Displaying publications 1 - 20 of 124 in total

  1. Mirzadeh A, Saadatnia G, Golkar M, Babaie J, Noordin R
    Protein Expr. Purif., 2017 05;133:66-74.
    PMID: 28263855 DOI: 10.1016/j.pep.2017.03.001
    SAG1-related sequence 3 (SRS3) is one of the major Toxoplasma gondii tachyzoite surface antigens and has been shown to be potentially useful for the detection of toxoplasmosis. This protein is highly conformational due to the presence of six disulfide bonds. To achieve solubility and antigenicity, SRS3 depends on proper disulfide bond formation. The aim of this study was to over-express the SRS3 protein with correct folding for use in serodiagnosis of the disease. To achieve this, a truncated SRS3 fusion protein (rtSRS3) was produced, containing six histidyl residues at both terminals and purified by immobilized metal affinity chromatography. The refolding process was performed through three methods, namely dialysis in the presence of chemical additives along with reduced/oxidized glutathione and drop-wise dilution methods with reduced/oxidized glutathione or reduced DTT/oxidized glutathione. Ellman's assay and ELISA showed that the protein folding obtained by the dialysis method was the most favorable, probably due to the correct folding. Subsequently, serum samples from individuals with chronic infection (n = 76), probable acute infection (n = 14), and healthy controls (n = 81) were used to determine the usefulness of the refolded rtSRS3 for Toxoplasma serodiagnosis. The results of the developed IgG-ELISA showed a diagnostic specificity of 91% and a sensitivity of 82.89% and 100% for chronic and acute serum samples, respectively. In conclusion, correctly folded rtSRS3 has the potential to be used as a soluble antigen for the detection of human toxoplasmosis.
    Matched MeSH terms: Toxoplasma/genetics*; Toxoplasma/immunology*; Toxoplasma/metabolism; Toxoplasma/chemistry
  2. De Silva JR, Ching XT, Lau YL
    Trop Biomed, 2020 Jun 01;37(2):324-332.
    PMID: 33612802
    The focus of the current study was to disrupt the Toxo 5699 gene via CRISPR/Cas9 to evaluate the effects of gene disruption on the parasite lytic cycle. In the present work, a single plasmid expressing both the guide RNA and Cas9 nuclease together with a selectable marker of human dihydrofolate reductase (DHFR) was introduced into Toxoplasma gondii. Targeted disruption of the Toxo 5699 gene was carried out via the CRISPR/Cas9 system and confirmed by PCR, sequencing, and immunofluorescence microscopy. Disrupted and nondisrupted control parasites were allowed to invade HS27 cell monolayers and plaques were counted. The average number of plaques from three replicates per group was obtained between the disrupted and non-disrupted T. gondii RH strain and was compared using a onetailed t-test. It was observed that there was a significant decrease in number and size of plaque formation in the Toxo 5699 gene disrupted parasite line. This is an indication that the Toxo 5699 gene may play a role in the lytic cycle of the parasite, particularly during the replication phase and thus would be a novel target for disruption or silencing. The Toxo 5699 gene presented in the current work is an important part of the T. gondii lytic cycle, therefore meriting further inquiry into its potential as a target for further genetic-silencing or disruption studies.
    Matched MeSH terms: Toxoplasma/genetics*; Toxoplasma/pathogenicity*
  3. Thomas V, Dissanaike AS
    Trans R Soc Trop Med Hyg, 1978;72(3):303-6.
    PMID: 97821
    Sera from 243 donors belonging to the four main ethnic groups in West Malaysia (Orang Asli, Malays, Chinese and Indians) were tested, using the indirect fluorescent antibody technique for the prevalence of antibodies to Sarcocystis. Almost 20% reacted positively at dilutions of 1:64 or higher and eight among the Orang Asli and Malays gave the highest titres of 1:256. Prevalence was highest in the Orang Asli and lowest in Chinese. 22 sera also reacted positively to Toxoplasma, whether due to polyparasitism or cross-reaction is, as yet, unknown.
    Matched MeSH terms: Toxoplasma/immunology
  4. Zaman V
    Med J Malaya, 1968 Mar;22(3):195-7.
