti-chlamydia protection [4].

It is well known that DNA vaccination represents a rapid system for directly testing subunit vaccination strategies without the need for production of the infectious agent or protein purification procedures. Although considerable interest has been generated by this technique, successful immunity has been most consistently induced by DNA immunization for viral diseases [5]. Results have been more variable with non-viral pathogens, a fact which may reflect differences in the complexity of the pathogen, the immunizing antigens and the routes of immunization [6], [7].

In the case of chlamydial infections, one effort of DNA vaccination with the ompA gene encoding the MOMP seemed to induce acquired immunity (to C. trachomatis) against lung infection [8], using a murine model of pneumonia; however, vaccination of mice with DNA plasmids expressing MOMP failed to protect against genital challenge [9].

This study aimed at evaluating the efficacy of DNA vaccination for the prevention of C. trachomatis infection using a murine model of ascending genital infection induced by a human isolate of the C. trachomatis D strain. Immunization was performed with the gene that encodes the C. trachomatis pgp3 protein [10], [11], [12]. Previous studies have shown that the majority of patients who are infected with C. trachomatis develops both humoral [10], [13], [14], [15] and mucosal (David Lewis, S. George’s Hospital Medical School, London, personal communication) immune responses to pgp3 protein. If this antigen is actively presented to the immune system during the natural infection, it may be a suitable candidate for inducing protective immunity through immunization. Therefore, in this study we evaluated the protective activity of pgp3 DNA vaccination in mice infected by vaginal inoculation with C. trachomatis.

Section snippets

Plasmids

The orf3 sequence of pCT-D plasmid [12] was amplified from a purified plasmid preparation, by a PCR using a pair of specific primers to which the NheI and XhoI restriction sites, respectively, had been added at the 5′ end. The amplified DNA segment was cloned into the NheI and XhoI sites of the pCMV-KA2 vector (this vector and the pCMV-KA/SF2.120 plasmid mentioned below were a gift from Chiron Corporation, Emeryville, CA, USA) [16] so that orf3 was positioned immediately downstream of, and in

Results

Non-immunized (no. 300), pgp3-immunized (no. 300) and pCMV-KA/SF2.120-immunized (no. 300) mice were sacrificed at weekly intervals, after vaginal infection with 10⁷ infectious C. trachomatis EBs, and quantitative isolations were performed on the salpinx homogenates. The results, comprehensive of three separate experiments, are summarized in Fig. 1.

Forty out of 50 (80%) salpinx homogenates of non-immunized control mice were positive starting 14 days after infection. Forty-eight out of 50 (96%)

Discussion

An effective vaccine against human salpingitis and consequent sterility caused by infection with the intracellular bacterium C. trachomatis is not yet available. Research in this field is still essentially confined to animal models of infection and disease, and the most convenient models of chlamydial infection have been obtained in the mouse [4], [17], [18]. Generally in these studies the animals are challenged with the mouse-adapted C. trachomatis strain MoPn (mouse pneumonitis) [2], [19],

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Citation Excerpt :
Due to the immunodominance in individuals infected with C. trachomatis [65,66], pGP3 has been evaluated as a biomarker for monitoring the C. trachomatis exposure in humans [67,68]. Furthermore, immunization of mice with the pgp3 gene or pGP3 protein has been shown to induce protective immunity [69–71]. However, assessing the role of the plasmid-encoded pGP3 in chlamydial pathogenesis was made possible only after the first report on the successful transformation of C. trachomatis L2 [72], which has permitted the detailed characterization of the plasmid-encoded ORFs in cell culture [17,73,74] and animal models [21] and encouraged the development of various genetic engineering tools for investigating chlamydial biology and pathogenesis [51,75–78].
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DNA immunization with pgp3 gene of Chlamydia trachomatis inhibits the spread of chlamydial infection from the lower to the upper genital tract in C3H/HeN mice

Abstract

Introduction

Section snippets

Plasmids

Results

Discussion

Vaccine

Vaccine

Vaccine

Plasmid

Vaccine

Vaccine

Sexually transmitted diseases, pelvic inflammatory disease and infertility: an epidemiologic update

Epidemiol. Rev.

Immunization with an acellular vaccine consisting of the outer membrane complex of Chlamydia trachomatis induces protection against a genital challenge

Infect. Immun.

Immunization with the Chlamydia trachomatis mouse pneumonitis major outer membrane protein can elicit a protective immune response against a genital challenge

Infect. Immun.

Immunity to murine chlamydial genital infection

Infect. Immun.

DNA vaccines

Ann. Rev. Immunol.

DNA vaccination with the major outer-membrane protein gene induces acquired immunity to Chlamydia trachomatis (mouse pneumonitis) infection

J. Infect. Dis.

Humoral immune response to plasmid protein pgp3 in patients with Chlamydia trachomatis infection

Infect. Immun.

Characterization of a new isolate of Chlamydia trachomatis which lacks the common plasmid and has properties of biovar trachoma

Infect. Immun.