Reduction in CD8+ cell noncytotoxic anti-HIV activity in individuals receiving highly active antiretroviral therapy during primary infection

Recent advances in the ability to detect people at the early stages of HIV infection now permit the initiation of antiretroviral treatment before the full complement of antiviral immune responses has evolved. However, the influence of early treatment interventions on the developing anti-HIV immune response is unknown. This study investigates the impact of standard highly active antiretroviral therapy (HAART) during the primary stages of HIV infection on the plasma HIV-1 RNA level, CD4(+) and CD8(+) lymphocyte counts, and the CD8(+) cell anti-HIV response. Individuals treated with HAART within 6 months of infection showed dramatic and rapid reductions in HIV-1 RNA levels along with modest increases in CD4(+) cell number and decreases in CD8(+) cell numbers. A significant reduction in the level of CD8(+) cell noncytotoxic suppression of HIV replication was observed over time in most participants receiving HAART. Importantly, those individuals choosing not to receive therapy maintained low but detectable HIV-1 RNA levels and showed no reduction in their CD8(+) cell antiviral response. These results suggest that either continued antigenic challenge is required to sustain CD8(+) cell-mediated anti-HIV activity, or that HAART has some inhibitory effect on this important immunologic function during the early stages of infection.     

Spatio-temporal variations in cell-free layer formation near bifurcations of small arterioles

Blood flow partitioning at an arteriolar bifurcation could lead to spatio-temporal variations in cell-free layer formation in the upstream and downstream vessels of the bifurcation. To investigate this effect, we quantitatively analyzed characteristics of the cell-free layer in the vicinity of an arteriolar bifurcation in the rat cremaster muscle in normal physiological flow conditions. To simulate hemorheological relevance to humans, red blood cell aggregation was elevated by infusion of Dextran 500 to levels seen in humans in normal states. Spatial variations of the layer width were observed in both the parent and larger daughter vessels. A more pronounced attenuation of the layer width was generally observed in the parent vessel at its wall adjacent to the side branch than at its opposite wall. A thicker layer width was consistently found at the opposite than adjacent wall of the larger daughter vessel. Accordingly, large asymmetries of the layer widths could be developed on opposite sides of the larger daughter vessel, which were significantly greater (P<0.01) than those observed in the parent vessel. A positive correlation was generally observed between mean layer widths in the downstream vessel and on the side of the parent vessel from which bulk of the flow enters the downstream vessel. The fraction of the downstream layer formation constituted by the side branch decreased with increasing flow fraction in this vessel. These findings confirmed the modulation of the cell-free layer formation near an arteriolar bifurcation, implicated by flow separation at the bifurcation.     

Malignant hyperthermia susceptibility arising from altered resting coupling between the skeletal muscle L-type Ca2+ channel and the type 1 ryanodine receptor

Malignant hyperthermia (MH) susceptibility is a dominantly inherited disorder in which volatile anesthetics trigger aberrant Ca(2+) release in skeletal muscle and a potentially fatal rise in perioperative body temperature. Mutations causing MH susceptibility have been identified in two proteins critical for excitation-contraction (EC) coupling, the type 1 ryanodine receptor (RyR1) and Ca(V)1.1, the principal subunit of the L-type Ca(2+) channel. All of the mutations that have been characterized previously augment EC coupling and/or increase the rate of L-type Ca(2+) entry. The Ca(V)1.1 mutation R174W associated with MH susceptibility occurs at the innermost basic residue of the IS4 voltage-sensing helix, a residue conserved among all Ca(V) channels [Carpenter D, et al. (2009) BMC Med Genet 10:104-115.]. To define the functional consequences of this mutation, we expressed it in dysgenic (Ca(V)1.1 null) myotubes. Unlike previously described MH-linked mutations in Ca(V)1.1, R174W ablated the L-type current and had no effect on EC coupling. Nonetheless, R174W increased sensitivity of Ca(2+) release to caffeine (used for MH diagnostic in vitro testing) and to volatile anesthetics. Moreover, in Ca(V)1.1 R174W-expressing myotubes, resting myoplasmic Ca(2+) levels were elevated, and sarcoplasmic reticulum (SR) stores were partially depleted, compared with myotubes expressing wild-type Ca(V)1.1. Our results indicate that Ca(V)1.1 functions not only to activate RyR1 during EC coupling, but also to suppress resting RyR1-mediated Ca(2+) leak from the SR, and that perturbation of Ca(V)1.1 negative regulation of RyR1 leak identifies a unique mechanism that can sensitize muscle cells to MH triggers.