    PMID: 4234355
    Matched MeSH terms: Toxoplasma/growth & development*
  5. Nimir A, Othman A, Ee S, Musa Z, Majid IA, Kamarudin Z, et al.
    J Clin Med Res, 2010 May 19;2(3):117-20.
    PMID: 21629523 DOI: 10.4021/jocmr2010.06.375w
    Seroprevalence of toxoplasmosis in different populations may vary according to different environments, social customs and habits. This study was designed to measure the seroprevalence of toxoplasmosis among patients with different malignancies and to ascertain the association between common risk factors and disease transmission.
    Matched MeSH terms: Toxoplasma
  6. Suresh K, Mak JW, Yong HS
    PMID: 1822869
    Thirty in vitro serial passages of Toxoplasman gondii cultures in Vero cell line performed once in every five days had a mean increase in parasite count of 74.4 +/- 14.8 times from that of initial counts. Long term cultures in Vero cell line did not alter the virulence of the parasite. The good correlation (r = 0.99) between the IFA titer and ELISA OD values using the parasite antigens from in vitro sources indicates that long term maintenance of T. gondii in culture does not affect significantly the ability to recognize antibodies to surface and soluble antigens. The results also show that soluble antigens containing host cells can be directly used for immunodiagnostic purposes without purification. The in vitro maintenance of T. gondii is safer and cheaper when compared to the in vivo method.
    Matched MeSH terms: Toxoplasma/growth & development*; Toxoplasma/immunology; Toxoplasma/pathogenicity
  7. Ahmad N., Osman, E., Abdul Ghani, N.A., Leong, W.Y., Arzaee, M.Z., Seow, Y.Y., et al.
    Medicine & Health, 2020;15(2):108-123.
    Toksoplasmosis pendam dapat menyebabkan pelbagai gangguan hormon dan tingkah laku dalam hos terjangkit. Kami berhasrat untuk mengkaji sero-prevalens Toxoplasma gondii (T. gondii) pendam serta hubungan antara jangkitan dengan pengetahuan dan tingkah laku dalam kalangan 400 ibu hamil. Sampel plasma diuji untuk kehadiran antibodi IgG T. gondii dan soal selidik berstruktur digunakan untuk merekodkan ciri-ciri sosio-demografi responden, maklumat umum dan pengetahuan mengenai faktor risiko, gejala, masa jangkitan, pengetahuan pencegahan serta tingkah laku pencegahan toksoplasmosis. Sero-prevalensi toksoplasmosis pendam dalam wanita hamil adalah 31.8%. Kajian menunjukkan, 69.5% daripada mereka mempunyai kurang pengetahuan mengenai toksoplasmosis. Walau bagaimanapun, majoritinya (99.8%) mengamalkan tingkah laku pencegahan. Analisis regresi logistik berganda menunjukkan wanita hamil dengan tahap pendidikan rendah mempunyai hampir dua kali lebih risiko (nisbah ods terlaras: 1.91, 95% SK 1.18, 3.10; p = 0.008) untuk T. gondii IgG seropositif. Wanita hamil yang mempunyai sejarah perubatan lalu mempunyai dua kali lebih kemungkinan (nisbah ods terlaras: 2.32, 95% SK 1.32, 4.06; p = 0.003) untuk T. gondii IgG seropositif. Selain itu, wanita yang tidak pasti mengenai mod penyebaran penyakit melalui pemindahan darah mempunyai empat kali lebih ods (nisbah ods terlaras: 3.93, 95% SK 1.54, 10.01; p = 0.004) untuk sero-prevalens kronik toksoplasmosis. Wanita yang tidak pasti mengenai keperluan menghindari kucing liar mempunyai nisbah ods terlaras: 0.42 (95% SK 0.24, 0.71, p = 0.001) untuk sero-prevalens kronik toksoplasmosis. Penterjemahan pengetahuan tentang toksoplasmosis kepada amalan tingkah laku pencegahan melalui program pendidikan kesihatan adalah penting untuk mengurangkan risiko penularan penyakit ini dalam kalangan wanita hamil.
