-
The Journal of Biological Chemistry May 2024The parasite Plasmodium vivax preferentially invades human reticulocytes. Its merozoite surface protein 1 paralog (PvMSP1P), particularly the 19-kDa C-terminal region...
The parasite Plasmodium vivax preferentially invades human reticulocytes. Its merozoite surface protein 1 paralog (PvMSP1P), particularly the 19-kDa C-terminal region (PvMSP1P-19), has been shown to bind to reticulocytes, and this binding can be inhibited by antisera obtained by PvMSP1P-19 immunization. The molecular mechanism of interactions between PvMSP1P-19 and reticulocytes during P. vivax invasion, however, remains unclear. In this study, we analyzed the ability of MSP1P-19 to bind to different concentrations of reticulocytes and confirmed its reticulocyte preference. LC-MS analysis was used to identify two potential reticulocyte receptors, band3 and CD71, that interact with MSP1P-19. Both PvMSP1P-19 and its sister taxon Plasmodium cynomolgi MSP1P-19 were found to bind to the extracellular loop (loop 5) of band3, where the interaction of MSP1P-19 with band3 was chymotrypsin sensitive. Antibodies against band3-P5, CD71, and MSP1P-19 reduced the binding activity of PvMSP1P-19 and Plasmodium cynomolgi MSP1P-19 to reticulocytes, while MSP1P-19 proteins inhibited Plasmodium falciparum invasion in vitro in a concentration-dependent manner. To sum up, identification and characterization of the reticulocyte receptor is important for understanding the binding of reticulocytes by MSP1P-19.
Topics: Plasmodium vivax; Reticulocytes; Humans; Protozoan Proteins; Antigens, CD; Receptors, Transferrin; Anion Exchange Protein 1, Erythrocyte; Protein Binding; Merozoite Surface Protein 1; Malaria, Vivax; Animals
PubMed: 38636656
DOI: 10.1016/j.jbc.2024.107285 -
Journal of Vector Borne Diseases Apr 2024Anopheles stephensi is responsible for the transmission of malaria in urban areas. Vector competence of An. stephensi from a non-malarious (Coimbatore) and highly...
BACKGROUND OBJECTIVES
Anopheles stephensi is responsible for the transmission of malaria in urban areas. Vector competence of An. stephensi from a non-malarious (Coimbatore) and highly malarious (Chennai) urban areas in Tamil Nadu state of India, was investigated to find the reason for non-transmission of malaria in Coimbatore.
METHODS
Vector competence (susceptibility/refractoriness) of An. stephensi mosquitoes from Chennai (malarious) and Coimbatore (non-malarious) to Plasmodium vivax (Chennai) was investigated. Bioassays were carried out concurrently in both these strains by artificial membrane feeding technique using the same malaria-infected blood. An. stephensi were dissected to observe infection in midgut and salivary gland. The parasite infection, oocyst and sporozoite positivity rate, the oocyst load, correlation between male-female gametocyte ratio and infection, and Survival Analysis of parasitic stages during sporogony were analyzed and compared.
RESULTS
The overall infection rate was 45.8 and 41.2 percent in Chennai and Coimbatore, respectively. Oocyst count ranged from 1-80 and 1-208 respectively and not statistically significant. Oocyst positivity was high from Day 8-21 in both strains. The Mean Survival Day (MSD) for oocyst was Day 14 in both strains. Sporozoite was observed in four experiments in each of the strains and the MSD for sporozoites was Day 20 in Chennai and Day 17 in Coimbatore.
INTERPRETATION CONCLUSION
An. stephensi of Chennai and Coimbatore are equally susceptible to P. vivax infection and non-transmission of malaria in Coimbatore can be attributed to external factors such as the presence of preferential breeding habitat, vector density, vector survival, and weather. The only difference observed was the comparatively shortened oocyst maturation time in the Coimbatore strain which requires further investigation.
PubMed: 38634456
DOI: 10.4103/JVBD.JVBD_7_24 -
MedRxiv : the Preprint Server For... Apr 2024Zoonotic and symptomatic and asymptomatic infections occur across endemic areas of Southeast Asia. Most infections are low-parasitemia, with an unknown proportion...
BACKGROUND
Zoonotic and symptomatic and asymptomatic infections occur across endemic areas of Southeast Asia. Most infections are low-parasitemia, with an unknown proportion below routine microscopy detection thresholds. Molecular surveillance tools optimizing the limit of detection (LOD) would allow more accurate estimates of zoonotic malaria prevalence.
