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

摘要

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 de scribe 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 trachoma tis. 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 anti gens. Splenocytes from C. trachomatis-infected mice were stimu lated 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 murida rum lung infection led to the identification of seven antigens con ferring 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 combi nations. This study paves the way for the development of an ef fective anti-Chlamydia vaccine and provides a general approach for the discovery of vaccines against other intracellular pathogens.