    Matched MeSH terms: Toxoplasma
  8. Nimir AR, Linn TC
    Acta Medica (Hradec Kralove), 2011;54(3):107-10.
    PMID: 22250479
    The local Chow Kit market is the largest wet market in the city of Kuala Lumpur. It is very close to the biggest government hospital in the city centre. However, the level of cleanliness in this area is always questionable and a matter of concern. The aim of this study was to identify the prevalence of T. gondii oocyst in water samples used by hawkers in that market and tissue cysts in rats' brains captured from the same area. Water samples were taken to the parasitology laboratory at the National Universtiy of MalaysiaUniversity and a sugar flotation concentration method was used. Supernatant microscopical examination was then performed. A total of 752 slides were screened for the presence of T. gondii oocyst. A hundred rats wandering in the same area were also captured by the hawkers using mousetraps. After each animal was sacrificed, and an electric microtome was used to cut out serial sections 5 microm thick from the rat brains. The de-waxed tissue sections were stained by the progressive Haematoxylin and Eosin (H&E) stain for microscopical examination. A total of 1000 slides were screened under a light microscope to detect the presence of T. gondii brain cysts. All the water samples were found to be negative for T. gondii oocyst. Out of the 100 rats captured, three rats were found to possess T. gondii cysts in their brains. Water samples reflect minimal or no solid food contamination, while the 3% of positive brain cysts influence the researchers to broaden their investigations for future projects.
    Matched MeSH terms: Toxoplasma/isolation & purification*
  9. Emelia O, Zeehaida M, Sulaiman O, Rohela M, Saadatnia G, Yeng C, et al.
    J Immunoassay Immunochem, 2010;31(1):79-91.
    PMID: 20391020 DOI: 10.1080/15321810903405134
    We have developed an ELISA that employs monoclonal anti-Toxoplasma SAG1 (p30) as the capture antibody to detect T. gondii circulating antigens in patients' serum samples. Using serum spiked with Toxoplasma soluble and with SAG1 recombinant proteins, the detection limits were 31.25 ng/mL and 62.50 ng/mL, respectively. We obtained positive results in 28% (21/75) and 11% (23/206) of probable active and chronic toxoplasmosis serum samples, respectively. Western blot analysis on pooled antigen-positive serum samples showed antigenic bands of molecular weights 25 and 75 kDa from sera of probable active infection and five antigenic bands ranging in size from 26 to 33 kDa from chronic infection sera. This assay would be useful as an initial serum selection step in developing a Toxoplasma antigen detection test and for characterization studies.
    Matched MeSH terms: Toxoplasma/immunology*
  10. Sahimin N, Mohd Hanapi IR, Nurikhan ZA, Behnke JM, Mohd Zain SN
    Acta Parasitol, 2021 Jun;66(2):524-534.
    PMID: 33219942 DOI: 10.1007/s11686-020-00304-0
    PURPOSE: Toxoplasmosis is a zoonotic infection linked to compromised hygiene and sanitation via the handling of infected cat faeces, eating undercooked contaminated meat or transplacental transmission. We conducted a study to determine seroprevalence and risk factors associated with toxoplasmosis among the urban poor communities in Malaysia.

    METHODS: The demographic profiles for each participant were obtained through a questionnaire survey prior to blood collection. A total of 389 participants were recruited and blood samples screened for the presence of anti-Toxoplasma IgG and IgM antibody using an ELISA commercial kit, SERION ELISA classic Toxoplasma gondii IgG and IgM.

    RESULTS: The overall T. gondii seroprevalence was 69.6% with 56.8% seropositive for anti-Toxoplasma IgG, 7.7% seropositive for anti-Toxoplasma IgM and 5.1% seropositive for both IgG and IgM antibodies. The presence of both antibody classes in blood samples indicated high avidity, suggesting latent infection. Univariate analysis revealed significant associations that included; age, ethnicity, location and employment status while, significant lifestyle factors included source of drinking water and eating style. A multifactorial statistical model that incorporated all the significant effects from the first-stage univariate analyses listed above revealed that age and ethnicity were the two dominant and independent effects on IgG seroprevalence. For seroprevalence of IgM, the multifactorial model revealed a significant interaction between work and accommodation. IgM seroprevalence was higher among the unemployed inhabitants of PPR (Program Perumahan Rakyat) than those living in non-PPR accommodation, and higher than among the employed irrespective of their accommodation.

