Toxoplasmic encephalitis: role of Human Leucocyte Antigens/alleles associated with rapid progression to Acquired Immunodeficiency Syndrome

Abstract Background/aims The frequency of Human Leucocyte Antigens/alleles associated with rapid progression from Human Immunodeficiency Virus infection to Acquired Immunodeficiency Syndrome was evaluated in Brazilian patients with Acquired Immunodeficiency Syndrome with and without Toxoplasmic Encephalitis. Methods 114 patients with Acquired Immunodeficiency Syndrome (41 with Toxoplasmic Encephalitis, 43 with anti-Toxoplasma gondii antibodies, without Toxoplasmic Eencephalitis, and 30 without anti-Toxoplasma gondii antibodies circulating and without Toxoplasmic Encephalitis) were studied. Results Human Leucocyte Antigens/alleles associated with rapid progression to Acquired Immunodeficiency Syndrome, particularly HLA-B35, -DR3, and -DR1 allele group, were significantly less represented in patients with Toxoplasmic Encephalitis and Acquired Immunodeficiency Syndrome. Conclusion The presence of these Human Leucocyte Antigens/Alleles that predispose to Acquired Immunodeficiency Syndrome progression was associated with resistance to Toxoplasmic Encephalitis among Human Immunodeficiency Virus-1 carriers.

Host genetic and epigenetic factors in toxoplasmosis

Analysing human genetic variation provides a powerful tool in understanding risk factors for disease. Toxoplasma gondii acquired by the mother can be transmitted to the fetus. Infants with the most severe clinical signs in brain and eye are those infected early in pregnancy when fetal immunity is least well developed. Genetic analysis could provide unique insight into events in utero that are otherwise difficult to determine. We tested the hypothesis that propensity for T. gondii to cause eye disease is associated with genes previously implicated in congenital or juvenile onset ocular disease. Using mother-child pairs from Europe (EMSCOT) and child/parent trios from North America (NCCCTS), we demonstrated that ocular and brain disease in congenital toxoplasmosis associate with polymorphisms in ABCA4 encoding ATP-binding cassette transporter, subfamily A, member 4 previously associated with juvenile onset retinal dystrophies including Stargardt's disease. Polymorphisms at COL2A1 encoding type II collagen, previously associated with Stickler syndrome, associated only with ocular disease in congenital toxoplasmosis. Experimental studies showed that both ABCA4 and COL2A1 show isoform-specific epigenetic modifications consistent with imprinting, which provided an explanation for the patterns of inheritance observed. These genetic and epigenetic risk factors provide unique insight into molecular pathways in the pathogenesis of disease.