Thymosin-alpha 1 plus interferon-alpha for naive patients with chronic hepatitis C: results of a randomized controlled pilot trial

Thymosin α1 and Its Role in Viral Infectious Diseases: The Mechanism and Clinical Application

Thymosin α1 (Tα1) is an immunostimulatory peptide that is commonly used as an immune enhancer in viral infectious diseases such as hepatitis B, hepatitis C, and acquired immune deficiency syndrome (AIDS). Tα1 can influence the functions of immune cells, such as T cells, B cells, macrophages, and natural killer cells, by interacting with various Toll-like receptors (TLRs). Generally, Tα1 can bind to TLR3/4/9 and activate downstream IRF3 and NF-κB signal pathways, thus promoting the proliferation and activation of target immune cells. Moreover, TLR2 and TLR7 are also associated with Tα1. TLR2/NF-κB, TLR2/p38MAPK, or TLR7/MyD88 signaling pathways are activated by Tα1 to promote the production of various cytokines, thereby enhancing the innate and adaptive immune responses. At present, there are many reports on the clinical application and pharmacological research of Tα1, but there is no systematic review to analyze its exact clinical efficacy in these viral infectious diseases via its modulation of immune function. This review offers an overview and discussion of the characteristics of Tα1, its immunomodulatory properties, the molecular mechanisms underlying its therapeutic effects, and its clinical applications in antiviral therapy.

Interferon α2-Thymosin α1 Fusion Protein (IFNα2-Tα1): A Genetically Engineered Fusion Protein with Enhanced Anticancer and Antiviral Effect

Human interferon α2 (IFNα2) and thymosin α1 (Tα1) are therapeutic proteins used for the treatment of viral infections and different types of cancer. Both IFNα2 and Tα1 show a synergic effect in their activities when used in combination. Furthermore, the therapeutic fusion proteins produced through the genetic fusion of two genes can exhibit several therapeutic functions in one molecule. In this study, we determined the anticancer and antiviral effect of human interferon α2-thymosin α1 fusion protein (IFNα2-Tα1) produced in our laboratory for the first time. The cytotoxic and genotoxic effect of IFNα2-Tα1 was evaluated in HepG2 and MDA-MB-231 cells. The in vitro assays confirmed that IFNα2-Tα1 inhibited the growth of cells more effectively than IFNα2 alone and showed an elevated genotoxic effect. The expression of proapoptotic genes was also significantly enhanced in IFNα2-Tα1-treated cells compared to IFNα2-treated cells. Furthermore, the HCV RNA level was significantly reduced in IFNα2-Tα1-treated HCV-infected Huh7 cells compared to IFNα2-treated cells. The quantitative PCR analysis showed that the expression of various genes, the products of which inhibit HCV replication, was significantly enhanced in IFNα2-Tα1-treated cells compared to IFNα2-treated cells. Our findings demonstrate that IFNα2-Tα1 is more effective than single IFNα2 as an anticancer and antiviral agent.

A Reappraisal of Thymosin Alpha1 in Cancer Therapy

Thymosin alpha1 (Tα1), an endogenous peptide first isolated from the thymic tissue in the mid-sixties, has gained considerable attention for its immunostimulatory activity that led to its application to diverse pathological conditions, including cancer. Studies in animal models and human patients have shown promising results in different types of malignancies, especially when Tα1 was used in combination with other chemo- and immune therapies. For this reason, the advancements in our knowledge on the adjuvant role of Tα1 have moved in parallel with the development of novel cancer therapies in a way that Tα1 was integrated to changing paradigms and protocols, and tested for increased efficacy and safety. Cancer immunotherapy has recently experienced a tremendous boost following the development and clinical application of immune checkpoint inhibitors. By unleashing the full potential of the adaptive immune response, checkpoint inhibitors were expected to be very effective against tumors, but it soon became clear that a widespread and successful application was not straightforward and shortcomings in efficacy and safety clearly emerged. This scenario led to the development of novel concepts in immunotherapy and the design of combination protocols to overcome these limitations, thus opening up novel opportunities for Tα1 application. Herein, we summarize in a historical perspective the use of Tα1 in cancer, with particular reference to melanoma, hepatocellular carcinoma and lung cancer. We will discuss the current limitations of checkpoint inhibitors in clinical practice and the mechanisms at the basis of a potential application of Tα1 in combination protocols.

