Hepatitis B vaccination and hepatocellular carcinoma rates in boys and girls

Male germ cell-specific RNA binding protein RBMY: a new oncogene explaining male predominance in liver cancer

Male gender is a risk factor for the development of hepatocellular carcinoma (HCC) but the mechanisms are not fully understood. The RNA binding motif gene on the Y chromosome (RBMY), encoding a male germ cell-specific RNA splicing regulator during spermatogenesis, is aberrantly activated in human male liver cancers. This study investigated the in vitro oncogenic effect and the possible mechanism of RBMY in human hepatoma cell line HepG2 and its in vivo effect with regards to the livers of human and transgenic mice. RBMY expression in HepG2 cells was knocked down by RNA interference and the cancer cell phenotype was characterized by soft-agar colony formation and sensitivity to hydrogen-peroxide-induced apoptosis. The results revealed that RBMY knockdown reduced the transformation and anti-apoptotic efficiency of HepG2 cells. The expression of RBMY, androgen receptor (AR) and its inhibitory variant AR45, AR-targeted genes insulin-like growth factor 1 (IGF-1) and insulin-like growth factor binding protein 3 (IGFBP-3) was analyzed by quantitative RT-PCR. Up-regulation of AR45 variant and reduction of IGF-1 and IGFBP-3 expression was only detected in RBMY knockdown cells. Moreover, RBMY positive human male HCC expressed lower level of AR45 as compared to RBMY negative HCC tissues. The oncogenic properties of RBMY were further assessed in a transgenic mouse model. Liver-specific RBMY transgenic mice developed hepatic pre-cancerous lesions, adenoma, and HCC. RBMY also accelerated chemical carcinogen-induced hepatocarcinogenesis in transgenic mice. Collectively, these findings suggest that Y chromosome-specific RBMY is likely involved in the regulation of androgen receptor activity and contributes to male predominance of HCC.

Epidemiology of primary and secondary liver cancers

Primary liver cancer is the sixth most common cancer worldwide with a wide geographic distribution. The incidence of primary liver cancer is increasing and there is still a higher prevalence in developing countries. Early recognition remains an obstacle and lack of it results in poor outcomes for hepatocellular carcinoma (HCC), the most prevalent primary liver cancer, and cholangiocarcinoma. The most common risk factors associated with HCC are hepatitis B and chronic hepatitis C infections, alcohol use, smoking, and aflatoxin exposure. Emerging risk factors such as obesity might play an important role in the future because of the increasing prevalence of this condition.

Hepatocellular carcinoma: prevention and therapy

Hepatocellular carcinoma (HCC) is an aggressive malignancy of the liver and occurs most often in the setting of chronic liver disease. The most common acquired causes for this are chronic viral hepatitis infections (mostly HBV and HCV), and alcohol. Other causes include nonalcoholic fatty liver disease-related nonalcoholic steatohepatitis, autoimmune liver disease, and biliary diseases. In addition, certain heritable diseases like hemochromatosis and α-1-antitrypsin deficiency can also lead to HCC. Therefore, prevention of HCC can be achieved by preventing and controlling these problems. For treatment, curative modalities are surgical resection and liver transplantation. However, most patients are not candidates for these surgical maneuvers, and outcomes are poor. New therapeutic developments have brought some improvement with both local and systemic disease control.

Natural history of chronic hepatitis B REVEALed

Chronic hepatitis B is a worldwide public health challenge. Knowledge of natural history of chronic hepatitis B is important for the management of the disease. A community-based prospective cohort study was carried out to evaluate the risk predictors of progression of chronic hepatitis B in Taiwan. A total of 23,820 participants were enrolled in 1991-1992 from seven townships in Taiwan. Their serum samples were collected at study entry and tested for hepatitis B surface antigen (HBsAg) and e antigen (HBeAg), antibodies against hepatitis C virus (anti-HCV), alanine aminotransferase (ALT), and α-fetoprotein (AFP). A subcohort of 3653 male and female participants who were seropositive for HBsAg and seronegative for anti-HCV was included in the Risk Evaluation of Viral Load Elevation and Associated Liver Disease/Cancer-Hepatitis B Virus (REVEAL-HBV) study. Newly developed cases of cirrhosis and hepatocellular carcinoma (HCC) were ascertained through follow-up examination and data linkage with profiles of the National Cancer Registry, National Health Insurance Database and Death Certification System. The incidence of both HCC and cirrhosis were significantly associated with serum HBV DNA levels in a dose-response relationship from <300 (undetectable) to ≥1,000,000 copies/mL. The biological gradients remained significant (P<0.001) after adjustment for age, sex, habits of cigarette smoking and alcohol drinking, HBeAg serostatus, and serum ALT level at cohort entry. A significant association with risk of cirrhosis and HCC was also observed for HBV genotype, precore G1896A mutant and basal core promoter A1762T/G1764A double mutant. Nomograms have been developed for the long-term risk prediction of cirrhosis and HCC for patients with chronic hepatitis B. Inactive carriers of HBV have an increased HCC incidence and liver-related mortality than HBsAg-seronegative controls. Serum HBV DNA level at study entry is a major predictor of spontaneous seroclearance of HBeAg, HBV DNA and HBsAg. These findings may inform the effective and efficient management of chronic hepatitis B.

Hepatitis B virus and cancer prevention

Prevention of chronic hepatitis B virus (HBV) infection can successfully reduce the incidence of liver cancer. It is the first example of cancer-preventive vaccine in human, which proves that prevention of the infection of an infectious agent can prevent its related cancer.Chronic HBV infection can lead to chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma (HCC). HCC is one of the five major cancers in the world population. Hepatitis B virus (HBV) is the most important etiologic agent of liver cancer globally, particularly in high-prevalence areas of liver cancer.The world's first universal HBV vaccination program was launched in Taiwan in July 1984. It has provided evidences that the prevalence of HBV infection has been reduced remarkably to approximately one-tenth of the original prevalence. Furthermore, reduction of the HCC incidence in children aged 6-14 years have been demonstrated in the vaccinated birth cohorts. Recently, we have further provided evidence that the prevention of HCC by this HBV vaccine extends from childhood to early adulthood.The risk of developing HCC for vaccinated cohorts was associated with incomplete HBV vaccination; prenatal maternal hepatitis B surface antigen (HBsAg) seropositivity; and prenatal maternal HBeAg seropositivity. Failure to prevent HCC results mostly from unsuccessful control of HBV infection by highly infectious mothers. Future strategies to increase the global coverage rate of HBV immunization and to interrupt mother-to- infant transmission may enhance the cancer prevention effect of HBV immunization.

