Comparison of the long‐term and short‐term protection in mouse model of Leishmania major infection following vaccination with Live Iranian Lizard Leishmania mixed with chitin microparticles

Abstract

Inducing long‐term immunity is the primary goal of vaccination. Leishmanisation using non‐pathogenic to human Leishmania spp. could be considered a reliable approach to immunising subjects against Leishmania infection. Here, we evaluated the long‐term immune responses (14 weeks) after immunisation with either live‐ or killed‐Iranian Lizard Leishmania (ILL) mixed with chitin microparticles (CMPs) against L. major infection in BALB/c mice. In total, nine groups of mice were included in the study. To evaluate short‐term immunity, mice were immunised with live‐ILL and CMPs and 3 weeks later were challenged with L. majorEGFP. To evaluate the long‐term immunity, mice were immunised with either live‐ or killed‐ILL both mixed with CMPs, and 14 weeks after immunisation, mice were challenged with L. majorEGFP. A group of healthy mice who received no injection was also included in the study. Eight weeks after the challenge with L. majorEGFP, all subjects were sacrificed and the parasite burden (quantitative real‐time PCR and in vivo imaging), cytokines levels (IFN‐γ, IL‐4 and IL‐10), Leishmania‐specific antibody concentration, and total levels of IgG1 and IgG2a were measured. In addition, nitric oxide concentration and arginase activity were evaluated. Results showed that in mice that were immunised using live‐ILL+CMP, the induced protective immune response lasted at least 14 weeks; since they were challenged with L. majorEGFP at the 14th‐week post‐immunisation, no open lesion was formed during the 8‐week follow‐up, and the footpad swelling was significantly lower than controls. They also showed a significant reduction in the parasite burden in splenocytes, compared to the control groups including the group that received killed‐ILL+CMP. The observed protection was associated with a higher IFN‐γ and a lower IL‐10 production by splenocytes. Additionally, the results demonstrated that arginase activity was decreased in the ILL+CMP group compared to other groups. Immunisation with ILL alone reduced the parasite burden compared to non‐immunised control; however, it was still significantly higher than the parasite burden in the ILL+CMP groups. In conclusion, the long‐term immune response against L. major infection induced by Live‐ILL+CMP was more competent than the response elicited by killed‐ILL+CMP to protect mice against infection with L. majorEGFP.

Live attenuated-nonpathogenic Leishmania and DNA structures as promising vaccine platforms against leishmaniasis: innovations can make waves

“…Leishmania tarentolae has also been investigated as vaccines against human pathogenic Leishmania species ( Bandi et al, 2023 ). After Breton et al showed that intra-peritoneal administration of live L. tarentolae in BALB/c mice induces a Th1 pathway with significant protection against L. donovani infectious challenge ( Breton et al, 2005 ), non-engineered live L. tarentolae promastigotes were assayed as candidate vaccines adjuvanted with CpG oligonucleotides ( Keshavarzian et al, 2020 ), or chitin microparticles against L. major ( Haghdoust et al, 2022 ; Noroozbeygi et al, 2023 ). Others employed genetically modified strains of L. tarentolae , engineered for overexpression of antigens from human pathogenic Leishmanias ( Saljoughian et al, 2013 ; Topuz Ata et al, 2023 ) or antigens from the vector saliva ( Katebi et al, 2015 ; Lajevardi et al, 2022 ).…”