Resistance to enfuvirtide, the first HIV fusion inhibitor

Fusion inhibitors are a new class of antiretroviral drugs (ARVs) for the treatment of human immunodeficiency virus infection. Enfuvirtide is the first in this class to reach market approval. Fusion inhibitors block the last step in the three-step viral entry process consisting of attachment, co-receptor binding and fusion, thereby preventing viral capsid entry into the host cell. Enfuvirtide has a unique mechanism of action and high viral target specificity, and in clinical trials has been shown to exhibit both high efficacy and low toxicity. Enfuvirtide is a peptide mimetic of an essential region within viral envelope glycoprotein gp41 that functions by blocking gp41 structural rearrangements at a transitional pre-fusion conformation. Although different clinical isolates show variation in susceptibility to enfuvirtide, primary resistance has not been observed, and thus enfuvirtide-naive isolates remain clinically sensitive. Acquired resistance centres round a 10 amino acid motif between residues 36 and 45 in gp41 that forms part of the binding site of enfuvirtide. The 10 amino acid motif is critical for viral fusion, and enfuvirtide-resistant mutants show poor replicative capacity compared with wild type. Reversion to a wild-type, drug-sensitive state has been reported following enfuvirtide withdrawal.     

A prospective clinical and pathological examination of injection site reactions with the HIV-1 fusion inhibitor enfuvirtide

OBJECTIVE: Antiretroviral regimens containing the fusion inhibitor enfuvirtide (ENF) are associated with sustained viral suppression and immunological benefit. However, local injection site reactions (ISR) occur in the majority of patients. The aim of this study was to determine the pathogenesis of ISRs. METHODS: Injection sites were evaluated prospectively from 30 min up to 15-30 days post-injection in ENF-experienced (Cohort I) and ENF-naive patients (Cohort II) during the first 2 weeks of therapy. Four to five injections were given in rotating abdominal sites by a nurse using a standardized technique and were rigorously evaluated. RESULTS: Reactions were observed in 80-100% of patients; the majority of the reactions were mild to moderate, generally appeared within 24-48 h post-injection, and pain, induration and erythema were the most common clinical signs. Whereas most patients experienced ISRs, the overall prevalence in Cohort II was low (35% maximum). Punch biopsies of injection sites in Cohort I consisted primarily of mixed lymphocytic infiltrates with eosinophils and neutrophils. Injection vehicle (ENF buffer minus ENF) and reduced volume (2 x 0.5 ml ENF [45 mg] versus 1.0 ml [90 mg] ENF) were investigated in Cohort II. Fewer reactions appeared with vehicle and pain was absent with the smaller injection volume. Pathology was indistinguishable between ENF, vehicle and normal tissue in Cohort II patients. CONCLUSION: These results suggest that injection technique, injection volume and peptide may influence ISR to ENF.     

Increased antiretroviral potency by the addition of enfuvirtide to a four-drug regimen in antiretroviral-naive, HIV-infected patients

OBJECTIVE: To assess if enfuvirtide (ENF) increases antiviral activity of a highly active four-drug antiretroviral (ARV) regimen containing lopinavir/ritonavir, efavirenz, lamivudine and tenofovir in ARV-naive, HIV-infected patients. METHODS: Pilot study in ARV-naive, HIV-infected patients with viral load (VL) >10,000 copies/ml and no documented resistance to any of the study drugs. Patients were randomized to receive ENF (ENF Group) or not (Control Group) in combination with lopinavir/ritonavir, efavirenz, lamivudine and tenofovir as a backbone. The primary endpoint was to assess differences in the HIV-1 RNA decay rate during the first phase of viral decay. VL and treatment adherence were measured at baseline, every 6 h during the first 3 days, and once daily from day 3 to 6. Individual HIV-1 RNA decay rates were obtained using a non-linear least squares regression model. RESULTS: Eight subjects were included in each study group. Mean (SD) baseline VL was 4.98 (0.38) log10 copies/ml in the ENF Group and 5.10 (0.49) log10 copies/ml in the Control Group (P=0.607). Baseline CD4+ cell count was 463 (306) and 362 (225) cells/mm3 in the ENF and the Control Group, respectively (P=0.484). First phase HIV-1 RNA decay rate was 0.802 (0.127) d(-1) in the ENF Group and 0.624 (0.182) d(-1) in the Control Group (P=0.045). By day 6, VL was 3.55 (0.40) and 3.92 (0.36) log10 copies/ml in the ENF and the Control Group, respectively (P=0.079). CONCLUSION: The addition of ENF increased the antiviral potency of a highly active four-drug ARV regimen by 28.5% in ARV-naive, HIV-infected patients. The clinical impact of this finding should be assessed.     

