Merozoite surface protein-3alpha is a reliable marker for population genetic analysis of Plasmodium vivax

Genetic diversity of the PvMSP-3α gene in Plasmodium vivax isolates circulating in the National Capital Region (NCR) of India

Malaria is still a public health problem in tropical countries like India; major malaria parasite species are Plasmodium falciparum and P. vivax. Of which, P. vivax is responsible for ∼40% of the malaria burden at least in the Indian scenario. Unfortunately, there is limited data on the population structure and genetic diversity of P. vivax parasites in India. In this study, we investigated the genetic diversity of P. vivax strains in the South-west district, Delhi and, Nuh district, Haryana [National Capital Region (NCR)], using a polymorphic marker- P. vivax merozoite surface protein-3α (PvMSP-3α) gene. Dried blood spots from microscopically confirmed P. vivax patients were used for investigation of the PvMSP-3α gene. PCR-RFLP was performed on the PvMSP-3α gene to investigate the genotypes and allelic variability with HhaI and AluI restriction enzymes. In total, 40 successfully PCR amplified PvMSP-3α gene segments were subjected to RFLP analysis. Amplified products showed three different base pair size variations viz. genotype A in 31(77.5%), genotype B in 4(10%) and genotype C in 5(12.5%) P. vivax specimens. RFLP with HhaI and AluI revealed 17 (H1-H17) and 25 (A1-A25) allelic variants, respectively. Interestingly, two similar sub-allelic variants, ie. H8 (with HhaI), and A4 (with AluI) clustered within the rural area of Nuh district, Haryana in two samples. With this study, we propose to commission such type of genetic diversity analysis of P. vivax to investigate the circulating genotypes of the parasites from distinct geographical locations across India, that can have significant implications in understanding the population structures of P. vivax.

Genetic Structure of Introduced Plasmodium vivax Malaria Isolates in Greece, 2015-2019

Greece has been malaria-free since 1974, after an intense malaria control program. However, as Greece hosts migrant populations from P. vivax malaria-endemic countries, there is a risk of introducing the disease to specific vulnerable and receptive areas of the country. Knowledge of the genetic diversity of P. vivax populations is essential for understanding the dynamics of malaria disease transmission in a given region. We used nine highly polymorphic markers to genotype 124 P. vivax-infected archived DNA samples from human blood specimens referred to the NMRL from all over Greece throughout 2015-2019. The genotypic variability of the samples studied was noted, as they comprised several unique haplotypes, indicative of the importation of a large number of different P. vivax strains in the country. However, only a few events of local transmission were recorded. Genotyping revealed and confirmed the same clusters as those identified through epidemiological investigation. In only one introduction event was the index case found. No sustained/ongoing malaria transmissions in/between the studied regions or during consecutive years or additional foci of local transmission were observed. Genotyping is an important component in assisting malaria surveillance, as it provides information concerning the patterns of introduction and the effectiveness of implemented malaria control and elimination measures.

Genetic Diversity of Plasmodium vivax Field Isolates from the Thai–Myanmar Border during the Period of 2006–2016

High levels of genetic variants of Plasmodium vivax have previously been reported in Thailand. Circumsporozoite surface protein (CSP), merozoite surface protein (MSP), and microsatellite markers were used to determine the genetic polymorphisms of P. vivax. This study aimed to investigate the molecular epidemiology of P. vivax populations at the Thai–Myanmar border by genotyping the PvCSP, PvMSP-3α, and PvMSP-3β genes. Four hundred and forty P. vivax clinical isolates were collected from the Mae Sot and Sai Yok districts from 2006–2007 and 2014–2016. Polymerase chain reaction with restriction fragment length polymorphism (RFLP) was used to investigate the genetic polymorphisms of the target genes. Based on PCR band size variations, 14 different PvCSP alleles were identified: eight for VK210 and six for VK247. The VK210 genotype was the dominant variant during both sample collection periods. Based on PCR genotyping, three distinct types (A, B, and C) for both PvMSP-3α and PvMSP-3β were observed. Following RFLP, 28 and 14 allelic variants of PvMSP-3α and 36 and 20 allelic variants of PvMSP-3β with varying frequencies were identified during the first and second periods, respectively. High genetic variants of PvMSP-3 and PvCSP were found in the study area. PvMSP-3β exhibited a higher level of genetic diversity and multiple-genotype infection versus PvMSP-3α.

Genetic diversity of Plasmodium vivax merozoite surface protein-3 alpha and beta from diverse geographic areas of Thailand

Malaria is parasitic disease cause by Plasmodium infection. In Thailand, co-infections of Plasmodium vivax and P. falciparum are commonly found. P. vivax infection has been increasing in the past decade. The objective of this study was to investigate the genetic diversity patterns of Plasmodium vivax merozoite surface protein 3 (PvMSP-3) genes in total of 450 isolates collected from Thai-neighboring border during two different periods (2009-20 14 and 2015 -2016) using polymerase chain reaction (PCR) - restriction fragment length polymorphism (RFLP) method. Three major types of PvMSP-3α (A, B, and C) and PvMSP-3β (A, B, and C) were detected based on PCR products size. Forty five and 23 of PvMSP-3α and, 41 and 30 alleles of PvMSP-3β genes from the first period and second period, respectively, with difference frequencies of samples were distinguished. The results strongly indicate genetic diversity patterns of PvMSP-3 in the second period especially samples from Thai-Myanmar border. These two polymorphic genes could be used as a molecular epidemiologic marker for genotyping P. vivax isolate in Thailand.

Polymorphic markers for identification of parasite population in Plasmodium malariae

Background

Molecular genotyping in Plasmodium serves many aims including providing tools for studying parasite population genetics and distinguishing recrudescence from reinfection. Microsatellite typing, insertion-deletion (INDEL) and single nucleotide polymorphisms is used for genotyping, but only limited information is available for Plasmodium malariae, an important human malaria species. This study aimed to provide a set of genetic markers to facilitate the study of P. malariae population genetics.

Methods

Markers for microsatellite genotyping and pmmsp1 gene polymorphisms were developed and validated in symptomatic P. malariae field isolates from Myanmar (N = 37). Fragment analysis was used to determine allele sizes at each locus to calculate multiplicity of infections (MOI), linkage disequilibrium, heterozygosity and construct dendrograms. Nucleotide diversity (π), number of haplotypes, and genetic diversity (H_d) were assessed and a phylogenetic tree was constructed. Genome-wide microsatellite maps with annotated regions of newly identified markers were constructed.

