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Vaccination challenges and strategies against long-lived Toxoplasma gondii

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*
Antibodies to Sarcocystis in Malaysians

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
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: Toxoplasma/immunology*
Fulltext Toxoplasma infection in pregnant women: a current status in Songklanagarind hospital, southern Thailand

Andiappan H, Nissapatorn V, Sawangjaroen N, Chemoh W, Lau YL, Kumar T, et al.

Parasit Vectors, 2014;7:239.
PMID: 24886651 DOI: 10.1186/1756-3305-7-239

Toxoplasmosis, being one of the TORCH's infections in pregnant women, is caused by Toxoplasma gondii, an obligate intracellular protozoan parasite. This parasitic infection in pregnancy congenitally causes severe outcomes to their fetus and newborn. This study aimed to determine the seroprevalence and stages of Toxoplasma infection in pregnant women and its associated risks exposures.

Matched MeSH terms: Toxoplasma/immunology
Isolation and genotyping of Toxoplasma gondii from free-range ducks in Malaysia

Puvanesuaran VR, Noordin R, Balakrishnan V

Avian Dis, 2013 Mar;57(1):128-32.
PMID: 23678741

Toxoplasma gondii is a parasitic protozoan that infects nearly one-third of humans. The present study was performed to isolate and genotype T. gondii from free-range ducks in Malaysia. Sera, heads, and hearts from 205 ducks were obtained from four states in Peninsular Malaysia, and 30 (14.63%) sera were found to be seropositive when assayed with the modified agglutination test (MAT > or = 1:6). All the positive samples were inoculated into mice, and T. gondii was successfully isolated from four individual duck samples (1.95%), which were initially found to be strongly seropositive (MAT > or = 1:24). The isolates were subjected to PCR-RFLP analysis, and two T. gondii strains were identified: type I and type II. This is the first reported study on the genetic characterization of T. gondii isolates from free-range farm animals in Southeast Asia.

Matched MeSH terms: Toxoplasma/immunology
Demonstration of antigenic similarities and variations in excretory/secretory antigens of Toxoplasma gondii

Rahmah N, Anuar AK

Biochem Biophys Res Commun, 1992 Aug 31;187(1):294-8.
PMID: 1520310

C57BL/6 mice were orally infected with different doses of cysts of ME49 strain of Toxoplasma gondii to produce groups of acutely and chronically infected mice. Sera were obtained at different periods post-infection. SDS-PAGE was ran with excretory/secretory antigens of ME49 and RH strains of T. gondii, followed by Western blot analyses using the above sera and anti- IgA, IgM, IgG as conjugates. The SDS-PAGE profiles of the two antigens were similar. However the antigenic bands showed variations in all blots, most evidently in IgA blots of chronic sera. IgG blots showed greatest similarities in reactive bands. In IgM blots, more common bands were shown in chronic sera than in acute sera. Variations and similarities in prominence of some bands and time of their appearance were also noted, especially in IgM and IgG blots of chronic sera. Thus antigenic variations and similarities are present in excretory/secretory products of different strains of T. gondii.

Matched MeSH terms: Toxoplasma/immunology*
Fulltext Seroprevalence of anti-Toxoplasma gondii IgG antibody in patients with schizophrenia

Emelia O, Amal RN, Ruzanna ZZ, Shahida H, Azzubair Z, Tan KS, et al.

Trop Biomed, 2012 Mar;29(1):151-9.
PMID: 22543615 MyJurnal

Schizophrenia is a pervasive neuropsychiatric disease of unknown cause. Previous studies have reported that toxoplasmosis may be a possible cause of schizophrenia. To ascertain possible relationship between Toxoplasma gondii and schizophrenia, a cross sectional study, employing an enzyme-linked immunosorbent assay (ELISA) was performed to study the seroprevalence of anti-T. gondii IgG antibody in schizophrenic patients. Furthermore, demographic data analysis from schizophrenic patients were analysed to associate toxoplasmosis with schizophrenia. A total of 288 serum samples from schizophrenic patients (n=144) and psychiatrically healthy volunteers (n=144) were recruited in this study. Interestingly, a significant result in the serointensity rate of anti-T. gondii IgG antibody (> 60 IU/mL) in schizophrenic patients (61.1%) was demonstrated as compared to psychiatrically healthy volunteers (40.8%) (X² = 4.236, p < 0.050). However, there was no significant difference between the seropositivity rate of anti-T. gondii IgG antibody between the two groups. Analysis from demographic data revealed that the seropositivity rate of anti-T. gondii IgG antibody in schizophrenic patients was significantly associated with age group of more than 40 years old (p=0.007) and between ethnic (p=0.046). Nevertheless, no significant association between seropositivity rate of anti-T. gondii IgG antibody with gender (p=0.897), duration of illness (p=0.344) and family history of schizophrenia (p=0.282) in these patients. Thus, this finding is essential as a preliminary data in Malaysia to establish the association between T. gondii and schizophrenia.

