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  1. Fulltext Two Genetically Distinct Plasmodium knowlesi Duffy Binding Protein Alpha Region II (PkDBPαII) Haplotypes Demonstrate Higher Binding Level to Fy(a+b+) Erythrocytes than Fy(a+b--) Erythrocytes
    Liew CC, Lau YL, Fong MY, Cheong FW
    Am J Trop Med Hyg, 2020 05;102(5):1068-1071.
    PMID: 32189613 DOI: 10.4269/ajtmh.19-0836
    Invasion of human erythrocytes by merozoites of Plasmodium knowlesi involves interaction between the P. knowlesi Duffy binding protein alpha region II (PkDBPαII) and Duffy antigen receptor for chemokines (DARCs) on the erythrocytes. Information is scarce on the binding level of PkDBPαII to different Duffy antigens, Fya and Fyb. This study aims to measure the binding level of two genetically distinct PkDBPαII haplotypes to Fy(a+b-) and Fy(a+b+) human erythrocytes using erythrocyte-binding assay. The binding level of PkDBPαII of Peninsular Malaysian and Malaysian Borneon haplotypes to erythrocytes was determined by counting the number of rosettes formed in the assay. Overall, the Peninsular Malaysian haplotype displayed higher binding activity than the Malaysian Borneon haplotype. Both haplotypes exhibit the same preference to Fy(a+b+) compared with Fy(a+b-), hence justifying the vital role of Fyb in the binding to PkDBPαII. Further studies are needed to investigate the P. knowlesi susceptibility on individuals with different Duffy blood groups.
    Matched MeSH terms: Antigens, Protozoan/immunology
  2. Toxoplasma gondii: serological characterization and immunogenicity of recombinant surface antigen 2 (SAG2) expressed in the yeast Pichia pastoris
    Lau YL, Fong MY
    Exp Parasitol, 2008 Jul;119(3):373-8.
    PMID: 18457835 DOI: 10.1016/j.exppara.2008.03.016
    The full length surface antigen 2 (SAG2) gene of the protozoan parasite Toxoplasma gondii was cloned and intracellularly expressed in the Pichia pastoris expression system. The molecular weight of the expressed recombinant SAG2 (36 kDa) was much larger than the native SAG2 (22 kDa). This discrepancy in size was due to hyperglycosylation, as deglycosylation assay reduced the size of the recombinant SAG2 to 22 kDa. Despite being hyperglycosylated, the recombinant SAG2 reacted strongly with pooled anti-Toxoplasma human serum, pooled anti-Toxoplasma mouse serum and a SAG2-specific monoclonal antibody. The glycosylated recombinant SAG2 was further evaluated in Western blot and in-house enzyme-linked immunosorbent assay (ELISA) using 80 human serum samples, including confirmed early acute (IgM positive, IgG negative; n=20), acute (IgM positive, IgG positive; n=20) and chronic (IgM negative, IgG positive; n=20) toxoplasmosis patients, and toxoplasmosis negative control patients (n=20). Results of the Western blot showed that the recombinant SAG2 reacted with all 60 samples of the toxoplasmosis cases but not with the Toxoplasma-negative samples. The sensitivity of in-house ELISA was 80%, 95% and 100% for early acute, acute and chronic patients' serum samples, respectively. Vaccination study showed that serum from mice immunised with the glycosylated recombinant SAG2 reacted specifically with the native SAG2 of T. gondii. The mice were significantly protected against lethal challenge with live T. gondii RH strain tachyzoites (P<0.01) and their survival time was increased compared to controls. Therefore, the present study shows that the P. pastoris-derived recombinant SAG2 was specific and suitable for use as antigen for detecting anti-Toxoplasma IgG and IgM antibodies. The vaccination study showed that recombinant SAG2 protein was immunoprotective in mice against lethal challenge.
    Matched MeSH terms: Antigens, Protozoan/immunology*
  3. Toxoplasma gondii excretory secretory antigenic proteins of diagnostic potential
    Saadatnia G, Mohamed Z, Ghaffarifar F, Osman E, Moghadam ZK, Noordin R
    APMIS, 2012 Jan;120(1):47-55.