Natural history of hepatitis B virus infection: pediatric perspective

Hepatitis B virus (HBV) infection is an important disease globally. Chronic HBV infection may result in serious complications. Its transmission may be either perinatal or horizontal. Perinatal transmission is particularly important after the implementation of a universal vaccination program. Through either route, chronic carrier status is usually established in early childhood. The course of the disease course is determined by the host-virus interaction. The host's immune system initially tolerates the virus, and then gradually attempts to clear it. The virus, on the other hand, tries to avoid host immune system attack by a strategy involving targeted epitope mutations. By generating mutants, the virus can survive attacks from the host's immune system, enabling the infection to persist. Different individuals have different responses to HBV infection; genetic polymorphisms in cytokines, hormones, and other immune modulators may affect the final outcome of chronic HBV infection. Due to the implementation of a universal infant HBV vaccination program, HBV infection is now under control. Unfortunately, there still are some cases of vaccination failure. Very high maternal viremia, in utero infection, or escape mutants are possible reasons for vaccination failure. Immunocompromised hosts also risk vaccination failure. Blood or organ donors with occult HBV infection are possible sources for immunocompromised hosts. These victims of vaccination failure may exhibit a different disease course due to chronic HBV infection from those who acquired the infection before the universal vaccination era. The achievement of our ultimate goal of HBV elimination depends on a globally effective universal vaccination program, as well as the application of some novel successful medications to control those who are already infected.

Reduction of hepatocellular carcinoma in childhood after introduction of selective vaccination against hepatitis B virus for infants born to HBV carrier mothers

OBJECTIVE

A nation-wide prevention program utilizing passive-active immunoprophylaxis for high-risk babies against maternal HBV transmission was introduced in Japan in January of 1986. The prevention program was expected to eradicate HBV-related hepatocellular carcinoma (HCC). The aim of this study was to evaluate the effect of this selective prevention program against maternal HBV transmission on the occurrence of HBV-related HCC.

METHODS

We reviewed the annual reports from a nation-wide survey of childhood solid tumors that was reported in the Journal of the Japanese Society of Pediatric Surgeons during the 28 years period from 1981 to 2008. The number of HCC cases were grouped for every 5-year period with an additional period of the past 3 years and compared with those of hepatoblastoma.

RESULTS

The reported number of children with hepatoblastoma in each period was constant during the 28 years study period. In contrast, both the number of patients with HBV-related HCC and the ratio of HBV-related HCC to hepatoblastoma gradually decreased over the study period, with a significant drop in the last two periods ranging from 2001 to 2008 (p < 0.001).

CONCLUSION

The prevention program against maternal HBV infection of infants born to HBV carrier mothers may have decreased the occurrence of HBV-related HCC in childhood.

Economic evaluation of infant and adolescent hepatitis B vaccination in the UK

A Markov model of hepatitis B virus (HBV) disease progression in the UK estimated that 81% of predicted HBV-associated morbidity and mortality could be prevented by universal infant vaccination at a cost of approximately £ 260,000 per QALY gained. Universal adolescent vaccination would be less effective (45% prevented) and less cost-effective (£ 493,000 per QALY gained). Higher HBV incidence rates in males and intermediate/high risk ethnic populations meant it was approximately 3 times more cost-effective to vaccinate these groups. At current vaccine costs a selective infant vaccination programme, based on vaccinating intermediate/high risk ethnic populations would not be considered cost effective. The threshold cost per vaccinated child at which the programme would be considered cost-effective was investigated. Universal infant vaccination would be cost-effective if the average cost of vaccinating each child against HBV, including vaccine and administration costs of all doses, was less than £ 4.09. Given the low cost of vaccination required to make a universal programme cost-effective the most feasible policy in the UK would be to use a suitably priced combined vaccine that included the other antigens in the current infant vaccination schedule.

In silico modeling and in vivo efficacy of cancer-preventive vaccinations

Cancer vaccine feasibility would benefit from reducing the number and duration of vaccinations without diminishing efficacy. However, the duration of in vivo studies and the huge number of possible variations in vaccination protocols have discouraged their optimization. In this study, we employed an established mouse model of preventive vaccination using HER-2/neu transgenic mice (BALB-neuT) to validate in silico-designed protocols that reduce the number of vaccinations and optimize efficacy. With biological training, the in silico model captured the overall in vivo behavior and highlighted certain critical issues. First, although vaccinations could be reduced in number without sacrificing efficacy, the intensity of early vaccinations was a key determinant of long-term tumor prevention needed for predictive utility in the model. Second, after vaccinations ended, older mice exhibited more rapid tumor onset and sharper decline in antibody levels than young mice, emphasizing immune aging as a key variable in models of vaccine protocols for elderly individuals. Long-term studies confirmed predictions of in silico modeling in which an immune plateau phase, once reached, could be maintained with a reduced number of vaccinations. Furthermore, that rapid priming in young mice is required for long-term antitumor protection, and that the accuracy of mathematical modeling of early immune responses is critical. Finally, that the design and modeling of cancer vaccines and vaccination protocols must take into account the progressive aging of the immune system, by striving to boost immune responses in elderly hosts. Our results show that an integrated in vivo-in silico approach could improve both mathematical and biological models of cancer immunoprevention.

Hepatitis B vaccination: disease and cancer prevention-a Taiwanese experience

Prevention is most cost effective toward successful control of hepatitis B virus (HBV) infection and its complications. It is particularly urgent where HBV infection and hepatocellular carcinoma (HCC) are prevalent. To achieve better results of primary HCC prevention globally, higher world coverage rates of HBV vaccine, better strategies against breakthrough infection/nonresponder, and good long-term protection are needed. With the universal hepatitis B vaccination program starting from neonates in most countries, HBV infection and its complications will be further reduced in this century. An effective decline in the incidence of HCC in adults is expected in the near future. The concept of a cancer preventive vaccine, using HBV as an example, can be applied further to other infectious agents and their related cancers.

Asian Pacific Association for the Study of the Liver consensus recommendations on hepatocellular carcinoma

INTRODUCTION

The Asian Pacific Association for the Study of the Liver (APASL) convened an international working party on the management of hepatocellular carcinoma (HCC) in December 2008 to develop consensus recommendations.

METHODS

The working party consisted of expert hepatologist, hepatobiliary surgeon, radiologist, and oncologist from Asian-Pacific region, who were requested to make drafts prior to the consensus meeting held at Bali, Indonesia on 4 December 2008. The quality of existing evidence and strength of recommendations were ranked from 1 (highest) to 5 (lowest) and from A (strongest) to D (weakest), respectively, according to the Oxford system of evidence-based approach for developing the consensus statements.

