1
|
Bajic M, Ravishankar S, Sheth M, Rowe LA, Pacheco MA, Patel DS, Batra D, Loparev V, Olsen C, Escalante AA, Vannberg F, Udhayakumar V, Barnwell JW, Talundzic E. The first complete genome of the simian malaria parasite Plasmodium brasilianum. Sci Rep 2022; 12:19802. [PMID: 36396703 PMCID: PMC9671904 DOI: 10.1038/s41598-022-20706-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 09/16/2022] [Indexed: 11/18/2022] Open
Abstract
Naturally occurring human infections by zoonotic Plasmodium species have been documented for P. knowlesi, P. cynomolgi, P. simium, P. simiovale, P. inui, P. inui-like, P. coatneyi, and P. brasilianum. Accurate detection of each species is complicated by their morphological similarities with other Plasmodium species. PCR-based assays offer a solution but require prior knowledge of adequate genomic targets that can distinguish the species. While whole genomes have been published for P. knowlesi, P. cynomolgi, P. simium, and P. inui, no complete genome for P. brasilianum has been available. Previously, we reported a draft genome for P. brasilianum, and here we report the completed genome for P. brasilianum. The genome is 31.4 Mb in size and comprises 14 chromosomes, the mitochondrial genome, the apicoplast genome, and 29 unplaced contigs. The chromosomes consist of 98.4% nucleotide sites that are identical to the P. malariae genome, the closest evolutionarily related species hypothesized to be the same species as P. brasilianum, with 41,125 non-synonymous SNPs (0.0722% of genome) identified between the two genomes. Furthermore, P. brasilianum had 4864 (82.1%) genes that share 80% or higher sequence similarity with 4970 (75.5%) P. malariae genes. This was demonstrated by the nearly identical genomic organization and multiple sequence alignments for the merozoite surface proteins msp3 and msp7. We observed a distinction in the repeat lengths of the circumsporozoite protein (CSP) gene sequences between P. brasilianum and P. malariae. Our results demonstrate a 97.3% pairwise identity between the P. brasilianum and the P. malariae genomes. These findings highlight the phylogenetic proximity of these two species, suggesting that P. malariae and P. brasilianum are strains of the same species, but this could not be fully evaluated with only a single genomic sequence for each species.
Collapse
Affiliation(s)
- Marko Bajic
- grid.422961.a0000 0001 0029 6188Association of Public Health Laboratories, Silver Spring, MD USA ,grid.416738.f0000 0001 2163 0069Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA USA
| | | | - Mili Sheth
- grid.416738.f0000 0001 2163 0069Biotechnology Core Facility Branch, Division of Scientific Resources, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Lori A. Rowe
- grid.416738.f0000 0001 2163 0069Biotechnology Core Facility Branch, Division of Scientific Resources, Centers for Disease Control and Prevention, Atlanta, GA USA ,grid.265219.b0000 0001 2217 8588Virus Characterization Isolation Production and Sequencing Core, Tulane National Primate Research Center, Covington, LA USA
| | - M. Andreina Pacheco
- grid.264727.20000 0001 2248 3398Biology Department/Institute of Genomics and Evolutionary Medicine (iGEM), Temple University, Philadelphia, PA USA
| | - Dhruviben S. Patel
- grid.416738.f0000 0001 2163 0069Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Dhwani Batra
- grid.416738.f0000 0001 2163 0069Biotechnology Core Facility Branch, Division of Scientific Resources, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Vladimir Loparev
- grid.416738.f0000 0001 2163 0069Biotechnology Core Facility Branch, Division of Scientific Resources, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Christian Olsen
- grid.416738.f0000 0001 2163 0069Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Ananias A. Escalante
- grid.264727.20000 0001 2248 3398Biology Department/Institute of Genomics and Evolutionary Medicine (iGEM), Temple University, Philadelphia, PA USA
| | - Fredrik Vannberg
- grid.213917.f0000 0001 2097 4943Center for Integrative Genomics at Georgia Tech, Georgia Institute of Technology, Atlanta, GA USA
| | - Venkatachalam Udhayakumar
- grid.416738.f0000 0001 2163 0069Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - John W. Barnwell
- grid.416738.f0000 0001 2163 0069Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Eldin Talundzic
- grid.416738.f0000 0001 2163 0069Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA USA
| |
Collapse
|
2
|
