A novel DNA vaccine containing multiple TB-specific epitopes casted in a natural structure (ECANS) confers protective immunity against pulmonary mycobacterial challenge

Abstract

Epitope-based DNA vaccines designed to induce T cell responses specific for Mycobacterium tuberculosis (M. tb) are being developed as a means of addressing vaccine potency. In this study, we predicted 4 T cell epitopes from ESAT-6, Ag85A/B and CFP-10 antigens and constructed an ECANS (epitopes casted in a natural structure) DNA vaccine by inserting the epitope DNA segments separately into the gene backbone of M. tb-derived HSP65 (heat shock protein 65) carrier. The immunogenicity and protective efficacy of pECANS DNA vaccine were assessed in BALB/c mice after intramuscular immunization with 4 doses of 50 microg ECANS DNA and followed by mycobaterial challenge 4 weeks after the last immunization. Compared to plasmid encoding HSP65, pECANS DNA immunization elicited remarkably higher levels of IFN-gamma production by both CD4(+) and CD8(+) T cells, which were coupled with higher frequencies of antigen-specific T cells and higher CTL activity. Significantly enhanced levels of Th1 cytokines (IFN-gamma and IL-12) and increased serum IgG2a/IgG1 ratio were also noted, indicating a predominant Th1 immune response achieved by pECANS DNA immunization. In the consequence, a better protection against Mycobacterium bovis BCG challenge was achieved which was evidenced by reduced bacterial loads in lungs and spleens and profound attenuation of lung inflammation and injury. Our results suggested that multi-T cell-epitope based ECANS gene vaccine induced T cell response to multiple T cell epitopes and led to enhanced protection against mycobacterial challenge. This strategy might be a useful platform to design multi-T cell epitope-based vaccine against M. tb infection.

A Multiepitope Subunit Vaccine Conveys Protection against Extraintestinal PathogenicEscherichia coliin Mice

“…To our knowledge, this technique has not been used previously for protein vaccination against bacteria. Only recently have DNAbased vaccination strategies using similarly constructed artificial targets been described (14,33). Using these DNA vaccines, strong cytotoxic T-lymphocyte (CTL)-mediated responses could be induced, but little attention was paid to antibody responses.…”

Mucosal co-immunization with AIM2 enhances protective SIgA response and increases prophylactic efficacy of chitosan-DNA vaccine against coxsackievirus B3-induced myocarditis

“…[36][37][38] However, delivery systems of mucosal vaccines remain a challenge to induce maximal mucosal protection simultaneously. In recent years, chitosan has gained increasing interest as a safe delivery system for plasmid DNA (pDNA).…”

Tuberculosis vaccine research in China

“…68 The protective effect of DNA expressing hsp65 against BCG challenge was enhanced by incorporating epitopes of ESAT6, Ag85A/B and CFP10 within the hsp65 backbone. 32 The protective effect of hsp65 DNA against H37Rv challenge was increased by expression as a fusion with hIL-2, but did not surpass that of BCG. 69 Expression of Ag85B fused to bovine herpes virus 1 VP22 protein, which facilitates dissemination of antigen to adjacent cells, resulted in protection against H37Rv challenge in mice that was better than protection by BCG.…”

“…Many have shown Th1-biased immunogenicity without additional adjuvanting, for example with Ag85B, 27,28 Ag85B/ESAT6 fusion, 29 ESAT6/CFP10 fusion, 30 Mtb8.4/38-kDa/Ag85B fusion 31 and epitopes from ESAT6, Ag85A, CFP10 and Ag85B inserted within hsp65. 32 Targeting the expressed product for degradation via the ubiquitin pathway has been used to enhance MHC Class 1 presentation of epitopes from MPT64 and 38-kDa, 33 MPT64, 34 and ESAT6. 35,36 Liposome associated Ag85A DNA vaccine was shown to be immunogenic with oral delivery.…”