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Background: Toxoplasma gondii (T. gondii) has been associated with acute food-borne illness, chronic low-grade inflammation, neuropsychiatric conditions and reactivation of chronic latent infection in immunocompetent hosts. Primary infection with T. gondii in pregnant women can lead to congenital toxoplasmosis. In addition to well-known oral tissue-cyst or oocyst ingestion, we hypothesized that the very high prevalence of T. gondii in certain populations exposed to agricultural dust could be, in part, a consequence of airborne infection with oocysts. Methods: We collected environmental dust samples from an area with a reportedly high T. gondii seroprevalence in the Old Order Amish population, in Lancaster, Pennsylvania. Samples included: a) air filters from air-conditioning units; b) swabs of settled dust; and c) vacuum filters containing airborne field dust. Pools of the swabs and shredded sub-samples of the air filters were fed to pigs, with inoculation into mice of heart tissue from seroconverted pigs. We also investigated the presence of T. gondii DNA using PCR amplification. Results: Only one pig seroconverted. However, bioassay of pig heart tissue further inoculated into mice showed no evidence of T. gondii infection. Consistently, no evidence of T. gondii DNA was revealed in any sample. Conclusions: No evidence of airborne transmission was found in the environmental samples that were examined.

JRA is a complex of disease subtypes which are normally identified by clinical features such as age of onset and extent of joint involvement both at onset and during the course of the disease. We previously identified an association between TCR BV6S1 null allele and one subgroup of early-onset pauciarticular patients positive for HLA-DQA1*0101, an HLA haplotype predisposing to a polyarticular course of the disease. In this report we extend this observation by identifying an increased prevalence of this nonfunctional or null allele in the patients with a polyarticular disease course regardless of the mode of onset. This increase was most prominent in clinical subsets that have early onset of the disease and a polyarticular outcome. In one clinical group, stratification of patients by the HLA allele DQA1*0101 strengthened the association considerably. This implies that there is an increased genetic load defined by specific alleles of both MHC and TCR genes.

We and others have shown an association between autoimmune disorders and the major histocompatibility complex extended haplotype HLA-A1,-B8,-SCO1,-DR3. The primary gene or genes within this haplotype conferring such susceptibility, however, have not been defined. In this study, we tested the hypothesis that linkage disequilibrium in this haplotype extends through the DP locus, and that DP type may be linked to membranoproliferative glomerulonephritis (MPGN) and systemic lupus erythematosus (SLE). DP and DQ typing was performed by restriction fragment length polymorphism analysis for 43 chromosomes (19 healthy controls, 9 SLE, 15 MPGN) bearing the -A1,-B8,-SCO1,-DR3 extended haplotype. Although all were DQw2, a variety of DP types were identified (DPw1, 0.26; DPw2, 0.09; DPw3, 0.14; DPw4, 0.44). Although DPw1 was represented on extended haplotypes with greater frequency than on 113 non-A1,-B8,-SCO1,-DR3 haplotypes (0.26 vs. 0.03; P < 0.001), there were no significant differences between healthy individuals with this haplotype and those with autoimmune disease. We conclude that the strong linkage disequilibrium of this haplotype breaks down between the DQ and DP loci. Loci important to disease susceptibility, therefore, are more likely to occur telomeric to DP.