HSP70 domain II of Mycobacterium tuberculosis modulates immune response and protective potential of F1 and LcrV antigens of Yersinia pestis in a mouse model

PLoS Negl Trop Dis. 2014 Dec 4;8(12):e3322. doi: 10.1371/journal.pntd.0003322. eCollection 2014 Dec.

Abstract

No ideal vaccine exists to control plague, a deadly dangerous disease caused by Yersinia pestis. In this context, we cloned, expressed and purified recombinant F1, LcrV antigens of Y. pestis and heat shock protein70 (HSP70) domain II of M. tuberculosis in E. coli. To evaluate the protective potential of each purified protein alone or in combination, Balb/C mice were immunized. Humoral and cell mediated immune responses were evaluated. Immunized animals were challenged with 100 LD50 of Y. pestis via intra-peritoneal route. Vaccine candidates i.e., F1 and LcrV generated highly significant titres of anti-F1 and anti-LcrV IgG antibodies. A significant difference was noticed in the expression level of IL-2, IFN-γ and TNF-α in splenocytes of immunized animals. Significantly increased percentages of CD4+ and CD8+ T cells producing IFN-γ in spleen of vaccinated animals were observed in comparison to control group by flow cytometric analysis. We investigated whether the F1, LcrV and HSP70(II) antigens alone or in combination can effectively protect immunized animals from any histopathological changes. Signs of histopathological lesions noticed in lung, liver, kidney and spleen of immunized animals on 3rd day post challenge whereas no lesions in animals that survived to day 20 post-infection were observed. Immunohistochemistry showed bacteria in lung, liver, spleen and kidney on 3rd day post-infection whereas no bacteria was observed on day 20 post-infection in surviving animals in LcrV, LcrV+HSP70(II), F1+LcrV, and F1+LcrV+HSP70(II) vaccinated groups. A significant difference was observed in the expression of IL-2, IFN-γ, TNF-α, and CD4+/CD8+ T cells secreting IFN-γ in the F1+LcrV+HSP70(II) vaccinated group in comparison to the F1+LcrV vaccinated group. Three combinations that included LcrV+HSP70(II), F1+LcrV or F1+LcrV+HSP70(II) provided 100% protection, whereas LcrV alone provided only 75% protection. These findings suggest that HSP70(II) of M. tuberculosis can be a potent immunomodulator for F1 and LcrV containing vaccine candidates against plague.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Bacterial / blood
  • Antigens, Bacterial / immunology*
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / immunology*
  • Disease Models, Animal
  • Female
  • HSP70 Heat-Shock Proteins / chemistry
  • HSP70 Heat-Shock Proteins / immunology*
  • Immunoglobulin G / blood
  • Mice
  • Mice, Inbred BALB C
  • Plague / pathology
  • Plague Vaccine / immunology*
  • Pore Forming Cytotoxic Proteins / immunology*
  • Protein Structure, Tertiary
  • Recombinant Proteins / immunology
  • T-Lymphocytes / immunology
  • Vaccination

Substances

  • Antibodies, Bacterial
  • Antigens, Bacterial
  • Bacterial Proteins
  • HSP70 Heat-Shock Proteins
  • HSP70 protein, Mycobacterium tuberculosis
  • Immunoglobulin G
  • LcrV protein, Yersinia
  • Plague Vaccine
  • Pore Forming Cytotoxic Proteins
  • Recombinant Proteins
  • caf1 protein, Yersinia pestis

Grants and funding

DRDE, Govt. of India, is the funding institute. Mr. Lalit Batra and Ms. Prachi Pathak are recipients of CSIR-UGC junior research fellowships. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.