METHODS
An established ultra-sensitive genus quantitative-PCR (qPCR) assay targeting the 18S rRNA gene underwent LOD evaluation with and without reverse transcription (RT) for , and using total nucleic acid preserved (DNA/RNA Shield) isolates and archived dried blood spots (DBS). LODs for selected specific assays, and reference and -specific assays were determined with RT. Assay specificities were assessed using clinical malaria samples and malaria-negative controls.
RESULTS
The use of reverse transcription improved species detection by up to 10,000-fold ( genus), 2759-fold (), 1000-fold () and 10-fold (). The median LOD with RT for the Kamau et al. genus RT-qPCR assay was ≤0.0002 parasites/μL for and 0.002 parasites/μL for both and . The LODs with RT for -specific PCRs were: Imwong et al. 18S rRNA (0.0007 parasites/μL); Divis et al. real-time 18S rRNA (0.0002 parasites/μL); Lubis et al. hemi-nested (1.1 parasites/μL) and Lee et al. nested 18S rRNA (11 parasites/μL). The LOD for and specific assays with RT were 0.02 and 0.20 parasites/μL respectively. For DBS samples the median LOD for the genus qPCR with RT was 0.08, and without RT was 19.89 parasites/uL (249-fold change); no LOD improvement was demonstrated in DBS archived beyond 6 years. The genus and -assays were 100% specific for species and detection, respectively, from 190 clinical infections and 48 healthy controls. Reference specific primers demonstrated known cross-reactivity with .
CONCLUSION
Our findings support the use of an 18S rRNA genus qPCR and species-specific nested PCR protocol with RT for highly-sensitive surveillance of zoonotic and human species infections.
PubMed: 38633782
DOI: 10.1101/2024.04.04.24305339 -
Malaria Journal Apr 2024Achieving effective control and elimination of malaria in endemic regions necessitates a comprehensive understanding of local mosquito species responsible for malaria...
BACKGROUND
Achieving effective control and elimination of malaria in endemic regions necessitates a comprehensive understanding of local mosquito species responsible for malaria transmission and their susceptibility to insecticides.
METHODS
The study was conducted in the highly malaria prone Ujina Primary Health Center of Nuh (Mewat) district of Haryana state of India. Monthly entomological surveys were carried out for adult mosquito collections via indoor resting collections, light trap collections, and pyrethrum spray collections. Larvae were also collected from different breeding sites prevalent in the region. Insecticide resistance bioassay, vector incrimination, blood meal analysis was done with the collected vector mosquitoes.
RESULTS
A total of 34,974 adult Anopheles mosquitoes were caught during the survey period, out of which Anopheles subpictus was predominant (54.7%). Among vectors, Anopheles stephensi was predominant (15.5%) followed by Anopheles culicifacies (10.1%). The Human Blood Index (HBI) in the case of An. culicifacies and An. stephensi was 6.66 and 9.09, respectively. Vector incrimination results revealed Plasmodium vivax positivity rate of 1.6% for An. culicifacies. Both the vector species were found resistant to DDT, malathion and deltamethrin.
CONCLUSION
The emergence of insecticide resistance in both vector species, compromises the effectiveness of commonly used public health insecticides. Consequently, the implementation of robust insecticide resistance management strategies becomes imperative. To effectively tackle the malaria transmission, a significant shift in vector control strategies is warranted, with careful consideration and adaptation to address specific challenges encountered in malaria elimination efforts.
Topics: Animals; Humans; Insecticides; Insecticide Resistance; Anopheles; Malaria; DDT; Mosquito Control; Mosquito Vectors; Nitriles; Pyrethrins; India
PubMed: 38632650
DOI: 10.1186/s12936-023-04797-8 -
Malaria Journal Apr 2024To gain a deeper understanding of protective immunity against relapsing malaria, this study examined sporozoite-specific T cell responses induced by a chemoprophylaxis...
Superior protection in a relapsing Plasmodium cynomolgi rhesus macaque model by a chemoprophylaxis with sporozoite immunization regimen with atovaquone-proguanil followed by primaquine.
BACKGROUND
To gain a deeper understanding of protective immunity against relapsing malaria, this study examined sporozoite-specific T cell responses induced by a chemoprophylaxis with sporozoite (CPS) immunization in a relapsing Plasmodium cynomolgi rhesus macaque model.