Darunavir: an effective protease inhibitor for HIV-infected patients

Darunavir is a new-generation nonpeptidic HIV protease inhibitor (PI), used with low doses of ritonavir for pharmacologic enhancement (boosting). It has demonstrated potent activity against multidrug-resistant HIV, with a robust resistance profile and a distinct set of mutations. In heavily treatment-experienced patients with HIV infection, darunavir administered twice daily with ritonavir has shown higher rates of efficacy than the control PI. In less treatment-experienced patients, boosted darunavir was noninferior to boosted lopinavir. In treatment-naive patients, boosted darunavir administered once daily was noninferior to boosted lopinavir, and showed higher virologic and immunological response rates in patients with high baseline viral load and low baseline CD4(+) cell counts. Monotherapy with boosted darunavir is an acceptable option in some specific conditions. Boosted darunavir was generally well tolerated, with lower incidence of diarrhea and a more favorable lipid profile than boosted lopinavir in treatment-naive patients.     

VapB-positive Rhodococcus equi infection in an HIV-infected patient in Japan

Rhodococcus equi, a bacterium present in soil, is a common cause of pneumonia in foals. This organism has been recognized as an opportunistic pathogen in humans, typically causing infection in immunocompromised hosts such as HIV-infected patients and organ transplant recipients. However, human infection with R. equi has not been reported in Japan except in a case involving a laboratory worker. We report the first human case of VapB-positive R. equi pneumonia, which involved an HIV-infected patient living in an urban area in Japan. The patient was treated successfully with 450mg rifampicin and 600mg tosufloxacin, even though his CD4+ lymphocyte count at the time of diagnosis was 10/µl. The patients dogs were suspected in the epidemiology of this infection, but unfortunately we could not isolate the organism from canine-associated specimens in this case. R. equi infections in companion animals have been thought to be very rare, but they may be increasing in dogs. Therefore, further epidemiological research may clarify the prevalence of R. equi infection and the factors predisposing dogs to this infection.     

Metformin in an HIV-infected patient with protease inhibitor-induced diabetic ketoacidosis

OBJECTIVE: To describe a case of diabetes mellitus and diabetic ketoacidosis in a patient receiving protease inhibitor therapy and to describe the patient's response to treatment with metformin. CASE SUMMARY: A 49-year-old HIV-positive white man who was receiving indinavir, stavudine, and lamivudine for more than two years presented with shortness of breath and significant weight loss over the previous month. On admission, he had a pH of 7.11 and PaCO2 of 12.9 mm Hg. Laboratory investigations revealed glucose 420 mg/dL, a total carbon dioxide 5 mEq/L, and anion gap of 32. Beta-hydroxybutyrate was 5.9 mmol/L (normal value <0.4 mmol/L). Urine was highly positive for glucose and ketones. The patient was given intravenous fluids and an insulin infusion was started. Five days later, he was discharged on 60 units of insulin per day. Following discharge, efavirenz was substituted for indinavir. Metformin was added and six months following discharge the patient's blood glucose was well controlled with 36 units of insulin per day. DISCUSSION: New-onset diabetes mellitus has been reported in HIV-infected patients receiving protease inhibitors. To date, diabetic ketoacidosis has been an infrequent acute complication. The mechanism by which protease inhibitors cause diabetes is unclear; however, studies have noted insulin resistance and increased proinsulin. Metformin increases the sensitivity of peripheral tissues to insulin and appeared to be useful in this patient. However, further clinical research is needed. CONCLUSIONS: Monitoring glucose concentrations in HIV-positive patients receiving protease inhibitors is important to prevent the development of acute complications, including diabetic ketoacidosis. We recommend that these patients have their fasting serum glucose concentration measured at baseline, with follow-up every three months. The role of metformin and the thiazolidinedione antidiabetic agents in the management of protease inhibitor-induced diabetes requires further study.     