Almeida-de-Oliveira NK, Abreu-Fernandes R, Lavigne AR, Pina-Costa A, Perce-da-Silva DDS, Catanho M, Rossi ÁD, Brasil P, Daniel-Ribeiro CT, Ferreira-da-Cruz MDF. Exploration of Plasmodium vivax merozoite surface proteins 1 and 7 genetic diversity in Brazilian Amazon and Rio de Janeiro Atlantic Forest. INFECTION GENETICS AND EVOLUTION 2020; 86:104592. [PMID: 33059085 DOI: 10.1016/j.meegid.2020.104592] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 09/22/2020] [Accepted: 10/07/2020] [Indexed: 11/29/2022]
Abstract
Plasmodium vivax merozoite surface proteins (PvMSP) 1 and 7 are considered vaccine targets. Genetic diversity knowledge is crucial to assess their potential as immunogens and to provide insights about population structure in different epidemiological contexts. Here, we investigate the variability of pvmsp-142, pvmsp-7E, and pvmsp-7F genes in 227 samples from the Brazilian Amazon (BA) and Rio de Janeiro Atlantic Forest (AF). pvmsp-142 has 63 polymorphisms - 57 nonsynonymous - generating a nucleotide diversity of π = 0.009 in AF, and π = 0.018 in BA. In pvmsp-7E, 134 polymorphisms - 103 nonsynonymous - generate the nucleotide diversity of π = 0.027 in AF, and π = 0.042 in BA. The pvmsp-7F has only two SNPs - A610G and A1054T -, with nucleotide diversity of π = 0.0004 in AF, and π = 0.0007 in BA. The haplotype diversity of pvmsp-142, pvmsp-7E, and pvmsp-7F genes is 0.997, 1.00, and 0.649, respectively. None of the pvmsp-142 or pvmsp-7E sequences are identical to the Salvador 1 strain's sequence. Conversely, most of pvmsp-7F sequences (94/48%) are identical to Sal-1. We evaluated eight B-cell epitopes in pvmsp-7E, four of them showed higher nucleotide diversity compared to pvmsp-7E's epitopes. Positive selection was detected in pvmsp-142, pvmsp-7E central region, and pvmsp-7F with Tajima's D. In pvmsp-7E, the significant nucleotide and haplotype diversities with low genetic differentiation, could be indicative of balancing selection. The genetic differentiation of pvmsp-142 (0.315) and pvmsp-7F (0.354) genes between AF and BA regions is significant, which is not the case for pvmsp-7E (0.193). We conclude that pvmsp-142 and pvmsp-7E have great genetic diversity even in AF region, an enclosure area with deficient transmission levels of P. vivax zoonotic malaria. In both Brazilian regions, pvmsp-119, pvmsp-7E, and pvmsp-7F are conserved, most likely due to their roles in parasite survival, and could be considered potential targets for a "blood-stage vaccine".
Collapse
Affiliation(s)
- Natália Ketrin Almeida-de-Oliveira
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, Brazil; Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Reference Laboratory for Malaria in the Extra-Amazonian Region for the Brazilian Ministry of Health, SVS & Fiocruz, Rio de Janeiro, RJ, Brazil.
| | - Rebecca Abreu-Fernandes
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, Brazil; Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Reference Laboratory for Malaria in the Extra-Amazonian Region for the Brazilian Ministry of Health, SVS & Fiocruz, Rio de Janeiro, RJ, Brazil
| | - Aline Rosa Lavigne
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, Brazil; Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Reference Laboratory for Malaria in the Extra-Amazonian Region for the Brazilian Ministry of Health, SVS & Fiocruz, Rio de Janeiro, RJ, Brazil
| | - Anielle Pina-Costa
- Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Reference Laboratory for Malaria in the Extra-Amazonian Region for the Brazilian Ministry of Health, SVS & Fiocruz, Rio de Janeiro, RJ, Brazil; Laboratório de Pesquisa Clínica em Doenças Febris Agudas, Instituto Nacional de Infectologia Evandro Chagas, Fiocruz, Rio de Janeiro, RJ, Brazil; Centro Universitário Serra dos Órgãos (UNIFESO), Teresópolis, RJ, Brazil
| | - Daiana de Souza Perce-da-Silva
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, Brazil; Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Reference Laboratory for Malaria in the Extra-Amazonian Region for the Brazilian Ministry of Health, SVS & Fiocruz, Rio de Janeiro, RJ, Brazil; Laboratório de Imunologia Básica e Aplicada, Faculdade de Medicina de Petrópolis - FMP/FASE, Petrópolis, RJ, Brazil
| | - Marcos Catanho
- Laboratório de Genética Molecular de Microrganismos, IOC, Fiocruz, Rio de Janeiro, RJ, Brazil
| | - Átila Duque Rossi
- Departamento de Genética, Instituto de Biologia, Universidade Federal do Rio de Janeiro, RJ, Brazil
| | - Patrícia Brasil
- Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Reference Laboratory for Malaria in the Extra-Amazonian Region for the Brazilian Ministry of Health, SVS & Fiocruz, Rio de Janeiro, RJ, Brazil; Laboratório de Pesquisa Clínica em Doenças Febris Agudas, Instituto Nacional de Infectologia Evandro Chagas, Fiocruz, Rio de Janeiro, RJ, Brazil.
