Status in Malaria Vaccine Development: Basic aspects of Vaccine, Mechanism of actions, Vaccine pipelines, Stage oriented immune response ‘Challenges and Opportunities’

Abstract

Malaria is considered as a systemic syndrome caused by infection of the red blood cells by intracellular protozoan parasites of the genus Plasmodium and is transmitted by the bite of infected and physiologically excited female anopheline mosquito, which feeds on mamamalian blood to produce and mature its eggs. Vaccination is  believed to be one of the most effective approaches to tackle morbidity and mortality  related  malaria and its approach targets the malaria life stage  factors like the pre-erythrocyticproteins (RTSs, ChAd63/MVA, METRAP, PSPZ, PfceITos…), the blood stage proteins (EBA175, AMA₁, GMZ₁, P_27A, MSP₃, MSP₁, RH₅, sexual stage proteins (Pfs₂₅, Pfs₄₈, Pfs₂₃₀ and Multi-stage /multi-epitope/antigen combination vaccines ((PfCP-2. 9 chimeric (AMA1 and MSP1–19)). Even if the vaccine trials against malaria was began early in 1930s, currently the one most advanced pre-erythrocyticvaccine, RTS, S vaccine has been launched with good safety profile (efficacy of 30-50%). New approaches like combining different types of adjuvants into antigen‐specific formulations improved efficacy of a particular vaccine and its formulations offer a wide spectrum of opportunities in malaria vaccine research. Frequent and multiple infections gradually lead to the development of anti-parasite immunity which results in very low or undetectable parasitemia in malaria-infected individuals. Sterilizing immunity against malarial parasite, though never fully achieved, results in a high degree of immune response, low levels of parasitemia, and an asymptomatic carrier status For unsuccessful trials of malaria vaccine, there are so many challenges that are associated to logistic (high cost-effective public health intervention to control and regulate pathway complicity ), immunologic (polymorphism of the malaria parasite antigens in each life stage, the immune evasion strategy of the parasite… ), and technical challenges related to miss identification of malaria vaccine candidates, selection adjuvants and route of administration. Although there were tackles to malarial vaccine trials, it was reported that there are fine opportunities to proceed on the track.