Validation of Resuscitation Promoting Factor B as a candidate antigen for DNA vaccine against tuberculosis

Abstract

Tuberculosis (TB) is a chronic infectious disease caused by bacteria Mycobacterium tuberculosis (M. tuberculosis). It is assumed that about one-third of the world’s population, approximately more than 2 billion population, is infected with M. tuberculosis. The most effective strategy to control TB epidemic is to prevent the spread of M. tuberculosis by vaccination. However, The only available vaccine against TB, BCG does not demonstrate consistent efficacy to adult, pulmonary TB. Thus, there is a need to develop new, efficacious vaccines against TB.In the present study, rpfB-encoding plasmid DNA (pcDNA3.1+/RpfB) was developed to evaluate possibility of developing TB vaccine using the RpfB as a candidate antigen. And recombinant RpfB protein was also produced to compare with DNA vaccine. To evaluate the immunogenicity, humoral immune response and cell-mediated immune response were assessed. Vaccine-induced humoral immune response, serum α-RpfB immunoglobulin was significantly increased in RpfB protein vaccine group. On the contrary, cell-mediated immune response, RpfB-specific T cell response was robust in RpfB DNA vaccine group. RpfB DNA vaccine induced strong IFN-γ producing response in ELISpot assay and polyfunctional CD8+ (IFN-γ+TNF-α+CD107a+) and CD4+ (IFN-γ+TNF-α+ or IFN-γ+TNF-α+CD107a+) T cells in multi-parameter flowcytometry. Especially, RpfB-specific CD8+ T cell response detected in RpfB DNA vaccine group only. DNA vaccine-induced CD4+ T cells were less polyfunctional and the frequency of responding cells were small compared to RpfB-specific CD8+ T cells, although it was much compared to protein vaccine-induced CD4+ T cells. To evaluate the protective efficacy of RpfB vaccines, bacterial reduction was assessed by colony forming unit (CFU) of M. tuberculosis murine infection model. The evaluation of the protective efficacy carried out compared with bacterial reduction in BCG vaccine group. RpfB DNA vaccine induced bacterial reduction, however the prote...