Identification of potential dual -targets anti- toxoplasma gondii compounds through structure-based virtual screening and in-vitro studies.

Toxoplasma gondii is the etiologic agent of toxoplasmosis, a disease which can lead to morbidity and mortality of the fetus and immunocompromised individuals. Due to the limited effectiveness or side effects of existing drugs, the search for better drug candidates is still ongoing. In this study, we performed structure-based screening of potential dual-targets inhibitors of active sites of T. gondii drug targets such as uracil phosphoribosyltransferase (UPRTase) and adenosine kinase (AK). First screening of virtual compounds from the National Cancer Institute (NCI) was performed via molecular docking. Subsequently, the hit compounds were tested in-vitro for anti- T. gondii effect using cell viability assay with Vero cells as host to determine cytotoxicity effects and drug selectivities. Clindamycin, as positive control, showed a selectivity index (SI) of 10.9, thus compounds with SI > 10.9 specifically target T. gondii proliferation with no significant effect on the host cells. Good anti- T. gondii effects were observed with NSC77468 (7-ethoxy-4-methyl-6,7-dihydro-5H-thiopyrano[2,3-d]pyrimidin-2-amine) which showed SI values of 25. This study showed that in-silico selection can serve as an effective way to discover potentially potent and selective compounds against T. gondii.

IgG avidity Western blot using Toxoplasma gondii rGRA-7 cloned from nucleotides 39-711 for serodiagnosis of acute toxoplasmosis.

Toxoplasmosis is an important cause of congenital infection. The present study was performed to evaluate the usefulness of recombinant (r) GRA-7 cloned from nucleotides (n) 39-711 in discriminating between acute and chronic toxoplasmosis. First, commercial IgM, IgG and IgG avidity ELISAs were used to determine the serological profile of the sera. Serum samples were from 20 symptomatic patients with acute infection (low IgG avidity, IgM positive), 10 with chronic infection (high IgG avidity, IgM negative) and 10 with indeterminate IgG avidity (IgM positive) which were tested for IgG avidity status with an in-house developed IgG avidity Western blot using the rGRA-7 recombinant antigen. All 20 sera from cases of probable acute infection showed bands which either faded out completely or reduced significantly in intensity after treatment with 8 M urea, whereas the band intensities of the 10 serum samples from chronic cases remained the same. Of the 10 sera with indeterminate IgG avidity status, after treatment with 8 M urea the band intensities with six sera remained the same, two sera had completely faded bands and another two sera had significantly reduced band intensities. Discrimination between acute and chronic toxoplasmosis was successfully performed by the in-house IgG avidity Western blot.

IgG AVIDITY WESTERN BLOT USING Toxoplasma gondii rGRA-7 CLONED FROM NUCLEOTIDES 39-711 FOR SERODIAGNOSIS OF ACUTE TOXOPLASMOSIS / Avidez do IgG pelo Western Blot usando o r GRA-7 do Toxoplasma gondii clonado de nucleotídeos 39-711 para sorodiagnóstico de toxoplasmose aguda

Toxoplasmosis is an important cause of congenital infection. The present study was performed to evaluate the usefulness of recombinant (r) GRA-7 cloned from nucleotides (n) 39-711 in discriminating between acute and chronic toxoplasmosis. First, commercial IgM, IgG and IgG avidity ELISAs were used to determine the serological profile of the sera. Serum samples were from 20 symptomatic patients with acute infection (low IgG avidity, IgM positive), 10 with chronic infection (high IgG avidity, IgM negative) and 10 with indeterminate IgG avidity (IgM positive) which were tested for IgG avidity status with an in-house developed IgG avidity Western blot using the rGRA-7 recombinant antigen. All 20 sera from cases of probable acute infection showed bands which either faded out completely or reduced significantly in intensity after treatment with 8 M urea, whereas the band intensities of the 10 serum samples from chronic cases remained the same. Of the 10 sera with indeterminate IgG avidity status, after treatment with 8 M urea the band intensities with six sera remained the same, two sera had completely faded bands and another two sera had significantly reduced band intensities. Discrimination between acute and chronic toxoplasmosis was successfully performed by the in-house IgG avidity Western blot.

Toxoplasmose é uma causa importante de infecção congênita. O presente estudo foi feito para avaliar o uso do recombinante (r) GRA-7 clonado de nucleotídeos (n) 30-711 para discriminar entre toxoplasmose aguda e crônica. Inicialmente IgM, IgG e ELISA avidez IgG comerciais foram usados para determinar o perfil sorológico do soro. Amostras de soro de 20 pacientes sintomáticos com infecção aguda (IgG avidez baixa, IgM positivo), 10 com infecção crônica (alta avidez IgG, IgM negativo) e 10 com avidez IgG indeterminada (IgM positivo) que foram testados para o status de avidez IgG com um doméstico Western Blot desenvolvendo avidez IgG usando o rGRA-7 antígeno recombinante. Todos os 20 soros de provável infecção aguda mostraram bandas que ou se apagaram completamente ou tiveram a sua intensidade significantemente reduzida após tratamento com uréia 8 M, enquanto as intensidades das bandas das 10 amostras de soros de casos crônicos permaneceram iguais. Dos 10 soros com status indeterminado de avidez de IgG, após tratamento com uréia 8 M a intensidade das bandas em seis soros permaneceram iguais, dois soros tiveram bandas apagadas completamente e dois outros tiveram significante redução da intensidade das bandas. Discriminação entre toxoplasmose aguda e crônica foi feita com sucesso através do IgG avidez Western blot doméstico.

Identification of Toxoplasma gondii in-vivo induced antigens by cDNA library immunoscreening with chronic toxoplasmosis sera.

Toxoplasmosis is an infection caused by the parasite Toxoplasma gondii. Chronically-infected individuals with a compromised immune system are at risk for reactivation of the disease. In-vivo induced antigen technology (IVIAT) is a promising method for the identification of antigens expressed in-vivo. The aim of the present study was to apply IVIAT to identify antigens which are expressed in-vivo during T. gondii infection using sera from individuals with chronic toxoplasmosis. Forty serum samples were pooled, pre-adsorped against three different preparations of antigens, from each in-vitro grown T. gondii and Escherichia coli XLBlue MRF', and then used to screen a T. gondii cDNA expression library. Sequencing of DNA inserts from positive clones showed eight open reading frames with high homology to T. gondii genes. Expression analysis using quantitative real-time PCR showed that SAG1-related sequence 3 (SRS3) and two hypothetical genes were up-regulated in-vivo relative to their expression levels in-vitro. These three proteins also showed high sensitivity and specificity when tested with individual serum samples. Five other proteins namely M16 domain peptidase, microneme protein, elongation factor 1-alpha, pre-mRNA-splicing factor and small nuclear ribonucleoprotein F had lower RNA expression in-vivo as compared to in-vitro. SRS3 and the two hypothetical proteins warrant further investigation into their roles in the pathogenesis of toxoplasmosis.