RESULTS

Participants of the consensus meeting assessed the quality of cited studies and assigned grades to the recommendation statements. Finalized recommendations were presented at the fourth APASL single topic conference on viral-related HCC at Bali, Indonesia and approved by the participants of the conference.

Asian Pacific Association for the Study of the Liver consensus recommendations on hepatocellular carcinoma

INTRODUCTION

The Asian Pacific Association for the Study of the Liver (APASL) convened an international working party on the management of hepatocellular carcinoma (HCC) in December 2008 to develop consensus recommendations.

METHODS

The working party consisted of expert hepatologist, hepatobiliary surgeon, radiologist, and oncologist from Asian-Pacific region, who were requested to make drafts prior to the consensus meeting held at Bali, Indonesia on 4 December 2008. The quality of existing evidence and strength of recommendations were ranked from 1 (highest) to 5 (lowest) and from A (strongest) to D (weakest), respectively, according to the Oxford system of evidence-based approach for developing the consensus statements.

RESULTS

Participants of the consensus meeting assessed the quality of cited studies and assigned grades to the recommendation statements. Finalized recommendations were presented at the fourth APASL single topic conference on viral-related HCC at Bali, Indonesia and approved by the participants of the conference.

HEPATITIS B AND PREGNANCY, THE SCIENTIFIC BASIS FOR PERINATAL PREVENTION

Hepatitis B and its complications are one of the major global health problems. Around 2 billion individuals are infected by hepatitis B virus (HBV) worldwide, more than 350 million are chronically infected, and approximately 15 to 40 percents of them will develop serious complications such as liver cirrhosis, hepatic failure, or hepatocellular carcinoma (HCC). The worldwide prevalence of chronic HBV infection ranges from 0.1 to 20 percent and varies widely in different geographic areas. According to the prevalence rate, WHO has classified countries into 3 levels: high areas (>8%) such as Africa, Asia, Western Pacific and Middle East; intermediate areas (2–8%) such as South America and Eastern Europe, and low areas (<2%) such as Western Europe, North America, and Australia.

Effect of puberty onset on spontaneous hepatitis B virus e antigen seroconversion in men

BACKGROUND

Male predominance is a remarkable phenomenon in hepatitis B virus (HBV)-related liver disease. This study elucidated the effects of puberty on spontaneous hepatitis B virus e antigen (HBeAg) seroconversion in boys.

METHODS

One-hundred HBeAg-positive chronic HBV-infected males recruited at younger than 10 years of age who had been followed for >10 years were selected randomly from our long-term followed cohort into this study. Serum testosterone levels, androgen receptor exon-1 CAG repeat number and steroid 5alpha reductase type II (SRD5A2, valine vs leucine alleles) polymorphism were determined. Serial clinical data, HBV genotype, and spontaneous HBeAg seroconversion age were also analyzed.

RESULTS

Seventy-two subjects had spontaneous HBeAg seroconversion during the follow-up period. Subjects with serum testosterone levels > or =2.5 ng/mL at 15 years old (earlier-onset puberty, n = 87) had earlier HBeAg seroconversion (median age, 13.2 vs 22.5 years; hazard ratio = 2.95; P = .005), higher peak alanine aminotransferase levels when HBeAg positive (305.7 +/- 372.7 vs 154.8 +/- 126.0 IU/L; P = .006), and a greater HBV viral load reduction from 10 to 20 years of age (1.6 +/- 2.4 vs 0.2 +/- 1.4 log10 copies/mL; P = .009) than those with serum testosterone levels <2.5 ng/mL (later-onset puberty, n = 13). Valine allele carrier at the SRD5A2 V89L polymorphism was also associated with earlier spontaneous HBeAg seroconversion (median age, 11.7 vs 18.7 years; hazard ratio = 1.88; P = .028).

CONCLUSION

Earlier-onset puberty and increased SRD5A2 enzyme activity are associated with earlier HBeAg seroconversion, higher serum alanine aminotransferase levels, and a greater HBV viral load decrement in chronic HBV infected males.

Management of hepatocellular carcinoma in Asia: consensus statement from the Asian Oncology Summit 2009

Asia has a disproportionately large share of the world's hepatocellular carcinoma (HCC), mainly because of the endemic status of chronic hepatitis B and C viruses, which leads to liver cirrhosis and an increased risk of HCC. This etiological factor presents important opportunities for prevention, early detection, diagnosis, and treatment of HCC. This consensus statement reviews the available medical evidence for management of HCC in Asia, and gives treatment recommendations that are adapted to resource availability in this diverse region with disparate health-care delivery systems.

[Hepatitis B vaccination: a major player in the control of primary liver cancer]

In worst cases, chronic hepatitis B ultimately leads to primary liver cancer. Populations the more at risk to develop hepatocellular carcinoma (HCC), i.e. patients infected perinatally, reside essentially in Asia. A quarter of century after its introduction in medical practice, data coming from Eastern Asia demonstrate a strong impact of the vaccine on HCC incidence. Strikingly, universal immunization of Taiwanese newborns reduced fourfold pediatric HCC incidence. However, residual cases still appear though among children infected at birth by HBe antigen-carrying mothers. Epidemiologic models indicate that the continuation of universal vaccination policy will reduce chronic hepatitis B endemicity 50-fold in three generations. Recently, mutant forms of HBV potentially escaping to vaccine appeared as a potential consequence of large-scale vaccination. Finally, lack of early immunization of newborns in developing countries still represents a major limitation to the progresses against liver cancer.

Control of hepatocellular carcinoma through hepatitis B vaccination in areas of high endemicity: perspectives for global liver cancer prevention

There are approximately 360 millions chronic carriers of Hepatitis B virus worldwide. Patterns of HB carriage are variable from one region to the other. Regions with rates of carriage over 8% are commonly considered as "high endemicity" regions. HB carriers have a very significant lifetime risk of developing chronic liver diseases such as cirrhosis and/or liver cancer (hepatocellular carcinoma, HCC). An efficient HB vaccine is available since the early eighties and has been used since for universal infant vaccination in regions of high endemicity. Observations from Taiwan, where universal infant vaccination was introduced from 1984, show a remarkable, long-lasting protection against carriage and reduction of HCC rates in adolescent and young adults born after the initiation of the programme. Two population-based trials have been set up in the mid-eighties to evaluate lifelong protective effects of infant HB vaccine against liver cancer, in The Gambia (West Africa) and in the area of Qidong, China. In other high-endemicity regions of Asia and Africa, universal infants vaccination has consistently showed a long-lasting high protection against chronic carriage and this is expected to lead to a dramatic decrease of chronic liver disease and liver cancer within the next decades. Here we briefly review the lessons of vaccination programmes and trials in high-endemicity regions, based on data gathered during 15-20years of implementation.

