Evaluation of the immunogenicity of a DNA vaccine for Leishmania major based on the Leishmania-activated C kinase antigen using calcium phosphate and chitosan adjuvants

Abstract

Background Leishmaniasis represents a significant parasitic disease with global health implications, and the development of an affordable and effective vaccine could provide a valuable solution. This study aimed to evaluate the immunogenicity of a DNA vaccine targeting Leishmania major specifically based on the Leishmania-activated C kinase (LACK) antigen, utilizing calcium phosphate nanoparticles (CaPNs) and chitosan nanoparticles (ChitNs) as adjuvants.Methods Seventy female BALB/c mice, aged 4-6 wk and weighing 20-22 g, were selected and divided into five groups, each consisting of 14 mice. The first group received the plasmid LACK vaccine (pcDN3+LACK), the second group received the pcDN3+LACK vaccine with the CaPN adjuvant (pcDN3+LACK+CaPN), the third group received the pcDN3+LACK vaccine with the ChitN adjuvant (pcDN3+LACK+ChitN), the fourth group was administered phosphate-buffered saline as a negative control and the fifth group did not receive any vaccine, serving as a positive control. The vaccination program involved two intramuscular injections at 3-wk intervals. Three weeks following the final vaccination, the mice were challenged with wild-type L. major promastigotes via intradermal injection at the base of their tails. Clinical signs and lesion sizes were evaluated biweekly using Vernier calipers. Immune responses, including levels of interferon-gamma (IFN-gamma) and interleukin-4 (IL-4), were assessed using ELISA.Results The groups receiving pcDN3+LACK+ChitN, pcDN3+LACK+CaPN and pcDN3+LACK exhibited the highest increases in IFN-gamma titers and the most significant reductions in IL-4 titers. Furthermore, lesion sizes associated with Leishmania infection were reduced in the vaccinated groups, with the most favorable outcomes observed in the pcDN3+LACK+ChitN group.Conclusions These findings suggest that vaccination utilizing the LACK antigen in conjunction with CaPN and ChitN adjuvants may represent an effective strategy for the control of cutaneous leishmaniasis.