Stacey A. Rizza

HIV induces TRAIL sensitivity in hepatocytes.

Background HIV infected patients have an increased susceptibility to liver disease due to Hepatitis B Virus (HBV), Hepatitis C Virus (HCV), alcoholic, and non-alcoholic steatohepatitis. Clinically, this results in limited options for antiretroviral therapy and accelerated rates of liver disease, causing liver disease to be the second leading cause of death for HIV infected patients. The mechanisms causing this propensity for liver dysfunction during HIV remains unknown. Methodology/Principal Findings We demonstrate that HIV and/or the HIV glycoprotein gp120 ligation of CXCR4 on hepatocytes selectively up-regulates TRAIL R2 expression and confers an acquired sensitivity to TRAIL mediated apoptosis which is mediated by JNK II, but not p38 nor G-proteins. Conclusions/Significance These findings suggest that HIV infection renders hepatocytes more susceptible to liver injury during disease states associated with enhanced TRAIL production such as HBV, HCV, or steatohepatitis.

HIV Protease Cleavage of Procaspase 8 is Necessary for Death of HIV-Infected Cells

Numerous host and viral factors are capable of causing death of HIV infected cells, uninfected bystander cells, or both. We assessed the relevance of HIV protease in infected cell killing by mutating its obligate substrate for death, procaspase 8. VSV pseudotyped HIV infection of cells expressing WT caspase 8 resulted in apoptotic cell death and generation of the HIV protease specific cleavage product of procaspase 8, casp8p41. Conversely, both cell death and casp8p41 production were inhibited in cells expressing procaspase 8 engineered to be resistant to HIV protease cleavage. Lymph nodes from HIV-infected patients with ongoing viral replication also selectively expressed casp8p41, which colocalized with both infected and apoptotic cells. HIV protease cleavage of procaspase 8 appears to be a necessary event for infected cell killing, which is responsible for infected cell death within lymphoid tissues from HIV-infected patients.

HIV protease inhibitors impact on apoptosis.

HIV protease inhibitors are the backbone of HIV therapy. In addition to blocking intracellular HIV protease and dramatically decreasing viral burden, the protease inhibitors also regulate apoptosis. A growing body of data has confirmed the immunomodulatory effects of HIV protease inhibitors which block CD4+ and CD8+ T cell death in models of HIV infection. The mechanism of this apoptosis inhibition is still under active investigation and supported by several proposed hypothesis for how they alter the fate of the cell. More recently, the anti-apoptotic effects of the HIV protease inhibitors has been extended to the non-HIV, non-immune cell, whereby protease inhibitors prevent apoptosis, and disease, in animal models of sepsis, hepatitis and stroke. Interestingly, when HIV protease inhibitors are used at supra-therapeutic concentrations, they exert pro-apoptotic effects. This has been demonstrated in a number of tumor models. Although it is unclear how HIV protease inhibitors can induce apoptosis at increased concentrations, future research will define the targets of the immunomodulation and reveal the full clinical potential of this intriguing class of drugs.

Infected Cell Killing by HIV-1 Protease Promotes NF-κB Dependent HIV-1 Replication

Acute HIV-1 infection of CD4 T cells often results in apoptotic death of infected cells, yet it is unclear what evolutionary advantage this offers to HIV-1. Given the independent observations that acute T cell HIV-1 infection results in (1) NF-κB activation, (2) caspase 8 dependent apoptosis, and that (3) caspase 8 directly activates NF-κB, we questioned whether these three events might be interrelated. We first show that HIV-1 infected T cell apoptosis, NF-κB activation, and caspase 8 cleavage by HIV-1 protease are coincident. Next we show that HIV-1 protease not only cleaves procaspase 8, producing Casp8p41, but also independently stimulates NF-κB activity. Finally, we demonstrate that the HIV protease cleavage of caspase 8 is necessary for optimal NF-κB activation and that the HIV-1 protease specific cleavage fragment Casp8p41 is sufficient to stimulate HIV-1 replication through NF-κB dependent HIV-LTR activation both in vitro as well as in cells from HIV infected donors. Consequently, the molecular events which promote death of HIV-1 infected T cells function dually to promote HIV-1 replication, thereby favoring the propagation and survival of HIV-1.

