Kalia, I. | bioRxiv Science

bioRxiv2021

SLTRiP induces long lasting and protective T-cell memory response

Major developments have been made in the past many years to characterize and explore potential vaccine candidates that can induce host immune responses against parasite. These advances were based on the fact that the induction of host immune responses could effectively target parasite at different stages of its life cycle and thus, abrogate Plasmodium infections. The role of T-cells against malaria comes from initial studies on rodents showing these cells could inhibit parasite development during pre-erythrocytic stages. Since then, the importance of the cellular immune responses against malaria has been increasingly emphasized, especially for vaccine development against pre-erythrocytic stages. Previous work in our laboratory has confirmed that SLTRiP confers protection against the pre-erythrocytic stage of Plasmodium growth in rodents. Here we report that the protection is mainly due to cell mediated immune responses and PbSLTRiP specific cellular memory responses could be efficiently recalled in mice challenged with P. berghei parasites even after a year following immunization. Our results thereby, highlight the role of the T cell response involved in protection. Characterization of T-cells by intracellular cytokine staining (ICS) revealed that the induced T cells were polyfunctional and involved in secretion of pro-inflammatory cytokines which mediate anti-parasitic activity. The findings contribute to our understanding of the immunological mechanisms underlying the protective vaccines.

immunology↗

bioRxiv2019

Supression of Perforin-like Protein pores inhibit Plasmodium multistage-growth, transmission and erythrocyte senescence

The pore forming Plasmodium perforin like proteins (PPLP), expressed in all stages of the parasite life cycle are central drivers for host interactions critical for completion of parasite life cycle and high transmission rates. The high sequence similarity in the central membrane attack complex/ perforin (MACPF) domain and consequent functional overlaps defines them as an attractive target for the development of multi-stage antimalarials. Herein we evaluated the mechanism of pan active function of central, highly conserved region of PPLPs, MACPF domain (PMD) and inhibitory potential of specifically designed anti-PMD chemo. The E. coli expressed rPMD interacts with erythrocyte membrane and form pores of ~10.5 nm height and ~24.3 nm diameter leading to haemoglobin release and dextran uptake. The treatment with PMD induced erythrocytes senescence at 48 hours which can account for the physiological effect of disseminated PLPs in loss of circulating erythrocytes inducing anemia during malaria infection. The anti-PMD inhibitors effectively blocked intraerythrocytic growth by suppressing invasion and egress of merozoites and protecting against erythrocyte senescence. Moreover, these inhibitors also blocked the hepatic stage and transmission stage parasite development suggesting multi-stage and transmission-blocking potential of these inhibitors. Additionally, the erythrocyte senescence protective potential of PMD inhibitors can be used to occlude PPLPs mediated severe malarial anemia. Further these inhibitors can be developed with a potential to protect against severity of the disease.\n\nAuthor SummaryMalaria continues to be a major global health threat despite of several exciting improvements in the treatment and prevention of the disease. One of the major concerns in the development of therapy is the emergence of the drug resistance. But for the efficient treatment regime, targeting multiple stages including host and vector would serve as an ideal therapy. Perforin like proteins (PLPs) are eukaryotic pore forming proteins that are highly conserved in the apicomplexan parasites. These play crucial roles in entry and exit of parasites from the host cells and establish infection at multiple stages of Plasmodium spp. life cycle. Understanding the mechanism of pore formation by smaller, functional, pan-active scaffold of PLPs can serve as a target for development of cross stage protection. Here, using various biochemical, biophysical and pharmacological evidences, we validate the activity and characterize the pore formation of PLPs on erythrocytes. Further, our specifically designed inhibitors could restrict this pore formation and impede the exit/entry of the parasites. Moreover, these inhibitors could also exert multiple stage inhibition and rescue the uninfected erythrocytes from death. Together, this study highlights the mechanism of pore formation by PPLPs and evaluates their potential for the development of pan-active inhibitors to provide both symptomatic and transmission blocking cure for malaria.

molecular biology↗