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Malaria Journal Sep 2020Circumsporozoite surface protein (CSP) of malaria parasites has been recognized as one of the leading vaccine candidates. Clinical trials of vaccines for vivax malaria...
BACKGROUND
Circumsporozoite surface protein (CSP) of malaria parasites has been recognized as one of the leading vaccine candidates. Clinical trials of vaccines for vivax malaria incorporating Plasmodium vivax CSP (PvCSP) have demonstrated their effectiveness in preventing malaria, at least in part. However, genetic diversity of pvcsp in the natural population remains a major concern.
METHODS
A total of 171 blood samples collected from patients infected with Plasmodium vivax in Myanmar were analysed in this study. The pvcsp was amplified by polymerase chain reaction, followed by cloning and sequencing. Polymorphic characteristics and natural selection of pvcsp population in Myanmar were analysed using DNASTAR, MEGA6 and DnaSP programs. The polymorphic pattern and natural selection of publicly accessible global pvcsp sequences were also comparatively analysed.
RESULTS
Myanmar pvcsp sequences were divided into two subtypes VK210 and VK247 comprising 143 and 28 sequences, respectively. The VK210 subtypes showed higher levels of genetic diversity and polymorphism than the VK247 subtypes. The N-terminal non-repeat region of pvcsp displayed limited genetic variations in the global population. Different patterns of octapeptide insertion (ANKKAEDA in VK210 and ANKKAGDA in VK247) and tetrapeptide repeat motif (GGNA) were identified in the C-terminal region of global pvcsp population. Meanwhile, the central repeat region (CRR) of Myanmar and global pvcsp, both in VK210 and VK247 variants, was highly polymorphic. The high level of genetic diversity in the CRR has been attributed to the different numbers, types and combinations of peptide repeat motifs (PRMs). Interestingly, 27 and 5 novel PRMs were found in Myanmar VK210 and VK247 variants, respectively.
CONCLUSION
Comparative analysis of the global pvcsp population suggests a complex genetic profile of pvcsp in the global population. These results widen understanding of the genetic make-up of pvcsp in the global P. vivax population and provide valuable information for the development of a vaccine based on PvCSP.
Topics: Adolescent; Adult; Humans; Malaria, Vivax; Middle Aged; Myanmar; Plasmodium vivax; Polymorphism, Genetic; Protozoan Proteins; Selection, Genetic; Young Adult
PubMed: 32883283
DOI: 10.1186/s12936-020-03366-7 -
The Journal of Infectious Diseases Apr 2022The presence of Plasmodium vivax malaria parasites in the human bone marrow (BM) is still controversial. However, recent data from a clinical case and experimental...
BACKGROUND
The presence of Plasmodium vivax malaria parasites in the human bone marrow (BM) is still controversial. However, recent data from a clinical case and experimental infections in splenectomized nonhuman primates unequivocally demonstrated the presence of parasites in this tissue.
METHODS
In the current study, we analyzed BM aspirates of 7 patients during the acute attack and 42 days after drug treatment. RNA extracted from CD71+ cell suspensions was used for sequencing and transcriptomic analysis.
RESULTS
We demonstrated the presence of parasites in all patients during acute infections. To provide further insights, we purified CD71+ BM cells and demonstrated dyserythropoiesis and inefficient erythropoiesis in all patients. In addition, RNA sequencing from 3 patients showed that genes related to erythroid maturation were down-regulated during acute infections, whereas immune response genes were up-regulated.
CONCLUSIONS
This study thus shows that during P. vivax infections, parasites are always present in the BM and that such infections induced dyserythropoiesis and ineffective erythropoiesis. Moreover, infections induce transcriptional changes associated with such altered erythropoietic response, thus highlighting the importance of this hidden niche during natural infections.
Topics: Anemia; Animals; Bone Marrow; Erythropoiesis; Humans; Malaria, Vivax; Plasmodium vivax
PubMed: 32556188
DOI: 10.1093/infdis/jiaa177 -
PLoS Neglected Tropical Diseases Jul 2020Plasmodium vivax is the most widespread and difficult to treat cause of human malaria. The development of vaccines against the blood stages of P. vivax remains a key...
