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Exp Parasitol ; 208: 107791, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31704144


Toxoplasma gondii is an obligate intracellular protozoan parasite that infects almost all warm-blooded animals, including humans, causing serious public health problems. In this study, the seroprevalence of T. gondii in captive jaguars in 10 Mexican zoos was determined using single and mixtures of recombinant surface antigens (SAG1) and dense granular antigens (GRA1 and GRA7) in immunoglobulin G (IgG) enzyme-linked immunosorbent assays (ELISAs). Their efficacy was compared with the tachyzoite lysate antigen. All recombinant antigens were characterised by high sensitivity (92.5-97.5%); the specificity of the IgG ELISAs was variable (83.3-91.6%). Mixtures of the two recombinant proteins were generally more reactive than single antigens. GRA7 + SAG1 showed the highest sensitivity (97.5%) and specificity (91.6%), almost perfect agreement (96.2%), and a kappa value of 0.89. An area under the curve value of 0.998 represented a highly accurate test with a cutoff value of 0.8. The seroprevalence of anti-T. gondii IgG antibodies in the single and mixed recombinant antigen ELISAs was 75.0-76.9%. This study shows that GRA7 + SAG1 can be successfully used to diagnose T. gondii infection in jaguars for effective monitoring of prevalence and for devising control methods and prevention strategies against toxoplasmosis.

Antígenos de Protozoários/imunologia , Panthera/parasitologia , Proteínas de Protozoários/imunologia , Toxoplasmose Animal/epidemiologia , Animais , Animais de Zoológico , Área Sob a Curva , Ensaio de Imunoadsorção Enzimática/veterinária , Feminino , Imunoglobulina G/sangue , Imunoglobulina G/imunologia , Masculino , México/epidemiologia , Prevalência , Proteínas de Protozoários/normas , Curva ROC , Proteínas Recombinantes/imunologia , Proteínas Recombinantes/normas , Sensibilidade e Especificidade , Estudos Soroepidemiológicos , Toxoplasmose Animal/diagnóstico , Toxoplasmose Animal/imunologia , Toxoplasmose Animal/prevenção & controle
PLoS One ; 13(12): e0208583, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30589853


INTRODUCTION: Internal and external quality control (QC) of rapid diagnostic tests (RDTs) is important to increase reliability of RDTs currently used to diagnose malaria. However, cross-checking of used RDTs as part of quality assurance can rarely be done by off-site personnel because there is no guarantee of retaining visible test lines after manufacturers' recommended reading time. Therefore, this study examined the potential of using Fionet™ technology for remote RDT quality monitoring at seven clinics, identifying reasons for making RDT processing and interpretation errors, and taking corrective actions for improvement of diagnosis and consequently improved management of febrile patients. METHODS: The study was conducted at seven military health facilities in Mainland Tanzania and utilized RDTs capable of detecting Plasmodium falciparum specific Histidine-rich protein 2 (Pf-HRP2) and the genus specific Plasmodium lactate dehydrogenase (pLDH) for other species of plasmodium (P. vivax, P. malariae or P. ovale; pan-pLDH). Patients' data and images of processed RDTs from seven clinics were uploaded on a Fionet web portal and reviewed regularly to monitor preparation procedures and visual interpretation of test results compared to automated analysis using the Deki reader of RDT. Problems detected were rapidly communicated to remote laboratory personnel at the clinic for corrective action and follow-up of patients who were falsely diagnosed as negative and missed treatment. Factors contributing to making errors in visual interpretation of RDT results were analyzed during visits to the health facilities. RESULTS: A total of 1,367 (1.6%) out of 83,294 RDT test images uploaded to the Fionet portal had discordant test results of which 822 (60.1%) and 545 (39.9%) were falsely reported as negative and positive, respectively. False negative and false positive test results were common for a single test line in 515 (62.7%) and 741 (54.2%) tests, respectively. Out of 1,367 RDT images assessed, 98 (7.2%) had quality problems related to preparation procedures of which 95(96.9%) errors were due to putting too much blood on the sample well or insufficient buffer in the respective wells. The reasons for discrepant results included, false reporting of none existent lines in 526 (38.5%) tests, missing a faint positive line in 493 (36.1%), missing a strong positive line in 248(18.1%) and errors caused by poorly processed RDTs in 96 (7.2%) tests. Among the false negative tests (n = 822), 669 (48.9%) patients were eligible for follow-up and only 339 (48.5%) were reached and 291 (85.8%) received appropriate anti-malaria therapy. CONCLUSION: Fionet technology enabled remote monitoring of RDT quality issues, identifying reasons contributing to laboratory personnel making errors and provided a rapid method to implement corrective actions at remote sites to improve malaria diagnosis and consequently improved health care management of febrile patients infected with malaria.

Testes Diagnósticos de Rotina , Pessoal de Saúde , Malária/diagnóstico , Análise e Desempenho de Tarefas , Adolescente , Adulto , Antígenos de Protozoários/análise , Criança , Pré-Escolar , Erros de Diagnóstico , Testes Diagnósticos de Rotina/normas , Feminino , Instalações de Saúde , Humanos , Lactente , Recém-Nascido , L-Lactato Desidrogenase/análise , L-Lactato Desidrogenase/normas , Masculino , Plasmodium falciparum/metabolismo , Proteínas de Protozoários/análise , Proteínas de Protozoários/normas , Controle de Qualidade , Tanzânia , Adulto Jovem
Malar J ; 16(1): 314, 2017 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-28779755