| | - Cláudio Tadeu Daniel-Ribeiro
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, Brazil; Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Reference Laboratory for Malaria in the Extra-Amazonian Region for the Brazilian Ministry of Health, SVS & Fiocruz, Rio de Janeiro, RJ, Brazil
| | - Maria de Fátima Ferreira-da-Cruz
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, Brazil; Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Reference Laboratory for Malaria in the Extra-Amazonian Region for the Brazilian Ministry of Health, SVS & Fiocruz, Rio de Janeiro, RJ, Brazil.
| |
Collapse
|
3
|
Brashear AM, Huckaby AC, Fan Q, Dillard LJ, Hu Y, Li Y, Zhao Y, Wang Z, Cao Y, Miao J, Guler JL, Cui L. New Plasmodium vivax Genomes From the China-Myanmar Border. Front Microbiol 2020; 11:1930. [PMID: 32849480 PMCID: PMC7432439 DOI: 10.3389/fmicb.2020.01930] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 07/22/2020] [Indexed: 11/13/2022] Open
Abstract
Plasmodium vivax is increasingly the dominant species of malaria in the Greater Mekong Subregion (GMS), which is pursuing regional malaria elimination. P. vivax lineages in the GMS are poorly characterized. Currently, P. vivax reference genomes are scarce due to difficulties in culturing the parasite and lack of high-quality samples. In addition, P. vivax is incredibly diverse, necessitating the procurement of reference genomes from different geographical regions. Here we present four new P. vivax draft genomes assembled de novo from clinical samples collected in the China-Myanmar border area. We demonstrate comparable length and content to existing genomes, with the majority of structural variation occurring around subtelomeric regions and exported proteins, which we corroborated with detection of copy number variations in these regions. We predicted peptides from all PIR gene subfamilies, except for PIR D. We confirmed that proteins classically labeled as PIR D family members are not identifiable by PIR motifs, and actually bear stronger resemblance to DUF (domain of unknown function) family DUF3671, potentially pointing to a new, closely related gene family. Further, phylogenetic analyses of MSP7 genes showed high variability within the MSP7-B family compared to MSP7-A and -C families, and the result was comparable to that from whole genome analyses. The new genome assemblies serve as a resource for studying P. vivax within the GMS.