Prevention of hepatocellular carcinoma in hepatitis B virus infection

Chronic hepatitis B is the main risk factor for hepatocellular carcinoma (HCC) in Asia. The most important preventive strategy's adoption of the universal hepatitis B vaccination program is now in its third decade. There is a clear reduction in both chronic hepatitis B virus (HBV) infection (hepatitis B surface antigen "carriage") but also in childhood HCC in Taiwan. An outstanding concern is variability in vaccine coverage between countries. For patients with chronic hepatitis B, serum HBV DNA levels have emerged as the key risk factor for development of HCC. The initial treatment for chronic hepatitis B was interferon. One randomized control trial, and several case-control or cohort studies have shown benefits for preventing HCC, particularly in cirrhotic patients who responded to therapy. With nucleos(t)ide analogs, the most important study has been the Asian Cirrhosis Lamivudine multicenter randomized controlled trial. This showed that lamivudine can reduce disease progression in HBV-related cirrhosis, including an approximately 50% decrease in HCC incidence. Such efficacy was achieved despite emergence of drug resistance in approximately 50% of cases. Case-control studies have suggested that hepatitis B cases without cirrhosis may also benefit. In conclusion, it is now possible to prevent HBV-related HCC. The most effective method is hepatitis B vaccination, which prevents chronic HBV infection and chronic liver disease resulting therefrom. Interferon therapy appears to confer benefit but the evidence is weaker. First-generation oral antiviral (lamivudine) reduces HCC risk, particularly in cirrhotics. Long-term outcome data with newer, more potent HBV antivirals that have a higher genetic barrier to drug resistance are eagerly awaited.

Immune therapy for cancer

Over the past decade, immune therapy has become a standard treatment for a variety of cancers. Monoclonal antibodies, immune adjuvants, and vaccines against oncogenic viruses are now well-established cancer therapies. Immune modulation is a principal element of supportive care for many high-dose chemotherapy regimens. In addition, immune activation is now appreciated as central to the therapeutic mechanism of bone marrow transplantation for hematologic malignancies. Advances in our understanding of the molecular interactions between tumors and the immune system have led to many novel investigational therapies and continue to inform efforts for devising more potent therapeutics. Novel approaches to immune-based cancer treatment strive to augment antitumor immune responses by expanding tumor-reactive T cells, providing exogenous immune-activating stimuli, and antagonizing regulatory pathways that induce immune tolerance. The future of immune therapy for cancer is likely to combine many of these approaches to generate more effective treatments.

Non-AIDS-defining malignancies in HIV-infected persons: etiologic puzzles, epidemiologic perils, prevention opportunities

Non-AIDS-defining malignancies have come to represent a growing fraction of the overall cancer burden in HIV-infected people, as improvements in HIV therapy prolong survival and reduce the incidence of AIDS-associated cancers. This review focuses on five non-AIDS-defining malignancies for which HIV-infected persons have an elevated risk, for which risk is substantial or increasing over time, and for which HIV infection may play an etiologic role. Among HIV-infected persons, lung cancer risk is high, in part due to frequent tobacco use in this population. Risks of anal cancer and liver cancer are also elevated, related to the high prevalence of infections with human papillomavirus and hepatitis B and C viruses. In addition, risk is elevated for Hodgkin lymphoma and several rare skin cancers, including Merkel cell carcinoma and sebaceous carcinoma. For anal cancer and Hodgkin lymphoma, it is particularly concerning that incidence in HIV-infected persons has risen in recent years, when highly active antiretroviral therapy has been available. Accumulating evidence supports the possibility that the high prevalence of known carcinogenic exposures (e.g., tobacco) and infections with oncogenic viruses does not completely explain the occurrence of these cancers. Indeed, HIV may act to increase the risk for each of these five non-AIDS-defining malignancies, although the mechanisms may vary, including immunosuppression, immune reconstitution, and chronic inflammation. These non-AIDS-defining cancers also present important opportunities for prevention (e.g., smoking cessation), screening (e.g., periodic anal Pap smear screening), and early detection.

Patterns of hepatoblastoma and hepatocellular carcinoma in children after universal hepatitis B vaccination in taiwan: a report from a single institution in southern Taiwan

BACKGROUND

To retrospectively evaluate clinical features, treatment, and outcome of patients with hepatoblastoma (HB) and hepatocellular carcinoma (HCC).

METHODS

From January 1994 to December 2007, 16 patients of HB and 13 cases of HCC were reviewed.

RESULTS

The mean age of HB patients was much younger than HCC patients (1.2 vs. 11.5 y). There was an 84.6% positive rate for hepatitis B surface antigen in HCC, but none for HB. Mean serum alpha-fetoprotein level was higher with HCC (654,158 ng/mL) than the HB patients (352,843 ng/mL), especially higher in HCC with lung metastasis. Among the HB patients, 12 (75%) had thrombocytosis and 6 (37.5%) had microcytic anemia with high or normal ferritin, whereas only 3 of 13 with HCC (23.1%) had thrombocytosis and none had microcytic anemia. All HBs were resectable either before or after chemotherapy, but only 4 (30.8%) HCCs were resectable. Five-year disease-free survival rate was significantly higher in HB (87%) than in HCC (30%, P<0.001).

CONCLUSIONS

Hepatitis B infection was still the most important factor associated with HCC in children even after the national vaccination program against hepatitis B. Extreme thrombocytosis, anemia, alpha-fetoprotein levels are important factors associated with difference in long-term outcomes in children with HB and HCC.

Increased childhood liver cancer mortality and arsenic in drinking water in northern Chile

Arsenic in drinking water is an established cause of lung, bladder, and skin cancers in adults and may also cause adult kidney and liver cancers. Some evidence for these effects originated from region II of Chile, which had a period of elevated arsenic levels in drinking water, in particular from 1958 to 1970. This unique exposure scenario provides a rare opportunity to investigate the effects of early-life arsenic exposure on childhood mortality; to our knowledge, this is the first study of childhood cancer mortality and high concentrations of arsenic in drinking water. In this article, we compare cancer mortality rates under the age of 20 in region II during 1950 to 2000 with those of unexposed region V, dividing subjects into those born before, during, or after the peak exposure period. Mortality from the most common childhood cancers, leukemia and brain cancer, was not increased in the exposed population. However, we found that childhood liver cancer mortality occurred at higher rates than expected. For those exposed as young children, liver cancer mortality between ages 0 and 19 was especially high: the relative risk (RR) for males born during this period was 8.9 [95% confidence interval (95% CI), 1.7-45.8; P = 0.009]; for females, the corresponding RR was 14.1 (95% CI, 1.6-126; P = 0.018); and for males and females pooled, the RR was 10.6 (95% CI, 2.9-39.2; P < 0.001). These findings suggest that exposure to arsenic in drinking water during early childhood may result in an increase in childhood liver cancer mortality.