    PMID: 22151308 DOI: 10.1111/j.1600-0463.2011.02810.x
    Infection with Toxoplasma gondii is widespread and important in humans, especially pregnant women and immunosuppressed patients. A panel of tests is usually required for diagnosis toxoplasmosis. Excretory secretory antigen (ESA) is highly immunogenic, and thus it is a good candidate for investigation into new infection markers. ESA was prepared from tachyzoites of RH strain of T. gondii by mice intraperitoneal infection. Sera were obtained from several categories of individuals who differed in their status of anti-Toxoplasma IgM, IgG and IgG avidity antibodies. The ESA was subjected to SDS-PAGE, two-dimensional gel electrophoresis and Western blot analysis. Antigenic bands of approximate molecular weights of 12, 20 and 30 kDa, when probed with anti-human IgM-HRP and IgA-HRP, showed good potential as infection markers. The highest sensitivity of the bands was 98.7% with combination of IgM and IgA blots with sera of patients with anti-Toxoplasma IgM+ IgG+. The specificities were 84% and 70% with sera from other infections and healthy controls in IgM blots and IgA blots respectively. By mass spectrometry, the 12 kDa protein was identified as thioredoxin. The two top proteins identified for 20 kDa molecule were microneme protein 10 and dense granule protein 7; whereas that for 30 kDa were phosphoglycerate mutase 1 and phosphoglycerate mutase.
    Matched MeSH terms: Antigens, Protozoan/immunology*
  4. Fulltext Theoretical investigation on structural, functional and epitope of a 12 kDa excretory-secretory protein from Toxoplasma gondii
    Tommy YB, Lim TS, Noordin R, Saadatnia G, Choong YS
    BMC Struct Biol, 2012 Nov 27;12:30.
    PMID: 23181504 DOI: 10.1186/1472-6807-12-30
    BACKGROUND: Toxoplasma gondii is an intracellular coccidian parasite that causes toxoplasmosis. It was estimated that more than one third of the world population is infected by T. gondii, and the disease is critical in fetuses and immunosuppressed patients. Thus, early detection is crucial for disease diagnosis and therapy. However, the current available toxoplasmosis diagnostic tests vary in their accuracy and the better ones are costly.

    RESULTS: An earlier published work discovered a highly antigenic 12 kDa excretory-secretory (ES) protein of T. gondii which may potentially be used for the development of an antigen detection test for toxoplasmosis. However, the three-dimensional structure of the protein is unknown. Since epitope identification is important prior to designing of a specific antibody for an antigen-detection based diagnostic test, the structural elucidation of this protein is essential. In this study, we constructed a three dimensional model of the 12 kDa ES protein. The built structure possesses a thioredoxin backbone which consists of four α-helices flanking five β-strands at the center. Three potential epitopes (6-8 residues) which can be combined into one "single" epitope have been identified from the built structure as the most potential antibody binding site.

    CONCLUSION: Together with specific antibody design, this work could contribute towards future development of an antigen detection test for toxoplasmosis.

    Matched MeSH terms: Antigens, Protozoan/immunology*
  5. The use of transgenic parasites in malaria vaccine research
    Othman AS, Marin-Mogollon C, Salman AM, Franke-Fayard BM, Janse CJ, Khan SM
    Expert Rev Vaccines, 2017 Jul;16(7):1-13.
    PMID: 28525963 DOI: 10.1080/14760584.2017.1333426
    INTRODUCTION: Transgenic malaria parasites expressing foreign genes, for example fluorescent and luminescent proteins, are used extensively to interrogate parasite biology and host-parasite interactions associated with malaria pathology. Increasingly transgenic parasites are also exploited to advance malaria vaccine development. Areas covered: We review how transgenic malaria parasites are used, in vitro and in vivo, to determine protective efficacy of different antigens and vaccination strategies and to determine immunological correlates of protection. We describe how chimeric rodent parasites expressing P. falciparum or P. vivax antigens are being used to directly evaluate and rank order human malaria vaccines before their advancement to clinical testing. In addition, we describe how transgenic human and rodent parasites are used to develop and evaluate live (genetically) attenuated vaccines. Expert commentary: Transgenic rodent and human malaria parasites are being used to both identify vaccine candidate antigens and to evaluate both sub-unit and whole organism vaccines before they are advanced into clinical testing. Transgenic parasites combined with in vivo pre-clinical testing models (e.g. mice) are used to evaluate vaccine safety, potency and the durability of protection as well as to uncover critical protective immune responses and to refine vaccination strategies.