Zidovudine-associated type B lactic acidosis and hepatic steatosis in an HIV-infected patient

A 34-year-old obese woman with human immunodeficiency virus (HIV) infection diagnosed a year earlier was seen because of nausea, vomiting, and intermittent diarrhea for 3 weeks. Her current medications included zidovudine. Physical examination revealed tachypnea and tender hepatomegaly. Computed tomography of the abdomen showed hepatomegaly with fatty infiltration. Liver enzymes were within normal range except for elevated lactate dehydrogenase (LDH). The serum bicarbonate value was low, with a lactate level three times normal. The tachypnea and dyspnea worsened as lactate concentrations rapidly increased to 15 times normal. Although her Po2 and cardiac index were initially adequate, the patient had acute respiratory failure. She died with multiorgan dysfunction, including hepatic failure, severe lactic acidemia, disseminated intravascular coagulation, and renal failure. Autopsy revealed hepatomegaly and massive steatosis. Physicians should consider lactic acidosis in patients taking zidovudine and having unexplained tachypnea, dyspnea, and low serum bicarbonate concentrations.     

Yin zi huang, an injectable multicomponent chinese herbal medicine, is a potent inhibitor of T-cell activation

OBJECTIVES: The clinical efficacy of many multiherbal Traditional Chinese Medicines (TCM) is partially attributable to their immunoregulatory properties. In this study we evaluated the effect of eight commonly used, commercially available multiherbal Chinese medicines on T-cell activation. We focused on Yin Zhi Huang (YZH, an injectable herbal medicine commonly used for the treatment of liver diseases in China), because it was the most potent inhibitor of T-cell activation in our experimental system. The effects of 10 ingredient components of YZH were also evaluated. METHODS: [3H] thymidine incorporation assay was used to assess mouse T-cell proliferation after stimulation with latex beads coated with anti-CD3/CD28 antibodies. CD25, CD69, PD-1, and I-COS expression by purified mouse CD4+ T cells treated with plate-bound anti-CD3 antibody and soluble anti-CD28 antibody was analyzed by fluorescent-activated cell sorter (FACS). Cytokine/chemokine production by human peripheral blood mononuclear cells (PBMC) stimulated with staphylococcal enterotoxin B (SEB) was determined by enzyme-linked immunosorbent assay (ELISA). RESULTS: Among tested herbal medicines, YZH was the most potent inhibitor of T-cell activation. In splenocyte proliferation assays, the inhibitory effect of YZH was dose-dependent, with a 50% inhibition concentration (IC50) of 1:3200-1:1600. Ten (10) purified compounds found in YZH were evaluated for their activity. Among them, ursolic acid (1-10 micromol), luteolin (1-10 micromol), baicalein (1-10 micromol), scopran (5-50 micromol), and crocin (5-50 micromol), exhibited dose-dependent inhibition. YZH also inhibited CD25, CD69, PD-1, and ICOS expression by stimulated mouse CD4+ T cells. In human PBMCs, YZH inhibited SEB-stimulated cytokine (interleukin [IL]-1, IL-2, IL-6, tumor necrosis factor[TNF]-alpha, interferon [IFN]-gamma) and chemokine (IP-10, MCP-1, MIP-1alpha and MIP-1beta) production in a dose-dependent manner. CONCLUSION: Our data show for the first time that YZH is a potent inhibitor of T-cell activation, and this property may be the major mechanism underlying the clinical efficacy of YZH. Our experimental results pave the way for identification of active component(s) and/or analysis of synergistic/additive effect of a YZH ingredient in future studies.     