HIV Screening in the Health Care Setting: Status, Barriers, and Potential Solutions

Thirty years into the human immunodeficiency virus (HIV) epidemic in the United States, an estimated 50,000 persons become infected each year: highest rates are in black and Hispanic populations and in men who have sex with men. Testing for HIV has become more widespread over time, with the highest rates of HIV testing in populations most affected by HIV. However, approximately 55% of adults in the United States have never received an HIV test. Because of the individual and community benefits of treatment for HIV, in 2006 the Centers for Disease Control and Prevention recommended routine screening for HIV infection in clinical settings. The adoption of this recommendation has been gradual owing to a variety of issues: lack of awareness and misconceptions related to HIV screening by physicians and patients, barriers at the facility and legislative levels, costs associated with testing, and conflicting recommendations concerning the value of routine screening. Reducing or eliminating these barriers is needed to increase the implementation of routine screening in clinical settings so that more people with unrecognized infection can be identified, linked to care, and provided treatment to improve their health and prevent new cases of HIV infection in the United States.

Nelfinavir/ritonavir reduces acinar injury but not inflammation during mouse caerulein pancreatitis

There is no clinical treatment that reduces acinar injury during pancreatitis. Human immunodeficiency virus (HIV) protease inhibitors (PI), including nelfinavir (NFV) and ritonavir (RTV), may reduce the rate of pancreatitis in HIV-infected patients. Since permeability transition pore (PTPC)-mediated mitochondrial dysfunction occurs during pancreatitis, and we have shown that PI prevents PTPC opening, we studied its effects in a model of pancreatitis. The effect of NFV plus RTV (NFV/RTV) or vehicle on caerulein-induced pancreatitis in mice was compared by measuring changes in mitochondrial membrane potential in vitro and cytochrome c leakage in vivo. Histological and inflammatory makers were also compared. NFV/RTV improved DiOC6 retention in acini exposed to caerulein in vitro. In vivo NFV prevented cytosolic leakage of cytochrome c and reduced pancreatic acinar injury, active caspase-3 staining, TUNEL-positive acinar cells, and serum amylase (P < 0.05). Conversely, trypsin activity, serum cytokine levels, and pancreatic and lung inflammation were unaffected. NFV/RTV reduces pancreatic injury and acinar cell death in experimental mouse caerulein-induced pancreatitis but does not impact inflammation.

Analysis of HIV Protease Killing Through Caspase 8 Reveals a Novel Interaction Between Caspase 8 and Mitochondria

Human Immunodeficiency Virus (HIV) protease initiates apoptosis of HIV-infected cells by proteolytic cleavage of procaspase 8, creating a novel peptide termed casp8p41. Expression of casp8p41 alone is sufficient to initiate caspase-dependent cell death associated with mitochondrial depolarization. Since casp8p41 does not contain the catalytic cysteine at position 360, the mechanism by which casp8p41 initiates apoptosis is unclear. We demonstrate that casp8p41 directly causes mitochondrial depolarization and release of cytochrome c with downstream caspase 9 activation. Moreover, death induced by casp8p41 requires the presence of mitochondria, and in intact cells, casp8p41 colocalizes with mitochondria. These results illuminate a novel mechanism of cell death induced by a caspase 8 cleavage fragment whereby mitochondrial interaction leads to depolarization and cytochrome c release.

Early changes in T-cell activation predict antiretroviral success in salvage therapy of HIV infection.