Collapse
Affiliation(s)
- Awtum M. Brashear
- Department of Internal Medicine, University of South Florida, Tampa, Tampa, FL, United States
| | - Adam C. Huckaby
- Department of Biology, University of Virginia, Charlottesville, VA, United States
| | - Qi Fan
- Dalian Institute of Science and Technology, Dalian, China
| | - Luke J. Dillard
- Department of Biology, University of Virginia, Charlottesville, VA, United States
| | - Yubing Hu
- Department of Immunology, College of Basic Medical Science, China Medical University, Shenyang, China
| | - Yuling Li
- Department of Immunology, College of Basic Medical Science, China Medical University, Shenyang, China
| | - Yan Zhao
- Department of Immunology, College of Basic Medical Science, China Medical University, Shenyang, China
| | - Zenglei Wang
- NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Yaming Cao
- Department of Immunology, College of Basic Medical Science, China Medical University, Shenyang, China
| | - Jun Miao
- Department of Internal Medicine, University of South Florida, Tampa, Tampa, FL, United States
| | - Jennifer L. Guler
- Department of Biology, University of Virginia, Charlottesville, VA, United States
| | - Liwang Cui
- Department of Internal Medicine, University of South Florida, Tampa, Tampa, FL, United States
| |
Collapse
|
4
|
Cheng CW, Jongwutiwes S, Putaporntip C, Jackson AP. Clinical expression and antigenic profiles of a Plasmodium vivax vaccine candidate: merozoite surface protein 7 (PvMSP-7). Malar J 2019; 18:197. [PMID: 31196098 PMCID: PMC6567670 DOI: 10.1186/s12936-019-2826-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 06/04/2019] [Indexed: 12/18/2022] Open
Abstract
Background Vivax malaria is the predominant form of malaria outside Africa, affecting about 14 million people worldwide, with about 2.5 billion people exposed. Development of a Plasmodium vivax vaccine is a priority, and merozoite surface protein 7 (MSP-7) has been proposed as a plausible candidate. The P. vivax genome contains 12 MSP-7 genes, which contribute to erythrocyte invasion during blood-stage infection. Previous analysis of MSP-7 sequence diversity suggested that not all paralogs are functionally equivalent. To explore MSP-7 functional diversity, and to identify the best vaccine candidate within the family, MSP-7 expression and antigenicity during bloodstream infections were examined directly from clinical isolates. Methods Merozoite surface protein 7 gene expression was profiled using RNA-seq data from blood samples isolated from ten human patients with vivax malaria. Differential expression analysis and co-expression cluster analysis were used to relate PvMSP-7 expression to genetic markers of life cycle stage. Plasma from vivax malaria patients was also assayed using a custom peptide microarray to measure antibody responses against the coding regions of 12 MSP-7 paralogs. Results Ten patients presented diverse transcriptional profiles that comprised four patient groups. Two MSP-7 paralogs, 7A and 7F, were expressed abundantly in all patients, while other MSP-7 genes were uniformly rare (e.g. 7J). MSP-7H and 7I were significantly more abundant in patient group 4 only, (two patients having experienced longer patency), and were co-expressed with a schizont-stage marker, while negatively associated with liver-stage and gametocyte-stage markers. Screening infections with a PvMSP-7 peptide array identified 13 linear B-cell epitopes in five MSP-7 paralogs that were recognized by plasma from all patients. Conclusions These results show that MSP-7 family members vary in expression profile during blood infections; MSP-7A and 7F are expressed throughout the intraerythrocytic development cycle, while expression of other paralogs is focused on the schizont. This may reflect developmental regulation, and potentially functional differentiation, within the gene family. The frequency of B-cell epitopes among paralogs also varies, with MSP-7A and 7L consistently the most immunogenic. Thus, MSP-7 paralogs cannot be assumed to have equal potential as vaccines. This analysis of clinical infections indicates that the most abundant and immunogenic paralog is MSP-7A. Electronic supplementary material The online version of this article (10.1186/s12936-019-2826-7) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Chew Weng Cheng
- Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, 146 Brownlow Hill, Liverpool, L3 5RF, UK.,Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Somchai Jongwutiwes
- Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Chaturong Putaporntip
- Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Andrew P Jackson
- Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, 146 Brownlow Hill, Liverpool, L3 5RF, UK.