    Matched MeSH terms: Antigens, Protozoan/immunology
  6. Significance of circumsporozoite-specific antibody in the natural transmission of Plasmodium falciparum, Plasmodium vivax, and Plasmodium malariae in an aboriginal (Orang Asli) population of central peninsula Malaysia
    Gordon DM, Davis DR, Lee M, Lambros C, Harrison BA, Samuel R, et al.
    Am J Trop Med Hyg, 1991 Jul;45(1):49-56.
    PMID: 1867348
    Two hundred and seventy-five Orang Asli volunteers living in nine villages in the Pos Legap Valley of Perak State, peninsular Malaysia, participated in a prospective study designed to characterize the epidemiological, parasitological, and entomological characteristics of Plasmodium falciparum, P. vivax, and P. malariae malaria transmission. Prevalence rates for the three plasmodial species at initiation of the study ranged from 56% in the 0-4-year-old age group to 0% in individuals over the age of 40. Entomological surveys were conducted, enabling us to determine mosquito salivary gland-positive rates and entomological inoculation rates of 1.2 infectious mosquito bites per person per month for P. falciparum, 2.4 for P. vivax, and 0.3 for P. malariae. Cumulative incidence rates over the 16 weeks of the study, following radical cure of all volunteers, were 22.5% for P. falciparum, 12.7% for P. vivax, and 1.5% for P. malariae. The median baseline antibody titer against the immunodominant repetitive B cell epitope of P. falciparum or P. vivax circumsporozoite protein was significantly higher for volunteers who did not become parasitemic. Volunteers were selected for further study if they had evidence of being challenged with P. falciparum sporozoites during the study, based on a two-fold or greater increase in antibody titer against the immunodominant repetitive B cell epitope of the circumsporozoite protein. Resistance to infection was seen in six of 10 individuals who had high (greater than 25 OD units) baseline ELISA titers, compared with only three of 24 individuals who had low baseline ELISA titers (chi 2 P less than 0.02). A similar analysis for P. vivax did not show a significant correlation.
    Matched MeSH terms: Antigens, Protozoan/immunology*
  7. Fulltext Seroprevalence of Sarcocystis falcatula in Two Islands of Malaysia using Recombinant Surface Antigen 4
    Nadzirah TTI, Yik FM, Ling LY
    Korean J Parasitol, 2020 Feb;58(1):1-5.
    PMID: 32145721 DOI: 10.3347/kjp.2020.58.1.1
    Sarcocystosis was diagnosed worldwide by serodiagnostic tests utilising the whole parasite, for which the protozoa were maintained in vitro are more costly. In this study, antigenicity of Sarcocystis falcatula recombinant protein (rSfSAG4) was investigated towards the local communities of Pangkor and Tioman Islands and its seroprevalence was surveyed in these islands. A total of 348 human sera were tested using rSfSAG4 by Western blot and ELISA. High prevalence of sarcocystosis was observed in Tioman Island (80.6%) than in Pangkor Island (50.0%) by Western blot. In ELISA, the seroprevalence observed in Tioman Island was 45.9%, whereas in Pangkor Island 63.0%. In other parasitic infections, the prevalence was 34.0% by Western blot and 46.0% by ELISA. In healthy control group, 7% by Western blot and 8% by ELISA showed positivity to rSfSAG4. It is suggested SfSAG4 is a candidate antigen to measure seroprevalence of sarcocystosis.
