Flying in the face of resistance: antiviral-independent benefit of HIV protease inhibitors on T-cell survival

Short communication: Apoptosis pathways in HIV-1-infected patients before and after highly active antiretroviral therapy: relevance to immune recovery

Investigations into apoptotic pathways, intrinsic and extrinsic, and the effects of highly active antiretroviral therapy (HAART) on T cell death via those pathways may provide insight into the mechanisms of and barriers to immune recovery. HIV-1-infected patients were enrolled into a randomized, controlled study of the immune effects of a lopinavir/ritonavir (LPV/r)-based versus an efavirenz (EFV)-based HAART regimen in antiretroviral-naive subjects with CD4(+) counts <350 cells/mm(3). Patients were randomized to receive TDF/FTC/EFZ or TDF/FTC plus LPV/r. Fourteen patients were enrolled and 10 patients completed 6 months of therapy as per the protocol. CD4(+) counts were measured before and during HAART therapy. We isolated T cell subsets to measure ex vivo apoptosis by propidium iodide staining. We also assessed caspase activation for the intrinsic and extrinsic pathways of apoptosis, as well as effector caspase activation. We also measured mitochondrial membrane potential. Cells were analyzed by flow cytometry. All patients had increased activation of caspase 8 (extrinsic pathway), caspase 9 (intrinsic pathway), effector caspases 3/7, and low mitochondrial membrane potential at baseline compared to controls. By 4 weeks, there was a decrease in activation of all caspases, but little further decrease by week 24. T cell mitochondrial membrane potential did not increase until week 12, but continued to increase until week 24. The only predictor of CD4(+) count increase was the increase in mitochondrial membrane potential of naive cells at 6 months (r=0.66, p=0.038). This suggests that positive selection of naive CD4(+) T cells in the thymus is the major determinant of CD4(+) recovery.

Choice of antiretroviral therapy differentially impacts survival of HIV-infected CD4 T cells

BACKGROUND

HIV eradication strategies are now being evaluated in vitro and in vivo. A cornerstone of such approaches is maximal suppression of viral replication with combination antiretroviral therapy (ART). Since many antiretroviral agents have off target effects, and different classes target different components of the viral life cycle, we questioned whether different classes of ART might differentially affect the survival and persistence of productively HIV-infected CD4 T cells.

METHODS

In vitro infections of primary CD4 T cells using clinical isolates of HIV-1 that were either protease inhibitor susceptible (HIV PI-S), or resistant (HIV PI-R) were treated with nothing, lopinavir, efavirenz or raltegravir. Cell viability, apoptosis, and the proportion of surviving cells that were P24 positive was assessed by flow cytometry.

RESULTS

In HIV PI-S infected primary cultures, all three antiretroviral agents decreased viral replication, and reduced the total number of cells that were undergoing apoptosis (P < 0.01) similarly. Similarly, in the HIV PI-R infected cultures, both efavirenz and raltegravir reduced viral replication and reduced apoptosis compared to untreated control (P < 0.01), while lopinavir did not, suggesting that HIV replication drives T cell apoptosis, which was confirmed by association by linear regression (P < 0.0001) . However since HIV protease has been suggested to directly induce apoptosis of infected CD4 T cells, and HIV PI are intrinsically antiapoptotic, we evaluated apoptosis in productively infected (HIV P24+) cells. More HIV p24 positive cells were apoptotic in the Efavirenz or raltegravir treated cultures than the lopinavir treated cultures (P = 0.0008 for HIV PI-R and P = 0.06 for the HIV PI-S), indicating that drug class impacts survival of productively infected CD4 T cells.

CONCLUSIONS

Inhibiting HIV replication with a PI, NNRTI or INSTI reduces total HIV-induced T cell apoptosis. However, blocking HIV replication with PI but not with NNRTI or INSTI promotes survival of productively HIV-infected cells. Thus, selection of antiretroviral agents may impact the success of HIV eradication strategies.

Choice of antiretroviral therapy differentially impacts survival of HIV-infected CD4 T cells

Background

HIV eradication strategies are now being evaluated in vitro and in vivo. A cornerstone of such approaches is maximal suppression of viral replication with combination antiretroviral therapy (ART). Since many antiretroviral agents have off target effects, and different classes target different components of the viral life cycle, we questioned whether different classes of ART might differentially affect the survival and persistence of productively HIV-infected CD4 T cells.