METHODS
The animals received three CPS immunizations with P. cynomolgi sporozoites, administered by mosquito bite, while under two anti-malarial drug regimens. Group 1 (n = 6) received artesunate/chloroquine (AS/CQ) followed by a radical cure with CQ plus primaquine (PQ). Group 2 (n = 6) received atovaquone-proguanil (AP) followed by PQ. After the final immunization, the animals were challenged with intravenous injection of 10 P. cynomolgi sporozoites, the dose that induced reliable infection and relapse rate. These animals, along with control animals (n = 6), were monitored for primary infection and subsequent relapses. Immunogenicity blood draws were done after each of the three CPS session, before and after the challenge, with liver, spleen and bone marrow sampling and analysis done after the challenge.
RESULTS
Group 2 animals demonstrated superior protection, with two achieving protection and two experiencing partial protection, while only one animal in group 1 had partial protection. These animals displayed high sporozoite-specific IFN-γ T cell responses in the liver, spleen, and bone marrow after the challenge with one protected animal having the highest frequency of IFN-γ CD8, IFN-γ CD4, and IFN-γ γδ T cells in the liver. Partially protected animals also demonstrated a relatively high frequency of IFN-γ CD8, IFN-γ CD4, and IFN-γ γδ T cells in the liver. It is important to highlight that the second animal in group 2, which experienced protection, exhibited deficient sporozoite-specific T cell responses in the liver while displaying average to high T cell responses in the spleen and bone marrow.
CONCLUSIONS
This research supports the notion that local liver T cell immunity plays a crucial role in defending against liver-stage infection. Nevertheless, there is an instance where protection occurs independently of T cell responses in the liver, suggesting the involvement of the liver's innate immunity. The relapsing P. cynomolgi rhesus macaque model holds promise for informing the development of vaccines against relapsing P. vivax.
Topics: Animals; Primaquine; Sporozoites; Macaca mulatta; Plasmodium cynomolgi; Immunization; Malaria Vaccines; Chemoprevention; CD8-Positive T-Lymphocytes; Proguanil; Drug Combinations; Atovaquone
PubMed: 38632607
DOI: 10.1186/s12936-024-04933-y -
The American Journal of Tropical... Jun 2024Plasmodium parasites replicate asexually in human hosts. The proportion of infections that carries gametocytes is a proxy for human-to-mosquito transmissibility. It is...
Plasmodium parasites replicate asexually in human hosts. The proportion of infections that carries gametocytes is a proxy for human-to-mosquito transmissibility. It is unclear which proportion of Plasmodium vivax infections in Duffy-negative populations carries gametocytes. We determined the prevalence and characteristics of P. vivax gametocytes in Duffy-positive and -negative populations across broad regions of Ethiopia. Finger-prick blood samples were collected for microscopic and molecular screening of Plasmodium parasites and Duffy status of individuals. Molecular screening of Plasmodium species and Duffy blood group genotyping was done using SYBR green and the Taqman quantitative polymerase chain reaction method. Of the 447 febrile patients who were shown to be P. vivax smear positive, 414 (92.6%) were confirmed by molecular screening as P. vivax and 16 (3.9%) of them were from Duffy-negative individuals. Of these, 5 of 16 (31.3%) Duffy-negative P. vivax-infected samples were detected with gametocytes. Of the 398 Duffy-positive P. vivax-infected samples, 150 (37.7%) were detected with gametocytes, slightly greater than that in Duffy-negative samples. This study highlights the presence of P. vivax gametocytes in Duffy-negative infections, suggestive of human-to-mosquito transmissibility. Although P. vivax infections in Duffy-negative individuals were commonly associated with low parasitemia, some of these infections were shown to have relatively high parasitemia and may represent a prominent erythrocyte invasion capability of P. vivax, and hidden reservoirs that can contribute to transmission. A better understanding of P. vivax transmission biology and gametocyte function particularly in Duffy-negative populations would aid future treatment and management of P. vivax malaria in Africa.
Topics: Humans; Ethiopia; Plasmodium vivax; Duffy Blood-Group System; Malaria, Vivax; Male; Adult; Adolescent; Female; Prevalence; Young Adult; Child; Middle Aged; Receptors, Cell Surface; Child, Preschool; Genotype; Cross-Sectional Studies
PubMed: 38626749
DOI: 10.4269/ajtmh.23-0877 -
Diagnostics (Basel, Switzerland) Mar 2024The early diagnosis of malaria is crucial to controlling morbidity and mortality. The World Health Organization (WHO) recommends diagnosing malaria either using light...