Hepatocellular carcinoma in viral hepatitis: improving standard therapy

Hepatocellular carcinoma (HCC) is a common malignancy worldwide, and its incidence is increasing in the United States and elsewhere. The prognosis of HCC patients depends not only on tumour stage but also on the background liver function reservoir. Current options for the treatment of HCC are surgical resection, liver transplantation, transcatheter arterial embolization, chemotherapy, and percutaneous ablation therapy. The choice of optimal treatment for individual patients, especially those at an earlier cancer stage, is sometimes controversial. Short-term prognosis of HCC patients has been much improved recently due to advances in early diagnosis and treatment, although long-term prognosis is as yet far from satisfactory as indicated by the overall survival at 10 years after apparently curative treatment of only 22-35%. Prevention of HCC recurrence, or tertiary prevention, is one of the most challenging tasks in current hepatology.

Cancer prevention by vaccination against hepatitis B

Chronic inflammation caused by persistent infection is closely related to a number of cancers; these include hepatitis B (HBV) or C and hepatoma, human papilloma virus and cervical cancer, and Helicobacter pylori and gastric cancer. The first evidence of cancer prevention by vaccination in humans was provided by HBV vaccination in infants. Chronic HBV is related to approximately 60%-90% of hepatocellular carcinomas (HCC) in adults and nearly 100% of childhood HCC in areas endemic for HBV infection. The first universal HBV vaccination program was launched in Taiwan and has continued for more than 20 years. Three or four doses of HBV vaccine were given to all infants starting from the first week of life. In addition, infants of high-risk mothers (with positive hepatitis B e antigen or high HBsAg titers) were given hepatitis B immunoglobulin within 24 h after birth. At 20 years after the launch of the HBV vaccination program in Taiwan, chronic HBV infection (HBsAg seropositive) rates in the general population below 20 years of age have revealed a remarkable reduction from 10%-17% before the vaccination program to 0.7%-1.7% after the program. HCC incidence rate in children 6-14 years old also fell from 0.52-0.54 to 0.13-0.20 per 100,000 (R.R. = 0.25-0.36). HCC prevention failure is mainly related to vaccine failure to prevent chronic HBV infection. The causes of vaccine failure have included intrauterine infection, vaccine escape mutants, genetic hyporesponsiveness, and poor compliance. Future efforts to reduce vaccine failure will improve the efficacy of liver cancer prevention by HBV vaccination. The experience of HCC prevention by HBV immunization may be applied to the prevention of other infection-related cancers.

Systemic therapy of hepatocellular carcinoma: are we making progress?

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide and the third most common cause of cancer deaths. Surgical resection, with or without transplantation, can result in long-term survival. However, surgery can only be performed in about 15% of patients with HCC and the 5-year survival rate is only approximately 33%-50% after potentially curative resection. Percutaneous ethanol injection, radiofrequency ablation, and transarterial chemoembolization are invasive techniques that have shown efficacy in reducing tumor bulk. Similarly, systemic chemotherapy may induce tumor responses, but a survival benefit has not been clearly demonstrated. In addition, the lack of efficacy of antiandrogens, tamoxifen, and single-agent interferon has now been confirmed.Sorafenib is a multikinase inhibitor with antiangiogenic, proapoptotic, and Raf kinase inhibitory activity. In a large, multicenter, randomized, phase 3 trial there was a significant improvement in both time to disease progression and overall survival with sorafenib compared with placebo. Sorafenib is the first agent to demonstrate a consistent improvement in overall survival for patients with advanced HCC. Further studies are required to determine the role of other molecular-targeted therapies, either alone or in combination with sorafenib in patients with advanced HCC. Further studies are also required to determine the role of sorafenib in combination with locoregional therapies (eg, transarterial chemoembolization), and the role of sorafenib as adjuvant therapy following surgery.

Management of combined hepatocellular and cholangiocarcinoma

Combined hepatocellular-cholangiocarcinoma (cHCC-CC) is a rare primary liver malignancy composed of cells with histopathological features of both cholangiocarcinoma (CC) and hepatocellular carcinoma (HCC). It reportedly accounts for 0.4-14.2% of all primary liver carcinomas, with incidence varying in different regions. The clinical features are similar to those of either HCC or CC. Preoperative noninvasive diagnosis of cHCC-CC with conventional radiography is difficult. Because the origin of cHCC-CC is from two different tumour entities, despite intensive preoperative imaging studies, most studied patients were misdiagnosed either as HCC or CC. Accurate preoperative diagnosis is important because the most appropriate treatment depends on the major component of the tumour (HCC or CC). A high index of suspicion, imaging studies (ultrasound, computed tomography, positron emission tomography), levels of serum tumour markers (alpha-fetoprotein, carbohydrate antigen 19-9), and histology assist case detection and treatment choice. Patients who qualify for surgery should have a partial hepatectomy with hilar lymph node dissection, which can result in 5-year survival rates exceeding 50%. The role of liver transplantation is not yet known.

Metabolic factors and risk of hepatocellular carcinoma by chronic hepatitis B/C infection: a follow-up study in Taiwan

BACKGROUND & AIMS

This study investigated whether obesity, diabetes, and other metabolic factors are independently associated with hepatocellular carcinoma (HCC), stratified by hepatitis B virus (HBV) and hepatitis C virus (HCV) serostatus, and explored the possible joint influence of obesity/diabetes and HBV/HCV infections on the risk of HCC.

METHODS

A total of 23,820 residents in Taiwan were recruited and followed up for 14 years. All analyses were stratified by hepatitis B surface antigen (HBsAg) and antibody to HCV (anti-HCV) at enrollment, and 218 subjects positive for both seromarkers were excluded. Incident HCC cases were identified via linkage to the national cancer registry. Multivariate-adjusted relative risk (RR(a)) and 95% confidence interval (95% CI) were estimated using Cox proportional hazards models.

