Toxoplasma gondii infection in humans and animals in the United States.

Purpose.To review the changing epidemiology of herpes simplex disease and correlate it with the epidemiology of ocular herpes simplex disease.Method.A review of pertinent reports in the world literature about the epidemiology of herpes simplex and specifically about ocular herpes simplex.Results.In

Herpes simplex virus epidemiology and ocular importance.

Toxoplasma gondii, an obligate intracellular parasite of the phylum Apicomplexa, can cause severe disease in humans with an immature or suppressed immune system. The outcome of Toxoplasma infection is highly dependent on the strain type, as are many of its in vitro growth properties1. Here we use genetic crosses between type II and III lines to show that strain-specific differences in the modulation of host cell transcription are mediated by a putative protein kinase, ROP16. Upon invasion by the parasite, this polymorphic protein is released from the apical organelles known as rhoptries and injected into the host cell, where it ultimately affects the activation of signal transducer and activator of transcription (STAT) signalling pathways and consequent downstream effects on a key host cytokine, interleukin (IL)-12. Our findings provide a new mechanism for how an intracellular eukaryotic pathogen can interact with its host and reveal important differences in how different Toxoplasma lineages have evolved to exploit this interaction.

/pdf/toxoplasma-co-opts-host-gene-expression-by-injection-of-a-3be4qu0hjp.pdf

Toxoplasma co-opts host gene expression by injection of a polymorphic kinase homologue

Purpose:To evaluate the prevalence of the most common serious adverse events associated with intravitreous (IVT) injection.Methods:A systematic search of the literature via PubMed from 1966 to March 1, 2004, was conducted to identify studies evaluating the safety of IVT injection. Data submitted in

Risks of intravitreous injection: a comprehensive review.

Toxoplasma gondii strains differ dramatically in virulence despite being genetically very similar. Genetic mapping revealed two closely adjacent quantitative trait loci on parasite chromosome VIIa that control the extreme virulence of the type I lineage. Positional cloning identified the candidate virulence gene ROP18, a highly polymorphic serine-threonine kinase that was secreted into the host cell during parasite invasion. Transfection of the virulent ROP18 allele into a nonpathogenic type III strain increased growth and enhanced mortality by 4 to 5 logs. These attributes of ROP18 required kinase activity, which revealed that secretion of effectors is a major component of parasite virulence.

https://science.sciencemag.org/content/sci/314/5806/1776.full.pdf

A secreted serine-threonine kinase determines virulence in the eukaryotic pathogen Toxoplasma gondii.

To facilitate genotyping of Toxoplasma gondii in vitreous fluid of patients with severe or atypical ocular toxoplasmosis, polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP) assays were developed for SAG3 (p43) and SAG4 (p18), 2 single-copy surface antigen genes. Together with strategies for SAG1, SAG2, and B1, multilocus RFLP analyses were performed on PCR-amplified parasite DNA present in 12 clinical specimens. Most samples (8/12) were not infected by type II or type III mouse-avirulent strains. Only 1 type III and 3 type II strains were identified, all from immunosuppressed patients. In 6 otherwise healthy adults and in 1 immunosuppressed patient, the SAG1 allele associated with mouse virulence was amplified. Of 12 samples, 3 possessed true type I strains; 5 of 12 had new recombinant genotypes with alleles typical of type I or III strains at all loci examined. The unusual bias toward type I and/or recombinant genotypes bearing the SAG1 type I allele associated with mouse virulence in immunocompetent adults has important implications for the epidemiology and efficacious treatment of ocular toxoplasmosis.

Jyotsom B Ganatra

Papers

Unusual abundance of atypical strains associated with human ocular toxoplasmosis.

Viral causes of the acute retinal necrosis syndrome