Publications

OBJECTIVE

To identify risk factors associated with kidney function decline in a contemporary cohort of treated and untreated HIV-infected patients.

METHODS

We followed individuals enrolled in the Study of the Consequences Of the Protease inhibitor Era cohort for longitudinal changes in kidney function, defined as glomerular filtration rate estimated from serum creatinine (eGFR). eGFR slope was calculated using linear mixed effects models adjusted for age, sex, race, and time-updated CD4 cell count, viral load, antiretroviral therapy (ART), and comorbid conditions.

RESULTS

We followed 615 patients for a mean of 3.4 (+/- 2.5) years. In multivariable adjusted analyses, predictors of eGFR decline included female sex, diabetes, and hyperlipidemia; CD4 cell count and viral load were not associated with eGFR loss. Among patients who initiated treatment, antiretroviral exposure was associated with a +2.8 (95% confidence interval 0.8-4.7) ml/min per 1.73 m per year effect on eGFR slope. Although these patients appeared to benefit from ART based on the slowing of their eGFR decline, they continued to lose kidney function at a rate of -1.9 (95% confidence interval -3.7 to -0.1) ml/min per 1.73 m per year. In the subgroup of individuals receiving suppressive ART with viral loads maintained below 500 copies/ml, intermittent viremic episodes (blips) were strongly associated with more rapid rates of eGFR loss [-6.7 (95% confidence interval -11.1 to -2.4) ml/min per 1.73 m per year].

CONCLUSION

Although ART appears to help curb kidney function decline, patients who achieved durable viral suppression continue to manifest substantial loss of eGFR. Loss of kidney function may be attributable to treatment-related factors, intermittent viremia, and traditional risk factors for kidney disease.

BACKGROUND

HIV-infected patients have accelerated atherosclerosis. Abacavir has been associated with increased risk of cardiovascular events, for reasons that remain to be elucidated. As endothelial dysfunction is central to the pathogenesis of atherosclerosis, we tested the hypothesis that current treatment with abacavir is associated with impaired endothelial function.

METHODS

We studied a cohort of 61 antiretroviral-treated patients who had undetectable plasma HIV RNA levels. Endothelial function was assessed by measuring flow-mediated dilation (FMD) of the brachial artery. We compared FMD in patients treated with or without abacavir, while adjusting for traditional risk factors and HIV-specific characteristics.

RESULTS

The median age was 50 years (interquartile range 45-57). The median duration of HIV infection was 18 years, and the median CD4 cell count was 369 cells/microl. Thirty patients (49%) were receiving abacavir. Overall, the median FMD in the HIV-infected patients was low (3.5%; interquartile range 2.3-5.6%). The FMD was lower in the abacavir-treated patients than those not on abacavir (2.8 vs. 4.9%, P = 0.01). After adjustment for traditional risk factors, HIV-specific factors, and baseline brachial artery diameter, current abacavir use was independently associated with lower FMD (P = 0.017). Duration of therapy and CD4 cell count were not associated with reduced FMD.

CONCLUSION

Endothelial function, a central mechanism in atherosclerosis and a marker of cardiovascular risk, is impaired among antiretroviral-treated patients with undetectable viral loads. Current use of abacavir was independently associated with impaired endothelial function. This finding suggests that abnormal endothelial function may underlie the clinically observed increased risk in myocardial infarction among abacavir-treated patients.

Expression of HLA-B57 is associated with restricted replication of human immunodeficiency virus (HIV), but the mechanism for its protective effect remains unknown. If this advantage depends upon CD8 T-cell recognition of B57-restricted epitopes, mother-to-child transmission of escape mutations within these epitopes could nullify its protective effect. However, if the B57 advantage is largely mediated by selection for fitness-attenuating viral mutations within B57-restricted epitopes, such as T242N in TW10-Gag, then the transmission of such mutations could facilitate viral control in the haploidentical infant. We assessed the consequences of B57-associated mutations on replication capacity, viral control, and clinical outcome after vertical transmission in 13 mother-child pairs. We found that expression of HLA-B57 was associated with exceptional control of HIV during infancy, even when mutations within TW10 and most other B57-restricted epitopes were transmitted, subverting the natural immunodominance of HLA-B57. In contrast, most B57-negative infants born to B57-positive mothers progressed rapidly to AIDS. The presence of T242N led to a reproducible reduction in viral fitness, as demonstrated by in vitro assays using NL4-3 constructs encoding p24 sequences from individual mothers and infants. Associated compensatory mutations within p24-Gag were observed to reverse this impairment and to influence the propensity of T242N to revert after transmission to B57-negative hosts. Moreover, primary failure to control viremia was observed in one infant to whom multiple compensatory mutations were transmitted along with T242N. These parallel in vivo and in vitro data suggest that HLA-B57 confers its advantage primarily by driving and maintaining a fitness-attenuating mutation in p24-Gag.