Matched MeSH terms: Toxoplasma/immunology*
Toxoplasmosis in HIV/AIDS patients: a current situation

Nissapatorn V, Lee C, Quek KF, Leong CL, Mahmud R, Abdullah KA

Jpn J Infect Dis, 2004 Aug;57(4):160-5.
PMID: 15329448

The seroprevalence of toxoplasmosis among 505 of human immunodeficiency virus (HIV)/AIDS patients was 226 (44.8%; 95% CI 42.64-51.76): 27 (47.4%) and 199 (44.4%) showed Toxoplasma seropositivity with and without toxoplasmic encephalitis (TE), respectively (P <0.05). The majority of these patients were in the 25-34 age group (44 versus 39%), male (86 versus 76%), and Chinese (49 versus 53%), though no statistical significance was found between the two. Significant differences between these two groups were noted, however, in terms of marital status, occupation, and present address. The heterosexual exhibited the most frequent behavior at risk for HIV infection, and accounted for 51 and 59% of patients with and without TE, respectively. Only 17/260 (6.5%) and 1/137 (0.7%) of them later acquired TE after receiving primary chemoprophylaxis (cotrimoxazole) and antiretroviral therapy including HAART (P <0.05). Fifty-seven (11.3%) out of those 505 patients were diagnosed with AIDS-related TE. The most common clinical manifestation was headache (56%). The computed tomography scan findings showed most lesions to be multiple (96.4%), hypodense (66.7%), and in the parietal region (39.3%). Twenty-seven (47.4%) patients had chronic (latent) Toxoplasma infection as evidenced by seropositivity for anti-Toxoplasma (IgG) antibody. At the time of diagnosis, the range of CD4 cell count was from 0-239 with a median of 25 cells/cumm. We also found that a CD4 count of less than 100 cells/cumm was significantly associated with development of TE (P <0.05). Clinical outcomes showed that among those who survived, 21 (36.8%), 16 (28.1%), and 2 (3.5%) of patients had completed treatment, transferred out, and were lost to follow up, respectively. Unfortunately, 18 (31.6%) of the cases were officially pronounced dead. Overall, 7 (12.3%) patients were detected as recurrent TE in this study.

Matched MeSH terms: Toxoplasma/immunology
Fulltext A Review on the Prevalence of Toxoplasma gondii in Humans and Animals Reported in Malaysia from 2008-2018

Nasiru Wana M, Mohd Moklas MA, Watanabe M, Nordin N, Zasmy Unyah N, Alhassan Abdullahi S, et al.

Int J Environ Res Public Health, 2020 07 03;17(13).
PMID: 32635389 DOI: 10.3390/ijerph17134809

Toxoplasmosis is a disease caused by the protozoan parasite Toxoplasma gondii (T. gondii). Human toxoplasmosis seroprevalence in Malaysia has increased since it was first reported in 1973 as shown in previous reviews of 1991 and 2007. However, over a decade since the last review, comprehensive data on toxoplasmosis in Malaysia is lacking. This work aimed at reviewing articles on toxoplasmosis research in Malaysia in order to identify the research gaps, create public awareness, and efforts made so far and proffer management options on the disease. The present review examines the available published research articles from 2008 to 2018 related to toxoplasmosis research conducted in Malaysia. The articles reviewed were retrieved from nine credible databases such as Web of Science, Google Scholar, ScienceDirect, PubMed, Scopus, Springer, Wiley online library, Ovid, and Cochrane using the keywords; Malaysia, toxoplasmosis, Toxoplasma gondii, toxoplasma encephalitis, seroprevalence, human immunodeficiency virus (HIV) patients, pregnant women, genotype strain, anti-toxoplasma antibodies, felines, and vaccine. The data highlighted seropositive cases from healthy community members in Pangkor Island (59.7%) and among migrant workers (57.4%) at alarming rates, as well as 42.5% in pregnant women. Data on animal seroprevalence were limited and there was no information on cats as the definitive host. Genetic characterization of Toxoplasma gondii from HIV patients; pregnant women, and domestic cats is lacking. This present review on toxoplasmosis is beneficial to researchers, health workers, animal health professionals, and policymakers. Therefore, attention is required to educate and enlighten health workers and the general public about the risk factors associated with T. gondii infection in Malaysia.

Matched MeSH terms: Toxoplasma/immunology