Coinfection with Human Immunodeficiency Virus and Hepatitis C Virus: Challenges and Therapeutic Advances Insights from the Society of Infectious Diseases Pharmacists

Antiviral Peptides as Anti-Influenza Agents

Influenza viruses represent a leading cause of high morbidity and mortality worldwide. Approaches for fighting flu are seasonal vaccines and some antiviral drugs. The development of the seasonal flu vaccine requires a great deal of effort, as careful studies are needed to select the strains to be included in each year's vaccine. Antiviral drugs available against Influenza virus infections have certain limitations due to the increased resistance rate and negative side effects. The highly mutative nature of these viruses leads to the emergence of new antigenic variants, against which the urgent development of new approaches for antiviral therapy is needed. Among these approaches, one of the emerging new fields of "peptide-based therapies" against Influenza viruses is being explored and looks promising. This review describes the recent findings on the antiviral activity, mechanism of action and therapeutic capability of antiviral peptides that bind HA, NA, PB1, and M2 as a means of countering Influenza virus infection.

Antiviral peptides as promising therapeutic drugs

While scientific advances have led to large-scale production and widespread distribution of vaccines and antiviral drugs, viruses still remain a major cause of human diseases today. The ever-increasing reports of viral resistance and the emergence and re-emergence of viral epidemics pressure the health and scientific community to constantly find novel molecules with antiviral potential. This search involves numerous different approaches, and the use of antimicrobial peptides has presented itself as an interesting alternative. Even though the number of antimicrobial peptides with antiviral activity is still low, they already show immense potential to become pharmaceutically available antiviral drugs. Such peptides can originate from natural sources, such as those isolated from mammals and from animal venoms, or from artificial sources, when bioinformatics tools are used. This review aims to shed some light on antimicrobial peptides with antiviral activities against human viruses and update the data about the already well-known peptides that are still undergoing studies, emphasizing the most promising ones that may become medicines for clinical use.

Boceprevir: a review of its use in the management of chronic hepatitis C genotype 1 infection

Boceprevir (Victrelis®) is an inhibitor of the hepatitis C virus (HCV) non-structural protein NS3-4A serine protease and is used in combination with pegylated interferon (peginterferon)-alpha and ribavirin in the treatment of adults with chronic HCV (chronic hepatitis C) genotype 1 infection. Of the various genotypes of HCV, genotype 1 is one of the least responsive to interferon and ribavirin-based therapy, and thus most in need of novel treatments. This article reviews the available pharmacological properties of boceprevir and its clinical efficacy and tolerability in the treatment of chronic hepatitis C genotype 1 infection in adult patients who are either treatment-naive or have failed previous standard therapy. Boceprevir, when co-administered with peginterferon-alpha and ribavirin in patients with chronic hepatitis C genotype 1 infection who were treatment-naive or had previously not fully responded to or had relapsed following treatment, was associated with a significantly higher sustained virological response rate (defined as the proportion of patients with an undetectable plasma HCV RNA level at week 24 of the follow-up period [week 72 overall]) [primary endpoint] than peginterferon-alpha-2b and ribavirin alone, regardless of the boceprevir administration regimen, in the phase III SPRINT-2 (treatment-naive patients) and RESPOND-2 (previously treated patients) trials. There was no significant difference between full-duration (44 weeks) and response-guided (24 or 32 weeks followed by follow-up or peginterferon-alpha-2b plus ribavirin alone) boceprevir regimen recipients with regard to sustained virological response rate. All patients received an initial 4-week lead-in treatment period before the comparative treatment period began. Overall, boceprevir is generally well tolerated when administered concomitantly with peginterferon-alpha plus ribavirin in patients with chronic hepatitis C genotype 1 infection. The most common adverse events in any treatment group were flu-like symptoms, which are typically reported in patients receiving peginterferon-ribavirin therapy. The addition of boceprevir to peginterferon-alpha and ribavirin is associated with an increased risk of anaemia and neutropenia. In conclusion, boceprevir in combination with peginterferon-alpha and ribavirin is an effective and generally well tolerated treatment for treatment-naive or previously treated adult patients with chronic hepatitis C genotype 1 infection. The drug is associated with higher sustained virological response rates in these patients, in whom treatment with interferon and ribavirin alone may not be successful. Thus, boceprevir in combination with peginterferon-alpha and ribavirin is a valuable new treatment option for use in patients with chronic hepatitis C genotype 1 infection.