    Matched MeSH terms: Antigens, Protozoan/immunology*
  8. Fulltext Serological evaluation of malaria patients in Thailand: antibody response against electrophoresed antigenic polypeptides of Plasmodium falciparum
    Kano S, Onda T, Matsumoto Y, Buchachart K, Krudsood S, Looareesuwan S, et al.
    Southeast Asian J. Trop. Med. Public Health, 1998 Jun;29(2):341-3.
    PMID: 9886125
    It was reported that a 47kDa antigenic polypeptide of Plasmodium falciparum had been strongly presented by the sera from 1) imported Japanese malaria patients with severe symptoms and 2) symptomatic and parasitemic inhabitants in endemic areas in the Sudan, Malaysia and the Philippines. In the present study, we observed the reactivity of the sera from falciparum malaria patients who had been hospitalized in the Bangkok Hospital for Tropical Diseases, Faculty of Tropical Medicine, Mahidol University, and compared the antibody response against the 47kDa antigenic polypeptide according to the severity of the patients. It was observed that antibodies to this molecule were more commonly shared in sera from severer patients, although the IFAT titers against the whole P. falciparum parasite antigen were lower in the group, which suggested that this antibody against the 47kDa molecule was playing a specific role at a severe stage of the infection. Determination of the immunological features of the antigenic molecules of parasites by this type of sero-epidemiological study will provide a new assay system for evaluation of immune status of individuals in different severity and suggest a way of vaccine development.
    Matched MeSH terms: Antigens, Protozoan/immunology*
  9. Research note: HLA degenerate T-cell epitopes from Plasmodium falciparum liver stage-specific antigen 1 (LSA-1) are highly conserved in isolates from geographically distinct areas
    Ravichandran M, Doolan DL, Cox-Singh J, Hoffman SL, Singh B
    Parasite Immunol., 2000 Sep;22(9):469-73.
    PMID: 10972854
    Considerable effort is directed at the development of a malaria vaccine that elicits antigen-specific T-cell responses against pre-erythrocytic antigens of Plasmodium falciparum. Genetic restriction of host T-cell responses and polymorphism of target epitopes on parasite antigens pose obstacles to the development of such a vaccine. Liver stage-specific antigen-1 (LSA-1) is a prime candidate vaccine antigen and five T-cell epitopes that are degenerately restricted by HLA molecules common in most populations have been identified on LSA-1. To define the extent of polymorphism within these T-cell epitopes, the N-terminal non-repetitive region of the LSA-1 gene from Malaysian P. falciparum field isolates was sequenced and compared with data of isolates from Brazil, Kenya and Papua New Guinea. Three of the T-cell epitopes were completely conserved while the remaining two were highly conserved in the isolates examined. Our findings underscore the potential of including these HLA-degenerate T-cell epitopes of LSA-1 in a subunit vaccine.
    Matched MeSH terms: Antigens, Protozoan/immunology
  10. Recombinant proteins in the diagnosis of toxoplasmosis
    Kotresha D, Noordin R
    APMIS, 2010 Aug;118(8):529-42.
    PMID: 20666734 DOI: 10.1111/j.1600-0463.2010.02629.x
    Toxoplasma gondii is an important human pathogen with a worldwide distribution. It is primarily of medical importance for pregnant women and immunocompromised patients. Primary infection of the former is often associated with fetal infection, which can lead to abortion or severe neonatal malformation. Immunocompromised patients are at risk of contracting the severe form of the disease that may be fatal. Thus, detection of T. gondii infection with high sensitivity and specificity is crucial in the management of the disease. Toxoplasmosis is generally diagnosed by demonstrating specific immunoglobulin M (IgM) and IgG antibodies to toxoplasma antigens in the patient's serum sample. Most of the commercially available tests use T. gondii native antigens and display wide variations in test accuracy. Recombinant antigens have great potential as diagnostic reagents for use in assays to detect toxoplasmosis. Thus in this review, we address recent advances in the use of Toxoplasma recombinant proteins for serodiagnosis of toxoplasmosis.
