Publications

In resource-limited settings--where a massive scale-up of HIV services has occurred in the last 5 years--both understanding the extent of and improving retention in care presents special challenges. First, retention in care within the decentralizing network of services is likely higher than existing estimates that account only for retention in clinic, and therefore antiretroviral therapy services may be more effective than currently believed. Second, both magnitude and determinants of patient retention vary substantially and therefore encouraging the conduct of locally relevant epidemiology is needed to inform programmatic decisions. Third, socio-structural factors such as program characteristics, transportation, poverty, work/child care responsibilities, and social relations are the major determinants of retention in care, and therefore interventions to improve retention in care should focus on implementation strategies. Research to assess and improve retention in care for HIV-infected patients can be strengthened by incorporating novel methods such as sampling-based approaches and a causal analytic framework.

OBJECTIVE

To determine the association of inflammatory markers, fibrinogen, and C-reactive protein (CRP), with 5-year mortality risk.

METHODS

Vital status was ascertained in 922 HIV-infected participants from the Study of Fat Redistribution and Metabolic Change in HIV infection. Multivariable logistic regression estimated odds ratios after adjustment for demographic, cardiovascular, and HIV-related factors.

RESULTS

Over a 5-year period, HIV-infected participants with fibrinogen levels in the highest tertile (>406 mg/dL) had 2.6-fold higher adjusted odds of death than those with fibrinogen in the lowest tertile (<319 mg/dL). Those with high CRP (>3 mg/L) had 2.7-fold higher adjusted odds of death than those with CRP <1 mg/L. When stratified by CD4 count category, fibrinogen (as a linear variable) remained independently associated [odds ratio (95% confidence intervals)] per 100 mg/dL increase in fibrinogen: 1.93 (1.57 to 2.37); 1.43 (1.14 to 1.79); 1.43 (1.14 to 1.81); and 1.30 (1.04 to 1.63) for CD4 <200, 200-350, >350 to 500, and >500 cells per microliter, respectively. Higher CRP also remained associated with higher odds of death overall and within each CD4 subgroup.

CONCLUSIONS

Fibrinogen and CRP are strong and independent predictors of mortality in HIV-infected adults. Our findings suggest that even in those with relatively preserved CD4 counts >500 cells per microliter, inflammation remains an important risk factor for mortality. Further investigation should determine whether interventions to reduce inflammation might decrease mortality risk in HIV-infected individuals.

BACKGROUND

Some HIV protease inhibitors (PIs), including full-dose ritonavir (800 mg) and ritonavir-boosted lopinavir, acutely induce insulin resistance in the absence of HIV infection and changes in body composition. Boosting dose ritonavir (100-200 mg) is the most commonly prescribed PI, yet its effects on glucose metabolism have not been described in the absence of another PI.

METHODS

In this randomized, double-blind, cross-over study, a single dose of ritonavir 200 mg or placebo was given to healthy HIV-seronegative volunteers before assessment of insulin sensitivity by euglycemic hyperinsulinemic clamp.

RESULTS

Boosting dose ritonavir had no effect on insulin-mediated glucose disposal (M/I, placebo: 8.59 ± 0.83 vs. ritonavir: 8.51 ± 0.64 mg/kg per minute per μU/mL insulin, P = 0.89).

CONCLUSIONS

A single boosting dose of ritonavir does not alter insulin sensitivity, suggesting lopinavir is likely responsible for the induction of insulin resistance demonstrated in prior short-term studies of lopinavir/ritonavir. There is a dose-dependent effect of ritonavir on insulin sensitivity.

Normal anatomic variation, study design, external factors, and tissue characteristics can all influence the manifestation of structures on magnetic resonance images (MRI). For the purpose of this review, imaging artifacts are considered to be nonpathologic abnormalities resulting from study design, intrinsic tissue characteristics, or external factors, while MRI pseudolesions are due to normal anatomic variation. Awareness of imaging artifacts and pseudolesions, as well as normal anatomic structures, is important when determining pathologic vs. normal or clinically insignificant abnormalities. The purpose of this report is to examine the literature to compile a review of selected artifacts and pseudolesions that are commonly encountered when imaging the canine and feline brain.

The human ATP-binding cassette (ABC) transporter superfamily consists of 48 integral membrane proteins that couple the action of ATP binding and hydrolysis to the transport of diverse substrates across cellular membranes. Defects in 18 transporters have been implicated in human disease. In hundreds of cases, disease phenotypes and defects in function can be traced to nonsynonymous single nucleotide polymorphisms (nsSNPs). The functional impact of the majority of ABC transporter nsSNPs has yet to be experimentally characterized. Here, we combine experimental mutational studies with sequence and structural analysis to describe the impact of nsSNPs in human ABC transporters. First, the disease associations of 39 nsSNPs in 10 transporters were rationalized by identifying two conserved loops and a small α-helical region that may be involved in interdomain communication necessary for transport of substrates. Second, an approach to discriminate between disease-associated and neutral nsSNPs was developed and tailored to this superfamily. Finally, the functional impact of 40 unannotated nsSNPs in seven ABC transporters identified in 247 ethnically diverse individuals studied by the Pharmacogenetics of Membrane Transporters consortium was predicted. Three predictions were experimentally tested using human embryonic kidney epithelial (HEK) 293 cells stably transfected with the reference multidrug resistance transporter 4 and its variants to examine functional differences in transport of the antiviral drug, tenofovir. The experimental results confirmed two predictions. Our analysis provides a structural and evolutionary framework for rationalizing and predicting the functional effects of nsSNPs in this clinically important membrane transporter superfamily.