Objective:Because effective antiretroviral therapy (ART) reduces immune activation, we hypothesize that early changes in immune activation are associated with subsequent virologic response to therapy. Design:Observational cohort study. Setting:Institutional HIV clinic. Subjects:Thirty-four adult HIV patients with virologic failure on their current antiretroviral regimen. Intervention:Change to salvage regimen selected by patients physician. Main Outcome Measures:Measures of immune activation at baseline and at 2, 4, 8, and 24 weeks after enrollment. Data were analyzed by proportional hazards (PH) models. Results:PH models showed that reductions between baseline and week 2 in expression of CD38 (P = 0.02) or CD95 (P = 0.02) on CD4+ T cells were associated with increased likelihood of achieving virologic suppression. Kaplan-Meier analysis demonstrated that patients who had reductions within the first 2 weeks of therapy in CD4+ T-cell expression of CD38 (P = 0.003) or CD95 (P = 0.08) were more likely to achieve viral suppression than those who did not. Conclusions:Reduced CD4+ T-cell expression of CD38 and CD95 occurring within 2 weeks of salvage therapy is associated with subsequent viral suppression. Monitoring CD38 and CD95 may allow earlier assessment of the response to ART.

Extensive virologic and immunologic characterization in an HIV-infected individual following allogeneic stem cell transplant and analytic cessation of antiretroviral therapy: A case study

Background Notwithstanding 1 documented case of HIV-1 cure following allogeneic stem cell transplantation (allo-SCT), several subsequent cases of allo-SCT in HIV-1 positive individuals have failed to cure HIV-1 infection. The aim of our study was to describe changes in the HIV reservoir in a single chronically HIV-infected patient on suppressive antiretroviral therapy who underwent allo-SCT for treatment of acute lymphoblastic leukemia. Methods and findings We prospectively collected peripheral blood mononuclear cells (PBMCs) by leukapheresis from a 55-year-old man with chronic HIV infection before and after allo-SCT to measure the size of the HIV-1 reservoir and characterize viral phylogeny and phenotypic changes in immune cells. At day 784 post-transplant, when HIV-1 was undetectable by multiple measures—including PCR measurements of both total and integrated HIV-1 DNA, replication-competent virus measurement by large cell input quantitative viral outgrowth assay, and in situ hybridization of colon tissue—the patient consented to an analytic treatment interruption (ATI) with frequent clinical monitoring. He remained aviremic off antiretroviral therapy until ATI day 288, when a low-level virus rebound of 60 HIV-1 copies/ml occurred, which increased to 1,640 HIV-1 copies/ml 5 days later, prompting reinitiation of ART. Rebounding plasma HIV-1 sequences were phylogenetically distinct from proviral HIV-1 DNA detected in circulating PBMCs before transplantation. The main limitations of this study are the insensitivity of reservoir measurements, and the fact that it describes a single case. Conclusions allo-SCT led to a significant reduction in the size of the HIV-1 reservoir and a >9-month-long ART-free remission from HIV-1 replication. Phylogenetic analyses suggest that the origin of rebound virus was distinct from the viruses identified pre-transplant in the PBMCs.

Isolation of a TRAIL Antagonist from the Serum of HIV-infected Patients

Background: The TRAIL:TRAIL receptor system has been implicated in the pathogenesis of a variety of malignant and infectious disorders, including HIV infection. Results: We show that HIV causes production of a novel TRAIL splice variant, that we call TRAIL-short, which binds TRAIL R2, antagonizes TRAIL signaling, and is present in HIV patient samples. Conclusion: Introduction of TRAIL-short causes resistance to TRAIL, whereas knockdown restores sensitivity. Significance: The identification of TRAIL-short impacts our understanding of TRAIL sensitivity and has implications for the pathogenesis of both infectious and malignant pathogenesis. Virus-host interactions are characterized by the selection of adaptive mechanisms by which to evade pathogenic and defense mechanisms, respectively. In primary T cells infected with HIV, HIV infection up-regulates TNF-related apoptosis inducing ligand (TRAIL) and death-inducing TRAIL receptors, but blockade of TRAIL:TRAIL receptor interaction does not alter HIV-induced cell death. Instead, HIV infection results in a novel splice variant that we call TRAIL-short (TRAIL-s), which antagonizes TRAIL-R2. In HIV patients, plasma TRAIL-s concentration increases with increasing viral load and renders cells resistant to TRAIL-induced death. Knockdown of TRAIL-s abrogates this resistance. We propose that TRAIL-s is a novel adaptive mechanism of apoptosis resistance acquired by HIV-infected cells to avoid their elimination by TRAIL-dependent effector mechanism.