Thymosin alpha 1: biological activities, applications and genetic engineering production

Thymosin alpha 1 (Tα1), a 28-amino acid peptide, was first described and characterized from calf thymuses in 1977. This peptide can enhance T-cell, dendritic cell (DC) and antibody responses, modulate cytokines and chemokines production and block steroid-induced apoptosis of thymocytes. Due to its pleiotropic biological activities, Tα1 has gained increasing interest in recent years and has been used for the treatment of various diseases in clinic. Accordingly, there is an increasing need for the production of this peptide. So far, Tα1 used in clinic is synthesized using solid phase peptide synthesis. Here, we summarize the genetic engineering methods to produce Tα1 using prokaryotic or eukaryotic expression systems. The effectiveness of these biological products in increasing the secretion of cytokines and in promoting lymphocyte proliferation were investigated in vitro studies. This opens the possibility for biotechnological production of Tα1 for the research and clinical applications.

Thymosin alpha 1 for treatment of hepatitis C virus: promise and proof

The hepatitis C virus (HCV) is a global public health problem, with chronic infection leading to development of cirrhosis, end-stage liver disease and hepatocellular carcinoma (HCC). Treatment of HCV is suboptimal with overall response rates of slightly greater than 50% when patients are treated with pegylated interferon alfa and ribavirin. Thymosin alpha 1 (Talpha1; TA-1) is an immunomodulatory peptide with intrinsic activities that might improve treatment outcomes for HCV by incorporation of this agent in current treatment paradigms. An extensive body of literature supports a possible role for this agent in difficult to treat populations. However, clinical trials to date have failed to conclusively support the role of TA-1 in combination interferon-based therapies. Therefore, the promise of TA-1 adjunctive therapy for HCV remains, but the proof will require investment in large randomized clinical trials of appropriate patient populations.

Thymosin Alpha-1 in Combination with Pegylated Interferon and Ribavirin in Chronic Hepatitis C Patients Who have Failed to Prior Pegylated Interferon and Ribavirin Treatment

Combination therapy with inteferon-alpha and ribavirin is an approved therapy for patients with chronic hepatitis C. However, even with the use of pegylated interferon, response rates are still poor in many difficult-to-treat groups, especially with genotype 1 and high viral loads. Retreatment of these patients remains challenging. Newer combinations are being investigated to optimize chances of attaining a sustained response in these groups. Thymosin alpha 1 is a polypeptide with immunomodulatory properties that has been suggested to increase response rates in patients with chronic hepatitis C. Herein, we describe two cases of retreatment patients with chronic hepatitis C who have failed prior pegylated interferon and ribavirin therapy. They received triple combination therapies of thymosin alpha 1, pegylated interferon and ribavirin and achieved sustained virological responses. These cases support that thymosin-alpha 1 may increase the efficacy of pegylated interferon plus ribavirin in the treatment of non-responders to previous combination therapy.

New treatment strategies against hepatitis C viral infection

Treatment of hepatitis C virus infection is currently based on a combination of pegylated interferon and ribavirin. Because efficacy of this therapy remains suboptimal and side effects sometimes problematic, major efforts have been put forward by scientists and the pharmaceutical industry to develop alternative treatments for this chronic infection. Over the past few years, clinical studies performed with some of these new agents have been presented at major international meetings. The present paper aims to review the rationale underlying the development of these new forms of treatment as well as the current available data concerning their clinical efficacy.

Antiviral treatment of hepatitis C

Therapy of hepatitis C virus (HCV) infection may prevent progression to cirrhosis, hepatocellular carcinoma and end-stage liver disease. The cornerstone of treatment has long been standard IFN-alpha, the use of which was associated with a sustained biochemical and viral response in only a small proportion of patients. More recently, the success of interferon-based regimens has substantially improved due to the combination with the guanosine analogue ribavirin and to the advent of pegylated interferon formulations. However, even the most up-to-date regimens fail to cure the infection in many cases and are limited by side effects and high costs. A better understanding of the HCV genomic organisation, the elucidation of the three-dimensional structures of virally encoded enzymes and the recent development of a HCV-replicon system in human hepatoma (Huh-7) cells have led to significant advances in the development of new antiviral compounds, many of which are under evaluation in clinical trials. The aim of this review is to trace a brief overview of the progress made by interferon-based treatments for hepatitis C since their introduction in the early 1990s, and to highlight the results of recent clinical studies concerning new and emerging drugs.