    CONCLUSION: High seroprevalence of Toxoplasmosis in the community calls for increased awareness of disease transmission and improvements in hygiene and sanitation.

    Matched MeSH terms: Toxoplasma*
  11. Saadatnia G, Haj Ghani H, Khoo BY, Maimunah A, Rahmah N
    Trop Biomed, 2010 Apr;27(1):125-30.
    PMID: 20562822
    In vitro culture of Toxoplasma gondii can provide tachyzoites which are active, viable and with desirable purity. Thus the aim of this study was to optimize the cell culture method for T. gondii propagation to obtain a consistent source of parasites with maximum yield and viability, but minimum host cell contamination for use in production of excretory-secretory antigen. Tachyzoites with seed counts of 1x10(6), 1x10(7) and 1x10(8) harvested from infected mice were added to VERO cells of different degrees of confluence, namely 50%, 85% and 100%, and examined periodically using an inverted microscope. When the maximum release of the tachyzoites was observed from the host cells, the culture supernatant was removed and the tachyzoites harvested. Using a Neubauer chamber, the percentages of viable tachyzoites and host cell contamination were determined using trypan blue stain. Parameters that gave the best yield and purity of viable tachyzoites were found to be as follows: VERO cells at 85% confluence in DMEM medium and inoculum comprising 1x10(7) tachyzoites. After about 3 days post infection, the tachyzoites multiplied 78x, with a yield of ~7.8x10(8) per flask, 99% viability and 3% host cell contamination. This study has successfully optimized the method of propagation of T. gondii tachyzoites in VERO cells which produce parasites with high yield, purity and viability.
    Matched MeSH terms: Toxoplasma/physiology*
  12. Fong MY, Lau YL, Zulqarnain M
    Biotechnol Lett, 2008 Apr;30(4):611-8.
    PMID: 18043869
    The surface antigen 2 (SAG2) gene of the protozoan parasite, Toxoplasma gondii, was cloned and extracellularly expressed in the yeast Pichia pastoris. The effectiveness of the secreted recombinant SAG2 (rSAG2-S) as a serodiagnosis reagent was assessed by western blots and ELISA. In the western blot assay, rSAG2-S reacted with all Toxoplasma-antibody positive human serum samples but not with Toxoplasma-negative samples. In the ELISA, rSAG2-S yielded sensitivity rates ranging from 80% (IgG negative, IgM positive) to 100% (IgG positive, IgM negative). In vivo experiments showed that serum from mice immunized with rSAG2-S reacted specifically with the native SAG2 of T. gondii. These mice were protected when challenged with live cells of T. gondii.
    Matched MeSH terms: Toxoplasma/genetics; Toxoplasma/immunology; Toxoplasma/metabolism*
  13. Hajissa K, Zakaria R, Suppian R, Mohamed Z
    J Adv Vet Anim Res, 2019 Jun;6(2):174-182.
    PMID: 31453188 DOI: 10.5455/javar.2019.f329
    Despite the significant progress in the recent efforts toward developing an effective vaccine against toxoplasmosis, the search for new protective vaccination strategy still remains a challenge and elusive goal because it becomes the appropriate way to prevent the disease. Various experimental approaches in the past few years showed that developing a potential vaccine against the disease can be achievable. The combination of multi-epitopes expressing different stages of the parasite life cycle has become an optimal strategy for acquiring a potent, safe, and effective vaccine. Epitope-based vaccines have gained attention as alternative vaccine candidates due to their ability of inducing protective immune responses. This mini-review highlights the current status and the prospects of Toxoplasma gondii vaccine development along with the application of epitope-based vaccine in the future parasite immunization as a novel under development and evaluation strategy.
    Matched MeSH terms: Toxoplasma
  14. Khairul Anuar A, Rahmah N, Dighe VC, Zurainee MN, Suresh K, Yano A
    JUMMEC, 1999;4:34-38.