    Matched MeSH terms: Antigens, Protozoan/immunology*
  11. Production of a monoclonal antibody against a mannose-binding protein of Acanthamoeba culbertsoni and its localization
    Kang AY, Park AY, Shin HJ, Khan NA, Maciver SK, Jung SY
    Exp Parasitol, 2018 Sep;192:19-24.
    PMID: 30031120 DOI: 10.1016/j.exppara.2018.07.009
    Amoebae from the genus Acanthamoeba are facultative pathogens of humans and other animals. In humans they most frequently infect the eye causing a sight threatening infection known as Acanthamoeba keratitis (AK), and also cause an often fatal encephalitis (GAE). A mannose-binding protein (MBP) has been identified as being important for Acanthamoeba infection especially in AK. This lectin has previously been characterized from Acanthamoeba castellanii as consisting of multiple 130 kDa subunits. MBP expression correlates with pathogenic potential and is expressed in a number of Acanthamoeba species. Here we report the purification of a similar lectin from Acanthamoeba culbertsoni and the production of a monoclonal antibody to it. The A. culbertsoni MBP was isolated by affinity chromatography using α-D-mannose agarose and has an apparent molecular weight of 83 kDa. The monoclonal antibody is an IgM that is useful in both western blots and immunofluorescence. We expect that this antibody will be useful in the study of the pathology of A. culbertsoni and in its identification in clinical samples.
    Matched MeSH terms: Antigens, Protozoan/immunology
  12. Parallel ELISAs using crude soluble antigen and excretory-secretory antigen for improved serodiagnosis of amoebic liver abscess
    Wong WK, Foo PC, Olivos-Garcia A, Noordin R, Mohamed Z, Othman N, et al.
    Acta Trop, 2017 Aug;172:208-212.
    PMID: 28506795 DOI: 10.1016/j.actatropica.2017.05.017
    Crude soluble antigen (CSA) produced from Entamoeba histolytica trophozoite is conventionally used for serodiagnosis of invasive amoebiasis. However, high background seropositivities by CSA-assay in endemic areas complicate the interpretation of positive result in clinical settings. Instead, incorporating a second assay which indicates active or recent infection into the routine amoebic serology could possibly complement the limitations of CSA-assay. Hence, the present study aimed to evaluate the diagnostic efficacies of indirect ELISAs using CSA and excretory-secretory antigen (ESA) for serodiagnosis of amoebic liver abscess (ALA). Reference standard for diagnosis of ALA at Hospital Universiti Sains Malaysia is based on clinical presentation, radiological imaging and positive indirect haemagglutination assay (titer ≥256). Five groups of human serum samples collected from the hospital included Group I - ALA diagnosed by the reference standard and pus aspirate analysis using real-time PCR (n=10), Group II - ALA diagnosed by the reference standard only (n=41), Group III - healthy control (n=45), Group IV - other diseases control (n=51) and Group V - other infectious diseases control (n=31). For serodiagnosis of ALA serum samples (Group I and II), CSA-ELISA showed sensitivities of 100% for both groups, while ESA-ELISA showed sensitivities of 100% and 88%, respectively. For serodiagnosis of non-ALA serum samples (Group III, IV and V), CSA-ELISA showed specificities of 91%, 75% and 100%, respectively; while ESA-ELISA showed specificities of 96%, 98% and 100%, respectively. Indirect ELISAs using CSA and ESA have shown distinct strength for serodiagnosis of ALA, in terms of sensitivity and specificity, respectively. In conclusion, parallel analysis by both assays improved the overall efficacies of amoebic serology as compared to either single assay.
    Matched MeSH terms: Antigens, Protozoan/immunology*
  13. Fulltext Naturally acquired antibody response to Plasmodium falciparum describes heterogeneity in transmission on islands in Lake Victoria
    Idris ZM, Chan CW, Kongere J, Hall T, Logedi J, Gitaka J, et al.
    Sci Rep, 2017 08 22;7(1):9123.
