Approach to discover T- and B-cell antigens of intracellular pathogens applied to the design of Chlamydia trachomatis vaccines.

Natural immunity against obligate and/or facultative intracellular pathogens is usually mediated by both humoral and cellular immunity. The identification of those antigens stimulating both arms of the immune system is instrumental for vaccine discovery. Although high-throughput technologies have been applied for the discovery of antibody-inducing antigens, few examples of their application for T-cell antigens have been reported. We describe how the compilation of the immunome, here defined as the pool of immunogenic antigens inducing T- and B-cell responses in vivo, can lead to vaccine candidates against Chlamydia trachomatis. We selected 120 C. trachomatis proteins and assessed their immunogenicity using two parallel high-throughput approaches. Protein arrays were generated and screened with sera from C. trachomatis-infected patients to identify antibody-inducing antigens. Splenocytes from C. trachomatis-infected mice were stimulated with 79 proteins, and the frequency of antigen-specific CD4(+)/IFN-γ(+) T cells was analyzed by flow cytometry. We identified 21 antibody-inducing antigens, 16 CD4(+)/IFN-γ(+)-inducing antigens, and five antigens eliciting both types of responses. Assessment of their protective activity in a mouse model of Chlamydia muridarum lung infection led to the identification of seven antigens conferring partial protection when administered with LTK63/CpG adjuvant. Protection was largely the result of cellular immunity as assessed by CD4(+) T-cell depletion. The seven antigens provided robust additive protection when combined in four-antigen combinations. This study paves the way for the development of an effective anti-Chlamydia vaccine and provides a general approach for the discovery of vaccines against other intracellular pathogens.

CT043, a protective antigen that induces a CD4+ Th1 response during Chlamydia trachomatis infection in mice and humans.

Despite several decades of intensive studies, no vaccines against Chlamydia trachomatis, an intracellular pathogen causing serious ocular and urogenital diseases, are available yet. Infection-induced immunity in both animal models and humans strongly supports the notion that for a vaccine to be effective a strong CD4(+) Th1 immune response should be induced. In the course of our vaccine screening program based on the selection of chlamydial proteins eliciting cell-mediated immunity, we have found that CT043, a protein annotated as hypothetical, induces CD4(+) Th1 cells both in chlamydia-infected mice and in human patients with diagnosed C. trachomatis genital infection. DNA priming/protein boost immunization with CT043 results in a 2.6-log inclusion-forming unit reduction in the murine lung infection model. Sequence analysis of CT043 from C. trachomatis human isolates belonging to the most representative genital serovars revealed a high degree of conservation, suggesting that this antigen could provide cross-serotype protection. Therefore, CT043 is a promising vaccine candidate against C. trachomatis infection.

Protein array profiling of tic patient sera reveals a broad range and enhanced immune response against Group A Streptococcus antigens.

The human pathogen Group A Streptococcus (Streptococcus pyogenes, GAS) is widely recognized as a major cause of common pharyngitis as well as of severe invasive diseases and non-suppurative sequelae associated with the existence of GAS antigens eliciting host autoantibodies. It has been proposed that a subset of paediatric disorders characterized by tics and obsessive-compulsive symptoms would exacerbate in association with relapses of GAS-associated pharyngitis. This hypothesis is however still controversial. In the attempt to shed light on the contribution of GAS infections to the onset of neuropsychiatric or behavioral disorders affecting as many as 3% of children and adolescents, we tested the antibody response of tic patient sera to a representative panel of GAS antigens. In particular, 102 recombinant proteins were spotted on nitrocellulose-coated glass slides and probed against 61 sera collected from young patients with typical tic neuropsychiatric symptoms but with no overt GAS infection. Sera from 35 children with neither tic disorder nor overt GAS infection were also analyzed. The protein recognition patterns of these two sera groups were compared with those obtained using 239 sera from children with GAS-associated pharyngitis. This comparative analysis identified 25 antigens recognized by sera of the three patient groups and 21 antigens recognized by tic and pharyngitis sera, but poorly or not recognized by sera from children without tic. Interestingly, these antigens appeared to be, in quantitative terms, more immunogenic in tic than in pharyngitis patients. Additionally, a third group of antigens appeared to be preferentially and specifically recognized by tic sera. These findings provide the first evidence that tic patient sera exhibit immunological profiles typical of individuals who elicited a broad, specific and strong immune response against GAS. This may be relevant in the context of one of the hypothesis proposing that GAS antigen-dependent induction of autoantibodies in susceptible individuals may be involved the occurrence of tic disorders.