RNA polymerase as an antiviral target of hepatitis C virus

Hepatitis C virus (HCV) infection is emerging as one of the most prevalent viral diseases of medical significance. It afflicts approximately 100 million people worldwide. Although HCV infections are mostly clinically inapparent during the acute stage, the majority of infected patients develop chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. Mainly as a result of ongoing HCV epidemics, the incidence of hepatocellular carcinoma and demands for liver transplantation have increased at a rapid pace in many countries in the last couple of decades. The current therapeutic options for HCV are limited; interferon-alpha (IFN-alpha) alone or IFN plus ribavirin are the only available treatments. Unfortunately, these treatments are efficacious for only a limited number of patients. They are particularly ineffective against genotype 1 HCV, which is the most common genotype in developed countries, including most European countries, the USA and Japan. Therefore, the development of new therapeutic strategies is urgently needed, so that the progression of hepatic diseases in HCV-infected patients can be halted before serious late-stage illnesses manifest themselves. Otherwise, HCV may exact a huge toll on health care budgets and the wellbeing of societies in the ensuing decades.     

Human immunodeficiency virus type 1 entry and chemokine receptors: a new therapeutic target.

After the identification of CD4 as the primary receptor for human immunodeficiency virus (HIV) type 1 entry into cells of the immune system, it soon became clear that CD4 alone was not sufficient to establish a productive infection. The search for the second receptors or co-receptors started over 10 years ago, and it was not until 1996 that G protein-coupled 7-transmembrane receptors, CXCR4 and CCR5 were finally identified as the co-receptors for HIV-1 entry. The 7-transmembrane receptor family is a familiar therapeutic target for a number of diseases, and therefore these recent findings represent an exciting opportunity for new therapeutic approaches to the treatment of HIV-1 infection.     

The herpesvirus proteases as targets for antiviral chemotherapy

Viruses of the family Herpesviridae are responsible for a diverse set of human diseases. The available treatments are largely ineffective, with the exception of a few drugs for treatment of herpes simplex virus (HSV) infections. For several members of this DNA virus family, advances have been made recently in the biochemistry and structural biology of the essential viral protease, revealing common features that may be possible to exploit in the development of a new class of anti-herpesvirus agents. The herpesvirus proteases have been identified as belonging to a unique class of serine protease, with a Ser-His-His catalytic triad. A new, single domain protein fold has been determined by X-ray crystallography for the proteases of at least three different herpesviruses. Also unique for serine proteases, dimerization has been shown to be required for activity of the cytomegalovirus and HSV proteases. The dimerization requirement seriously impacts methods needed for productive, functional analysis and inhibitor discovery. The conserved functional and catalytic properties of the herpesvirus proteases lead to common considerations for this group of proteases in the early phases of inhibitor discovery. In general, classical serine protease inhibitors that react with active site residues do not readily inactivate the herpesvirus proteases. There has been progress however, with activated carbonyls that exploit the selective nucleophilicity of the active site serine. In addition, screening of chemical libraries has yielded novel structures as starting points for drug development. Recent crystal structures of the herpesvirus proteases now allow more direct interpretation of ligand structure-activity relationships. This review first describes basic functional aspects of herpesvirus protease biology and enzymology. Then we discuss inhibitors identified to date and the prospects for their future development.     

High-throughput human immunodeficiency virus type 1 (HIV-1) full replication assay that includes HIV-1 Vif as an antiviral target

Antiviral screens have proved useful for the identification of novel human immunodeficiency virus type 1 (HIV-1) inhibitors. In this study, we describe an HIV-1 full replication (HIV-1 Rep) assay that incorporates all of the targets required for replication in T-cell lines, including the HIV-1 Vif gene. The HIV-1 Rep assay was designed to exhibit optimal sensitivity to late-stage as well as early-stage inhibitors to maximize the likelihood of identification of novel target antiviral compounds in a screen. In addition, the flexibility of the HIV-1 Rep assay allows the rapid evaluation of antiviral compounds against different virus strains in different T-cell lines without significant modification of the assay format. We demonstrate that the HIV-1 Rep assay exhibits characteristics (e.g., a favorable Z' value) compatible with high-throughput screening in a 384-well format. The utility of the HIV-1 Rep assay was demonstrated in a high-throughput screen of >10(6) compounds. To our knowledge, this study represents the first example of an HIV-1 antiviral screen that includes Vif as a functional target and was executed on an industrial scale.     