| |
Collapse
|
5
|
Ahmed MA, Quan FS. Plasmodium knowlesi clinical isolates from Malaysia show extensive diversity and strong differential selection pressure at the merozoite surface protein 7D (MSP7D). Malar J 2019; 18:150. [PMID: 31035999 PMCID: PMC6489361 DOI: 10.1186/s12936-019-2782-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 04/16/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The high proportion of human cases due to the simian malaria parasite Plasmodium knowlesi in Malaysia is a cause of concern, as they can be severe and even fatal. Merozoite surface protein 7 (MSP7) is a multigene family which forms a non-covalent complex with MSP-1 prior to receptor-ligand recognition in Plasmodium falciparum and thus an important antigen for vaccine development. However, no study has been done in any of the ortholog family members in P. knowlesi from clinical samples. This study investigates the level of polymorphism, haplotypes, and natural selection acting at the pkmsp-7D gene in clinical samples from Malaysia. METHODS Thirty-six full-length pkmsp7D gene sequences (along with the reference H-strain: PKNH_1266000) obtained from clinical isolates of Malaysia, which were orthologous to pvmsp7H (PVX_082680) were downloaded from public databases. Population genetic, evolutionary and phylogenetic analyses were performed to determine the level of genetic diversity, polymorphism, recombination and natural selection. RESULTS Analysis of 36 full-length pkmsp7D sequences identified 147 SNPs (91 non-synonymous and 56 synonymous substitutions). Nucleotide diversity across the full-length gene was higher than its ortholog in Plasmodium vivax (msp7H). Region-wise analysis of the gene indicated that the nucleotide diversity at the central region was very high (π = 0.14) compared to the 5' and 3' regions. Most hyper-variable SNPs were detected at the central domain. Multiple test for natural selection indicated the central region was under strong positive natural selection however, the 5' and 3' regions were under negative/purifying selection. Evidence of intragenic recombination were detected at the central region of the gene. Phylogenetic analysis using full-length msp7D genes indicated there was no geographical clustering of parasite population. CONCLUSIONS High genetic diversity with hyper-variable SNPs and strong evidence of positive natural selection at the central region of MSP7D indicated exposure of the region to host immune pressure. Negative selection at the 5' and the 3' regions of MSP7D might be because of functional constraints at the unexposed regions during the merozoite invasion process of P. knowlesi. No evidence of geographical clustering among the clinical isolates from Malaysia indicated uniform selection pressure in all populations. These findings highlight the further evaluation of the regions and functional characterization of the protein as a potential blood stage vaccine candidate for P. knowlesi.
Collapse
Affiliation(s)
- Md Atique Ahmed
- Department of Medical Zoology, School of Medicine, Kyung Hee University, Seoul, 02447, Republic of Korea
| | - Fu-Shi Quan
- Department of Medical Zoology, School of Medicine, Kyung Hee University, Seoul, 02447, Republic of Korea. .,Medical Research Center for Bioreaction to Reactive Oxygen Species and Biomedical Science Institute, School of Medicine, Graduate School, Kyung Hee University, Seoul, Republic of Korea.
| |
Collapse
|
6
|
Cheng CW, Putaporntip C, Jongwutiwes S. Polymorphism in merozoite surface protein-7E of Plasmodium vivax in Thailand: Natural selection related to protein secondary structure. PLoS One 2018; 13:e0196765. [PMID: 29718980 PMCID: PMC5931635 DOI: 10.1371/journal.pone.0196765] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 04/19/2018] [Indexed: 11/18/2022] Open
Abstract
Merozoite surface protein 7 (MSP-7) is a multigene family expressed during malaria blood-stage infection. MSP-7 forms complex with MSP-1 prior to merozoite egress from erythrocytes, and could affect merozoite invasion of erythrocytes. To characterize sequence variation in the orthologue in P. vivax (PvMSP-7), a gene member encoding PvMSP-7E was analyzed among 92 Thai isolates collected from 3 major endemic areas of Thailand (Northwest: Tak, Northeast: Ubon Ratchathani, and South: Yala and Narathiwat provinces). In total, 52 distinct haplotypes were found to circulate in these areas. Although population structure based on this locus was observed between each endemic area, no genetic differentiation occurred between populations collected from different periods in the same endemic area, suggesting spatial but not temporal genetic variation. Sequence microheterogeneity in both N- and C- terminal regions was predicted to display 4 and 6 α-helical domains, respectively. Signals of purifying selection were observed in α-helices II-X, suggesting structural or functional constraint in these domains. By contrast, α-helix-I spanning the putative signal peptide was under positive selection, in which amino acid substitutions could alter predicted CD4+ T helper cell epitopes. The central region of PvMSP-7E comprised the 5’-trimorphic and the 3’-dimorphic subregions. Positive selection was identified in the 3’ dimorphic subregion of the central domain. A consensus of intrinsically unstructured or disordered protein was predicted to encompass the entire central domain that contained a number of putative B cell epitopes and putative protein binding regions. Evidences of intragenic recombination were more common in the central region than the remainders of the gene. These results suggest that the extent of sequence variation, recombination events and selective pressures in the PvMSP-7E locus seem to be differentially affected by protein secondary structure.
Collapse
Affiliation(s)
- Chew Weng Cheng
- Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Chaturong Putaporntip
- Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Somchai Jongwutiwes
- Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
- * E-mail:
| |
Collapse
|