Plasmodium vivax is the most widespread and difficult to treat cause of human malaria. The development of vaccines against the blood stages of P. vivax remains a key objective for the control and elimination of vivax malaria. Erythrocyte binding-like (EBL) protein family members such as Duffy binding protein (PvDBP) are of critical importance to erythrocyte invasion and have been the major target for vivax malaria vaccine development. In this study, we focus on another member of EBL protein family, P. vivax erythrocyte binding protein (PvEBP). PvEBP was first identified in Cambodian (C127) field isolates and has subsequently been showed its preferences for binding reticulocytes which is directly inhibited by antibodies. We analysed PvEBP sequence from 316 vivax clinical isolates from eight countries including China (n = 4), Ethiopia (n = 24), Malaysia (n = 53), Myanmar (n = 10), Papua New Guinea (n = 16), Republic of Korea (n = 10), Thailand (n = 174), and Vietnam (n = 25). PvEBP gene exhibited four different phenotypic clusters based on the insertion/deletion (indels) variation. PvEBP-RII (179-479 aa.) showed highest polymorphism similar to other EBL family proteins in various Plasmodium species. Whereas even though PvEBP-RIII-V (480-690 aa.) was the most conserved domain, that showed strong neutral selection pressure for gene purifying with significant population expansion. Antigenicity of both of PvEBP-RII (16.1%) and PvEBP-RIII-V (21.5%) domains were comparatively lower than other P. vivax antigen which expected antigens associated with merozoite invasion. Total IgG recognition level of PvEBP-RII was stronger than PvEBP-RIII-V domain, whereas total IgG inducing level was stronger in PvEBP-RIII-V domain. These results suggest that PvEBP-RII is mainly recognized by natural IgG for innate protection, whereas PvEBP-RIII-V stimulates IgG production activity by B-cell for acquired immunity. Overall, the low antigenicity of both regions in patients with vivax malaria likely reflects genetic polymorphism for strong positive selection in PvEBP-RII and purifying selection in PvEBP-RIII-V domain. These observations pose challenging questions to the selection of EBP and point out the importance of immune pressure and polymorphism required for inclusion of PvEBP as a vaccine candidate.
Topics: Amino Acid Sequence; Antibodies, Protozoan; Asia; Genetic Variation; Humans; Immunity, Humoral; Malaria, Vivax; Plasmodium vivax; Polymorphism, Genetic; Protozoan Proteins; Selection, Genetic; Sequence Alignment
PubMed: 32645098
DOI: 10.1371/journal.pntd.0008202 -
Scientific Reports Jun 2018Malaria control program in the Arabian Peninsula, backed by adequate logistical support, has interrupted transmission with exception of limited sites in Saudi Arabia and...
Malaria control program in the Arabian Peninsula, backed by adequate logistical support, has interrupted transmission with exception of limited sites in Saudi Arabia and sporadic outbreaks in Oman. However, sustained influx of imported malaria represents a direct threat to the above success. Here we examined the extent of genetic diversity among imported P. vivax in Qatar, and its ability to produce gametocytes, compared to parasites in main sites of imported cases, the Indian subcontinent (india) and East Africa (Sudan and Ethiopia). High diversity was seen among imported P. vivax in Qatar, comparable to parasites in the Indian subcontinent and East Africa. Limited genetic differentiation was seen among imported P. vivax, which overlapped with parasites in India, but differentiated from that in Sudan and Ethiopia. Parasite density among imported cases, ranged widely between 26.25-7985934.1 Pv18S rRNA copies/µl blood, with a high prevalence of infections carried gametocytes detectable by qRT-PCR. Parasitaemia was a stronger predictor for P. vivax gametocytes density (r = 0.211, P = 0.04). The extensive diversity of imported P. vivax and its ability to produce gametocytes represent a major threat for re-introduction of malaria in Qatar. The genetic relatedness between P. vivax reported in Qatar and those in India suggest that elimination strategy should target flow and dispersal of imported malaria into the region.
Topics: Africa, Eastern; Communicable Diseases, Imported; Disease Transmission, Infectious; Genetic Variation; Genotype; Humans; India; Malaria, Vivax; Molecular Epidemiology; Parasite Load; Plasmodium vivax; Qatar; RNA, Protozoan; RNA, Ribosomal, 18S; Real-Time Polymerase Chain Reaction
PubMed: 29891983
DOI: 10.1038/s41598-018-27229-z -
Antimicrobial Agents and Chemotherapy Apr 2018chloroquine resistance has been documented in nearly every region where this malaria-causing parasite is endemic. Unfortunately, resistance surveillance and drug...