Results

Six microsatellite markers were developed and tested in 37 P. malariae isolates which showed sufficient heterozygosity (0.530–0.922), and absence of linkage disequilibrium (I_A^S=0.03, p value > 0.05) (N = 37). In addition, a tandem repeat (VNTR)-based pmmsp1 INDEL polymorphisms marker was developed and assessed in 27 P. malariae isolates showing a nucleotide diversity of 0.0976, haplotype gene diversity of 0.698 and identified 14 unique variants. The size of VNTR consensus repeat unit adopted as allele was 27 base pairs. The markers Pm12_426 and pmmsp1 showed greatest diversity with heterozygosity scores of 0.920 and 0.835, respectively. Using six microsatellites markers, the likelihood that any two parasite strains would have the same microsatellite genotypes was 8.46 × 10⁻⁴ and was further reduced to 1.66 × 10⁻⁴ when pmmsp1 polymorphisms were included.

Conclusions

Six novel microsatellites genotyping markers and a set of pmmsp1 VNTR-based INDEL polymorphisms markers for P. malariae were developed and validated. Each marker could be independently or in combination employed to access genotyping of the parasite. The newly developed markers may serve as a useful tool for investigating parasite diversity, population genetics, molecular epidemiology and for distinguishing recrudescence from reinfection in drug efficacy studies.

Genetic Diversity of Plasmodium vivax in Clinical Isolates from Southern Thailand using PvMSP1, PvMSP3 (PvMSP3α, PvMSP3β) Genes and Eight Microsatellite Markers

Plasmodium vivax is usually considered morbidity in endemic areas of Asia, Central and South America, and some part of Africa. In Thailand, previous studies indicated the genetic diversity of P. vivax in malaria-endemic regions such as the western part of Thailand bordering with Myanmar. The objective of the study is to investigate the genetic diversity of P. vivax circulating in Southern Thailand by using 3 antigenic markers and 8 microsatellite markers. Dried blood spots were collected from Chumphon, Phang Nga, Ranong and, Surat Thani provinces of Thailand. By PCR, 3 distinct sizes of PvMSP3α, 2 sizes of PvMSP3β and 2 sizes of PvMSP1 F2 were detected based on the length of PCR products, respectively. PCR/RFLP analyses of these antigen genes revealed high levels of genetic diversity. The genotyping of 8 microsatellite loci showed high genetic diversity as indicated by high alleles per locus and high expected heterozygosity (HE). The genotyping markers also showed multiple-clones of infection. Mixed genotypes were detected in 4.8% of PvMSP3α, 29.1% in PvMSP3β and 55.3% of microsatellite markers. These results showed that there was high genetic diversity of P. vivax isolated from Southern Thailand, indicating that the genetic diversity of P. vivax in this region was comparable to those observed other areas of Thailand.

The Role of Molecular Techniques on Malaria Control and Elimination Programs in Iran: A Review Article

BACKGROUND

The aim of this review was to describe the application of molecular methods in epidemiological aspects of malaria vectors, parasites, and human hosts in Iran and their critical role in malaria control and elimination programs.

METHODS

Medline, EMBASE, Web of Science, Scopus, and Google Scholar databases were searched systematically for original published papers on PCR, the molecular identification of malaria vectors, the molecular epidemiology of malaria, insecticide resistance, and drug-resistant parasites, in Iran. In total, 51 studies on molecular entomology and 36 studies on molecular parasitology of malaria and three on human host were selected.

RESULTS

Molecular methods are essential for improving the detection of malaria infection and monitoring antimalarial drugs and insecticide resistance in malaria elimination settings such as Iran.

CONCLUSION

The application of molecular methods may be of particular interest for malaria control/elimination programs, for monitoring progress towards malaria elimination, and for optimal orientation of program activities.

Variable number of tandem repeats of 9 Plasmodium vivax genes among Southeast Asian isolates

The variable number of tandem repeats (VNTRs) provides valuable information about both the functional and evolutionary aspects of genetic diversity. Comparative analysis of 3 Plasmodium falciparum genomes has shown that more than 9% of its open reading frames (ORFs) harbor VNTRs. Although microsatellites and VNTR genes of P. vivax were reported, the VNTR polymorphism of genes has not been examined widely. In this study, 230 P. vivax genes were analyzed for VNTRs by SERV, and 33 kinds of TR deletions or insertions from 29 P. vivax genes (12.6%) were found. Of these, 9 VNTR fragments from 8 P. vivax genes were used for PCR amplification and sequence analysis to examine the genetic diversity among 134 isolates from four Southeast Asian countries (China, Republic of Korea, Thailand, and Myanmar) with different malaria endemicity. We confirmed the existence of extensive polymorphism of VNTR fragments in field isolates. This detection provides several suitable markers for analysis of the molecular epidemiology of P. vivax field isolates.

PCR-RFLP for Rapid Subtyping of Plasmodium vivax Korean Isolates

Vivax malaria reemerged in Korea in 1993 and the outbreak has been continued with fluctuating numbers of annual indigenous cases. Understanding the nature of the genetic population of Plasmodium vivax circulating in Korea is beneficial for the knowledge of the nationwide parasite heterogeneity and in the implementation of malaria control programs in the country. Previously, we analyzed polymorphic nature of merozoite surface protein-1 (MSP-1) and MSP-3α in Korean P. vivax population and identified the Korean P. vivax population has been diversifying rapidly, with the appearance of parasites with new genetic subtypes, despite the recent reduction of the disease incidence. In the present study, we developed simple PCR-RFLP methods for rapid subtyping of MSP-1 and MSP-3α of Korean P. vivax isolates. These PCR-RFLP methods were able to easily distinguish each subtype of Korean P. vivax MSP-1 and MSP-3α with high accuracy. The PCR-RFLP subtyping methods developed here would be easily applied to massive epidemiological studies for molecular surveillance to understand genetic population of P. vivax and to supervise the genetic variation of the parasite circulating in Korea.

Plasmodium vivax msp-3α polymorphisms: analysis in the Indian subcontinent

BACKGROUND

Plasmodium vivax is the most widely distributed human malaria parasite and accounts for approximately the same number of malaria cases as Plasmodium falciparum in India. Compared with P. falciparum, P. vivax is difficult to eradicate because of its tendency to cause relapses, which impacts treatment and control strategies. The genetic diversity of these parasites, particularly of the merozoite surface protein-3 alpha (msp-3α) gene, can be used to help develop a potential vaccine. The present study aimed to investigate the genetic diversity of P. vivax using the highly polymorphic antigen gene msp-3α and to assess the suitability of using this gene for population genetic studies of P. vivax isolates and was carried out in 2004-06. No recent study has been reported for MSP 3α in the recent decade in India. Limited reports are available on the genetic diversity of the P. vivax population in India; hence, this report aimed to improve the understanding of the molecular epidemiology of the parasite by studying the P. vivax msp-3α (Pvmsp-3α) marker from P. vivax field isolates from India.

