Development of novel prime-boost strategies based on a tri-gene fusion recombinant L. tarentolae vaccine against experimental murine visceral leishmaniasis

PLoS Negl Trop Dis. 2013 Apr 18;7(4):e2174. doi: 10.1371/journal.pntd.0002174. Print 2013.

Abstract

Visceral leishmaniasis (VL) is a vector-borne disease affecting humans and domestic animals that constitutes a serious public health problem in many countries. Although many antigens have been examined so far as protein- or DNA-based vaccines, none of them conferred complete long-term protection. The use of the lizard non-pathogenic to humans Leishmania (L.) tarentolae species as a live vaccine vector to deliver specific Leishmania antigens is a recent approach that needs to be explored further. In this study, we evaluated the effectiveness of live vaccination in protecting BALB/c mice against L. infantum infection using prime-boost regimens, namely Live/Live and DNA/Live. As a live vaccine, we used recombinant L. tarentolae expressing the L. donovani A2 antigen along with cysteine proteinases (CPA and CPB without its unusual C-terminal extension (CPB(-CTE))) as a tri-fusion gene. For DNA priming, the tri-fusion gene was encoded in pcDNA formulated with cationic solid lipid nanoparticles (cSLN) acting as an adjuvant. At different time points post-challenge, parasite burden and histopathological changes as well as humoral and cellular immune responses were assessed. Our results showed that immunization with both prime-boost A2-CPA-CPB(-CTE)-recombinant L. tarentolae protects BALB/c mice against L. infantum challenge. This protective immunity is associated with a Th1-type immune response due to high levels of IFN-γ production prior and after challenge and with lower levels of IL-10 production after challenge, leading to a significantly higher IFN-γ/IL-10 ratio compared to the control groups. Moreover, this immunization elicited high IgG1 and IgG2a humoral immune responses. Protection in mice was also correlated with a high nitric oxide production and low parasite burden. Altogether, these results indicate the promise of the A2-CPA-CPB(-CTE)-recombinant L. tarentolae as a safe live vaccine candidate against VL.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Protozoan / immunology
  • Female
  • Gene Fusion / genetics
  • Immunity, Humoral / immunology
  • Immunoglobulin G / metabolism
  • Interferon-gamma / metabolism
  • Interleukin-10 / metabolism
  • Leishmaniasis, Visceral / immunology*
  • Leishmaniasis, Visceral / prevention & control*
  • Mice
  • Mice, Inbred BALB C
  • Protozoan Vaccines / therapeutic use*
  • Vaccines, DNA / therapeutic use*
  • Vaccines, Synthetic / therapeutic use*

Substances

  • Antibodies, Protozoan
  • Immunoglobulin G
  • Protozoan Vaccines
  • Vaccines, DNA
  • Vaccines, Synthetic
  • Interleukin-10
  • Interferon-gamma

Grants and funding

This work was financially supported by grants from Pasteur Institute of Iran for N. Saljoughian's PhD studentship. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.