The early diagnosis of malaria is crucial to controlling morbidity and mortality. The World Health Organization (WHO) recommends diagnosing malaria either using light microscopy or a malaria rapid diagnostic test (RDT). Most RDTs use antibodies to detect two histidine-rich proteins named PfHRP2 and PfHRP3. However, false-negative results are known to occur due to the poor performance of RDTs depending on the species and the deletion of the and genes. This study evaluated new malaria RDTs for the detection of the human species. The Acro Malaria P.f./P.v./Pan Rapid Test Cassette allows the qualitative detection of parasite antigens, such as PfHRP2 specific to , PvLDH specific to , and/or panLDH genus lactate dehydrogenase, in the blood of infected individuals. This RDT was assessed against 229 samples collected from imported malaria cases, mainly from Africa. The samples were previously diagnosed using light microscopy and RDT (SD Malaria Ag P.f./Pan, SD Bioline Alere Abbott), then confirmed using real time PCR. The two RDTs were evaluated using a comparison with real time PCR as the reference method, and their performances were compared with each other. Compared to SD RDT, the Acro RDT showed a better sensitivity to (96.8% vs. 89.8%), (78.6% vs. 64.3%), (73.7% vs. 5.3%), and (20.0% vs. 0%). The respective specificities of the Acro RDT and SD RDT are 90.7% vs. 95.3% to , 100% to , and 100% vs. 100% to genus. Therefore, Acro RDT showed better performance in the identification of and low parasitaemia of . In addition, Acro RDT has the advantage of detecting PvLDH-specific antigens. The Acro Malaria RDT presents the benefits of detecting a antigen (PfHRP2) and a antigen (PvLDH) with high sensitivity (96.8% and 73.7%, respectively) and specificity (90.7% and 100%, respectively). Acro Malaria P.f./P.v./Pan rapid diagnostic tests could be effectively used in endemic areas, especially when microscopic examination cannot be performed.
PubMed: 38611637
DOI: 10.3390/diagnostics14070721 -
Malaria Journal Apr 2024While Plasmodium falciparum and Plasmodium vivax cause the majority of malaria cases and deaths, infection by Plasmodium malariae and other Plasmodium species also...
BACKGROUND
While Plasmodium falciparum and Plasmodium vivax cause the majority of malaria cases and deaths, infection by Plasmodium malariae and other Plasmodium species also causes morbidity and mortality. Current understanding of these infections is limited in part by existing point-of-care diagnostics that fail to differentiate them and have poor sensitivity for low-density infections. Accurate diagnosis currently requires molecular assays performed in well-resourced laboratories. This report describes the development of a P. malariae diagnostic assay that uses rapid, isothermal recombinase polymerase amplification (RPA) and lateral-flow-strip detection.
METHODS
Multiple combinations of custom RPA primers and probes were designed using publicly available P. malariae genomic sequences, and by modifying published primer sets. Based on manufacturer RPA reaction conditions (TwistDx nfo kit), an isothermal assay was optimized targeting the multicopy P. malariae 18S rRNA gene with 39 °C incubation and 30-min run time. RPA product was visualized using lateral strips (FAM-labeled, biotinylated amplicon detected by a sandwich immunoassay, visualized using gold nanoparticles). Analytical sensitivity was evaluated using 18S rRNA plasmid DNA, and clinical sensitivity determined using qPCR-confirmed samples collected from Tanzania, Ethiopia, and the Democratic Republic of the Congo.
RESULTS
Using 18S rRNA plasmid DNA, the assay demonstrates a detection limit of 10 copies/µL (~ 1.7 genome equivalents) and 100% analytical specificity. Testing in field samples showed 95% clinical sensitivity and 88% specificity compared to qPCR. Total assay time was less than 40 min.
CONCLUSION
Combined with simplified DNA extraction methods, the assay has potential for future field-deployable, point-of-care use to detect P. malariae infection, which remains largely undiagnosed but a neglected cause of chronic malaria. The assay provides a rapid, simple readout on a lateral flow strip without the need for expensive laboratory equipment.
Topics: Gold; Metal Nanoparticles; RNA, Ribosomal, 18S; Biological Assay; DNA
PubMed: 38609964
DOI: 10.1186/s12936-024-04928-9 -
Journal of Tropical Medicine 2024This study determines the incidence of common viral and helminth coinfections with malaria in the tertiary care hospital set up in southern Khyber Pakhtunkhwa, Pakistan.