METHODS

Field isolates were collected from different sites distributed across eight states in India. A total of 182 blood samples were analysed by a nested polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique using the HhaI and AluI restriction enzymes to determine genetic msp-3α variation among clinical P. vivax isolates.

RESULTS

Based on the length variants of the PCR products of Pvmsp-3α gene, three allele sizes, Type A (1.8 kb), Type B (1.5 kb) and Type C (1.2 kb) were detected among the 182 samples. Type A PCR amplicon was more predominant (75.4 %) in the samples compared with the Type B (14.3 %) and Type C (10.0 %) polymorphisms. Among all of the samples analysed, 8.2 % were mixed infections detected by PCR alone. Restriction fragment length polymorphism (RFLP) analysis involving the restriction enzymes AluI and HhaI generated fragment sizes that were highly polymorphic and revealed substantial diversity at the nucleotide level.

CONCLUSIONS

The present study is the first extensive study in India using the Pvmsp-3α marker. The results indicated that Pvmps-3α, a polymorphic genetic marker of P. vivax, exhibited considerable variability in infection prevalence in field isolates from India. Additionally, the mean multiplicity of infection observed at all of the study sites indicated that P. vivax is highly diverse in nature in India, and Pvmsp-3α is likely an effective and promising epidemiological marker.

Characteristics of Imported Malaria and Species of Plasmodium Involved in Shandong Province, China (2012-2014)

Malaria remains a serious public health problem in Shandong Province, China; therefore, it is important to explore the characteristics of the current malaria prevalence situation in the province. In this study, data of malaria cases reported in Shandong during 2012-2014 were analyzed, and Plasmodium species were confirmed by smear microscopy and nested-PCR. A total of 374 malaria cases were reported, 80.8% of which were reported from 6 prefectures. Of all cases, P. falciparum was dominant (81.3%), followed by P. vivax (11.8%); P. ovale and P. malariae together accounted for 6.4% of cases. Notably, for the first time since 2012, no indigenous case had been reported in Shandong Province, a situation that continued through 2014. Total 95.2% of cases were imported from Africa. The ratio of male/female was 92.5:1, and 96.8% of cases occurred in people 20-54 years of age. Farmers or laborers represented 77.5% of cases. No significant trends of monthly pattern were found in the reported cases. All patients were in good condition after treatment, except for 3 who died. These results indicate that imported malaria has increased significantly since 2012 in Shandong Province, especially for P. falciparum, and there is an emergence of species diversity.

Genotyping of Plasmodium vivax by minisatellite marker and its application in differentiating relapse and new infection

BACKGROUND

Plasmodium vivax malaria is a major public health problem in India. Control of vivax malaria is challenging due to various factors including relapse which increase the burden significantly. There is no well studied marker to differentiate relapse from reinfection. This creates hindrance in search for anti-relapse medicines. The genomic study of minisatellite can help in characterization of relapse and new infection of vivax malaria.

METHODS

Eighty-eight samples of P. vivax were collected from malaria clinic. All the 14 chromosomes of P. vivax were scanned for minisatellite marker by Tandem Repeat Finder software Version 4.07b. Minisatellite marker CH1T1M13779 from chromosome one was applied for genotyping in 88 samples of P. vivax including 2 recurrence cases.

RESULTS

Whole genome of P. vivax was scanned and found to have one hundred minisatellite markers. CH1T1M13779 minisatellite marker from chromosome-1 was used for amplification in 88 samples of P. vivax. Of 66 amplified samples, 14 alleles were found with varied allele frequency. The base size of 280 (13.63 %) 320 bp (13.63 %) and 300 bp (16.66 %) showed the predominant allele in the P. vivax population. Genotyping of two paired samples (day 0 and day relapse) could demonstrate the presence of relapse and reinfection.

CONCLUSION

The CH1T1M13779 can be potential minisatellite marker which can be used to differentiate between relapse and new infection of P. vivax strain.

Assessment of an automated capillary system for Plasmodium vivax microsatellite genotyping

BACKGROUND

Several platforms have been used to generate the primary data for microsatellite analysis of malaria parasite genotypes. Each has relative advantages but share a limitation of being time- and cost-intensive. A commercially available automated capillary gel cartridge system was assessed in the microsatellite analysis of Plasmodium vivax diversity in the Peruvian Amazon.

METHODS

The reproducibility and accuracy of a commercially-available automated capillary system, QIAxcel, was assessed using a sequenced PCR product of 227 base pairs. This product was measured 42 times, then 27 P. vivax samples from Peruvian Amazon subjects were analyzed with this instrument using five informative microsatellites. Results from the QIAxcel system were compared with a Sanger-type sequencing machine, the ABI PRISM(®) 3100 Genetic Analyzer.

RESULTS

Significant differences were seen between the sequenced amplicons and the results from the QIAxcel instrument. Different runs, plates and cartridges yielded significantly different results. Additionally, allele size decreased with each run by 0.045, or 1 bp, every three plates. QIAxcel and ABI PRISM systems differed in giving different values than those obtained by ABI PRISM, and too many (i.e. inaccurate) alleles per locus were also seen with the automated instrument.

CONCLUSIONS

While P. vivax diversity could generally be estimated using an automated capillary gel cartridge system, the data demonstrate that this system is not sufficiently precise for reliably identifying parasite strains via microsatellite analysis. This conclusion reached after systematic analysis was due both to inadequate precision and poor reproducibility in measuring PCR product size.

Molecular genetic analysis of Plasmodium vivax isolates from Eastern and Central Sudan using pvcsp and pvmsp-3α genes as molecular markers

In Sudan, Plasmodium vivax accounts for approximately 5-10% of malaria cases. This study was carried out to determine the genetic diversity of P. vivax population from Sudan by analyzing the polymorphism of P. vivax csp (pvcsp) and pvmsp-3α genes. Blood samples (n=76) were taken from suspected malaria cases from 2012-2013 in three health centers of Eastern and Central Sudan. Parasite detection was performed by microscopy and molecular techniques, and genotyping of both genes was performed by PCR-RFLP followed by DNA sequence for only pvcsp gene (n=30). Based on microscopy analysis, 76 (%100) patients were infected with P. vivax, whereas nested-PCR results showed that 86.8% (n=66), 3.9% (n=3), and 3.9% (n=3) of tested samples had P. vivax as well as Plasmodium falciparum mono- and mixed infections, respectively. Four out of 76 samples had no results in molecular diagnosis. All sequenced samples were found to be of VK210 (100%) genotype with six distinct amino acid haplotypes, and 210A (66.7%) was the most prevalent haplotype. The Sudanese isolates displayed variations in the peptide repeat motifs (PRMs) ranging from 17 to 19 with GDRADGQPA (PRM1), GDRAAGQPA (PRM2) and DDRAAGQPA (PRM3). Also, 54 polymorphic sites with 56 mutations were found in repeat and post-repeat regions of the pvcsp and the overall nucleotide diversity (π) was 0.02149±0.00539. A negative value of dN-dS (-0.0344) was found that suggested a significant purifying selection of Sudanese pvcsp, (Z test, P<0.05). Regarding pvmsp-3α, three types were detected: types A (94.6%, 52/55), type C (3.6%, 2/55), and type B (1.8%, 1/55). No multiclonal infections were detected, and RFLP analysis identified 13 (Hha I, A1-A11, B1, and C1) and 16 (Alu I, A1-A14, B1, and C1) distinct allelic forms. In conclusion, genetic investigation among Sudanese P. vivax isolates indicated that this antigen showed limited antigenic diversity.