Methods

In vitro infections of primary CD4 T cells using clinical isolates of HIV-1 that were either protease inhibitor susceptible (HIV PI-S), or resistant (HIV PI-R) were treated with nothing, lopinavir, efavirenz or raltegravir. Cell viability, apoptosis, and the proportion of surviving cells that were P24 positive was assessed by flow cytometry.

Results

In HIV PI-S infected primary cultures, all three antiretroviral agents decreased viral replication, and reduced the total number of cells that were undergoing apoptosis (P < 0.01) similarly. Similarly, in the HIV PI-R infected cultures, both efavirenz and raltegravir reduced viral replication and reduced apoptosis compared to untreated control (P < 0.01), while lopinavir did not, suggesting that HIV replication drives T cell apoptosis, which was confirmed by association by linear regression (P < 0.0001) . However since HIV protease has been suggested to directly induce apoptosis of infected CD4 T cells, and HIV PI are intrinsically antiapoptotic, we evaluated apoptosis in productively infected (HIV P24+) cells. More HIV p24 positive cells were apoptotic in the Efavirenz or raltegravir treated cultures than the lopinavir treated cultures (P = 0.0008 for HIV PI-R and P = 0.06 for the HIV PI-S), indicating that drug class impacts survival of productively infected CD4 T cells.

Conclusions

Inhibiting HIV replication with a PI, NNRTI or INSTI reduces total HIV-induced T cell apoptosis. However, blocking HIV replication with PI but not with NNRTI or INSTI promotes survival of productively HIV-infected cells. Thus, selection of antiretroviral agents may impact the success of HIV eradication strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/2052-8426-2-1) contains supplementary material, which is available to authorized users.

Peripheral T-cell apoptosis is not differentially affected by antiretroviral regimens in HIV-infected patients

BACKGROUND

HIV-induced CD4(+) and CD8(+) T-cell apoptosis decreases upon start of combination antiretroviral therapy (cART). Although in vitro evidence suggests an anti-apoptotic effect of protease inhibitors (PIs) as opposed to non-nucleoside reverse transcriptase inhibitors (NNRTIs), in vivo studies are inconclusive about effects of differential cART regimens on T-cell apoptosis.

METHODS

Peripheral T-cell apoptosis was evaluated in a cross-sectional study including 20 patients on PI- and 19 on NNRTI-based combination antiretroviral therapy (cART), all with backbone therapy of tenofovir and emtricitabine and undetectable viral loads 6 months before inclusion. Spontaneous T-cell apoptosis was measured in freshly isolated peripheral blood mononuclear cells (<4 h after venipuncture) using annexin V, propidium iodide and staining for caspase activity and levels of the anti-apoptotic protein Bcl-2.

RESULTS

The groups were comparable in general- and HIV-specific characteristics. In addition, T-cell activation was similar in both groups. We observed no difference in T-cell apoptosis as measured by annexin V, propidium iodide or caspase staining between PI- and NNRTI-treated patients. Interestingly, the level of anti-apoptotic protein Bcl-2 was higher in PI-treated than in NNRTI-treated patients.

CONCLUSIONS

In this cross-sectional study on HIV-infected patients, direct ex vivo spontaneous T-cell apoptosis rates are not differentially affected by NNRTI- or PI-based cART.

Systematic review of antiretroviral-associated lipodystrophy: lipoatrophy, but not central fat gain, is an antiretroviral adverse drug reaction

Background

Lipoatrophy and/or central fat gain are observed frequently in patients on antiretroviral therapy (ART). Both are assumed to be antiretroviral adverse drug reactions.

Methods

We conducted a systematic review to determine whether fat loss or gain was more common in HIV-infected patients on ART than in uninfected controls; was associated with specific antiretrovirals; and would reverse after switching antiretrovirals.

Results

Twenty-seven studies met our inclusion criteria. One cohort study reported more lipoatrophy, less subcutaneous fat gain, but no difference in central fat gain in HIV-infected patients on ART than in controls. Randomised controlled trials (RCTs) showed more limb fat loss (or less fat gain) with the following regimens: stavudine (versus other nucleoside reverse transcriptase inhibitors (NRTIs)); efavirenz (versus protease inhibitors (PIs)); and NRTI-containing (versus NRTI-sparing). RCTs showed increased subcutaneous fat after switching to NRTI-sparing regimens or from stavudine/zidovudine to abacavir/tenofovir. There were no significant between-group differences in trunk and/or visceral fat gain in RCTs of various regimens, but results from efavirenz versus PI regimens were inconsistent. There was no significant between-group differences in central fat gain in RCTs switched to NRTI-sparing regimens, or from PI-containing regimens.