    PMID: 28831122 DOI: 10.1038/s41598-017-09585-4
    As markers of exposure anti-malaria antibody responses can help characterise heterogeneity in malaria transmission. In the present study antibody responses to Plasmodium falciparum AMA-1, MSP-119 and CSP were measured with the aim to describe transmission patterns in meso-endemic settings in Lake Victoria. Two cross-sectional surveys were conducted in Lake Victoria in January and August 2012. The study area comprised of three settings: mainland (Ungoye), large island (Mfangano) and small islands (Takawiri, Kibuogi, Ngodhe). Individuals provided a finger-blood sample to assess malaria infection by microscopy and PCR. Antibody response to P. falciparum was determined in 4,112 individuals by ELISA using eluted dried blood from filter paper. The overall seroprevalence was 64.0% for AMA-1, 39.5% for MSP-119, and 12.9% for CSP. Between settings, seroprevalences for merozoite antigens were similar between Ungoye and Mfangano, but higher when compared to the small islands. For AMA-1, the seroconversion rates (SCRs) ranged from 0.121 (Ngodhe) to 0.202 (Ungoye), and were strongly correlated to parasite prevalence. We observed heterogeneity in serological indices across study sites in Lake Victoria. These data suggest that AMA-1 and MSP-119 sero-epidemiological analysis may provide further evidence in assessing variation in malaria exposure and evaluating malaria control efforts in high endemic area.
    Matched MeSH terms: Antigens, Protozoan/immunology
  14. Mature Erythrocyte Surface Antigen Protein Identified in the Serum of Plasmodium falciparum-Infected Patients
    Zainudin NS, Othman N, Muhi J, Abdu Sani AA, Noordin R
    Am J Trop Med Hyg, 2015 Dec;93(6):1268-73.
    PMID: 26392156 DOI: 10.4269/ajtmh.15-0333
    This study was performed to identify circulating Plasmodium falciparum proteins in patient serum, which may be useful as diagnostic markers. Depletion of highly abundant proteins from each pooled serum sample obtained from P. falciparum-infected patients and healthy individuals was performed using the Proteoseek Antibody-Based Albumin/IgG Removal Kit (Thermo Scientific, Rockford, IL). In analysis 1, the depleted serum was analyzed directly by NanoLC-MS/MS. In analysis 2, the depleted serum was separated by two-dimensional electrophoresis followed by western blot analysis. Subsequently, the selected band was analyzed by NanoLC-MS/MS. The result of analysis 1 revealed the presence of two mature erythrocyte surface antigen (MESA) proteins and chloroquine resistance transporter protein (PfCRT). In addition, analysis 2 revealed an antigenic 75-kDa band when the membrane was probed with purified IgG from the pooled serum obtained from P. falciparum-infected patients. MS/MS analysis of this protein band revealed fragments of P. falciparum MESA proteins. Thus, in this study, two different analyses revealed the presence of Plasmodium MESA protein in pooled serum from malaria patients; thus, this protein should be further investigated to determine its usefulness as a diagnostic marker.
    Matched MeSH terms: Antigens, Protozoan/immunology*
  15. Fulltext Low Levels of Polymorphisms and Negative Selection in Plasmodum knowlesi Merozoite Surface Protein 8 in Malaysian Isolates
    Atique Ahmed M, Kang HJ, Quan FS
    Korean J Parasitol, 2019 Aug;57(4):445-450.
    PMID: 31533414 DOI: 10.3347/kjp.2019.57.4.445
    Human infections due to the monkey malaria parasite Plasmodium knowlesi is increasingly being reported from most Southeast Asian countries specifically Malaysia. The parasite causes severe and fatal malaria thus there is a need for urgent measures for its control. In this study, the level of polymorphisms, haplotypes and natural selection of full-length pkmsp8 in 37 clinical samples from Malaysian Borneo along with 6 lab-adapted strains were investigated. Low levels of polymorphism were observed across the full-length gene, the double epidermal growth factor (EGF) domains were mostly conserved, and non-synonymous substitutions were absent. Evidence of strong negative selection pressure in the non-EGF regions were found indicating functional constrains acting at different domains. Phylogenetic haplotype network analysis identified shared haplotypes and indicated geographical clustering of samples originating from Peninsular Malaysia and Malaysian Borneo. This is the first study to genetically characterize the full-length msp8 gene from clinical isolates of P. knowlesi from Malaysia; however, further functional characterization would be useful for future rational vaccine design.
