MAIT cells (CD8+CD161++TCR7.2++) are functionally impaired during chronic SHIV infection

Mucosa-associated invariant T-cells (MAIT) are abundant in humans and recognize bacterial ligands. Here, we have studied the distribution and function of MAIT cells during chronic SHIV infection using rhesus macaques (RM). Two groups of RM, healthy and SHIV infected were studied. lymphocytes from various tissues were analysed for MAIT (TCR7.2++ CD161++) cells using multicolor flow cytometry and characterized for their distribution, phenotype and function during chronic SHIV infection. Similar to human, we found significant fraction of (~2%) RM CD8 T cells co-express MAIT cell markers TCR7.2, CD161, IL-18R, CCR6 and display central memory (CCR7+CD45RA−) phenotype. The frequency of MAIT cells were decreased during chronic SHIV infection and tissue analysis showed a significant enrichment of MAIT cells in liver (~8%) and BAL (3%) than in blood (1%), spleen(0.5%), lymph node(0.13%) and gut (0.2%). Importantly, during chronic SHIV infection more than 80% of MAIT cells expressed T cell exhaustion marker PD-1 in blood and the level of expression was higher (>95%) in tissue resident CD69+MAIT cells. These cells lack proliferating capacity (Ki-67) and cytokine production (IFN- g and IL-17) in the blood, suggesting their functional impairment. The preserved blood and gut MAIT cells correlate inversely with plasma viral RNA levels and associate directly with gut CD4 T cell levels, suggesting that CD4 help maintains MAIT cell frequencies in the gut. These data demonstrate that MAIT cells are decreased in blood and are functionally exhausted during chronic SHIV infection. Future studies focused on blocking the PD-1 pathway to retrive MAIT cell exhaustion during chronic SHIV/HIV infection may yield therapeutic benefit to HIV/SHIV infection.

Fibrocellular tissue responses to endovascular and external beam irradiation in the porcine model of restenosis

PURPOSE

Endovascular radiation has reduced postangioplasty restenosis in preclinical and early clinical studies. External radiation treatment may have advantages over endovascular therapy. We examined vascular and perivascular tissue responses to endovascular and external irradiation in pig coronary arteries.

METHODS AND MATERIALS

Ninety-one animals received endovascular or external radiation following balloon injury and were sacrificed at 14, 30, or 180 days. Injured segments of coronary vessels including perivascular and myocardial tissues were evaluated with histochemistry.

RESULTS

Endovascular radiation was associated with delayed arterial wound healing as late as 6 months, evidenced by paucity of smooth muscle alpha-actin in neointimal cells compared to control. External treatment was associated with increased collagen in neointima and adventitia, and focal interstitial necrosis in adjacent myocardium.

CONCLUSIONS

These investigations showed whole-heart 14 Gy external radiation treatment following coronary injury exacerbated certain aspects of arterial healing. In addition focal myocardial necrosis and fibrosis was observed following external but not endovascular irradiation. Endovascular radiation has some advantages over external irradiation; however the persistence of a synthetic smooth muscle cell phenotype in the neointima at 6 months suggests ionizing radiation in general may have profound effects on vessel architecture over the long term.

Meridional differences in temporal response characteristics

It is well established that a large variety of psychophysical factors influence the critical flicker fusion frequency (CFF). Several recent studies have examined the relationship between CFF and retinal location with confounding and contradictory results. The aim of this study was to determine the CFF for a number of stimulus sizes and luminances in an attempt to evaluate the interactive effects of these parameters and the quadrantic variation in temporal sensitivity. Retinal sensitivity gradients were measured along the two major oblique meridians out to an eccentricity of 50 degrees. CFF profiles for the 1.724 and 0.431 degree targets were shown to decrease with increasing eccentricity more rapidly in the inferior nasal quadrant (superior temporal retina). No significant difference between superior and inferior visual field temporal processing was evident.