Conclusions

There is clear evidence of a causal relationship between NRTIs (especially thymidine analogues) and lipoatrophy, with concomitant PIs possibly having an ameliorating effect or efavirenz causing additive toxicity. By contrast, central fat gain appears to be a consequence of treating HIV infection, because it is not different from controls, is not linked to any antiretroviral class, and doesn't improve on switching.

Effect of different antiretroviral drug regimens on body fat distribution of HIV-infected South African women

No African studies have examined the effect of first-line nonnucleoside reverse transcriptase inhibitor (NNRTI)-based and second-line protease inhibitor (PI)-based antiretroviral therapy (ART) on body composition. We compared body composition in HIV-infected black South African women receiving NNRTI-based ART (ART1, n=344), PI-based ART (ART2, n=91), and those not on ART (ART-naive, n=309). Accordingly, body composition was measured using dual energy x-ray absorptiometry (DXA) and anthropometry in a cross-sectional study. Despite similar body mass index (BMI), ART1 and ART2 had greater central fat mass (FM) [median (IQR): 44.2 (39.4-50.1) and 46.9 (39.3-52.8) vs. 41.1 (36.3-45.2) %FM, p<0.01] and less leg FM [41.2 (34.8-45.8) and 40.2 (32.9-45.7) vs. 43.9 (39.3-48.1) %FM, p<0.01] than ART-naive women. Within ART1, waist:hip was greater [0.87 (0.81-0.92) vs. 0.84 (0.78-0.89), p=0.006], while calf skinfold was lower [15.2 (9.4-21.5) vs. 17.4 (12.0-23.6) mm, p=0.033] in women receiving efavirenz compared to nevirapine. ART2 had a greater waist:hip, and abdominal, subscapular, and suprailiac skinfolds than ART1 (p<0.05). After adjusting for time on d4T (stavudine), ART2 had greater body fat than ART1 (p<0.05). With increasing time on d4T, the decrease in leg fat (%FM) was higher in ART1 than ART2 (p=0.012, for time×treatment effect). A similar interaction was reported for total time on ART treatment (p=0.002 for time×treatment effect). In conclusion, ART was associated with increased central fat and reduced peripheral fat. Changing to a PI-based regimen in ART2, which also substitutes stavudine with zidovudine, partially reversed the peripheral fat loss observed on ART1.

Beneficial effects of a switch to a Lopinavir/ritonavir-containing regimen for patients with partial or no immune reconstitution with highly active antiretroviral therapy despite complete viral suppression

The purpose of this study was to determine if switching to an Lopinavir/ritonavir (LPV/r)-containing regimen resulted in greater immune reconstitution in patients with immunologic failure despite complete viral suppression with highly active antiretroviral therapy (HAART). Twenty patients with partial or no immune response to HAART despite viral suppression were enrolled. Ten were randomized to stay on their current regimen and 10 were randomized to LPV/r plus their current NRTI backbone. T cell subsets, ex vivo apoptosis, and the percent of circulating cells with detectable intracellular HIV-1 RNA were measured. The mean increase in CD4(+) count at 6 months was 116/mm(3) (172-288) for the LPV/r-containing arm versus 32/mm(3) (264-296) for continuation regimens (p = 0.03). The number of patients with an increase ≥50 cells/mm(3) was also greater in the LPV/r arm (7/9 versus 2/10, p = 0.01). This paralleled a decrease in ex vivo apoptosis of naive CD4(+) T cells at 6 months (21.7-11.0% for the LPV/r arm versus 17.3-18.9% for the continuation arm, p = 0.04) and memory cells (21.1-14.1% for LPV/r versus 20.2-17.9% for continuation arm, NSS). Switching patients to an LPV/r-containing regimen improved CD4(+) counts in patients with prior immunologic failure, and this may be due to an effect of LPV/r on apoptosis.

