Influência da heparina na invasão de células de retina por Toxoplasma gondii

Abstract

The purpose of this work was to analyze, in an in vitro model, the influence of the heparin on the susceptibility of retinal cells to infection by Toxoplasma gondii. Primary cultures of retinas from chick embryos of 8 and 11 days-old and astrocytes from human optic nerve heads were maintained in coverslips for one week, when were infected with T. gondii tachyzoites for 24 hours. Chick embryo and human foreskin fibroblasts were used as controls for chick and human experiments, respectively. Parasites were pre-treated with heparin and anti-T. gondii surface antigen 1 (SAG-1) antibody and the astrocytes were stimulated with interferon gamma (IFN-y) before ante after infection. The number of cells infected with T. gondii and the number of parasites per cell were determined by counting at least 100 cells in each experimental condition. Monoclonal anti-heparin antibody was used to determine the distribution of heparin on the surface of cells. Pre-treatment with heparin increased the rates of replication E8 cells, while, in human astrocytes heparin pre-treatment decreased intracellular parasite replication. The labeling for heparin was more discrete in the chick embryo fibroblasts, while in the retinal cells there was strong labeling. Astrocytes stimulated with IFN-y showed a little difference in the rates of infection and there was no detectable nitric oxide (NO) production in the stimulated cells. Retinal cells of chick embryos (E8) were more susceptible to infection by T. gondii than fibroblasts possible by differential distribution of heparin on the surface of these cells, which may facilitate adhesion and invasion by T. gondii. The inhibition of the replication of T. gondii by IFN-y in human astrocytes probably is independent from mechanisms involving NO production.