    Matched MeSH terms: Antigens, Protozoan/immunology
  16. Isolation of Balamuthia mandrillaris-specific antibody fragments from a bacteriophage antibody display library
    Siddiqui R, Kulsoom H, Lalani S, Khan NA
    Exp Parasitol, 2016 Jul;166:94-6.
    PMID: 27055361 DOI: 10.1016/j.exppara.2016.04.001
    Balamuthia mandrillaris is a protist pathogen that can cause encephalitis with a mortality rate of more than 95%. Early diagnosis followed by aggressive treatment is a pre-requisite for successful prognosis. Current methods for identifying this organism rely on culture and microscopy, antibody-based methods using animals, or involve the use of molecular tools that are expensive. Here, we describe the isolation of antibody fragments that can be used for the unequivocal identification of B. mandrillaris. B. mandrillaris-specific antibody fragments were isolated from a bacteriophage antibody display library. Individual clones were studied by enzyme-linked immunosorbent assay, and immunofluorescence. Four antibody clones showed specific binding to B. mandrillaris. The usefulness of phage antibody display technology as a diagnostic tool for isolating antibody fragments against B. mandrillaris antigens and studying their biological role(s) is discussed further.
    Matched MeSH terms: Antigens, Protozoan/immunology
  17. Interaction of Malaysian sera with Plasmodium vivax sporozoite antigen
    Lee M, Davis DR, Ballou WR, Folena-Wasserman G, Lewis GE
    Am J Trop Med Hyg, 1988 Dec;39(6):535-9.
    PMID: 3061309
    A seroepidemiologic survey of Plasmodium vivax and Plasmodium falciparum transmission was conducted in 94 Orang Asli children and adults. The prevalence of malaria was 46% in this population, and infections due to P. vivax and P. falciparum occurred with equal frequency. Multi-species infection was common, particularly in children less than 10 years of age. Circumsporozoite (CS) antibodies to P. vivax were detected by ELISA, using the recombinant protein NS181V20, in sera from 53-95% of all subjects in this study. The specificity of reactivity to NS181V20 was confirmed by immunofluorescence using air-dried sporozoites. CS antibodies to P. falciparum were present in less than 50% of the population less than 30 years of age. These data support further testing of this protein as a candidate vivax vaccine.
    Matched MeSH terms: Antigens, Protozoan/immunology*
  18. Fulltext Induction and Kinetics of Complement-Fixing Antibodies Against Plasmodium vivax Merozoite Surface Protein 3α and Relationship With Immunoglobulin G Subclasses and Immunoglobulin M
    Oyong DA, Wilson DW, Barber BE, William T, Jiang J, Galinski MR, et al.
    J Infect Dis, 2019 11 06;220(12):1950-1961.
    PMID: 31419296 DOI: 10.1093/infdis/jiz407
    BACKGROUND: Complement-fixing antibodies are important mediators of protection against Plasmodium falciparum malaria. However, complement-fixing antibodies remain uncharacterized for Plasmodium vivax malaria. P. vivax merozoite surface protein 3α (PvMSP3α) is a target of acquired immunity and a potential vaccine candidate.

    METHODS: Plasma from children and adults with P. vivax malaria in Sabah, Malaysia, were collected during acute infection, 7 and 28 days after drug treatment. Complement-fixing antibodies and immunoglobulin M and G (IgM and IgG), targeting 3 distinctive regions of PvMSP3α, were measured by means of enzyme-linked immunosorbent assay.

    RESULTS: The seroprevalence of complement-fixing antibodies was highest against the PvMSP3α central region (77.6%). IgG1, IgG3, and IgM were significantly correlated with C1q fixation, and both purified IgG and IgM were capable of mediating C1q fixation to PvMSP3α. Complement-fixing antibody levels were similar between age groups, but IgM was predominant in children and IgG3 more prevalent in adults. Levels of functional antibodies increased after acute infection through 7 days after treatment but rapidly waned by day 28.