Hyperglycemia associated with protease inhibitors in an urban HIV-infected minority patient population

BACKGROUND: Hyperglycemia and new-onset diabetes mellitus have been reported to occur in HIV-infected patients treated with protease inhibitors. OBJECTIVE: To determine the effect of protease inhibitor therapy on serum glucose in a predominantly minority patient population. DESIGN: Retrospective record review. SETTING: Clinical HIV program of an urban Veterans Affairs medical center. PATIENTS: All HIV-infected patients receiving a protease inhibitor over a one-year period from September 1996 through August 1997. RESULTS: One hundred seventeen patients not previously known to be diabetic received protease inhibitors; seven (6%) developed symptomatic diabetes mellitus. Eight other patients had one or more serum glucose values >150 mg/dL. Mean random glucose values for patients who did not develop diabetes were higher during therapy than prior to initiation of protease inhibitors. CONCLUSIONS: Urban minority HIV-infected patients receiving combination antiretroviral therapy including a protease inhibitor may be at increased risk for the development of hyperglycemia and diabetes mellitus. Risk factors for diabetes mellitus should be identified and blood glucose monitored in all patients receiving protease inhibitors.     

Round opacity as a presentation of pneumocystis jirovecii pneumonia in an HIV-infected patient

We present the case of a human immunodeficiency virus (HIV)-infected patient who arrived at our emergency department with fever, headache and exertional dyspnea. Throughout their stay, a chest x-ray was taken and a rounded opacity in his left lung was observed. CT images showed same abnormality and also ground glass opacities were seen. Symptoms and images strongly suggested a pulmonary infection due to pneumocystis jirovecii, however a presence of a round lesion should always lead to neoplasia being suspected. We empirically started treatment based on trimethoprim and sulfamethoxazole. Once available, flexible bronchoscopy and bronchoalveolar lavage was performed and stained preparations from his respiratory specimens confirmed the diagnosis of pulmonary pneumocystis infection. Finally, after 4?days of antibiotic therapy, an important clinical improvement was documented; a new chest x-ray was performed and the previous rounded opacity was absent. This finding strongly suggested a case of round pneumonia.     

Venous thromboembolic disease in the HIV-infected patient

Objective

Infection with the HIV has developed into a chronic illness, with longer-term complications increasingly being seen. There is increasing evidence that infection with HIV may be associated with a hypercoagulable state. This study examines the association of HIV infection with the incidence of both pulmonary embolism and deep venous thrombosis.

Methods

This study was a weighted analysis of data from National Hospital Discharge Survey, a national annual probability survey of discharges from short-stay non-Federal hospitals, from 1996-2004. The risk of pulmonary embolism and/or deep venous thrombosis in an HIV+ individual was ascertained for each age group by calculation of an odds ratio (OR) with a 95% confidence interval (CI). A common OR was computed across strata to evaluate the overall association between PE/DVT and HIV while adjusting for effects of age.

Results

The overall age-adjusted OR indicates a statistically significant increase of 43% for PE in HIV+ individuals as opposed to HIV− individuals (OR, 1.43; 95% CI, 1.39-1.46). This increase differs by age group, with age group 21 to 50 years having the highest odds for PE among HIV+ individuals (OR, 1.58; 95% CI, 1.54-1.63).

Conclusions

The data supports the hypothesis that HIV-infected individuals are more likely to have clinically detected thromboembolic disease as opposed to non-HIV-infected individuals. This study reveals up to a 43% increase in OR of developing a PE, 10% increase in developing a DVT, and 40% increase in developing PE or DVT in an HIV-infected individual over the 9-year study period after adjusting for age.