Genetic diversity of Plasmodium vivax population before elimination of malaria in Hainan Province, China

BACKGROUND

Hainan Province is one of the most severe endemic regions with high transmission of Plasmodium falciparum and Plasmodium vivax in China. However, the incidence of P. falciparum and P. vivax has dropped dramatically since 2007 and a national elimination malaria programme (NEMP) was launched after 2010. To better understand the genetic information on P. vivax population before elimination of malaria in Hainan Province, the extent of genetic diversity of P. vivax isolates in Hainan Province was investigated using four polymorphic genetic markers, including P. vivax merozoite surface proteins 1, 3α, and 3β (pvmsp-1, pvmsp-3α, and pvmsp-3β) and circumsporozoite protein (pvcsp).

METHODS

Isolates of P. vivax (n = 27) from Hainan Province were collected from 2009 to 2010 and pvmsp-1 and pvcsp were analysed by DNA sequencing, respectively. Using polymerase chain reaction-restriction fragment length polymorphism were analysed in pvmsp-3α, and pvmsp-3β.

RESULTS

The DNA sequencing analysis on pvmsp1 revealed that there were three allele types: Salvador-1 (Sal-1), Belem and recombinant (R) types. Among them, Sal-1 type was a dominant strain with eight variant subtypes (88.9%), whereas R- (3.7%) and Belem-type strains (7.4%) had one variant subtypes, respectively. All the isolates carried pvcsp with VK210 type accounting for 85.2% (23/27 isolates) and VK247 type accounting for 14.8% (4/27). Only type A and type B alleles were successfully amplified in pvmsp-3α gene, and a high level of polymorphism was observed in pvmsp-3α. Considering pvmsp-3β gene, type A was the predominant type in 17 isolates (63%), whereas type B was dominant in only ten isolates (37%).

CONCLUSION

The present data indicate that there was high degree of genetic diversity among P. vivax population in Hainan Province of China during the pre-elimination stage of malaria, with 26 unique haplotypes observed among 27 samples.

The Plasmodium vivax merozoite surface protein 3β sequence reveals contrasting parasite populations in southern and northwestern Thailand

BACKGROUND

Malaria control efforts have a significant impact on the epidemiology and parasite population dynamics. In countries aiming for malaria elimination, malaria transmission may be restricted to limited transmission hot spots, where parasite populations may be isolated from each other and experience different selection forces. Here we aim to examine the Plasmodium vivax population divergence in geographically isolated transmission zones in Thailand.

METHODOLOGY

We employed the P. vivax merozoite surface protein 3β (PvMSP3β) as a molecular marker for characterizing P. vivax populations based on the extensive diversity of this gene in Southeast Asian parasite populations. To examine two parasite populations with different transmission levels in Thailand, we obtained 45 P. vivax isolates from Tak Province, northwestern Thailand, where the annual parasite incidence (API) was more than 2%, and 28 isolates from Yala and Narathiwat Provinces, southern Thailand, where the API was less than 0.02%. We sequenced the PvMSP3β gene and examined its genetic diversity and molecular evolution between the parasite populations.

PRINCIPAL FINDINGS

Of 58 isolates containing single PvMSP3β alleles, 31 sequence types were identified. The overall haplotype diversity was 0.77 ± 0.06 and nucleotide diversity 0.0877±0.0054. The northwestern vivax malaria population exhibited extensive haplotype diversity (HD) of PvMSP3β (HD=1.0). In contrast, the southern parasite population displayed a single PvMSP3β allele (HD=0), suggesting a clonal population expansion. This result revealed that the extent of allelic diversity in P. vivax populations in Thailand varies among endemic areas.

CONCLUSION

Malaria parasite populations in a given region may vary significantly in genetic diversity, which may be the result of control and influenced by the magnitude of malaria transmission intensity. This is an issue that should be taken into account for the implementation of P. vivax control measures such as drug policy and vaccine development.

Genetic diversity of Plasmodium vivax population in Anhui province of China

Background

Although the numbers of malaria cases in China have been declining in recent years, outbreaks of Plasmodium vivax malaria were still being reported in rural areas south of the Yellow River. To better understand the transmission dynamics of P. vivax parasites in China, the extent of genetic diversity of P. vivax populations circulating in Bozhou of Anhui province of China were investigated using three polymorphic genetic markers: merozoite surface proteins 1 and 3α (pvmsp-1 and pvmsp-3α) and circumsporozoite protein (pvcsp).

Methods

Forty-five P. vivax clinical isolates from Bouzhou of Anhui province were collected from 2009 to 2010 and were analysed using PCR/RFLP or DNA sequencing.

Results

Seven and six distinct allelic variants were identified using PCR/RFLP analysis of pvmsp-3α with HhaI and AluI, respectively. DNA sequence analysis of pvmsp-1 (variable block 5) revealed that there were Sal-I and recombinant types but not Belem type, and seven distinct allelic variants in pvmsp-1 were detected, with recombinant subtype 2 (R2) being predominant (66.7%). All the isolates carried pvcsp with VK210 type but not VK247 or P. vivax-like types in the samples. Sequence analysis of pvcsp gene revealed 12 distinct allelic variants, with VK210-1 being predominant (41.5%).

Conclusions

The present data indicate that there is some degree of genetic diversity among P. vivax populations in Anhui province of China. The genetic data obtained may assist in the surveillance of P. vivax infection in endemic areas or in tracking potential future disease outbreak.

Genotyping Plasmodium vivax isolates from the 2011 outbreak in Greece

BACKGROUND

Plasmodium vivax malaria was common in Greece until the 1950s with epidemics involving thousands of cases every year. Greece was declared free of malaria by the World Health Organization in 1974. From 1974 to 2010, an average of 39 cases per year were reported, which were mainly imported. However, in 2009 and 2010 six and one autochthonous cases were reported culminating with a total of 40 autochthonous cases reported in 2011, of which 34 originated from a single region: Laconia of Southern Peloponnese. In this study the genotypic complexity of the P. vivax infections from the outbreak in Greece during 2011 is described, to elucidate the possible origin and spread of the disease.

