Toxoplasma gondii mutants identified as defective in the establishment of chronic infection were screened to isolate those specifically impaired in their ability to replicate within activated macrophages. One of the identified mutants contains an insertion in the hypothetical gene TGME49_111670. Genetic complementation restores the ability of the mutant to replicate in immune cells and produce ...

Gametes of the unicellular green alga Chlamydomonas reinhardtii undergo sexual adhesion via enormous chimeric Hyp-rich glycoproteins (HRGPs), the plus and minus sexual agglutinins, that are displayed on their flagellar membrane surfaces. We have previously purified the agglutinins and analyzed their structural organization using electron microscopy. We report here the cloning and sequencing of ...

Toxoplasma gondii is an obligate intracellular parasite infecting 25% of the world population and enormous number of animals. It can exist in two forms in intermediate hosts: the fast replicating tachyzoites responsible for acute infection and the slowly replicating bradyzoites responsible for life-long chronic infection. The interconversion between tachyzoites and bradyzoites plays critical ro...

Protein diversification is commonly driven by single amino acid changes at random positions followed by selection, but, in some cases, the structure of the gene itself favors the occurrence of particular kinds of mutations. Genes encoding hydroxyproline-rich glycoproteins (HRGPs) in green organisms, key protein constituents of the cell wall, carry short-repeat modules that are posited to specif...

The protozoan parasite, Toxoplasma gondii, interconverts between fast-growing tachyzoites and slow-growing bradyzoites within intermediate hosts. The surface of T. gondii is covered by the SAG1-related sequence (SRS) superfamily of glycosyl phosphatidyl inositol-anchored proteins, many of which are stage-specific. Previous transient transfection of BSR4, a member of the SRS superfamily, showed ...

Cyclin-dependent kinase 7 in conjunction with CyclinH and Mat1 activates cell cycle CDKs and is a part of the general transcription factor TFIIH. Role of Cdk7 is well characterized in model eukaryotes however its relevance in protozoan parasites has not been investigated. This important regulator of key processes warrants closer examination particularly in this parasite given its unique cell cy...

Recent studies of Toxoplasma gondii isolates from animals in Brazil have revealed high genetic diversity. Many of these isolates are virulent to mice. It is speculated that these isolates may also be virulent to humans. However, there is very limited data regarding T. gondii strains from human infection. Therefore, it is not clear whether there is any association between parasite genotypes and ...

The role of rodents in the epidemiology of toxoplasmosis was investigated in Londrina, Paraná State, Brazil. One hundred and eighty-one Rattus rattus and one Mus musculus were caught in 37 places. Blood and tissues were collected and submitted to the indirect fluorescence antibody test (IFAT) and the bioassay. Serum samples from 61 contacting dogs were also collected. Sixteen rats (8.8%) were p...

We have evaluated the diagnostic utility of six antigenic regions of the Toxoplasma gondii MIC2, MIC3, M2AP, GRA3, GRA7, and SAG1 gene products, assembled in recombinant chimeric antigens by genetic engineering, in order to replace the soluble, whole-cell tachyzoite extract in serological assays. Serum samples from 100 adults with acquired T. gondii infection and from 30 infants born to mothers...