Challenges in the treatment of chronic hepatitis C in the HIV/HCV-coinfected patient

Hepatitis C virus (HCV) and HIV are common coinfections that convey a shortened lifespan, mostly related to liver disease. Treatment against HCV in the coinfected patient is notoriously more complex and challenging. There are no optimal treatment algorithms for HIV/HCV coinfected patients as efficacy of approved anti-HCV therapies is low with relevant side effects. The use of direct-acting antivirals for anti-HCV therapy has the potential to improve therapeutic efficacy, but also increase side effects and drug-drug interactions. In spite of all of this, the most important and significant fact is that chronic hepatitis C is potentially curable, and the eradication of the HCV infection is a crucial outcome in this population. The establishment of a productive collaboration among the regulatory agencies, the medical community and the pharmaceutical industry could lead to faster access to more effective HCV therapies for the coinfected patient and eventually stop the progression of liver disease in these patients.

Focus on drug interactions: the challenge of treating hepatitis C virus infection with direct-acting antiviral drugs in the HIV-positive patient

PURPOSE OF REVIEW

Successful treatment of hepatitis C virus (HCV) infection is necessary for the survival of HIV-infected patients. This review covers the outcomes of current therapy, first-generation HCV direct-acting antivirals (DAAs) and their drug-to-drug interactions (DDIs). Understanding DDIs between HIV antiretroviral therapy (ART) and the DAAs in development is important to assure the best management of the HIV/HCV coinfected individuals.

RECENT FINDINGS

The two first-in-class DAAs were approved for clinical use in 2011. The first trials with boceprevir or telaprevir added to standard therapy in HIV/HCV coinfected patients revealed triple therapy to be efficacious with significantly improved sustained virological response rates. However, these DAAs were associated with more and worse adverse effects, as well as with significant DDIs with multiple drugs, including ART. Early data on DAAs in development suggest improved efficacy and safety and the potential for lesser DDIs.

SUMMARY

Anti-HCV therapy is fundamental in coinfected patients, but the approved therapies are suboptimal. The first-generation of approved HCV DAAs improved efficacy of therapy in coinfected patients, but have multiple safety concerns, including potentially serious drug interactions with ART. Early results from newer DAAs are promising.

Antiviral peptide nanocomplexes as a potential therapeutic modality for HIV/HCV co-infection

It is estimated that 4 to 5 million people are currently co-infected with Human Immunodeficiency Virus (HIV) and Hepatitis C Virus (HCV). HIV/HCV co-infection is associated with unique health risks including increased hepatotoxicity of antiretrovirals, accelerated progression of HCV and liver diseases. The standard interferon-based therapy is effective only in about 50% of patients and often is associated with autoimmune and neuro-psychiatric complications. The treatment of co-infection (HIV/HCV) requires new strategic approaches. To this end, the formulations of an amphiphatic α-helical peptide, a positively charged analog of C5A peptide derived from the HCV NS5A protein, with a reported virocidal activity were prepared by electrostatic coupling with anionic poly(amino acid)-based block copolymers. The self-assembled antiviral peptide nanocomplexes (APN) were ca. 35 nm in size, stable at physiological pH and ionic strength, and retained in vitro antiviral activity against HCV and HIV. Moreover, incorporation of the peptide into APN attenuated its cytotoxicity associated with the positive charge. In vivo APN were able to decrease the viral load in mice transplanted with human lymphocytes and HIV-1-infected. Overall, these findings indicate the potential of these formulations for stabilization and delivery of antiviral peptides while maintaining their functional activity.

Silibinin inhibits HIV-1 infection by reducing cellular activation and proliferation

Purified silymarin-derived natural products from the milk thistle plant (Silybum marianum) block hepatitis C virus (HCV) infection and inhibit T cell proliferation in vitro. An intravenous formulation of silibinin (SIL), a major component of silymarin, displays anti-HCV effects in humans and also inhibits T-cell proliferation in vitro. We show that SIL inhibited replication of HIV-1 in TZM-bl cells, PBMCs, and CEM cells in vitro. SIL suppression of HIV-1 coincided with dose-dependent reductions in actively proliferating CD19+, CD4+, and CD8+ cells, resulting in fewer CD4+ T cells expressing the HIV-1 co-receptors CXCR4 and CCR5. SIL inhibition of T-cell growth was not due to cytotoxicity measured by cell cycle arrest, apoptosis, or necrosis. SIL also blocked induction of the activation markers CD38, HLA-DR, Ki67, and CCR5 on CD4+ T cells. The data suggest that SIL attenuated cellular functions involved in T-cell activation, proliferation, and HIV-1 infection. Silymarin-derived compounds provide cytoprotection by suppressing virus infection, immune activation, and inflammation, and as such may be relevant for both HIV mono-infected and HIV/HCV co-infected subjects.