chloroquine resistance has been documented in nearly every region where this malaria-causing parasite is endemic. Unfortunately, resistance surveillance and drug discovery are challenging due to the low parasitemias of patient isolates and poor parasite survival through maturation that reduce the sensitivity and scalability of current antimalarial assays. Using cryopreserved patient isolates from Brazil and fresh patient isolates from India, we established a robust enrichment method for parasites. We next performed a medium screen for formulations that enhance survival. Finally, we optimized an isotopic metabolic labeling assay for measuring maturation and its sensitivity to antimalarials. A KCl Percoll density gradient enrichment method increased parasitemias from small-volume isolates by an average of >40-fold. The use of Iscove's modified Dulbecco's medium for culture approximately doubled the parasite survival through maturation. Coupling these with [H]hypoxanthine metabolic labeling permitted sensitive and robust measurements of parasite maturation, which was used to measure the sensitivities of Brazilian isolates to chloroquine and several novel antimalarials. These techniques can be applied to rapidly and robustly assess the isolate sensitivities to antimalarials for resistance surveillance and drug discovery.
Topics: Antimalarials; Brazil; Chloroquine; Humans; India; Parasitic Sensitivity Tests; Plasmodium vivax
PubMed: 29378713
DOI: 10.1128/AAC.02519-17 -
Malaria Journal Jun 2018As much as 80% of global Plasmodium vivax infections occur in South Asia and there is a shortage of direct studies on infectivity of P. vivax in Anopheles stephensi, the...
BACKGROUND
As much as 80% of global Plasmodium vivax infections occur in South Asia and there is a shortage of direct studies on infectivity of P. vivax in Anopheles stephensi, the most common urban mosquito carrying human malaria. In this quest, the possible effects of laboratory colonization of mosquitoes on infectivity and development of P. vivax is of interest given that colonized mosquitoes can be genetically less divergent than the field population from which they originated.
METHODS
Patient-derived P. vivax infected blood was fed to age-matched wild and colonized An. stephensi. Such a comparison requires coordinated availability of same-age wild and colonized mosquito populations. Here, P. vivax infection are studied in colonized An. stephensi in their 66th-86th generation and fresh field-caught An. stephensi. Wild mosquitoes were caught as larvae and pupae and allowed to develop into adult mosquitoes in the insectary. Parasite development to oocyst and sporozoite stages were assessed on days 7/8 and 12/13, respectively.
RESULTS
While there were batch to batch variations in infectivity of individual patient-derived P. vivax samples, both wild and colonized An. stephensi were roughly equally susceptible to oocyst stage Plasmodium infection. At the level of sporozoite development, significantly more mosquitoes with sporozoite load of 4+ were seen in wild than in colonized populations.
Topics: Animals; Anopheles; Female; India; Mosquito Vectors; Plasmodium vivax
PubMed: 29871629
DOI: 10.1186/s12936-018-2343-0 -
Frontiers in Immunology 2018Malaria is a widespread disease caused mainly by the (Pf) and (Pv) protozoan parasites. Depending on the parasite responsible for the infection, high morbidity and... (Review)
Review
Malaria is a widespread disease caused mainly by the (Pf) and (Pv) protozoan parasites. Depending on the parasite responsible for the infection, high morbidity and mortality can be triggered. To escape the host immune responses, parasites disturb the functionality of B cell subsets among other cell types. However, some antibodies elicited during a malaria infection have the potential to block pathogen invasion and dissemination into the host. Thus, the question remains, why is protection not developed and maintained after the primary parasite exposure? In this review, we discuss different aspects of B cell responses against antigens during malaria infection. Since most studies have focused on the quantification of serum antibody titers, those B cell responses have not been fully characterized. However, to secrete antibodies, a complex cellular response is set up, including not only the activation and differentiation of B cells into antibody-secreting cells, but also the participation of other cell subsets in the germinal center reactions. Therefore, a better understanding of how B cell subsets are stimulated during malaria infection will provide essential insights toward the design of potent interventions.
Topics: Antibodies, Protozoan; Antigens, Protozoan; B-Lymphocytes; Host-Parasite Interactions; Humans; Immunity, Cellular; Malaria, Falciparum; Malaria, Vivax; Plasmodium falciparum; Plasmodium vivax
PubMed: 30619319
DOI: 10.3389/fimmu.2018.02961 -
Malaria Journal Jun 2021Plasmodium vivax is the most prevalent malaria parasite in many countries. A better understanding of human immunity to this parasite can provide new insights for vaccine...
BACKGROUND
Plasmodium vivax is the most prevalent malaria parasite in many countries. A better understanding of human immunity to this parasite can provide new insights for vaccine development. Plasmodium vivax Reticulocyte Binding Proteins (RBPs) are key parasite proteins that interact with human proteins during erythrocyte invasion and are targets of the human immune response. The aim of this study is to characterize the human antibody response to RBP2P1, the most recently described member of the RBP family.