    In vitro lymphocyte proliferative response of peripheral blood leucocytes (PBL) to purified Toxoplasma gondii antigen were evaluated by 3[H] methyl thymidine incorporation in patients acutely and chronically infected with Toxoplama gondii. PBL from three patients with acute sylnptonlatic toxoplaslnosis showed no response to T. gondii antigen during the emergence of anti-Toxoplasma 1gM antibodies and the response returned as the infection became chronic. Lymphocytes of twelve chronically-infected patients responded positively to the antigen. In all patients the lymphocyte proliferative response to the mitogen, Concanavalill A (Con A) was normal. Analysis of Toxoplasma proliferative response of PBL from a patient with acute toxoplasrnosis showed that CD8+ cells were responsible for induction of suppression while the response during the chronic infection was lnediated by CD4+ cells. In human toxoplasmosis there was antigen-specific lymphocyte unresponsiveness during the acute phase of the infection and it appears that the initnunesuppression was mediated by CD8+ cells. KEYWORDS: Toxoplasmosis-lymphocyte blastogenesis-antigen specific-CD4+, CD8+
    Matched MeSH terms: Toxoplasma
  15. Zurainee MN, Khairul Anuar A, Fong MY, Hoh HB, Choon J, Rahmah N
    JUMMEC, 2000;5:98-102.
    During the period 1996-1998, 134 patients suspected of having ocular toxoplasmosis were seen in the Ophthalmology Clinic of the University Hospital, Kuala Lumpur. Clinical presentations in these patients ranged from poor vision to severe retinal detachment. Of these patients, 72% were confirmed positive for Toxoplasma gondii infection by serological methods. Chorioretinjtis and vitritis were found to be the most apparent symptoms, both having 100%correlation with serological positivity, This was followed by uveitis, floaters, and retinal detachment with correlation at 78%, 75%and 75%, respectively. However, there was no correlation between level of serotitre and ocular presentations. KEYWORDS: Toxoplasmosis, serology, chorioretinitis, uveitis
    Matched MeSH terms: Toxoplasma
  16. Molan A, Nosaka K, Hunter M, Wang W
    Trop Biomed, 2019 Dec 01;36(4):898-925.
    PMID: 33597463
    Our group sought to determine the global status of T. gondii infection and to evaluate any continental and geographical trends by systematically examining the currently available epidemiological data on the prevalence of T. gondii infection. A comprehensive literature search was conducted from 10 electronic databases (Google Scholar, Science Direct, Embase, PubMed, PLOS ONE, Web of Knowledge, SciELO, MyAIS, Free Medical Journals, and Scopus) without date or language restrictions. Specific medical subject heading terms were used to search for human T. gondii seroprevalence studies that recruited subjects from general apparently healthy populations. The data were collated and analysed for both continental and global trends. The search identified 152 published studies that examined a total of 648,010 subjects. From these, 166,255 were seropositive for T. gondii infection indicating an average global seroprevalence rate of 25.7% (95% CI: 25.6 - 25.8%). The overall range of seroprevalence was determined to be 0.5 - 87.7%. African countries had the highest average seroprevalence rate of 61.4%, followed by Oceania with 38.5%, South America with 31.2%, Europe with 29.6%, USA/Canada with 17.5%, and Asia with 16.4%. Numerous environmental and human factors affect the differences in T. gondii seroprevalence rates observed between the various countries and continents. Monitoring the source and transmission may assist public health authorities to clarify the risk factors involved, as well as focus on implementing optimal state-specific health policies targeting T. gondii transmission control.
    Matched MeSH terms: Toxoplasma
  17. Puvanesuaran VR, Noordin R, Balakrishnan V
    PLoS One, 2013;8(4):e61730.
    PMID: 23613920 DOI: 10.1371/journal.pone.0061730
    Toxoplasma gondii is a parasitic protozoan that infects nearly one-third of the world population. The present study was done to isolate and genotype T. gondii from wild boar from forests of Pahang, Malaysia. A total of 30 wild boars' blood, heads and hearts were obtained for this study and 30 (100.0%) were found to be seropositive when assayed with modified agglutination test (MAT ≥ 6). The positive samples were inoculated into mice and T. gondii was only isolated from samples that had strong seropositivity (MAT ≥ 1:24).The isolates were subjected to PCR-RFLP analysis and all the Peninsular Malaysia isolates of T. gondii are of clonal type I.