Human immunodeficiency virus associated anemia.

Anemia in HIV-infected patients is often overshadowed by other disorders associated with this viral disease, but it can markedly contribute to morbidity and limit antiviral therapy. Evaluation of this patient population is difficult because of the probability of a multifactorial etiology and spurious laboratory indicators. Ineffective or reduced erythropoiesis is a hallmark of most anemic HIV-infected patients, leading to usage and continuing research of recombinant hematopoietic cytokine therapy. The continuing explosion in knowledge of this virus, its effects, and treatment possibilities will, hopefully, lead to improved diagnostic and therapeutic options in approaching HIV-associated anemia.     

Telomerase as a novel and potentially selective target for cancer chemotherapy

Telomeres are the structures that protect eukaryotic chromosomes from recognition by DNA damage surveillance mechanisms and are maintained in the germ line of multicellular animals by telomerase. In most human somatic cells telomerase is silenced during development and after extensive cell division telomeres shorten to trigger growth arrest. Around 80% of human cancers escape from this growth arrest by re-activating telomerase but at diagnosis many cancers still have very short telomeres making them very vulnerable to the inhibition of telomerase. As normal cells have a considerable telomere reserve, even in elderly humans, this makes telomerase an attractive and potentially selective anti-cancer drug target. Proof-of-principle experiments are reviewed which show that this optimism may be justified at least for the subset of human cancers with short telomeres. I also address many of the commonly raised concerns that surround telomerase as a target for anti-cancer drug design.     

Telomerase as a novel and potentially selective target for cancer chemotherapy

Telomeres are the structures that protect eukaryotic chromosomes from recognition by DNA damage surveillance mechanisms and are maintained in the germ line of multicellular animals by telomerase. In most human somatic cells telomerase is silenced during development and after extensive cell division telomeres shorten to trigger growth arrest. Around 80% of human cancers escape from this growth arrest by re‐activating telomerase but at diagnosis many cancers still have very short telomeres making them very vulnerable to the inhibition of telomerase. As normal cells have a considerable telomere reserve, even in elderly humans, this makes telomerase an attractive and potentially selective anti‐cancer drug target. Proof‐of‐principle experiments are reviewed which show that this optimism may be justified at least for the subset of human cancers with short telomeres. I also address many of the commonly raised concerns that surround telomerase as a target for anti‐cancer drug design.     

Human immunodeficiency virus infection in elderly patients

BACKGROUND: The proportion of older individuals infected with the human immunodeficiency virus (HIV) is rising. METHODS: We performed a retrospective case-control study of 58 patients more than 60 years old at the time of diagnosis of HIV infection and compared them with 232 controls (matched by CD4+ lymphocyte count). Clinical and demographic data were obtained from the Adult Spectrum of Diseases (ASD) database at the Medical Center of Louisiana. RESULTS: Patients in the older age group were more likely to be male and African American or Hispanic. The most common risk factor for acquisition of HIV infection among the patients was homosexual contact (53%). Disease staging was similar in both groups as determined by CD4+ lymphocyte counts and history of opportunistic infections. There was no difference in the use of antiretroviral therapy. In a Cox proportional hazard model and regression models, age > or = 60 years was associated with shorter survival. CONCLUSION: Patients who are older than 60 years at the time of diagnosis of HIV infection have a shorter survival than younger patients.     

Approaches to gene therapy for human immunodeficiency virus infection

Much progress has been made in developing new and more efficient treatments for human immunodeficiency virus (HIV) infection, the cause of acquired immunodeficiency syndrome (AIDS). However, the scope of the HIV epidemic and the limitations of existing treatments necessitate the continued development of novel treatment strategies. Gene therapy is one such forward-looking strategy. Gene therapy approaches for HIV infection include efforts to interfere with viral replication directly by engineering HIV-resistant cells or indirectly by eliminating infected cells from the body, primarily by eliciting a therapeutic immune response to destroy HIV-infected cells. Although the prospect of gene therapy as a routine treatment for HIV infection remains distant, continuous progress is being made, which should also have implications for gene therapy strategies for a variety of other diseases. This article reviews some of the strategies for investigating the feasibility of gene transfer for the treatment of HIV infection.     