METHODS

Three polymorphic markers of P. vivax were used; Pvmsp-3α and the microsatellites m1501 and m3502 on P. vivax isolates sampled from individuals diagnosed in Greece. Thirty-nine isolates were available for this study (20 autochthonous and 19 imported), mostly from Evrotas municipality in Laconia region, in southern Greece, (n = 29), with the remaining representing sporadic cases originating from other areas of Greece.

RESULTS

Genotyping the Evrotas samples revealed seven different haplotypes where the majority of the P. vivax infections expressed two particular Pvmsp-3α-m1501-m3502 haplotypes, A10-128-151 (n = 14) and A10-121-142 (n = 7). These haplotypes appeared throughout the period in autochthonous and imported cases, indicating continuous transmission. In contrast, the P. vivax autochthonous cases from other parts of Greece were largely comprised of unique haplotypes, indicating limited transmission in these other areas.

CONCLUSIONS

The results indicate that several P. vivax strains were imported into various areas of Greece in 2011, thereby increasing the risk of re-introduction of malaria. In the region of Evrotas ongoing transmission occurred exemplifying that further control measures are urgently needed in this region of southern Europe. In circumstances where medical or travel history is scarce, methods of molecular epidemiology may prove highly useful for the correct classification of the cases.

Merozoite surface protein-3 alpha as a genetic marker for epidemiologic studies in Plasmodium vivax: a cautionary note

Background

Plasmodium vivax is the most widespread of the human malaria parasites in terms of geography, and is thought to present unique challenges to local efforts aimed at control and elimination. Parasite molecular markers can provide much needed data on P. vivax populations, but few such markers have been critically evaluated. One marker that has seen extensive use is the gene encoding merozoite surface protein 3-alpha (MSP-3α), a blood-stage antigen known to be highly variable among P. vivax isolates. Here, a sample of complete msp-3α gene sequences is analysed in order to assess its utility as a molecular marker for epidemiologic investigations.

Methods

Amplification, cloning and sequencing of additional P. vivax isolates from different geographic locations, including a set of Venezuelan field isolates (n = 10), yielded a sample of 48 complete msp-3α coding sequences. Characterization of standard population genetic measures of diversity, phylogenetic analysis, and tests for recombination were performed. This allowed comparisons to patterns inferred from the in silico simulation of a polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) protocol used widely.

Results

The larger sample of MSP-3α diversity revealed incongruence between the observed levels of nucleotide polymorphism, which were high in all populations, and the pattern of PCR-RFLP haplotype diversity. Indeed, PCR-RFLP haplotypes were not informative of a population’s genetic diversity and identical haplotypes could be produced from analogous bands in the commonly used protocol. Evidence of frequent and variable insertion-deletion mutations and recurrent recombination between MSP-3α haplotypes complicated the inference of genetic diversity patterns and reduced the phylogenetic signal.

Conclusions

The genetic diversity of P. vivax msp-3α involves intragenic recombination events. Whereas the high genetic diversity of msp-3α makes it a promising marker for some epidemiological applications, the ability of msp-3α PCR-RFLP analysis to accurately track parasites is limited. Local studies of the circulating alleles are needed before implementing PCR-RFLP approaches. Furthermore, evidence from the global sample analysed here suggests such msp-3α PCR-RFLP methods are not suitable for broad geographic studies or tracking parasite populations for an extended period of time.

Microgeographical differences of Plasmodium vivax relapse and re-infection in the Peruvian Amazon

To determine the magnitude of Plasmodium vivax relapsing malaria in rural Amazonia, we carried out a study in four sites in northeastern Peru. Polymerase chain reaction-restriction fragment length polymorphism of PvMSP-3α and tandem repeat (TR) markers were compared for their ability to distinguish relapse versus reinfection. Of 1,507 subjects with P. vivax malaria, 354 developed > 1 episode during the study; 97 of 354 (27.5%) were defined as relapse using Pvmsp-3α alone. The addition of TR polymorphism analysis significantly reduced the number of definitively defined relapses to 26 of 354 (7.4%) (P < 0.05). Multivariate logistic regression modeling showed that the probability of having > 1 infection was associated with the following: subjects in Mazan (odds ratio [OR] = 2.56; 95% confidence interval [CI] 1.87, 3.51), 15-44 years of age (OR = 1.49; 95% CI 1.03, 2.15), traveling for job purposes (OR = 1.45; 95%CI 1.03, 2.06), and travel within past month (OR = 1.46; 95% CI 1.0, 2.14). The high discriminatory capacity of the molecular tools shown here is useful for understanding the micro-geography of malaria transmission.

Population genetic structure and polymorphism analysis of gene encoding apical membrane antigen-1 (AMA-1) of Iranian Plasmodium vivax wild isolates

Plasmodium vivax apical membrane antigen-1 (PvAMA-1) is a major candidate antigen for human malaria vaccine. In the present study, polymorphism of pvama-1 among Iranian isolates was investigated to generate useful information on this vaccine candidate antigen, which is required for the rational design of a vaccine against P. vivax. Blood samples were collected from P. vivax-infected Iranian patients during 2009-2010. Of 99 collected isolates, 37 were analyzed for almost the entire pvama-1 gene using sequencing. The overall nucleotide diversity (π) was 0.00826 ± 0.0004 and the majority of polymorphic sites were identified in domain I (DI) of the pvama-1 gene. Neutrality analysis using Tajima's D, Fu and Li's D* and F* and McDonald Kreitman tests showed a significant positive departure from neutral substitution patterns, indicating a possible balancing selection across the entire ectodomain and DI sequences of pvama-1 gene. However, no evidence was found for the balancing selection in DII and DIII regions of Iranian PvAMA-1. Also, 29 haplotypes with different frequencies were identified and the overall haplotype diversity was 0.982 ± 0.012. Epitope mapping prediction of PvAMA-1 showed the potential B-cell epitopes across DI-DIII overlap with E145K, P210S, R249H, G253E, K352E, R438H and N445D mutations; however, no mutation has been found in intrinsically unstructured/disordered regions. The fixation index (Fst) estimation between Iran and the closest geographical sites such as India (0.0707) showed a slight geographical genetic differentiation; however, the Fst estimation between Iran and Thailand (0.1253) suggested a moderate geographical isolation. In summary, genetic investigation in pvama-1 among Iranian P. vivax isolates indicates that this antigen showed limited antigenic diversity and most of the detected mutations are located outside B-cell epitopes. Therefore, the present results have significant implications in understanding the nature of P. vivax population circulating in Iran as well as in providing useful information for malaria vaccine development based on this antigen.