A Multicenter, Open Labeled, Randomized, Phase III Study Comparing Lopinavir/Ritonavir Plus Atazanavir to Lopinavir/Ritonavir Plus Zidovudine and Lamivudine in Naive HIV-1-Infected Patients: 48-Week Analysis of the LORAN Trial

OBJECTIVE

The primary aim of the study was to compare the metabolic side effects of a nucleoside analogue-containing regimen with a nucleoside analogue-sparing double protease inhibitor regimen. A secondary goal was to test for efficacy of a double-PI regimen.

DESIGN

Multicenter, randomized, open-label, phase III clinical trial.

SUBJECTS

Adult HIV-1-infected individuals naïve to antiretroviral therapy with viral load above 400 HIV-RNA copies/ml were randomized (1:1) to either 400 mg lopinavir /100 mg ritonavir (LPV/r) BID plus 150 mg lamivudine/300 mg zidovudine (CBV) BID versus LPV/r BID plus 300 mg atazanavir (ATV) QD. Main outcome measure was the virologic failure in both groups, defined as viral load ≥50 copies/ml at week 48.

RESULTS

In the CBV/LPV/r-arm, 29 out of 35 patients [(83%; 95% confidence interval (CI) 66.9-92.2%] and 18 out of 40 patients (45%; 95% CI 29.7-61.5%) in the ATV/LPV/r-arm had a HIV-RNA level <50 copies/ml at week 48. The intent-to-treat analysis revealed inferior virologic response in the ATV/LPV/r arm (Chi-Q and Fisher´s Exact Test p<0.001) and resulted in premature termination of the trial. Eleven patients in the ATV/LPV/r-arm discontinued therapy because of virological failure. These failures mostly presented with low level replication (<1,000 copies/ml). Increases in CD4 cell counts was significantly more rapid in the ATV/LPV/r arm (p=0.02), but comparable at week 48.

CONCLUSIONS

ATV/LPV/r had less virologic efficacy than the conventional RTI-based regimen and resulted in a high virological failure rate with low level replication.

Predicting the magnitude of short-term CD4+ T-cell recovery in HIV-infected patients during first-line highly active antiretroviral therapy

BACKGROUND

The extent of short-term CD4(+) T-cell recovery in patients tolerating first-line highly active antiretroviral therapy (HAART) and attaining undetectable HIV RNA levels is inadequately defined.

METHODS

We retrospectively analysed patients in four Italian cohorts who started HAART between January 1996 and September 2006. All patients had known HCV coinfection status, did not modify the regimen for 6 months and had <50 HIV RNA copies/ml at the end of the sixth month.

RESULTS

The analysis involved 1,488 patients (1,096 males, 73.7%) with a median age of 43 years (interquartile range [IQR] 39-49); 435 (29.2%) were positive for HCV, 71 (4.8%) were positive for hepatitis B surface antigen (HBsAg) and 76 (5.1%) had experienced a previous AIDS-defining event. At baseline, patient CD4(+) T-cell counts were 226 cells/microl (IQR 99-332), CD4(+) T-cell percentages were 14.7% (IQR 8.7-21.2) and HIV RNA levels were 4.91 log(10) copies/ml (IQR 4.38-5.34). Overall, 24-week CD4(+) T-cell recovery was 144 cells/microl (IQR 70-240). At multivariable analysis, T-cell recovery was positively related to the use of a boosted protease inhibitor (P<0.0001) or thymidine analogues (P<0.0001), baseline HIV RNA levels (P<0.0001), the baseline percentage of CD4(+) T-cells (P<0.0001) and the absence of HCV coinfection (P=0.006). Age, gender, baseline CD4(+)/CD8(+) T-cell ratio and a history of AIDS-defining events had no independent effect on CD4(+) T-cell recovery.

CONCLUSIONS

Among HIV-infected patients tolerating first-line HAART and with undetectable HIV RNA after 6 months, CD4(+) T-cell recovery is significantly greater in those without HCV coinfection, with a high baseline viral load, a high baseline percentage of CD4(+) T-cells and in those treated with a boosted protease inhibitor.

Role of HIV Gp41 mediated fusion/hemifusion in bystander apoptosis

Mechanisms of HIV-mediated CD4+ T cell loss leading to immunodeficiency are amongst the most extensively studied yet unanswered questions in HIV biology. The level of CD4+ T cell depletion in HIV infected patients far exceeds the number of infected T cells, suggesting an indirect mechanism of HIV pathogenesis termed bystander cell death. Evidence is accumulating that the HIV envelope glycoprotein (Env) is a major determinant of HIV pathogenesis and plays a critical role in bystander cell death. The complex structure and function of HIV Env makes the determination of the mechanism of Env mediated apoptosis more complex than previously thought. This review will examine the complex relationship between HIV Env phenotype, coreceptor expression and immune activation in determining HIV pathogenesis. We review data here corresponding to the role of HIV Env hemifusion activity in HIV pathogenesis and how it interplays with other AIDS associated factors such as chemokine receptor expression and immune activation.