    CONCLUSION: Our study demonstrates that PvMSP3α antibodies acquired during P. vivax infection can mediate complement fixation and shows the important influence of age in shaping these specific antibody responses. Further studies are warranted to understand the role of these functional antibodies in protective immunity against P. vivax malaria.

    Matched MeSH terms: Antigens, Protozoan/immunology*
  19. Fulltext In vitro invasion inhibition assay using antibodies against Plasmodium knowlesi Duffy binding protein alpha and apical membrane antigen protein 1 in human erythrocyte-adapted P. knowlesi A1-H.1 strain
    Muh F, Lee SK, Hoque MR, Han JH, Park JH, Firdaus ER, et al.
    Malar J, 2018 Jul 27;17(1):272.
    PMID: 30049277 DOI: 10.1186/s12936-018-2420-4
    BACKGROUND: The rapid process of malaria erythrocyte invasion involves ligand-receptor interactions. Inducing antibodies against specific ligands or receptors that abrogate the invasion process is a key challenge for blood stage vaccine development. However, few candidates were reported and remain to be validated for the discovery of new vaccine candidates in Plasmodium knowlesi.

    METHODS: In order to investigate the efficacy of pre-clinical vaccine candidates in P. knowlesi-infected human cases, this study describes an in vitro invasion inhibition assay, using a P. knowlesi strain adapted to in vitro growth in human erythrocytes, PkA1-H.1. Recombinant proteins of P. knowlesi Duffy binding protein alpha (PkDBPα) and apical membrane antigen 1 (PkAMA1) were produced in Escherichia coli system and rabbit antibodies were generated from immune animals.

    RESULTS: PkDBPα and PkAMA1 recombinant proteins were expressed as insoluble and produced as a functional refolded form for this study. Antibodies against PkDBPα and PkAMA1 specifically recognized recombinant proteins and native parasite proteins in schizont-stage parasites on the merozoite organelles. Single and combination of anti-PkDBPα and anti-PkAMA1 antibodies elicited strong growth inhibitory effects on the parasite in concentration-dependent manner. Meanwhile, IgG prevalence of PkDBPα and PkAMA1 were observed in 13.0 and 46.7% in human clinical patients, respectively.

    CONCLUSION: These data provide support for the validation of in vitro growth inhibition assay using antibodies of DBPα and AMA1 in human-adapted P. knowlesi parasite PkA1-H.1 strain.

    Matched MeSH terms: Antigens, Protozoan/immunology*
  20. Fulltext Immunogenicity of recombinant BCG-based vaccine expressing the 22 kDa of serine repeat antigen (SE22) of Plasmodium falciparum
    Teo WH, Nurul AA, Norazmi MN
    Trop Biomed, 2012 Jun;29(2):239-53.
    PMID: 22735846 MyJurnal
    The Plasmodium falciparum serine repeat antigen (SERA) is one of the promising blood-stage malarial vaccine candidates. In this study, recombinant Mycobacterium bovis bacille Calmette-Guerin (rBCG) expressing the 22 kDa protein (SE22) from the 47 kDa Nterminal domain of serine repeat antigen (SERA), generated in favour of mycobacterium codon usage, elicited specific immune response in BALB/c mice with a mixed Th1/Th2 profile. Immunized sera containing high levels of specific IgG1 and IgG2a against the epitope (as determined by ELISA) were reactive with fixed P. falciparum merozoites as demonstrated by indirect immunofluorescence assay (IFA). Furthermore, the lymphocyte proliferative response to SE22 antigen from rBCG-immunized mice was higher than that of controls. The expression of intracellular cytokines (IL-2, IL-4 and IFNγ) in CD4+- and CD8+-cells was also enhanced following in-vitro stimulation with SE22. These findings indicate that a rBCG-based vaccine candidate expressing a blood-stage antigen of P. falciparum could enhance both humoral and cellular immune responses, thus paving the way for the rational use of rBCG as a vaccine candidate against malaria.
    Matched MeSH terms: Antigens, Protozoan/immunology*
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