Assessing sources of inconsistencies in genotypes and their effects on genome-wide association studies with HapMap samples

The discordance in results of independent genome-wide association studies (GWAS) indicates the potential for Type I and Type II errors. We assessed the repeatibility of current Affymetrix technologies that support GWAS. Reasonable reproducibility was observed for both raw intensity and the genotypes/copy number variants. We also assessed consistencies between different SNP arrays and between genotype calling algorithms. We observed that the inconsistency in genotypes was generally small at the specimen level. To further examine whether the differences from genotyping and genotype calling are possible sources of variation in GWAS results, an association analysis was applied to compare the associated SNPs. We observed that the inconsistency in genotypes not only propagated to the association analysis, but was amplified in the associated SNPs. Our studies show that inconsistencies between SNP arrays and between genotype calling algorithms are potential sources for the lack of reproducibility in GWAS results.

Multimodality treatment with intensity modulated radiation therapy for esophageal cancer

The objective of this study is to determine the feasibility and report the outcome of patients with locally advanced esophageal cancer treated with preoperative or definitive chemoradiotherapy (CRT) using intensity-modulated radiation therapy (IMRT). Between 2003 and 2007, 30 patients with non-cervical esophageal cancer received concurrent chemotherapy and IMRT at Stanford University. Eighteen patients were planned for definitive CRT and 12 were planned for preoperative CRT. All patients had computed tomography-based treatment planning and received IMRT. The median dose delivered was 50.4 Gy. Patients planned for preoperative CRT underwent surgery 4-13 weeks (median 8.3 weeks) following completion of CRT. Median follow-up of surviving patients from start of RT was 24.2 months (range 8.2-38.3 months). The majority of tumors were adenocarcinomas (67%) and poorly differentiated (57%). Tumor location was 7% upper, 20% mid, 47% lower, and 27% gastroesophageal junction. Actuarial 2-year local-regional control (LRC) was 64%. High tumor grade was an adverse prognostic factor for LRC and overall survival (OS) (P= 0.015 and 0.012, respectively). The 2-year LRC was 83% vs. 51% for patients treated preoperatively vs. definitively (P= 0.32). The 2-year disease-free and OS were 38% and 56%, respectively. Twelve patients (40%) required feeding tube placement, and the average weight loss from baseline was 4.8%. Twelve (40%) patients experienced grade 3+ acute complications and one patient died of complications following feeding tube placement. Three patients (10%) required a treatment break. Eight patients (27%) experienced grade 3 late complications. No grade 4 complications were seen. IMRT was effective and well tolerated. Disease recurrence remains a challenge and further investigation with dose escalation to improve LRC and OS is warranted.

Neurocognitive effects of treatment interruption in stable HIV-positive patients in an observational cohort

OBJECTIVE

Prior studies have shown improved neurocognition with initiation of antiretroviral treatment (ART) in HIV. We hypothesized that stopping ART would be associated with poorer neurocognitive function.

METHODS

Neurocognitive function was assessed as part of ACTG 5170, a multicenter, prospective observational study of HIV-infected subjects who elected to discontinue ART. Eligible subjects had CD4 count >350 cells/mm(3), had HIV RNA viral load <55,000 cp/mL, and were on ART (>or=2 drugs) for >or=6 months. Subjects stopped ART at study entry and were followed for 96 weeks with a neurocognitive examination.

RESULTS

A total of 167 subjects enrolled with a median nadir CD4 of 436 cells/mm(3) and 4.5 median years on ART. Significant improvements in mean neuropsychological scores of 0.22, 0.39, 0.53, and 0.74 were found at weeks 24, 48, 72, and 96 (all p < 0.001). In the 46 subjects who restarted ART prior to week 96, no significant changes in neurocognitive function were observed.

CONCLUSION

Subjects with preserved immune function found that neurocognition improved significantly following antiretroviral treatment (ART) discontinuation. The balance between the neurocognitive cost of untreated HIV viremia and the possible toxicities of ART require consideration.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that discontinuing ART is associated with an improvement in 2 neuropsychological tests (Trail-Making Test A & B and the Wechsler Adult Intelligence Scale-Revised Digit Symbol subtest) for up to 96 weeks. Resuming ART was not associated with a decline in these scores for up to 45 weeks.

The rag locus of Porphyromonas gingivalis might arise from Bacteroides via horizontal gene transfer

Porphyromonas gingivalis is regarded as one of the risk factors of periodontitis. P. gingivalis exhibits a wide variety of genotypes. Many insertion sequences (ISs), located in their chromosomes, made P. gingivalis differentiate into virulent and avirulent strains. In this research, we investigated the prevalence of P. gingivalis in the gingival crevicular fluid (GCF) among periodontitis patients from Zhenjiang, China, detected the P. gingivalis rag locus distributions by multiplex polymerase chain reaction (PCR), and analyzed the origin of the P. gingivalis rag locus based on evolution. There were three rag locus variants co-existing in Zhenjiang. The results showed that the rag locus may be associated with severe periodontitis. This work also firstly ascertained that the rag locus might arise, in theory, from Bacteroides sp. via horizontal gene transfer.