Plasmodium vivax merozoite surface protein-3 (PvMSP3): expression of an 11 member multigene family in blood-stage parasites

Background

Three members of the Plasmodium vivax merozoite surface protein-3 (PvMSP3) family (PvMSP3-α, PvMSP3-β and PvMSP3-γ) were initially characterized and later shown to be part of a larger highly diverse family, encoded by a cluster of genes arranged head-to-tail in chromosome 10. PvMSP3-α and PvMSP3-β have become genetic markers in epidemiological studies, and are being evaluated as vaccine candidates. This research investigates the gene and protein expression of the entire family and pertinent implications.

Methodology/Principal Findings

A 60 kb multigene locus from chromosome 10 in P. vivax (Salvador 1 strain) was studied to classify the number of pvmsp3 genes present, and compare their transcription, translation and protein localization patterns during blood-stage development. Eleven pvmsp3 paralogs encode an N-terminal NLRNG signature motif, a central domain containing repeated variable heptad sequences, and conserved hydrophilic C-terminal features. One additional ORF in the locus lacks these features and was excluded as a member of the family. Transcripts representing all eleven pvmsp3 genes were detected in trophozoite- and schizont-stage RNA. Quantitative immunoblots using schizont-stage extracts and antibodies specific for each PvMSP3 protein demonstrated that all but PvMSP3.11 could be detected. Homologs were also detected by immunoblot in the closely related simian species, P. cynomolgi and P. knowlesi. Immunofluorescence assays confirmed that eight of the PvMSP3s are present in mature schizonts. Uniquely, PvMSP3.7 was expressed exclusively at the apical end of merozoites.

Conclusion/Significance

Specific proteins were detected representing the expression of 10 out of 11 genes confirmed as members of the pvmsp3 family. Eight PvMSP3s were visualized surrounding merozoites. In contrast, PvMSP3.7 was detected at the apical end of the merozoites. Pvmsp3.11 transcripts were present, though no corresponding protein was detected. PvMSP3 functions remain unknown. The ten expressed PvMSP3s are predicted to have unique and complementary functions in merozoite biology.

Molecular and epidemiological characterization of Plasmodium vivax recurrent infections in southern Mexico

Background

In southern Mexico, malaria transmission is low, seasonal, and persistent. Because many patients are affected by two or more malaria episodes caused by Plasmodium vivax, we carried out a study to determine the timing, frequency, and genetic identity of recurrent malaria episodes in the region between 1998 and 2008.

Methods

Symptomatic patients with more than one P. vivax infection were followed up, and blood samples were collected from primary and recurrent infections. DNA extracted from infected blood samples was analyzed for restriction fragment length polymorphism (RFLP) in genes encoding csp and msp3α, as well as size variation in seven microsatellites.

Results

One hundred and forty six parasite samples were collected from 70 patients; of these, 65 patients had one recurrent infection, four had two, and one had three recurrent infections. The majority of recurrent infections occurred within one year of the primary infection, some of which were genetically homologous to the primary infection. As the genetic diversity in the background population was high, the probability of homologous re-infection was low and the homologous recurrences likely reflected relapses. These homologous recurrent infections generally had short (< 6 months) or long (6–12 months) intervals between the primary (PI) and recurrent (RI) infections; whereas infections containing heterologous genotypes had relatively longer intervals. The epidemiological data indicate that heterologous recurrences could be either relapse or re-infections.

Conclusions

Genetic and temporal analysis of P. vivax recurrence patterns in southern Mexico indicated that relapses play an important role in initiating malaria transmission each season. The manifestation of these infections during the active transmission season allowed the propagation of diverse hypnozoite genotypes. Both short- and long-interval relapses have contributed to parasite persistence and must be considered as targets of treatment for malaria elimination programs in the region to be successful.

Duffy Blood Group System and the malaria adaptation process in humans

Malaria is an acute infectious disease caused by the protozoa of the genus Plasmodium. The antigens of the Duffy Blood Group System, in addition to incompatibilities in transfusions and hemolytic disease of the newborn, are of great interest in medicine due to their association with the invasion of red blood cells by the parasite Plasmodium vivax. For invasions to occur an interaction between the parasites and antigens of the Duffy Blood Group System is necessary. In Caucasians six antigens are produced by the Duffy locus (Fya, Fyb, F3, F4, F5 and F6). It has been observed that Fy(a-b-) individuals are resistant to Plasmodium knowlesi and P. vivax infection, because the invasion requires at least one of these antigens. The P. vivax Duffy Binding Protein (PvDBP) is functionally important in the invasion process of these parasites in Duffy / DARC positive humans. The proteins or fractions may be considered, therefore, an important and potential inoculum to be used in immunization against malaria.

Molecular markers and genetic diversity of Plasmodium vivax

Enhanced understanding of the transmission dynamics and population genetics for Plasmodium vivax is crucial in predicting the emergence and spread of novel parasite phenotypes with major public health implications, such as new relapsing patterns, drug resistance and increased virulence. Suitable molecular markers are required for these population genetic studies. Here, we focus on two groups of molecular markers that are commonly used to analyse natural populations of P. vivax. We use markers under selective pressure, for instance, antigen-coding polymorphic genes, and markers that are not under strong natural selection, such as most minisatellite and microsatellite loci. First, we review data obtained using genes encoding for P. vivax antigens: circumsporozoite protein, merozoite surface proteins 1 and 3α, apical membrane antigen 1 and Duffy binding antigen. We next address neutral or nearly neutral molecular markers, especially microsatellite loci, providing a complete list of markers that have already been used in P. vivax populations studies. We also analyse the microsatellite loci identified in the P. vivax genome project. Finally, we discuss some practical uses for P. vivax genotyping, for example, detecting multiple-clone infections and tracking the geographic origin of isolates.

Understanding the population genetics of Plasmodium vivax is essential for malaria control and elimination

Traditionally, infection with Plasmodium vivax was thought to be benign and self-limiting, however, recent evidence has demonstrated that infection with P. vivax can also result in severe illness and death. Research into P. vivax has been relatively neglected and much remains unknown regarding the biology, pathogenesis and epidemiology of this parasite. One of the fundamental factors governing transmission and immunity is parasite diversity. An understanding of parasite population genetic structure is necessary to understand the epidemiology, diversity, distribution and dynamics of natural P. vivax populations. In addition, studying the population structure of genes under immune selection also enables investigation of the dynamic interplay between transmission and immunity, which is crucial for vaccine development. A lack of knowledge regarding the transmission and spread of P. vivax has been particularly highlighted in areas where malaria control and elimination programmes have made progress in reducing the burden of Plasmodium falciparum, yet P. vivax remains as a substantial obstacle. With malaria elimination back on the global agenda, mapping of global and local P. vivax population structure is essential prior to establishing goals for elimination and the roll-out of interventions. A detailed knowledge of the spatial distribution, transmission and clinical burden of P. vivax is required to act as a benchmark against which control targets can be set and measured. This paper presents an overview of what is known and what is yet to be fully understood regarding P. vivax population genetics, as well as the importance and application of P. vivax population genetics studies.

