HIV protease and the pathogenesis of AIDS

Coronary Vasculature and Myocardial Structure in HIV: Physiologic Insights From the Renin-Angiotensin-Aldosterone System

The landscape of HIV medicine dramatically changed with the advent of contemporary antiretroviral therapies, which has allowed persons with HIV (PWH) to achieve good virologic control, essentially eliminating HIV-related complications and increasing life expectancy. As PWH are living longer, noncommunicable diseases, such as cardiovascular disease (CVD), have become a leading cause of morbidity and mortality in PWH with rates that are 50% to 100% higher than in well-matched persons without HIV. In this review, we focus on disease of the coronary microvasculature and myocardium in HIV. We highlight a key hormonal system important to cardiovascular endocrinology, the renin-angiotensin-aldosterone system (RAAS), as a potential mediator of inflammatory driven-vascular and myocardial injury and consider RAAS blockade as a physiologically targeted strategy to reduce CVD in HIV.

Targeted disruption of Toxoplasma gondii serine protease inhibitor 1 increases bradyzoite cyst formation in vitro and parasite tissue burden in mice

As an intracellular protozoan parasite, Toxoplasma gondii is likely to exploit proteases for host cell invasion, acquisition of nutrients, avoidance of host protective responses, escape from the parasitophorous vacuole, differentiation, and other activities. T. gondii serine protease inhibitor 1 (TgPI1) is the most abundantly expressed protease inhibitor in parasite tachyzoites. We show here that alternative splicing produces two TgPI1 isoforms, both of which are secreted via dense granules into the parasitophorous vacuole shortly after invasion, become progressively more abundant over the course of the infectious cycle, and can be detected in the infected host cell cytoplasm. To investigate TgPI1 function, the endogenous genomic locus was disrupted in the RH strain background. ΔTgPI1 parasites replicate normally as tachyzoites but exhibit increased bradyzoite gene transcription and labeling of vacuoles with Dolichos biflorus lectin under conditions promoting in vitro differentiation. The differentiation phenotype can be partially complemented by either TgPI1 isoform. Mice infected with the ΔTgPI1 mutant display ∼3-fold-increased parasite burden in the spleen and liver, and this in vivo phenotype is also complemented by either TgPI1 isoform. These results demonstrate that TgPI1 influences both parasite virulence and bradyzoite differentiation, presumably by inhibiting parasite and/or host serine proteases.

Oral Glucose Tolerance and Insulin Sensitivity Are Unaffected by HIV Infection or Antiretroviral Therapy in Overweight Women

OBJECTIVE

To assess the frequency of diabetes, prediabetes, and insulin resistance among a subset of participants in the Women's Interagency HIV Study (WIHS).

DESIGN

Cross-sectional substudy nested within a prospective multicenter cohort study. Women underwent 75 g oral glucose tolerance testing. Diagnoses of diabetes and prediabetes were made according to the American Diabetes Association criteria, and insulin resistance was determined by area under the curve insulin and homeostasis model assessment values.

SETTING

Six urban clinical sites in the United States (Brooklyn, NY; Bronx, NY; Washington, DC; Chicago, IL; San Francisco, CA; Los Angeles, CA) participate in the entire WIHS. The Bronx, NY, and San Francisco, CA, WIHS sites participated in this substudy.

PARTICIPANTS

A total of 258 women, 88 HIV negative, 74 HIV positive not on highly active antiretroviral therapy (HAART), and 96 HIV positive taking HAART were enrolled in the study.

MAIN OUTCOMES

Prevalence of diabetes, prediabetes, and insulin resistance was compared among the HIV-uninfected and HIV-infected women.

RESULTS

The frequency of diabetes, prediabetes, or insulin resistance was unrelated to HIV status or antiretroviral treatment. Increasing body mass index was the only characteristic associated with the combined endpoints of diabetes and prediabetes (odds ratio = 1.104, P = 0.0002).

CONCLUSIONS

Routine oral glucose tolerance testing of HIV-infected women is not supported by these findings. Elucidation of putative perturbations from HIV or antiretroviral medications requires direct studies of insulin resistance and beta-cell function.