RESULTS

Extreme obesity (body mass index >or=30 kg/m(2)) was independently associated with a 4-fold risk of HCC (RR(a), 4.13; 95% CI, 1.38-12.4) among anti-HCV-seropositive subjects and a 2-fold risk (RR(a), 2.36; 95% CI, 0.91-6.17) in persons without HBV and HCV infections, after controlling for other metabolic components, but not in HBsAg-seropositive subjects (RR(a), 1.36; 95% CI, 0.64-2.89). Diabetes was associated with HCC in all 3 groups, with the highest risk in those with HCV infection (RR(a), 3.52; 95% CI, 1.29-9.24) and lowest in HBV carriers (RR(a), 2.27; 95% CI, 1.10-4.66). We found more than 100-fold increased risk in HBV or HCV carriers with both obesity and diabetes, indicating synergistic effects of metabolic factors and hepatitis.

CONCLUSIONS

The finding that both obesity and diabetes are predictors of HCC risk, possibly differently depending on HBV and HCV infection status, may shed some light in preventing HCC.

National incidence of percutaneous injury in Taiwan healthcare workers

We established a standardized surveillance system using the Chinese Exposure Prevention Information Network to estimate the frequency of percutaneous injuries (PCIs) in Taiwanese healthcare workers (HCWs). Fourteen hospitals employing 8,132 HCWs participated and a total of 583 PCIs were reported. The annual number was estimated to be 8,058 PCIs per hospital size, 8,100 per HCWs, and 8,286 per inpatient-day; indicating similar estimates using different denominators. The estimated annual frequency of pathogen-specific PCIs was 1,168 for hepatitis B, 1,263 for hepatitis C, and 59 for HIV. This study documents the annual incidence of PCI among HCWs showing important potential exposure to viral hepatitis and HIV in Taiwan.

High-dimensional biology to comprehend hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide and is the third leading cause of death from cancer. The diverse etiology, high morbidity/mortality, lack of diagnostic markers for early diagnosis and the highly variable clinical course of HCC have hindered advances in diagnosis and treatment. Microsatellite instability, chromosomal aberrations, mutations in key cell cycle genes and epigenetic changes have been reported in HCC. Availability of modern technologies advance 'high-dimensional biology' (HDB), a term that refers to the simultaneous study of the genetic variants (genome), transcription (mRNA; transcriptome), peptides and proteins (proteomics), and metabolites (metabolomics) for the intermediate products of metabolism of an organ, tissue or organism. The growing interest in omics-based research has enabled the simultaneous examination of thousands of genes, transcripts and proteins of interest, with high-throughput techniques and advanced analytical tools for data analysis. The use of each approach towards functional omics has lead to the classification of HCC into molecular subgroups. Here we review the use of HDB as a tool for the identification of markers for screening, diagnosis, molecular classification and the discovery of new therapeutic drug targets of HCC. With the extensive use of HDB, it may be possible in the near future, to have custom-made therapeutic regimens for HCC based on the molecular subtype, ultimately leading to an improved survival of HCC patients.

Hepatocarcinoma in viral and metabolic liver disease

It is becoming increasingly evident that children, like adults, with chronic viral or metabolic liver diseases are at risk for the development of hepatocarcinoma. The aims of this article are to review the risk factors for hepatocarcinoma in chronic viral or metabolic liver disease, outline potential pathogenic mechanisms of hepatocarcinoma, and describe surveillance strategies, clinical evaluation, and management of hepatocarcinoma in children.

Hepatitis B virus infection contributes to oxidative stress in a population exposed to aflatoxin B1 and high-risk for hepatocellular carcinoma

Biomarkers of hepatitis B virus (HBV) infection, aflatoxin B1 (AFB1) exposure and oxidative stress were detected in 71 hepatocellular carcinoma (HCC) patients and 694 controls from southern China. Plasma level of AFB1-albumin-adducts (AAA) and protein carbonyl content (PCC) were significantly higher in the 71 HCC cases than in any age/gender matched HBV sero-status groups (p<0.001). HCC patients positive for the p53-249 G-T mutation had a marginally higher level of PCC than those negative for the mutation (p=0.077). HBV infection had a prominent influence on the association between AFB1 exposure and oxidative stress biomarkers in the controls. Our study indicates a significant contribution from HBV infection to oxidative stress in a population with AFB1 exposure which might substantially increase risk for HCC in this region.

Hepatitis B virus infection among pregnant women in Taiwan: comparison between women born in Taiwan and other southeast countries

BACKGROUND

Taiwan's national vaccination program has successfully decreased the prevalence of hepatitis B infection after twenty years of implementation and might be indirectly beneficial to the second generation. In this study, we compared the hepatitis B infection status of two groups: pregnant Taiwanese women and other Southeast Asian women, who because they had immigrated later in life to Taiwan by marriage to a Taiwanese man, had not been exposed to that vaccination program to evaluate the effect of hepatitis vaccination program on women of child-bearing age and further explored the potential impact of immigration on the hepatitis B public health policy in Taiwan.

METHODS

Data was collected from 10,327 women born in Taiwan and 1,418 women born in other Southeast Asian countries, both groups receiving prenatal examinations at Fooyin University Hospital between 1996 and 2005. The results of serum hepatitis B s-Antigen (HBsAg) and hepatitis B e-Antigen (HBeAg) tests and other demographic data were obtained by medical chart review.

RESULTS

The pregnant women from Taiwan had a higher HBsAg positive rate (15.5%) but lower HBeAg(+)/HBsAg(+) ratio (32.1%) than the women from other countries (8.9% and 52.4%). For those born before July, 1984, the period of no national vaccination program, Taiwanese women had a higher HBsAg positive rate than other Southeast Asian women (15.7% vs. 8.4%), but for women born after that day and before June 1986, the period of vaccination for high risk newborns, the HBsAg positive rates found to be slightly lower for Taiwanese women than for other Southeast Asian women (11.4% vs. 12.3%) and the difference was more significant (3.1% vs. 28.6%) after June 1986, the period of vaccination for all newborns. While the HBeAg(+)/HBsAg(+) ratios decreased with age in both groups, they were consistently higher in women from other Southeast Asian countries than in women born in Taiwan after age 20.

CONCLUSION

In Taiwan, the neonatal vaccination program that was implemented in 1984 has successfully reduced hepatitis B infection among pregnant women in present day, and is likely to indirectly prevent hepatitis B infection in the next generation. However, the increasing number of pregnant women from other Southeast Asian countries without a national neonatal vaccination program or with a program that was introduced later than the one in Taiwan will likely lessen the positive impact of this program and should be further assessed.

Pediatric liver tumors: initial presentation, image finding and outcome

BACKGROUND

Few reports have been carried out on the characteristics of pediatric liver tumors.