METHODS
The levels of total IgG and IgM against RBP2P1 were measured using plasmas from 68 P. vivax malaria patients and 525 villagers in a malarious village of western Thailand. The latter group comprises asymptomatic carriers and healthy uninfected individuals. Subsets of plasma samples were evaluated for anti-RBP2P1 IgG subtypes and complement-fixing activity.
RESULTS
As age increased, it was found that the level of anti-RBP2P1 IgG increased while the level of IgM decreased. The main anti-RBP2P1 IgG subtypes were IgG1 and IgG3. The IgG3-seropositive rate was higher in asymptomatic carriers than in patients. The higher level of IgG3 was correlated with higher in vitro RBP2P1-mediated complement fixing activity.
CONCLUSIONS
In natural infection, the primary IgG response to RBP2P1 was IgG1 and IgG3. The predominance of these cytophilic subtypes and the elevated level of IgG3 correlating with complement fixing activity, suggest a possible role of anti-RBP2P1 antibodies in immunity against P. vivax.
Topics: Adolescent; Adult; Aged; Child; Child, Preschool; Female; Humans; Immunity, Humoral; Infant; Infant, Newborn; Malaria, Vivax; Male; Membrane Proteins; Middle Aged; Plasmodium vivax; Protozoan Proteins; Young Adult
PubMed: 34082763
DOI: 10.1186/s12936-021-03784-1 -
Emerging Infectious Diseases Jun 2024During May-July 2023, a cluster of 7 patients at local hospitals in Florida, USA, received a diagnosis of Plasmodium vivax malaria. Whole-genome sequencing of the...
During May-July 2023, a cluster of 7 patients at local hospitals in Florida, USA, received a diagnosis of Plasmodium vivax malaria. Whole-genome sequencing of the organism from 4 patients and phylogenetic analysis with worldwide representative P. vivax genomes indicated probable single parasite introduction from Central/South America.
Topics: Humans; Malaria, Vivax; Florida; Plasmodium vivax; Phylogeny; Male; Whole Genome Sequencing; Female; Adult; Middle Aged
PubMed: 38662728
DOI: 10.3201/eid3006.240336 -
Malaria Journal Feb 2021Recent studies from different malaria-endemic regions including western Africa have now shown that Plasmodium vivax can infect red blood cells (RBCs) and cause clinical...
BACKGROUND
Recent studies from different malaria-endemic regions including western Africa have now shown that Plasmodium vivax can infect red blood cells (RBCs) and cause clinical disease in Duffy-negative people, though the Duffy-negative phenotype was thought to confer complete refractoriness against blood invasion with P. vivax. The actual prevalence of P. vivax in local populations in Ghana is unknown and little information is available about the distribution of Duffy genotypes. The aim of this study was to assess the prevalence of P. vivax in both asymptomatic and symptomatic outpatients and the distribution of Duffy genotypes in Ghana.
METHODS
DNA was extracted from dried blood spots (DBS) collected from 952 subjects (845 malaria patients and 107 asymptomatic persons) from nine locations in Ghana. Plasmodium species identification was carried out by nested polymerase chain reaction (PCR) amplification of the small-subunit (SSU) rRNA genes. For P. vivax detection, a second PCR of the central region of the Pvcsp gene was carried out. Duffy blood group genotyping was performed by allele-specific PCR to detect the presence of the FY allele.
RESULTS
No cases of P. vivax were detected in any of the samples by both PCR methods used. Majority of infections (542, 94.8%) in the malaria patient samples were due to P. falciparum with only 1 infection (0.0017%) due to Plasmodium malariae, and 2 infections (0.0034%) due to Plasmodium ovale. No case of mixed infection was identified. Of the samples tested for the FY allele from all the sites, 90.5% (862/952) had the FY allele. All positive samples were genotyped as FY*B-33/FY*B-33 (Duffy-negative homozygous) and therefore classified as Fy(a-b-).
CONCLUSIONS
No cases of P. vivax were detected by both PCRs and majority of the subjects tested carried the FY allele. The lack of P. vivax infections observed can be attributed to the high frequency of the FY allele that silences erythroid expression of the Duffy. These results provide insights on the host susceptibility for P. vivax infections that had not been investigated in Ghana before.
Topics: Duffy Blood-Group System; Gene Frequency; Genotype; Ghana; Malaria, Vivax; Plasmodium vivax; Prevalence
PubMed: 33596926
DOI: 10.1186/s12936-021-03618-0