Influence of mitochondrial control of apoptosis on the pathogenesis, complications and treatment of HIV infection

HIV infection is inexorably linked with disordered regulation of apoptosis, and consequent alterations in mitochondrial homeostasis, resulting in CD4 T cell death and enhanced susceptibility to opportunistic infections and malignancies. Effective treatment of HIV reverses the changes in mitochondrial homeostasis and apoptosis, and enhances immunocompetence. This review will summarize current knowledge of: i) the associations of apoptosis with HIV disease progression; ii) mechanisms of enhanced apoptosis in HIV infection; iii) putative role of apoptosis in HIV complications; iv) direct effects of HIV therapies on mitochondria and apoptosis; and finally v) treatment strategies for HIV based upon modifying the apoptotic response.

Apoptosis and HIV infection: T-cells fiddle while the immune system burns

Enhancement of programmed cell death (apoptosis) of CD4 T-cells by human immunodeficiency virus (HIV) is thought to be an important factor in the pathogenesis of HIV disease. Recent studies have cast doubt on this concept, however, portraying apoptosis as a potent antiviral strategy to eliminate infected cells. These studies have shed new light on the role of apoptosis in HIV infection. While cellular and immunologic mechanisms of apoptosis purge the HIV-infected lymphoid cell population, HIV thwarts apoptosis in myeloid cells, particularly monocyte/macrophages. Although HIV protease inhibitor therapy partially reverses the lymphoid cell process, this therapeutic approach fails to counter the persistence of HIV infection in myeloid cells. Thus apoptosis of T-cells may be a futile host attempt to control the spread of HIV while the infection smoulders in monocyte/macrophages. In other words, the antiviral defense system fiddles while the immune system burns.

Changes in CD4+ and CD8+ T cell subsets in response to highly active antiretroviral therapy in HIV type 1-infected patients with prior protease inhibitor experience

This study explores whether previous failures on antiretroviral drug regimens preclude the possibility of immune restoration. This was assessed by evaluating T cell subset changes in individuals who received a salvage regimen of highly active antiretroviral therapy (HAART) after initially failing protease inhibitor monotherapy. Ten HIV-1-infected asymptomatic patients received a regimen of indinavir, zidovudine, and 3TC after failing saquinavir monotherapy. Changes in absolute numbers of naive, memory, and activated CD4+ and CD8+ T cells expressing a selection of CD45RA, CD62L, CD45RO, HLA-DR, and CD38 markers were monitored prospectively over 6 months. These measurements were correlated with plasma viral load along with alterations in a selected CD8+ V alpha/Vbeta T cell receptor (TCR) repertoire. Over 6 months there was a progressive increase in numbers of CD4+ memory (CD45RA-CD62L+) and naive (CD45RA+CD62L+) T cells, which displayed a modest inverse correlation with viral load. Two phases of CD8+ memory cell changes were identified, consisting of a transient increase in CD45RA+CD62L- numbers after 2 months and thereafter a progressive rise in CD45RA-CD62L+ cells until 6 months. A strong correlation existed between reduced viral load and loss of activated CD8+CD38+HLA-DR+ cell numbers. There was also a temporary broadening of the CD8+ V alpha/Vbeta TCR repertoire at 8 weeks, which became skewed after 6 months in parallel with reduced viral suppression. Closer analysis of naive and memory cell subset proportions in individual patients revealed that enlarged pools of naive subsets were evident in those patients with rebounds in viral load. Overall, drug-experienced patients responding to HAART displayed increased numbers of naive and memory CD4+ subsets, and reduced CD8+ cell activation with a loss of TCR skewing.

Weight gain associated with protease inhibitor therapy in HIV-infected patients

Weight loss and wasting are significant complications of HIV disease. HIV protease inhibitor therapy promotes clinical, immunologic and virologic improvement in HIV-infected patients. In this study, we sought to determine the specific effect of HIV protease inhibitors on patient weight. Ten consecutive HIV patients were treated with protease inhibitor-containing regimens over six months. CD4 T-cell counts, plasma viral load levels and bariatric changes were monitored during the study. Patients experienced a mean weight gain of 19 Pounds (P = 0.006). There was a significant increase in mean CD4 T-cell count (P = 0.008) and a significant decrease in mean viral load level (P = 0.004). The increase in CD4 T cells did not correlate with weight gain, whereas the decrease in viral load did show a significant correlation with the weight increase (P = 0.003). The mechanism of protease inhibitor-induced weight gain is discussed. The medications may also be useful for wasting diseases unrelated to HIV.