METHODS

A retrospective study of 57 patients diagnosed with liver tumors from 1989 through 2004 was conducted. They were classified into groups; 10 benign, 33 primary malignant and 14 metastatic liver tumors. Their demographics, initial presentations, laboratory data, image findings and outcomes were investigated and compared.

RESULTS

Hepatocellular carcinoma (HCC) with 91% hepatitis B virus-related, constituted 23 of 33 primary malignant liver tumors and had the poorest survival rate. Initially, 70% of patients with primary malignant liver tumors were at disseminated stages. All of HCC and 88% of hepatoblastoma had elevated serum levels of aphal-fetoprotein. However, abnormal liver function tests as alanine aminotransferase, total bilirubin, albumin and alkaline phosphatase were uncommon in patients with pediatric liver tumors. Metastatic liver tumors compared with primary malignant liver tumors showed hypo-echogenicity in abdominal ultrasound (US) exam and a lesser presence of vessel invasion and contrast enhancement in computed tomography studies (P < 0.01).

CONCLUSIONS

It is important to diagnose primary malignant liver tumors before their clinical symptoms and signs develop. Children with chronic hepatitis B virus infection must be followed every 6 months by serum aphal-fetoprotein and abdominal US even when their liver function tests are normal. Image studies with abdominal US and computed tomography scan can differentiate between primary and metastatic liver tumors.

Seroepidemiology of hepatitis B virus infection among children in Mongolia: results of a nationwide survey

BACKGROUND

Because Mongolia is one of the highly endemic countries for hepatitis B virus (HBV) infection in the world, hepatitis B (HB) vaccine was introduced into the National Expanded Program on Immunization in 1991. However, relatively few data are available concerning HBV infection among children born after the start of the program, so far. The aim of the present paper was to describe the seroepidemiology of HBV infection among primary school children using representative national data.

METHODS

In 2004, a nationwide school-based cross-sectional serosurvey was carried out throughout Mongolia, covering both urban and rural areas. Serum samples were tested for hepatitis B surface antigen (HBsAg), antibody to hepatitis B core antigen (anti-HBc) and hepatitis B e antigen (HBeAg) as well as for liver enzymes.

RESULTS

A total of 1145 children aged 7-12 years were studied, which represents nearly 2% of the second grade population of elementary schools in Mongolia. The overall prevalence of HBsAg and anti-HBc was 5.2% (95% confidence interval [CI]: 3.9-6.5%) and 15.6% (95%CI: 13.5-17.7%), respectively. Among HBsAg-positive children 67.8% (95%CI: 55.9-79.7%) were also positive for HBeAg. The prevalence of chronic HBV infection increased by age and was significantly higher among children from rural areas compared to those from urban areas (7.7% vs 3.0%; P < 0.001). In the multivariate logistic regression analysis, rural residence (odds ratio [OR]: 2.57; 95%CI: 1.45-4.58), male sex (OR: 1.9; 95%CI: 1.08-3.26) and age (OR: 1.5; 95%CI: 1.10-2.05) were independent demographic predictors for chronic HBV infection.

CONCLUSIONS

The prevalence of chronic HBV infection has been decreasing in the Mongolian young generation, most likely due to infant HB vaccination. However, significant rural-urban differences in the prevalence of HBV infection were found that demand further investigation to estimate the potential causes.

Impact of the universal hepatitis B immunization program in Mongolia: achievements and challenges

BACKGROUND

The impact of the universal infant hepatitis B (HB) immunization program initiated in 1991 in Mongolia is still unclear.

METHODS

A nationwide school-based cross-sectional serosurvey was conducted in 2004, with stratified, multistage, random cluster sampling from all public elementary schools (n=593) in Mongolia. All children were tested for serological markers of hepatitis B virus (HBV).

RESULTS

Serology results were available for 1,145 children (592 boys and 553 girls) aged 7-12 years (survey response rate: 93%). Immunization card was available for 702 (61.3%) children. The coverage of complete HB vaccination was 60.1% and it was increased by birth cohort from 44% to 76%. Significantly higher proportion of children in Metropolitan cities (75.2%) was completely vaccinated with HB compared to those in Province centers (55.7%) and rural areas (59.1%). HBV infection occurred in 5.9%, 13.2%, and 20.8% of complete vaccinees living in Metropolitan, Province centers, and rural areas, respectively; of whom 1.2%, 2.9%, and 8.6% were HB surface antigen (HBsAg) carriers, respectively. Only 17.0% of the children had protective anti-HBs which decreased from 31.1% to 16.3% among 7 to 12-year-olds indicating its decay with time.

CONCLUSIONS

Prevalence of HBV infection and carriage among young generation meaningfully declined compared with those of previous studies in Mongolia. The coverage of birth dose and complete HB vaccination was significantly low in Province centers and rural areas which should be taken into consideration.

Trends in childhood cancer incidence: review of environmental linkages

Cancer in children is rare and accounts for about 1% of all malignancies. In the developed world, however, it is the commonest cause of disease-related deaths in childhood, carrying with it a great economic and emotional cost. Cancers are assumed to be multivariate, multifactorial diseases that occur when a complex and prolonged process involving genetic and environmental factors interact in a multistage sequence. This article explores the available evidence for this process, primarily from the environmental linkages perspective but including some evidence of the genetic factors.

Natural history of chronic hepatitis B virus infection in children of different ethnic origins: a cohort study with up to 12 years' follow-up in northern Greece

AIM

To investigate the mode of transmission and the natural history of chronic hepatitis B virus (HBV) infection in children of different ethnicities in Greece. This study was part of the Interreg I-II EC project.

PATIENTS AND METHODS

One hundred seventy-three hepatitis B surface antigen (HBsAg)(+) carriers, median age 6.9 (5-12) y, were prospectively followed-up for a mean period of 5.3 (1-12) y for serological markers of HBV infection, serum alanine aminotransferase (ALT), HBV-DNA, alpha-fetoprotein levels and ultrasonography.

RESULTS

Vertical transmission predominates (61.8%) in Moslem children and horizontal (44%) in those born in Russia. At entry, 73 of 173 (42%) HBsAg(+) genotype D children were hepatitis B e antigen (HBeAg)(+), ranging from 27% to 67% among ethnic groups; 55 of 173 (32%) had ALT > 2 x upper normal limit (UNL), ranging from 21% to 39%. Of 100 anti-HBe(+) children, 85 (85%) were inactive carriers. During the follow-up period, seroconversion to anti-HBe was observed in 40 of 73 (55%) children with an annual rate of 11%; 35 of 40 (87.5%) had biochemical remission, and 28 of 35 (80%) lost HBV-DNA. In the anti-HBe(+) group, 27 of 100 (27%) lost HBV-DNA and 9 of 100 (9%) lost HBsAg. The annual seroconversion rate for HBeAg was significantly lower: in children with vertical transmission compared with horizontal (7.7% vs 14.8%, respectively, P < 0.001) and in Muslim children compared with both Christian children and those born in Russia (8.6% vs 12%, respectively, P < 0.001). No differences were found among the ethnic groups after adjusting for the mode of infection. Two of 173 children had progression of liver disease.

