Diversity pattern of Plasmodium knowlesi merozoite surface protein 4 (MSP4) in natural population of Malaysia

Abstract

Human infections due to the monkey malaria parasite Plasmodium knowlesi are increasingly being reported from Malaysia. The parasite causes high parasitaemia, severe and fatal malaria in humans thus there is a need for urgent measures for its control. The MSP4 is a potential vaccine candidate, which is well studied in Plasmodium falciparum and Plasmodium vivax; however, no study has been conducted in the orthologous gene of P. knowlesi. In this study, we investigated the level of polymorphisms, haplotypes, natural selection and population structure of full-length pkmsp4 in 32 clinical samples from Malaysian Borneo along with 4 lab-adapted strains. We found low levels of polymorphism across the gene with exon I showing higher diversity than the exon II. The C- terminal epidermal growth factor (EGF) domains and GPI-anchored region within exon II were mostly conserved with only 2 non-synonymous substitutions. Although 21 amino acid haplotypes were found, the frequency of mutation at the majority of the polymorphic positions was low. We found evidence of negative selection at the exon II of the gene indicating existence of functional constraints. Phylogenetic haplotype network analysis identified shared haplotypes and indicated geographical clustering of samples originating from Peninsular Malaysia and Malaysian Borneo. High population differentiation values were observed within parasite populations originating from Malaysian Borneo (Kapit, Sarikei and Betong) and laboratory-adapted strains obtained from Peninsular Malaysia and Philippines indicating distinct population structure. This is the first study to genetically characterize the full-length msp4 gene from clinical isolates of P. knowlesi from Malaysia and thus would be very useful for future rational vaccine studies. Further studies with higher number of samples and functional characterization of the protein will be necessary.

Identification, Mapping, and Genetic Diversity of Novel Conserved Cross-Species Epitopes of RhopH2 in Plasmodium knowlesi With Plasmodium vivax

“…The ML phylogenetic tree identified 3 subpopulations of PkRhopH2, cluster 1 and cluster 2 from Malaysian Borneo and cluster 3 comprising only the laboratory lines as observed in other invasion genes and population genomic studies ( Assefa et al., 2015 ; Pinheiro et al., 2015 ; Ahmed et al., 2016 ; Yusof et al., 2016 ; Divis et al., 2017 ; Ahmed et al., 2018a ; Ahmed et al., 2018b ; Ahmed et al., 2018c ; Ahmed et al., 2019 ).…”

“…The ML phylogenetic tree identified 3 subpopulations of PkRhopH2, cluster 1 and cluster 2 from Malaysian Borneo and cluster 3 comprising only the laboratory lines as observed in other invasion genes and population genomic studies (Assefa et al, 2015;Pinheiro et al, 2015;Ahmed et al, 2016;Yusof et al, 2016;Divis et al, 2017;Ahmed et al, 2018a;Ahmed et al, 2018b;Ahmed et al, 2018c;Ahmed et al, 2019). In this study, we also investigated whether shared epitopes are present in both species in the RhopH2 domain where high cross reactivity and immunogenicity have been observed by Muh et al (2020).…”

Plasmodium knowlesi: the game changer for malaria eradication

“…Malaysia, Malaysian Borneo H 65 Purifying selection 2 distinct geographical clusters between Pen. Malaysia and Malaysian Borneo Ahmed et al (2019) [ 152 ] Merozoite surface protein 4 ( msp4 ) Surface antigen Pen. Malaysia, Sarawak, the Philippines H 36 Purifying selection in Exon II 2 distinct geographical clusters between Pen.…”

“…For example, P. knowlesi shares a more recent common ancestor with Plasmodium coatneyi , another simian malaria parasite [ 55 ]. Dimorphisms, especially in association with geographical origins (between Peninsular Malaysia and Malaysian Borneo) were observed in many gene candidates [ 137 , 150 – 152 , 154 , 156 ]. Following the application of multilocus microsatellite typing and whole-genome sequence analyses, three divergent subpopulations of P. knowlesi were unravelled in Malaysia [ 157 , 159 ].…”

Identification and Characterization of Eimeria tenella Microneme Protein (EtMIC8)

“…The EGF domain of TgMIC3 has been reported to induce a strong cellular immune response ( 41 ). Numerous Plasmodium merozoite surface proteins (PMSPs) containing the EGF domains have been considered good candidate vaccine antigens ( 41 , 42 ). In the present study, our results also revealed that the EGF domains of EtMIC8 showed higher immunogenicity and protective efficacy, with an ACI as high as 169.7.…”