Intraspecific functional diversity in hosts and its effect on disease risk across a climatic gradient

The effects of host biodiversity on disease risk may vary greatly depending on host population structure and climatic conditions. Agricultural diseases such as potato late blight, caused by Phytophthora infestans, provide the opportunity to study the effects of intraspecific host diversity that is relatively well-defined in terms of disease resistance phenotypes and may have functional impacts on disease levels. When these systems are present across a climatic gradient, it is also possible to study how season length and conduciveness of the environment to disease may influence the effects of host diversity on disease risk. We developed a simple model of epidemic progress to evaluate the effects on disease risk of season length, environmental disease conduciveness, and host functional divergence for mixtures of a susceptible host and a host with some resistance. Differences in disease levels for the susceptible vs. resistant genotypes shifted over time, with the divergence in disease levels first increasing and then decreasing. Disease reductions from host diversity were greatest for high host divergence and combinations of environmental disease conduciveness and season length that led to moderate disease severity. We also compared the effects of host functional divergence on potato late-blight risk in Ecuador (long seasons), two sites in Peru (intermediate seasons) in El Niño and La Niña years, and the United States (short seasons). There was some evidence for greater disease risk reduction from host diversity where seasons were shorter, probably because of lower regional inoculum loads. There was strong evidence for greater disease reduction when host functional divergence was greater. These results indicate that consideration of season length, environmental conduciveness to disease, and host functional divergence can help to explain the variability in disease response to host diversity.

Modulation of malaria-induced immunopathology by concurrent gastrointestinal nematode infection in mice

We investigated malaria-associated pathology in mice co-infected with Heligmosomoides polygyrus (Hp) and Plasmodium chabaudi AS (Pc). Despite higher peak parasitemia, co-infected wild-type (WT) C57BL/6 mice displayed similar body weight losses, malarial anaemia, and tissue damage but less severe hypothermia and hypoglycaemia, and earlier reticulocytosis than Pc-infected WT mice. Co-infected STAT6(-/-) mice, deficient in nematode-induced Th2 responses, experienced similar peak parasitemias and generally suffered malaria-associated pathology to a similar degree as co-infected WT mice. These data indicate a complex relationship amongst helminths, malaria and host immune responses resulting in modulation of some but not all aspects of malaria-associated pathology.

Tat-modified leptin is more accessible to hypothalamus through brain-blood barrier with a significant inhibition of body-weight gain in high-fat-diet fed mice

Obesity in human was found mainly due to the poor transportation of leptin through brain-blood barrier (BBB), called as leptin resistance. To produce a leptin capable of penetrating BBB, we have added Tat-PTD(9) to the C terminal of leptin to construct a fusion protein. The fusion Tat-leptin and native leptin genes were synthesized by single-step insertion of a polymerase chain reaction and expressed in Escherichia coli BL21 (Rosseta). The expressing products were purified and renatured by Ni-NTA affinity chromatography, and identified by the molecular size in SDS-PAGE gel and by its immunoreactivity to specific antibody with Western-blotting assay. To bio-functionally evaluate the fusion protein, Balb/c mice fed with high-fat diet (HFD) were given Tat-leptin, leptin or saline for 19 days. The immunohistochemical staining showed the increases in positive stains for the leptin in the region of hypothalamus of the HFD mice with either Tat-leptin or leptin as compared to saline group, but the staining intensity and frequency in the group with Tat-leptin were stronger and higher than those in the group with leptin. Furthermore, the most efficiency in preventing the body-weight gain caused by HFD was found in Tat-leptin group among these three groups. These results suggest that Tat-modified leptin may become a great potential candidate for the prevention or therapy of obese patients.

Healthy but not RSV-infected lung epithelial cells profoundly inhibit T cell activation

BACKGROUND

Respiratory viruses, including respiratory syncytial virus (RSV), can cause asthma exacerbations and bronchiolitis. Both conditions are associated with enhanced cognate immune responses and inflammation and reduced immune regulation. Lung epithelial cells (LECs) can contribute to antiviral and allergic immune responses while gut epithelial cells can inhibit effector T cell responses. A study was performed to determine whether healthy LECs regulate antigen-specific T cell responses and if this regulation is lost during RSV infection.

METHODS

LA4 cells, a murine LEC line, infected with RSV or primary murine LECs were co-cultured with ovalbumin-specific T cell receptor transgenic CD4+ T cells from DO11.10 mice and ovalbumin-pulsed bone marrow-derived dendritic cells (DC) to assess T cell proliferation by flow cytometry and cytokine production.

RESULTS

The presence of LECs abrogated DC-induced T cell proliferation and significantly reduced T cell cytokine release. These effects of LECs were predominantly contact-dependent, primarily affected T cells directly and were partly mediated by transforming growth factor beta. Soluble factors and DC-mediated effects also contributed to T cell inhibition. RSV infection of LECs reduced their inhibitory capacity in an infection dose-dependent manner. This was independent of proinflammatory cytokines released by infected LECs, but in part due to Toll-like receptor activation and to infection-induced cell death.

CONCLUSION

Healthy LECs are potent inhibitors of T cell activation, but this regulatory function is lost after RSV infection. These findings suggest a central role for LECs in maintaining the tolerogenic environment of healthy lungs. Loss of this regulatory capacity after viral infection may allow development of excessive cognate immune responses and pulmonary inflammation.