The management of coronavirus infections with particular reference to SARS

The human coronaviruses (HCoV) OC43 and 229E are common causes of upper respiratory tract infections. Severe diseases were rare, however, until the emergence of the severe acute respiratory syndrome (SARS)-CoV in 2003. Since then, other novel CoV (NL63 and HKU1) have been described, and they have caused respiratory infections worldwide. Potentially exposed laboratory workers or animal handlers with rapidly progressive pneumonia not responding to standard antibacterial coverage must be isolated with contact and droplet, and for specific situations, airborne precautions, till rapid tests of respiratory and faecal samples are negative for SARS-CoV. Generally, the viral loads collected at different anatomical sites correlate with the severity of symptoms and mortality. Shedding of SARS-CoV peaks at day 10 after the onset of symptoms, which theoretically allows ample time for antiviral treatment. The disease is characterized by uncontrolled replication of the virus and a prominent pro-inflammatory response. No randomized controlled trials with a specific anti-coronavirus agent have been conducted with respect to therapy or prophylaxis. Reports using historical matched controls have suggested that treatment with interferon alfacon-1 (a synthetic interferon) combined with steroid, protease inhibitors together with ribavirin, or convalescent plasma containing neutralizing antibody, could be useful. Prophylaxis with interferon or hyperimmune globulin may be considered for unprotected exposure. The role of immunomodulators to decrease excessive inflammation remains elusive. Other non-SARS-CoV infections are generally milder in immunocompetent hosts, and scientific data on antiviral treatment of these viruses are scarce.

Class-sparing regimens for initial treatment of HIV-1 infection

BACKGROUND

The use of either efavirenz or lopinavir-ritonavir plus two nucleoside reverse-transcriptase inhibitors (NRTIs) is recommended for initial therapy for patients with human immunodeficiency virus type 1 (HIV-1) infection, but which of the two regimens has greater efficacy is not known. The alternative regimen of lopinavir-ritonavir plus efavirenz may prevent toxic effects associated with NRTIs.

METHODS

In an open-label study, we compared three regimens for initial therapy: efavirenz plus two NRTIs (efavirenz group), lopinavir-ritonavir plus two NRTIs (lopinavir-ritonavir group), and lopinavir-ritonavir plus efavirenz (NRTI-sparing group). We randomly assigned 757 patients with a median CD4 count of 191 cells per cubic millimeter and a median HIV-1 RNA level of 4.8 log10 copies per milliliter to the three groups.

RESULTS

At a median follow-up of 112 weeks, the time to virologic failure was longer in the efavirenz group than in the lopinavir-ritonavir group (P=0.006) but was not significantly different in the NRTI-sparing group from the time in either of the other two groups. At week 96, the proportion of patients with fewer than 50 copies of plasma HIV-1 RNA per milliliter was 89% in the efavirenz group, 77% in the lopinavir-ritonavir group, and 83% in the NRTI-sparing group (P=0.003 for the comparison between the efavirenz group and the lopinavir-ritonavir group). The groups did not differ significantly in the time to discontinuation because of toxic effects. At virologic failure, antiretroviral resistance mutations were more frequent in the NRTI-sparing group than in the other two groups.

CONCLUSIONS

Virologic failure was less likely in the efavirenz group than in the lopinavir-ritonavir group. The virologic efficacy of the NRTI-sparing regimen was similar to that of the efavirenz regimen but was more likely to be associated with drug resistance. (ClinicalTrials.gov number, NCT00050895 [ClinicalTrials.gov].).

Protease Inhibitors as Immunomodulatory Drugs for HIV Infection

More than 20 drugs from four therapeutic drug classes are widely available for the management of human immunodeficiency virus (HIV) infection, with promising drugs from two new drug classes expected to be approved by the US Food and Drug Administration (FDA) in mid-to-late 2007 (Table 1). When used in combination, these drugs can lead to durable and perhaps indefinite suppression of viral replication.