Analysis of polymorphisms in the merozoite surface protein-3α gene and two microsatellite loci in Sri Lankan Plasmodium vivax: evidence of population substructure in Sri Lanka

The geographical distribution of genetic variation in Plasmodium vivax samples (N = 386) from nine districts across Sri Lanka is described using three markers; the P. vivax merozoite surface protein-3α (Pvmsp-3α) gene, and the two microsatellites m1501 and m3502. At Pvmsp-3α, 11 alleles were found with an expected heterozygosity (H(e)) of 0.81, whereas at m1501 and m3502, 24 alleles (H(e) = 0.85) and 8 alleles (H(e) = 0.74) were detected, respectively. Overall, 95 unique three locus genotypes were detected among the 279 samples positive at all three loci (H(e) = 0.95). Calculating the pairwise fixation index (F(ST)) revealed statistically significant population structure. The presence of identical 2-loci microsatellite genotypes in a significant proportion of samples revealed local clusters of closely related isolates contributing to strong linkage disequilibrium between marker alleles. The results show evidence of high genetic diversity and possible population substructure of P. vivax populations in Sri Lanka.

Genotyping of polymorphic marker (MSP3α and MSP3β) genes of Plasmodium vivax field isolates from malaria endemic of Thailand

Two polymorphic marker genes, merozoite surface protein 3α (PvMSP3α) and merozoite surface protein 3β (PvMSP3β), from 100 Plasmodium vivax field isolates, were investigated using polymerase chain reaction and restriction fragment length polymorphism (PCR/RFLP). Genotyping of PvMSP3α and PvMSP3β revealed marked polymorphisms in length and sequence. Three major types of PvMSP3α (Type A, B and C) and two major types of PvMSP3β (Type A and B) were detected based on the length of PCR products. Fourteen alleles of both genes with difference frequencies were distinguished by restriction fragment length polymorphism, and these results strongly support that P. vivax isolates in Thailand are markedly diverse. PvMSP3α and PvMSP3β are reliable polymorphic markers for population genetic analysis of P. vivax, and PCR/RFLP provides a powerful method for genotyping and identification of mixed parasite infections without requirement of gene sequencing.

Molecular Monitoring of Plasmodium vivax Infection after Radical Treatment in Southeastern Iran

BACKGROUND

The aim was to evaluate the relapse risk of vivax malaria in patients who received radical treatment in Hormozgan Province, a malarious area located on southeast of Iran.

METHODS

A total of 95 symptomatic vivax malaria infected patients were enrolled in urban health centers of Bandar-Abbas, Minab, Bandar-Jask and Bashagard districts of Hormozgan Province, southeast of Iran from January 2008 to March 2009 for consideration as a case- series study. DNA was extracted from parasite infected whole blood samples. A polymorphic region of Plasmodium vivax merozoite surface protein 1 (pvMSP1) was selected and a PCR method was employed for all the samples to amplify the specific variable gene fragment. The obtained fragments in primary and secondary samples were sequenced. Both nucleotide and amino acid sequences of the samples were investigated for returned patients.

RESULTS

3.2% of the patients experienced a second attack between 83-199 days after the initial episode of infection. Alignment of nucleotide and their deduced amino acid sequences between pair sequences of primary and secondary isolates revealed 8 and 6 dissimilarities respectively for the first case, and 9 and 7 dissimilarities for the second case. Although microscopical examination of recurrent thick blood smear of the third patient confirmed new P. vivax infection, the venous blood sample was accidentally missed. Sequencing results of primary and returned isolates 1P, 1S, 2P, 2S and 3P in this study showed an identity with BP13, T117, BP13, TC28 and Chesson genotypes respectively.

CONCLUSION

The returned (secondary) isolates may account to be for the sake of reinfection.

Genetic structure of Plasmodium vivax and Plasmodium falciparum in the Bannu district of Pakistan

BACKGROUND

Plasmodium vivax and Plasmodium falciparum are the major causative agents of malaria. While knowledge of the genetic structure of malaria parasites is useful for understanding the evolution of parasite virulence, designing anti-malarial vaccines and assessing the impact of malaria control measures, there is a paucity of information on genetic diversity of these two malaria parasites in Pakistan. This study sought to shed some light on the genetic structure of P. vivax and P. falciparum in this understudied region.

METHODS

The genetic diversities of P. vivax and P. falciparum populations from the densely populated, malaria-endemic Bannu district of Pakistan were evaluated by analysis of their merozoite surface protein (msp) genes by PCR-RFLP. Specifically, the Pvmsp-3alpha and Pvmsp-3beta genes of P. vivax and the Pfmsp-1 and Pfmsp-2 genes of P. falciparum were analysed.

RESULTS

In P. vivax, genotyping of Pvmsp-3alpha and Pvmsp-3beta genes showed a high level of diversity at these loci. Four distinct allele groups: A (1.9 kb), B (1.5 kb), C (1.2 kb), and D (0.3 kb) were detected for Pvmsp-3alpha, type A being the most prevalent (82%). Conversely, amplification of the P. vivax msp-3beta locus produced two allele groups: A (1.7-2.2 kb, 62%) and B (1.4-1.5 kb, 33%), with 5% mixed-strain infections. Restriction analysis of Pvmsp-3alpha and Pvmsp-3beta yielded 12 and 8 distinct alleles, respectively, with a combined mixed genotype prevalence of 20%. In P. falciparum, all three known genotypes of Pfmsp-1 and two of Pfmsp-2 were observed, with MAD20 occurring in 67% and 3D7/IC in 65% of the isolates, respectively. Overall, 24% P. falciparum samples exhibited mixed-strain infections.

CONCLUSION

These results indicate that both P. vivax and P. falciparum populations in Pakistan are highly diverse.

Genetic characteristics of polymorphic antigenic markers among Korean isolates of Plasmodium vivax

Plasmodium vivax, a protozoan malaria parasite of humans, represents a major public health concern in the Republic of Korea (= South Korea). However, little is known about the genetic properties and population structures of the P. vivax isolates circulating in South Korea. This article reviews known polymorphic genetic markers in South Korean isolates of P. vivax and briefly summarizes the current issues surrounding the gene and population structures of this parasite. The critical genetic characteristics of major antigens of the parasite, such as circumsporozoite protein (CSP), merozoite surface protein 1 (MSP-1) and MSP-3, Duffy binding protein (DBP), apical membrane antigen 1 (AMA-1), and GAM-1, are also discussed.