CONCLUSIONS

The differences in HBeAg(+) status and seroconversion rate among the ethnic groups are related to the time/mode of HBV infection. The majority of children who developed anti-HBe immunity had biochemical remission, and a substantial number of the inactive carriers lost viremia during the observation period of up to 12 y.

Hepatocellular carcinoma prevention: A worldwide emergence between the opulence of developed countries and the economic constraints of developing nations

Hepatocellular carcinoma (HCC) is the fifth most common neoplasm, the major cause of death in patients with liver cirrhosis, and the third most common cause of cancer-related death in the world. The geographic distribution of HCC varies significantly and 80% of cases occur in developing countries (Far East and South Asia) where the prevalence of viral hepatitis is higher. The treatment of HCC is difficult because most patients are diagnosed when the tumour is in an advanced stage and is not amenable to potential curative therapy, thus prevention is the key to reducing HCC and its related morbidity and mortality. HCC is unique among cancers, occurring mostly in patients with a known risk factor. Ninety percent of HCCs develop in the context of chronic liver diseases and mainly in patients with cirrhosis. Viral hepatitis is the most common cause of HCC worldwide, followed by alcoholic liver disease (ALD) and other causes such as non-alcoholic fatty liver disease (NAFLD), genetic haemocromatosis (GH) and primary biliary cirrhosis in an advanced stage (III-V). In certain areas of the People’s Republic of China, exposure to aflatoxin and HBV infection are thought to be responsible for the extraordinary high risk of HCC. Substantial progresses in the prevention of virusl-related hepatitis (screening of blood units, use of disposable sanitary tools, HBV vaccination) have been achieved in developed countries, but in the same areas, alcohol- and dysmetabolism-related HCCs are emerging problems which require specific interventions in terms of public health measures. In developing countries, economic constraints limit the development of any program for the prevention of viral hepatitis transmission (including health education campaigns, healthcare politics, primary prevention and the improvement of hygienic and sanitary conditions). When viral liver disease is established, only a minority of patients are treated worldwide and benefit a possible preventive effect of medical treatment on HCC development. Thus the real contribution of medical treatment to HCC prevention in patients with chronic viral hepatitis is small. Great efforts are needed to identify more effective medical measures for primary and secondary prevention of HCC.

Prevención de las hepatitis virales

Prevention of viral hepatitis infection involves health measures designed to avert transmission of viral agents and promote the use of gammaglobulin and vaccines. The availability of safe drinking water and improvements in quality of life result in better individual hygiene; these factors have had the greatest impact on hepatitis A prevention. Serum gammaglobulin administration has been replaced by vaccinations for pre-exposure, and to a great extent for post-exposure prophylaxis because of the progressively lower anti-HAV content of gammaglobulin and the short duration of the protective effect. Universal vaccination in childhood is the recommended measure for controlling hepatitis A. Adults belonging to high-risk groups should also undergo vaccination. The incidence of hepatitis B has decreased worldwide because of universal vaccination programs, initiated in preadolescence and childhood. Prevention of hepatitis C requires control of situations in which there is a likelihood of parenteral infection with the virus. Post-transfusion hepatitis has been virtually eradicated, but considerable effort is still needed to prevent nosocomial hepatitis.

Progress in chemoprevention drug development: the promise of molecular biomarkers for prevention of intraepithelial neoplasia and cancer--a plan to move forward

This article reviews progress in chemopreventive drug development, especially data and concepts that are new since the 2002 AACR report on treatment and prevention of intraepithelial neoplasia. Molecular biomarker expressions involved in mechanisms of carcinogenesis and genetic progression models of intraepithelial neoplasia are discussed and analyzed for how they can inform mechanism-based, molecularly targeted drug development as well as risk stratification, cohort selection, and end-point selection for clinical trials. We outline the concept of augmenting the risk, mechanistic, and disease data from histopathologic intraepithelial neoplasia assessments with molecular biomarker data. Updates of work in 10 clinical target organ sites include new data on molecular progression, significant completed trials, new agents of interest, and promising directions for future clinical studies. This overview concludes with strategies for accelerating chemopreventive drug development, such as integrating the best science into chemopreventive strategies and regulatory policy, providing incentives for industry to accelerate preventive drugs, fostering multisector cooperation in sharing clinical samples and data, and creating public-private partnerships to foster new regulatory policies and public education.

Hepatitis B virus mutation in children

Due to the lack of proof reading activity of hepatitis B virus (HBV) polymerase, mutation/variation of the viral sequence is frequently found during long term follow-ups. In the majority of children with chronic HBV infection, wild type HBV is the dominant viral strain during the natural course of chronic HBV infection. During long-term follow-up, HBV precore mutants developed spontaneously in approximately 10 to 24% of children before HBeAg seroconversion and in around 50% of children after HBeAg seroconversion mutants. Occasionally, children may be infected primarily by mutant strains of HBV. Approximately 36% of children with fulminant hepatitis and 30% of children with acute hepatitis B were infected by precore mutants of HBV transmitted by their mothers or blood donors. In addition, after universal HBV vaccination, HBV surface gene variants emerge or are selected under the immune pressure generated by the host or by administration of hepatitis B immune globulin and hepatitis B vaccination. In HBV DNA positive children from four sequential surveys in Taiwan, the prevalence of hepatitis B surface gene a determinant mutants increased from 7.8% before the vaccination program, to 19.6%, 28.1% and 23.1% at 5, 10 and 15 years after the program. Nucleoside analogue may also induce mutant strains, which reduces the antiviral effects. The most common example is the YMDD mutation of the HBV polymerase gene after antiviral therapy with lamivudine. It developed in 19% of the treated children. In conclusion, children may be infected primarily by mutant strains of HBV either naturally during acute HBV infection. Those infected with wild type HBV initially may develop mutant strains gradually during the course of chronic infection under the host immune pressure. Vaccine escape mutants may develop after immunoprophylaxis. In addition, antiviral therapy with nucleoside analogues may also induce drug resistant mutant strains. Understanding the viral mutation status will help to design accurate strategies of immmunoprophylaxis and antiviral therapy against HBV infection.