BACKGROUND: At a World Health Organization (WHO) sponsored meeting it was concluded that there is an urgent need for a reference preparation that contains antibodies against malaria antigens in order to support serology studies and vaccine development. It was proposed that this reference would take the form of a lyophilized serum or plasma pool from a malaria-endemic area. In response, an immunoassay standard, comprising defibrinated human plasma has been prepared and evaluated in a collaborative study. RESULTS: A pool of human plasma from a malaria endemic region was collected from 140 single plasma donations selected for reactivity to Plasmodium falciparum apical membrane antigen-1 (AMA-1) and merozoite surface proteins (MSP-119, MSP-142, MSP-2 and MSP-3). This pool was defibrinated, filled and freeze dried into a single batch of ampoules to yield a stable source of naturally occurring antibodies to P. falciparum. The preparation was evaluated by an enzyme-linked immunosorbent assay (ELISA) in a collaborative study with sixteen participants from twelve different countries. This anti-malaria human serum preparation (NIBSC Code: 10/198) was adopted by the WHO Expert Committee on Biological Standardization (ECBS) in October 2014, as the first WHO reference reagent for anti-malaria (Plasmodium falciparum) human serum with an assigned arbitrary unitage of 100 units (U) per ampoule. CONCLUSION: Analysis of the reference reagent in a collaborative study has demonstrated the benefit of this preparation for the reduction in inter- and intra-laboratory variability in ELISA. Whilst locally sourced pools are regularly use for harmonization both within and between a few laboratories, the presence of a WHO-endorsed reference reagent should enable optimal harmonization of malaria serological assays either by direct use of the reference reagent or calibration of local standards against this WHO reference. The intended uses of this reference reagent, a multivalent preparation, are (1) to allow cross-comparisons of results of vaccine trials performed in different centres/with different products; (2) to facilitate standardization and harmonization of immunological assays used in epidemiology research; and (3) to allow optimization and validation of immunological assays used in malaria vaccine development.

Antígenos de Protozoários , Imunoensaio/normas , Malária Falciparum/sangue , Plasmodium falciparum/imunologia , Testes Sorológicos/normas , Anticorpos Antiprotozoários/sangue , Liofilização , Humanos , Proteínas de Membrana/normas , Proteínas de Protozoários/normas , Padrões de Referência , Organização Mundial da Saúde
Vaccine ; 26(48): 6143-50, 2008 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-18804135


Plasmodium falciparum apical membrane antigen 1 (PfAMA1) is a leading asexual blood stage vaccine candidate for malaria. In preparation for clinical trials, PfAMA1 ectodomain (amino acid 25-545, FVO strain) was produced in Pichia pastoris by 35L scale fed batch fermentation under current Good Manufacturing Practice (cGMP). Fermentation was followed by a three-step chromatographic purification procedure resulting in a yield of 5.8g of purified protein. As judged by size exclusion chromatography, the cGMP-product comprised >95% PfAMA1 monomer, the remainder being predominantly PfAMA1 dimer. In SDS-PAGE two main bands of 68 and 70kDa and some minor bands were evident. Under reducing conditions a site of limited proteolytic cleavage within a disulphide bonded region became evident; less than 15% of the protein had this internal cleavage. By mass-spectrometric analysis, all bands analyzed in overloaded SDS-PAGE gels comprised PfAMA1 derived products. The protein was quantitatively bound by immobilized 4G2, a monoclonal antibody reactive with a reduction sensitive conformational determinant. The lyophilized product was stable for over 1 year. Immunopotency did not diminish, and storage did not lead to alterations in the behaviour of the protein upon formulation with adjuvants selected for Phase I clinical evaluation. These formulations also showed no pharmacotoxicity in rabbits. The final product conformed to preset criteria and was judged suitable for use in human clinical trials.

Antígenos de Protozoários/biossíntese , Indústria Farmacêutica/normas , Vacinas Antimaláricas/biossíntese , Vacinas Antimaláricas/normas , Proteínas de Membrana/biossíntese , Proteínas de Membrana/normas , Pichia/genética , Plasmodium falciparum/genética , Proteínas de Protozoários/biossíntese , Proteínas de Protozoários/normas , Adjuvantes Imunológicos , Sequência de Aminoácidos , Animais , Antígenos de Protozoários/toxicidade , Western Blotting , Clonagem Molecular , Estabilidade de Medicamentos , Eletroforese em Gel de Poliacrilamida , Ensaio de Imunoadsorção Enzimática , Feminino , Fermentação , Liofilização , Cobaias , Vacinas Antimaláricas/toxicidade , Masculino , Espectrometria de Massas , Proteínas de Membrana/toxicidade , Camundongos , Dados de Sequência Molecular , Pichia/metabolismo , Plasmodium falciparum/imunologia , Plasmodium falciparum/metabolismo , Proteínas de Protozoários/toxicidade , Controle de Qualidade , Coelhos , Vacinas Sintéticas/biossíntese , Vacinas Sintéticas/normas , Vacinas Sintéticas/toxicidade
Vaccine ; 24(31-32): 5839-51, 2006 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-16735084


Region II of the erythrocyte-binding antigen (EBA-175 RII) has been identified as a promising target for a malaria vaccine. A systematic approach to identify optimal preformulation conditions of a non-glycosylated (NG) antigen, EBA-175 RII-NG, has been developed. This approach consists of development of an empirical temperature/pH phase diagram, high throughput stabilizer screening and aluminum salt adjuvant adsorption studies. Using these physical methods, we developed a stable formulation for EBA-175 RII-NG at pH 6.0 with sucrose and Brij 35 as stabilizers and Adju-Phos as an adjuvant. This approach should be generally applicable to guiding the development of stable vaccine formulations.

Vacinas Antimaláricas/síntese química , Plasmodium falciparum , Proteínas de Protozoários/síntese química , Animais , Antígenos de Protozoários , Química Farmacêutica , Estabilidade de Medicamentos , Vacinas Antimaláricas/normas , Proteínas de Protozoários/normas