Future prevention and treatment of chronic hepatitis B infection

Antiviral therapy for the sexually transmitted viruses: recent updates on vaccine development

INTRODUCTION

The sexually transmitted infections (STIs) caused by viruses including human T cell leukemia virus type-1 (HTLV-1), human immunodeficiency virus-1 (HIV-1), human simplex virus-2 (HSV-2), hepatitis C virus (HCV), hepatitis B virus (HBV), and human papillomavirus (HPV) are major public health issues. These infections can cause cancer or result in long-term health problems. Due to high prevalence of STIs, a safe and effective vaccine is required to overcome these fatal viruses.

AREAS COVERED

This review includes a comprehensive overview of the literatures relevant to vaccine development against the sexually transmitted viruses (STVs) using PubMed and Sciencedirect electronic search engines. Herein, we discuss the efforts directed toward development of effective vaccines using different laboratory animal models including mice, guinea pig or non-human primates in preclinical trials, and human in clinical trials with different phases.

EXPERT OPINION

There is no effective FDA approved vaccine against the sexually transmitted viruses (STVs) except for HBV and HPV as prophylactic vaccines. Many attempts are underway to develop vaccines against these viruses. There are several approaches for improving prophylactic or therapeutic vaccines such as heterologous prime/boost immunization, delivery system, administration route, adjuvants, etc. In this line, further studies can be helpful for understanding the immunobiology of STVs in human. Moreover, development of more relevant animal models is a worthy goal to induce effective immune responses in humans.

The natural course of chronic hepatitis B virus infection and its management

Chronic infection with the hepatitis B virus (HBV) runs a long natural course during which underlying changes in liver histology can progress to cirrhosis and hepatic decompensation, as well as to hepatocellular carcinoma. Therapeutic intervention is currently aiming at suppression of HBV replication by applying a number of pharmacological agents. For an optimum use of available therapies, good knowledge of the natural course of chronic infection, as well as of the role played by several viral, host, and environmental factors, is mandatory. The larger part of this chapter deals with how to treat the various subsets of patients with chronic hepatitis B (CHB), using mainly three first-line drugs: pegylated interferon-α2a, entecavir, and tenofovir, administered either in finite courses or indefinitely. The frequency of virological, serological, biochemical, and histological responses in the various subsets of patients, both during and after stopping treatment, is reviewed. It is stressed that the application of the highly potent antivirals entecavir and tenofovir, with acceptable safety records and with a high barrier to HBV resistance, represents major progress in the treatment of CHB. Despite the hitherto important developments in the treatment of viral hepatitis B, clinical cure of chronic HBV infection with HBsAg loss is achievable only in a few treated patients while eradication of HBV infection appears unrealistic. Development of new pharmacological agents acting at multiple targets of the replicative cycle of HBV may achieve higher efficacy and even cure of CHB.

Changes of HBsAg and HBV DNA levels in Chinese chronic hepatitis B patients after 5 years of entecavir treatment

BACKGROUND AND AIM

Hepatitis B surface antigen (HBsAg) kinetics during long-term entecavir therapy has not been well investigated.

METHODS

We described the cumulative serologic, virologic, and biochemical outcomes and the occurrence of signature entecavir mutations among 222 Chinese treatment-naïve chronic hepatitis B (CHB) patients receiving entecavir for up to 5 years.

RESULTS

The median rate of HBsAg reduction over 5 years was 0.125 log IU/mL/year. Patients with high baseline HBV DNA levels (≥ 8 log copies/mL or ≥ 7.3 log IU/mL), when compared with those with baseline hepatitis B virus (HBV) DNA < 7.3 log IU/mL, had a significantly greater median rate of HBsAg reduction (0.178 and 0.102 log IU/mL/year, respectively, P < 0.001). The difference in HBsAg decline was most prominent in the first year (0.324 and 0.062 log IU/mL/year, respectively, P < 0.001). Greater median rates of HBsAg reduction were also found in hepatitis B e antigen (HBeAg)-positive patients when compared with HBeAg-negative patients (0.144 and 0.098 log IU/mL/year, P = 0.015), and in patients with high baseline HBsAg levels (≥ 3 log IU/mL), when compared with patients with low baseline HBsAg < 3 log IU/mL (0.131 and 0.045 log IU/mL/year, respectively, P = 0.001). The 5-year cumulative rate of HBV DNA undetectability (< 20 IU/mL) was 97.1%. There were two cases of entecavir resistance, resulting in a 5-year cumulative resistance rate of 1.2%.

CONCLUSION

In contrast to the profound HBV DNA suppression, long-term entecavir treatment achieved only a slow decline in serum HBsAg. Although certain patient subgroups exhibit a more rapid HBsAg reduction, additional therapeutic agents are needed to increase the chance of HBsAg seroclearance in CHB.

Reduction of hepatitis B surface antigen levels and hepatitis B surface antigen seroclearance in chronic hepatitis B patients receiving 10 years of nucleoside analogue therapy

The profile and clinical significance of serum hepatitis B surface antigen (HBsAg) levels during long-term nucleoside analogue (NA) therapy in chronic hepatitis B (CHB) is undetermined. From 1994 to 2002, 322 Chinese CHB patients were started on lamivudine in our center. Patients were recruited if they were continuously treated with lamivudine for at least 10 years and maintained favorable virologic responses throughout therapy (HBV DNA <2,000 IU/mL). HBsAg and HBV DNA levels were measured serially, and the predictability of HBsAg kinetics in determining NA-related HBsAg seroclearance was determined. Seventy patients were recruited, of which 43 (61.4%) were hepatitis B e antigen (HBeAg)-positive. Fifty-two (74.3%) patients had undetectable viremia (HBV DNA <20 IU/mL) during therapy. Fifteen (21.4%) patients were followed up for 15 years. The median rate of HBsAg reduction was 0.104 log IU/mL/year, with no significant difference found when comparing patients who were HBeAg-positive versus HBeAg-negative, were genotype B versus C, and had detectable versus undetectable viremia during therapy (all P > 0.05). Seven (10%) patients achieved HBsAg seroclearance, and when compared with the remaining 63 patients, had significantly lower median baseline HBsAg levels (P = 0.012) and a greater median rate of HBsAg reduction (P < 0.001). Baseline HBsAg levels and the rate of HBsAg reduction achieved an area under the receiver operating characteristic curve of 0.860 (P = 0.004; 95% confidence interval [CI], 0.742-0.978) and 0.794 (P = 0.018; 95% CI, 0.608-0.979), respectively. Baseline HBsAg <1,000 IU/mL and on-treatment reduction of HBsAg >0.166 log IU/mL/year were optimal cutoff levels in predicting subsequent HBsAg seroclearance (negative predictive values, 98.1% and 97.8%, respectively).

CONCLUSION

Low baseline HBsAg levels and greater rate of HBsAg reduction achieved high predictive values for predicting HBsAg seroclearance, strengthening the prognostic role of HBsAg measurements during NA therapy.