INTRODUCTION
This study determines the incidence of common viral and helminth coinfections with malaria in the tertiary care hospital set up in southern Khyber Pakhtunkhwa, Pakistan.
MATERIALS AND METHODS
The multidimensional research included malaria patients admitted to different hospitals of district Kohat during January and December 2021. Stool samples and blood were assembled from the patients. Giemsa-stained microscopy-positive samples were processed by the immunochromatography technique (ICT) to identify species. Common viral infections such as viral hepatitis (A, B, and C), HIV, and dengue (DENV) were analyzed by ICT kits while SARS-CoV-2 was confirmed through real-time PCR. Furthermore, the intestinal helminths were identified using the Kato-Katz thick smear method.
RESULTS
Among 1278 patients, 548 were diagnosed with malaria, 412 (75.2%) were positive for infection, 115 (21%) for , and 21 (3.8%) for mixed malaria infection (), with a higher incidence among males (65.2%) than females (34.8%). Coinfection with helminths was positive in 215 (39.3%) malaria patients. The most common infections were caused by the species (42.6%) followed by (31.7%) and hookworm. A total of 24.6% of malaria-positive cases were also coinfected with different viruses with higher frequencies of confection for HAV (8.2%) and DENV (6.2%), respectively. The patients revealed higher incidence of coinfections with (57%) as compared with (39.2%) and mixed infections (3.7%).
CONCLUSION
This study demonstrated that the study population exhibited a significant incidence of coinfections with intestinal helminth and viral malaria.
PubMed: 38576602
DOI: 10.1155/2024/8529788 -
Parasites & Vectors Mar 2024Malaria is a major public health concern in Ethiopia, and its incidence could worsen with the spread of the invasive mosquito species Anopheles stephensi in the country....
BACKGROUND
Malaria is a major public health concern in Ethiopia, and its incidence could worsen with the spread of the invasive mosquito species Anopheles stephensi in the country. This study aimed to provide updates on the distribution of An. stephensi and likely household exposure in Ethiopia.
METHODS
Entomological surveillance was performed in 26 urban settings in Ethiopia from 2021 to 2023. A kilometer-by-kilometer quadrant was established per town, and approximately 20 structures per quadrant were surveyed every 3 months. Additional extensive sampling was conducted in 50 randomly selected structures in four urban centers in 2022 and 2023 to assess households' exposure to An. stephensi. Prokopack aspirators and CDC light traps were used to collect adult mosquitoes, and standard dippers were used to collect immature stages. The collected mosquitoes were identified to species level by morphological keys and molecular methods. PCR assays were used to assess Plasmodium infection and mosquito blood meal source.
RESULTS
Catches of adult An. stephensi were generally low (mean: 0.15 per trap), with eight positive sites among the 26 surveyed. This mosquito species was reported for the first time in Assosa, western Ethiopia. Anopheles stephensi was the predominant species in four of the eight positive sites, accounting for 75-100% relative abundance of the adult Anopheles catches. Household-level exposure, defined as the percentage of households with a peridomestic presence of An. stephensi, ranged from 18% in Metehara to 30% in Danan. Anopheles arabiensis was the predominant species in 20 of the 26 sites, accounting for 42.9-100% of the Anopheles catches. Bovine blood index, ovine blood index and human blood index values were 69.2%, 32.3% and 24.6%, respectively, for An. stephensi, and 65.4%, 46.7% and 35.8%, respectively, for An. arabiensis. None of the 197 An. stephensi mosquitoes assayed tested positive for Plasmodium sporozoite, while of the 1434 An. arabiensis mosquitoes assayed, 62 were positive for Plasmodium (10 for P. falciparum and 52 for P. vivax).
CONCLUSIONS
This study shows that the geographical range of An. stephensi has expanded to western Ethiopia. Strongly zoophagic behavior coupled with low adult catches might explain the absence of Plasmodium infection. The level of household exposure to An. stephensi in this study varied across positive sites. Further research is needed to better understand the bionomics and contribution of An. stephensi to malaria transmission.
Topics: Animals; Cattle; Anopheles; Ecology; Ethiopia; Malaria; Malaria, Falciparum; Malaria, Vivax; Mosquito Vectors
PubMed: 38556881
DOI: 10.1186/s13071-024-06243-3