Human immunodeficiency virus and the older person

This article outlines some of the issues which older people who are infected and/or affected by human immunodeficiency virus (HIV) may face. HIV does not discriminate against age, however, clinicians are now seeing an increasing number of HIV positive older people in their everyday practice. This trend is set to continue as HIV becomes more of a chronic health condition as a consequence of more sophisticated treatment regimens. The older population has largely been ignored in the quest to reduce the incidence of HIV infection. This article calls for more research to be conducted taking into account the unique needs of the older population. There is no place in contemporary nursing practice for practitioners to hold erroneous and outdated myths concerning the sexuality and lifestyle choice of the older person.     

Human immunodeficiency virus and the nervous system

In conclusion, there are a number of neurological manifestations of HIV infection, affecting both the central and peripheral nervous systems. Involvement of the CNS may occur very early in the course of infection and manifest itself as an acute aseptic meningitis. HIV encephalopathy is currently the most commonly diagnosed neurologic disorder associated with HIV and may in fact occur as a direct result of HIV infection in the brain. In years to come, HIV encephalopathy may assume epidemic proportions. Thus, nurses and other health care workers will have to be well versed in the major symptoms as well as the subtleties associated with this disease. Any drugs effective in treating these neurologic disorders must be capable of crossing the blood-brain barrier. AZT is currently being evaluated in the treatment of HIV encephalopathy. Only carefully designed prospective studies will define the natural history of neurologic disorders seen with HIV infection, as well as drugs effective in their treatment.     

Human immunodeficiency virus infection, Part II

The acceptance of highly active antiretroviral therapy (HAART) among patients and health care providers has had a dramatic impact on the epidemiology and clinical characteristics of many opportunistic infections associated with human immunodeficiency virus (HIV). Previously intractable opportunistic infections and syndromes are now far less common. In addition, effective antibiotic prophylactic therapies have had a profound impact on the risk of patients developing particular infections and on the incidence of these infections overall. Most notable among these are Pneumocystis carinii, disseminated Mycobacterium avium complex, tuberculosis, and toxoplasmosis. Nevertheless, infections continue to cause significant morbidity and mortality among patients who are infected with HIVThe role of HAART in many clinical situations is unquestioned. Compelling data from clinical trials support the use of these therapies during pregnancy to prevent perinatal transmission of HIV HAART is also recommended for health care workers who have had a ‘significant’ exposure to the blood of an HIV infected patient. Both of these situations are discussed in detail in this article. In addition, although more controversial, increasing evidence supports the use of HAART during the acute HIV seroconversion syndrome. An “umnune reconstitution syndrome” has been newly described for patients in the early phases of treatment with HAART who develop tuberculosis, M avium complex, and cytomegalovirus disease.Accumulating data support the use of hydroxyurea, an agent with a long history in the field of myeloproliferative disorders, for the treatment of HIV Newer agents, particularly abacavir and adefovir dipivoxil, are available through expanded access protocols, and their roles are being defined and clarified.     

Muscle as a target for supplementary factor IX gene transfer

Immune responses to the factor IX (F.IX) transgene product are a concern in gene therapy for the X-linked bleeding disorder hemophilia B. The risk for such responses is determined by several factors, including the vector, target tissue, and others. Previously, we have demonstrated that hepatic gene transfer with adeno-associated viral (AAV) vectors can induce F.IX-specific immune tolerance. Muscle-derived F.IX expression, however, is limited by a local immune response. Here, skeletal muscle was investigated as a target for supplemental gene transfer. Given the low invasiveness of intramuscular injections, this route would be ideal for secondary gene transfer, thereby boosting levels of transgene expression. However, this is feasible only if immune tolerance established by compartmentalization of expression to the liver extends to other sites. Immune tolerance to human F.IX established by prior hepatic AAV-2 gene transfer was maintained after subsequent injection of AAV-1 or adenoviral vector into skeletal muscle, and tolerized mice failed to form antibodies or an interferon (IFN)-gamma(+) T cell response to human F.IX. A sustained increase in systemic transgene expression was obtained for AAV-1, whereas an increase after adenoviral gene transfer was transient. A CD8(+) T cell response specifically against adenovirus-transduced fibers was observed, suggesting that cytotoxic T cell responses against viral antigens were sufficient to eliminate expression in muscle. In summary, the data demonstrate that supplemental F.IX gene transfer to skeletal muscle does not break tolerance achieved by liver-derived expression. The approach is efficacious, if the vector for muscle gene transfer does not express immunogenic viral proteins.