Plasmodium falciparum and Plasmodium vivax infections in the Peruvian Amazon: propagation of complex, multiple allele-type infections without super-infection

Outcrossing potential between Plasmodium parasites is defined by the population-level diversity (PLD) and complexity of infection (COI). There have been few studies of PLD and COI in low transmission regions. Since the 1995-1998 Peruvian Amazon epidemic, there has been sustained transmission with < 0.5 P. falciparum and < 1.6 P. vivax infections/person/year. Using weekly active case detection, we described PLD by heterozygosity (H(e)) and COI using P. falciparum Pfmsp1-B2 and P. vivax Pvmsp3alpha. Not being homologous genes, we limited comparisons to within species. P. falciparum (N = 293) had low (H(e) = 0.581) and P. vivax (N = 186) had high (H(e) = 0.845) PLD. A total of 9.5% P. falciparum infections and 26.3% P. vivax infections had COI > 1. Certain allele types were in more mixed infections than expected by chance. The few appearances of new alleles could be explained by stochastic polymerase chain reaction detection or synchronization/sequestration. The results suggest propagation of mixed infections by multiple inocula, not super-infection, implying decade-long opportunity for outcrossing in these mixed infections.

Genetic structure of Plasmodium vivax isolates from two malaria endemic areas in Afghanistan

In this study, the nature and extent of genetic diversity of Plasmodium vivax populations circulating in Afghanistan have been investigated by analyzing three genetic markers: csp, msp-1, and msp-3 alpha. Blood samples (n=202) were collected from patients presenting with vivax malaria from south-western (Herat) and south-eastern (Nangarhar) parts of Afghanistan, and analysed using nested-PCR/RFLP and sequencing methods. Genotyping pvmsp-1 revealed type 1, type 2 and recombinant type 3 allelic variants, with type 1 predominant in parasites in both study areas. The sequence analysis of 57 P. vivax isolates identified a total of 26 distinct alleles. Genotyping pvcsp gene showed that VK210 type (86.6%) is predominant in Afghanistan. Moreover, three major types of the pvmsp-3 alpha locus: type A, type B and type C were distinguished among Afghani isolates. The predominant fragments among Nangarhar and Herat parasites were type A (70.8% and 67.9%, respectively). PCR/RFLP products with Hha I and Alu I were detected 52 and 38 distinct variants among Nangarhar and Herat isolates, respectively. These results strongly indicate that the P. vivax populations in Afghanistan are highly diverse.

Molecular characterization of Plasmodium vivax clinical isolates in Pakistan and Iran using pvmsp-1, pvmsp-3alpha and pvcsp genes as molecular markers

In this study, the diversity of Plasmodium vivax populations circulating in Pakistan and Iran has been investigated by using circumsporozoite protein (csp) and merozoite surface proteins 1 and 3alpha (msp-1 and msp-3alpha) genes as genetic markers. Infected P. vivax blood samples were collected from Pakistan (n=187) and Iran (n=150) during April to October 2008, and were analyzed using nested-PCR/RFLP and sequencing methods. Genotyping pvmsp-1 (variable block 5) revealed the presence of type 1, type 2 and recombinant type 3 allelic variants, with type 1 predominant, in both study areas. The sequence analysis of 33 P. vivax isolates from Pakistan and 30 from Iran identified 16 distinct alleles each, with one allele (R-8) from Iran which was not reported previously. Genotyping pvcsp gene also showed that VK210 type is predominant in both countries. Moreover, based on the size of amplified fragment of pvmsp-3alpha, three major types: type A (1800bp), type B (1500bp) and type C (1200bp), were distinguished among the examined isolates that type A was predominant among Pakistani (72.7%) and Iranian (77.3%) parasites. PCR/RFLP products of pvmsp-3alpha with HhaI and AluI have detected 40 and 39 distinct variants among Pakistani and Iranian examined isolates, respectively. Based on these three studied genes, the rate of combined multiple genotypes were 30% and 24.6% for Pakistani and Iranian P. vivax isolates, respectively. These results indicate an extensive diversity in the P. vivax populations in both studies.

Genetic diversity of msp3alpha and msp1_b5 markers of Plasmodium vivax in French Guiana

Background

Reliable molecular typing tools are required for a better understanding of the molecular epidemiology of Plasmodium vivax. The genes msp3a and msp1_block5 are highly polymorphic and have been used as markers in many P. vivax population studies. These markers were used to assess the genetic diversity of P. vivax strains from French Guiana (South America) and to develop a molecular typing protocol.

Methods

A total of 120 blood samples from 109 patients (including 10 patients suffered from more than one malaria episode, samples were collected during each episode) with P. vivax infection were genotyped. All samples were analysed by msp3a PCR-RFLP and msp1_b5 gene sequencing was performed on 57 samples. Genotyping protocol applied to distinguish between new infection or relapse from heterologus hypnozoites and treatment failure or relapse from homologus hypnozoites was based on analysing first msp3a by PCR-RFLP and secondly, only if the genotypes of the two samples are identical, on sequencing the msp1_b5 gene.

Results

msp3a alleles of three sizes were amplified by PCR: types A, B and C. Eleven different genotypes were identified among the 109 samples analysed by msp3a PCR-RFLP. In 13.8% of cases, a mixed genotype infection was observed. The sequence of msp1_b5 gene revealed 22 unique genotypes and 12.3% of cases with mixed infection. In the 57 samples analysed by both methods, 45 genotypes were found and 21% were mixed. Among ten patients with two or three malaria episodes, the protocol allowed to identify five new infections or relapses from heterologous hypnozoites and six treatment failures of relapses from homologous hypnozoites.

Conclusion

The study showed a high diversity of msp3a and msp1_b5 genetic markers among P. vivax strains in French Guiana with a low polyclonal infection rate. These results indicated that the P. vivax genotyping protocol presented has a good discrimination power and can be used in clinical drug trials or epidemiological studies.

Polymorphism in the Plasmodium vivax msp 3: gene in field samples from Tierralta, Colombia

We evaluated the Plasmodium vivax polymorphism by studying the Pvmsp-3alpha gene's polymorphic region by PCR-RFLP in 55 samples from patients living in Tierralta, Colombia. Three different sizes of the Pvmsp-3 alpha gene were found, type A (1,900 bp), type B (1,500 bp) and type C (1,100 bp); most of the samples were type A (96.4 %). The Pvmsp-3alpha gene exhibited high polymorphism. Seven restriction patterns were found when using Alu I, and nine were found with Hha I; 12 different alleles were obtained when these patterns were combined. The findings suggest that this gene could be used in Colombia as a molecular epidemiologic marker for genotyping P. vivax.