Challenges for HCV vaccine development in HIV-HCV coinfection

It is estimated that 4-5 million HIV-infected patients are coinfected with HCV. The impact of HIV on the natural course of HCV infection is deleterious. This includes a higher rate of HCV persistence and a faster rate of fibrosis progression. Coinfected patients show poor treatment outcome following standard HCV therapy. Although direct antiviral agents offer new therapeutic options, their use is hindered by potential drug interactions and toxicity in HIV-infected patients under HAART. Overtime, a large reservoir of HCV genotype 1 patients will accumulate in resource poor countries where the hepatitis C treatment is not easily affordable and HIV therapy remains the primary health issue for coinfected individuals. HCV vaccines represent a promising strategy as an adjunct or alternative to current HCV therapy. Here, the authors review the pathogenesis of hepatitis C in HIV-infected patients, with a focus on the impact of HIV on HCV-specific immune responses and discuss the challenges for vaccine development in HIV-HCV coinfection.

Challenges in Providing Treatment and Care for Viral Hepatitis among Individuals Co-Infected with HIV in Resource-Limited Settings

Hepatitis B and C infections are prevalent among HIV-infected individuals with different epidemiologic profiles, modes of transmission, natural histories, and treatments. Southeast Asian countries are classified as "highly prevalent zones," with a rate of hepatitis B and C coinfection in people living with HIV/AIDS of approximately 3.2-11%. Majority of hepatitis B coinfection is of genotype C. Most of the patients infected with hepatitis C in Thailand have genotype 3 which is significantly related to intravenous drug use whereas, in Vietnam, it is genotype 6. The options for antiretroviral drugs are limited and rely on global funds and research facilities. Only HBV treatment is available for free through the national health scheme. Screening tests for HBV and HCV prior to commencing antiretroviral treatment are low. Insufficient concern on hepatitis-virus-related liver malignancy and long-term hepatic morbidities is noted. Cost-effective HCV treatment can be incorporated into the national health program for those who need it by utilizing data obtained from clinical research studies. For example, patients infected with HCV genotype 2/3 with a certain IL-28B polymorphism can be treated with a shorter course of interferon and ribavirin which can also help reduce costs.

PD 404,182 is a virocidal small molecule that disrupts hepatitis C virus and human immunodeficiency virus

We describe a virucidal small molecule, PD 404,182, that is effective against hepatitis C virus (HCV) and human immunodeficiency virus (HIV). The median 50% inhibitory concentrations (IC(50)s) for the antiviral effect of PD 404,182 against HCV and HIV in cell culture are 11 and 1 μM, respectively. The antiviral activity of PD 404,182 is due to the physical disruption of virions that is accompanied to various degrees (depending on the virus and exposure temperature/time) by the release of viral nucleic acids into the surrounding medium. PD 404,182 does not directly lyse liposomal membranes even after extended exposure, and it shows no attenuation in antiviral activity when preincubated with liposomes of various lipid compositions, suggesting that the compound inactivates viruses through interaction with a nonlipid structural component of the virus. The virucidal activity of PD 404,182 appears to be virus specific, as little to no viral inactivation was detected with the enveloped Dengue and Sindbis viruses. PD 404,182 effectively inactivates a broad range of primary isolates of HIV-1 as well as HIV-2 and simian immunodeficiency virus (SIV), and it does not exhibit significant cytotoxicity with multiple human cell lines in vitro (50% cytotoxic concentration, >300 μM). The compound is fully active in cervical fluids, although it exhibits decreased potency in the presence of human serum, retains its full antiviral potency for 8 h when in contact with cells, and is effective against both cell-free and cell-associated HIV. These qualities make PD 404,182 an attractive candidate anti-HIV microbicide for the prevention of HIV transmission through sexual intercourse.