    Matched MeSH terms: Toxoplasma/genetics*; Toxoplasma/isolation & purification*
  18. Chang PY, Fong MY, Nissapatorn V, Lau YL
    Am J Trop Med Hyg, 2011 Sep;85(3):485-9.
    PMID: 21896809 DOI: 10.4269/ajtmh.2011.11-0351
    Rhoptry protein 2 (ROP2) of Toxoplasma gondii is a rhoptry-secreted protein that plays a critical role in parasitophorous vacuole membrane formation during invasion. In previous studies, ROP2 has been shown to be efficient in triggering humoral and cell-mediated responses. High immunogenicity of ROP2 makes it a potential candidate for diagnosis and vaccination against toxoplasmosis. In this study, the ROP2 gene was cloned into pPICZα A expression vector and extracellularly expressed in the yeast Pichia pastoris, which has numerous advantages over other expression systems for eukaryotic proteins expression. The effectiveness of the secreted recombinant ROP2 as a diagnosis agent was assessed by Western Blot with 200 human serum samples. Recombinant ROP2 reacted with toxoplasmosis-positive human serum samples and yielded an overall sensitivity of 90% and specificity of 95%. However, recombinant ROP2 is a better marker for detection of IgG (91.7%) rather than IgM (80%).
    Matched MeSH terms: Toxoplasma/genetics; Toxoplasma/metabolism*
  19. Chew WK, Wah MJ, Ambu S, Segarra I
    Exp Parasitol, 2012 Jan;130(1):22-5.
    PMID: 22027550 DOI: 10.1016/j.exppara.2011.10.004
    Toxoplasma gondii is an intra-cellular parasite that infects humans through vertical and horizontal transmission. The cysts remain dormant in the brain of infected humans and can reactivate in immunocompromised hosts resulting in acute toxoplasmic encephalitis which may be fatal. We determined the onset and progression of brain cysts generation in a mouse model following acute toxoplasmosis as well as the ability of brain cysts to reactivate in vitro. Male Balb/c mice, (uninfected control group, n = 10) were infected orally (study group, n = 50) with 1000 tachyzoites of T. gondii (ME49 strain) and euthanized at 1, 2, 4, 8 and 16 weeks post infection. Brain tissue was harvested, homogenized, stained and the number of brain cysts counted. Aliquots of brain homogenate with cysts were cultured in vitro with confluent Vero cells and the number of cysts and tachyzoites counted after 1 week. Brain cysts but not tachyzoites were detected at week 2 post infection and reached a plateau by week 4. In vitro Vero cells culture showed similar pattern for cysts and tachyzoites and reactivation of cyst in vitro was not influenced by the age of the brain cysts.
    Matched MeSH terms: Toxoplasma/growth & development; Toxoplasma/physiology*
  20. Loh FK, Nathan S, Chow SC, Fang CM
    Vaccine, 2019 07 09;37(30):3989-4000.
    PMID: 31186188 DOI: 10.1016/j.vaccine.2019.05.083
    Since the discovery of Toxoplasma gondii in 1908, it is estimated that one-third of the global population has been exposed to this ubiquitous intracellular protozoan. The complex life cycle of T. gondii has enabled itself to overcome stress and transmit easily within a broad host range thus achieving a high seroprevalence worldwide. To date, toxoplasmosis remains one of the most prevalent HIV-associated opportunistic central nervous system infections. This review presents a comprehensive overview of different vaccination approaches ranging from traditional inactivated whole-T. gondii vaccines to the popular DNA vaccines. Extensive discussions are made to highlight the challenges in constructing these vaccines, selecting adjuvants as well as delivery methods, immunisation approaches and developing study models. Herein we also deliberate over the latest and promising enhancement strategies that can address the limitations in developing an effective T. gondii prophylactic vaccine.
    Matched MeSH terms: Toxoplasma/immunology*; Toxoplasma/pathogenicity*
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