Thymalfasin for the treatment of chronic hepatitis C infection

Approximately 50% of treatment-naive hepatitis C patients fail to achieve a sustained virologic response with standard peginterferon and ribavirin therapy. Patients who are infected with genotype 1 have high viral loads and are nonresponders to previous therapy, and are even more difficult to treat, underscoring the need for new therapeutic options. Thymalfasin (thymosin-alpha1), in combination with peginterferon-alpha2a, has demonstrated efficacy among difficult-to-treat patients with hepatitis C. The addition of ribavirin to thymalfasin and peginterferon-alpha2a has also exhibited promising results among patients who have genotype 1 hepatitis C, high viral loads and are nonresponders to previous therapy.

[New therapies for hepatitis C]

Hepatitis C virus is an important public health threat, not only because of the high prevalence of this infection in western and third world countries, but also because of the high rate of resistance to the available antiviral therapy that consists on the use of pegylated interferon plus ribavirin. Currently, new forms of therapy are being developed based on a more precise knowledge of the structure and function of the viral proteins and of the strategies used by the virus to escape the immune and interferon systems. The new therapeutic approaches aim at different objectives: a) the inhibition of viral replication by blocking the viral protease and/or replicase; b) the use of other types of interferon with more potent antiviral effect, c) the induction of a specific anti-viral immune response by means of immunomodulatory compounds or therapeutic vaccination, d) the blockade of "de novo" infection of other cells with neutralizing antibodies, e) the induction of a antiviral state in the liver by transferring to this organ the gene of interferon and/or immunostimulating cytokines.

Treatment of chronic hepatitis C in non-responsive patients with pegylated interferon associated with ribavirin and thalidomide: report of six cases of total remission

Hepatitis C virus (HCV) infection is an important public health issue worldwide. It is estimated that over 170 million people are infected with the virus. The present study reports six cases in which patients did not respond to combination therapy with pegylated interferon and ribavirin. However, after the addition of thalidomide to the therapy, the patients presented negative RNA PCR. The use of thalidomide combined with pegylated interferon and ribavirin for the treatment of hepatitis C is described here for the first time in the related literature.

Prospects of vaccines for invasive aspergillosis

Invasive aspergillosis is a disease of immunocompromised hosts and the pathogenesis of this disorder is heavily dependent upon the defect within a given host. Consequently, vaccine development is limited by our understanding of effective host responses and by limitations in our knowledge of fungal molecules that elicit protective immunity. Nonetheless, the past few years have witnessed advances in our understanding both of the immune response to this organism and in the relationship between antigenicity and the ability to confer protection. Manipulations that promote the development of T(H)1-associated responses correlate with increased resistance to disease, at least partly because of consequent enhancement of innate cellular effector function. Two areas of investigation most actively being pursued include the search for adjuvants that will allow products of Aspergillus fumigatus to become effective vaccine candidates, regardless of the form of immunity they ordinarily induce, and the identification of the specific antigens that will most effectively elicit beneficial responses. Strategies using antigen-exposed dendritic cells as adjuvants appear to be particularly promising. Though we currently are far away from a candidate that is applicable for human trials, recent progress is encouraging.

Novel Approaches to New Therapies for Hepatitis B Virus Infection

Hepatitis B is one of the most prevalent viral diseases in the world. It leads to chronic liver disease in 10% of infected individuals, putting them at an increased risk for liver-related morbidity and mortality from complications of cirrhosis and hepatocellular carcinoma. Despite the success of universal hepatitis B vaccination in many countries, this disease remains a major public health problem, resulting in more than 500,000 deaths per year. Although the current therapy for chronic hepatitis B (CHB) is effective, it is not optimal; novel approaches to the management of CHB are needed. An improved understanding of virus-host interactions, advances in gene therapy, the development of molecular therapies targeted at different stages of the hepatitis B virus life cycle, and new insights into various approaches of immune modulation will lead to the development of better therapeutic agents for the management of CHB. These advances herald a new era of combination therapy. In this review, we will discuss emerging therapies and potential mechanisms, and highlight the promises and pitfalls of these new treatment strategies.

N/A

N/A