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Progress in hepatitis B: A 30-year journey through three continents

2014; Lippincott Williams & Wilkins; Volume: 60; Issue: 1 Linguagem: Inglês

10.1002/hep.27120

1527-3350

Anna Suk‐Fong Lok,

Hepatitis C virus research

Being asked to contribute a Master Perspective article in Hepatology is a great honor that I accepted with trepidation. In preparation for this article, I reviewed the previous ones and realized each tells a different story. I hope this article will illustrate how much progress we have made in our understanding of hepatitis B in the last 30 years. I also hope that my personal journey will inspire young readers to believe in their dreams and to strive towards their goals even when the path is tortuous and riddled with hurdles. I grew up in Hong Kong in a family where there had never been a physician. In fact, I was the first in my family to choose a science track in high school (we were forced to choose between science and humanity tracks at the end of 8th grade). My father cautioned that science is not for girls. When I got a "C" for my first physics test, I thought I should have listened to the old man. Fortunately, history did not repeat itself. After my "O Level" exam (an exam that kids from all schools take at the end of 11th grade), I applied to a boys' school with a reputation in science (a move from an all-girls' school strong in language and humanities) and was accepted as the only girl in a class of 31 boys. Being the odd person out, the boys were super nice and polite, and the teachers were so sympathetic that I ended up ranking top of the class 2 years in a row. When I announced that I would be applying for medical school at the end of 13th grade (college was an unnecessary waste of time), my father advised that nursing would be more appropriate for girls but he was delighted when I was accepted into medical school. The 5 years of medical school flew by quickly. After a year of internship, I was offered a lecturer position in the Department of Medicine, University of Hong Kong. There were very few faculty then and residents like myself were drafted to teach medical students (on top of all the clinical duties, there were no work-hour limits). Salaries were the same as other residents with no teaching duties but the perk was university sponsorship of overseas fellowship training. I fell in love with hepatology during my first rotation as a resident. Two people had a big influence on my decision to be a hepatologist. Dr. K.C. Lam1 was my attending and Dr. Rudi Schmid (Chief of Gastroenterology and Hepatology at University of California-San Francisco) was a visiting professor. Both were inspiring teachers who asked a lot of questions on rounds and made me think and want to know more. It is amazing how our lives are shaped by fate or chance encounter. As I mentioned earlier, the perk of taking on additional teaching duties as a resident was sponsorship of overseas fellowship training. Being a freebie made it easier for me to get into the best program. The Royal Free Hospital in London, headed by Dame Sheila Sherlock, was the mecca of hepatology at that time. My 2 years at the Royal Free were some of the best times in my life. The training and experience at the Royal Free provided solid foundations for my academic career. Just as important, if not more, I became a member of the Sherlock Hepatology Family (Fig. 1) and the Sherlock brand name was a major reason how I landed with a faculty position in the United States despite never having any training in the country. Hepatology was a fairly new specialty in the early 1980s (the Journal Hepatology was inaugurated in January 1981). Coming from Hong Kong, it was natural for me to choose hepatitis B as the research focus. Figuring out what topic to study was more difficult. I knew very little about hepatitis B (still don't know enough), had no research experience, and was not familiar with the research ongoing at that time. My first meeting with Professor Howard Thomas, my research mentor, did not go well. I was not able to articulate what topic I wanted to research on and how I would go about doing it. It took time, patience, and perseverance to prove that I was trainable. Hepatitis B in the early 1980s was fairly simple. Hepatitis B virus (HBV) had been established as a DNA virus that causes chronic hepatitis and cirrhosis but an etiological association with hepatocellular carcinoma (HCC) was still debated. Assays for HBV DNA were in its infancy. The assays used hybridization with limit of detection ∼1 million IU/mL. The results were usually scored from 0 to 4+. The natural history of chronic HBV infection was thought to comprise two distinct phases: hepatitis B e antigen (HBeAg)-positive when virus replication and liver inflammation are active and HBeAg-negative when virus replication ceases and liver inflammation subsides. Seroconversion from HBeAg to HBe antibody (anti-HBe) was thought to be an irreversible process. There was no approved treatment for hepatitis B. Although the tools were crude, the early 1980s was a golden era for HBV research. Molecular diagnostic tests were rapidly developing and there were few distractions. The latter changed by mid 1980s with the AIDS epidemic and the realization that it was caused by a virus. Because of the high rate of mortality and devastating complications affecting mainly young people, a lot of funding and resources were earmarked for human immunodeficiency virus (HIV) research and many HBV investigators defected. Of those who stayed, many left in the early 1990s when the elusive non-A, non-B hepatitis virus was found. One of my first projects at the Royal Free was to study the use of interferon (IFN) in the treatment of chronic hepatitis B. In 1976, Tom Merigan and his colleagues at Stanford reported promising results in a study of four patients treated with IFN.2 The IFN we used was produced by a human lymphoblastoid cell line (recombinant DNA technology was not available yet) and administered as an intravenous infusion in doses of up to 100 million units/m2. Because of the intensity of the adverse reactions, the infusion had to be administered by a physician (yours truly) who would stay by the patient's bedside for the next few hours in case a catastrophic reaction occurred. This early experience spurred the evaluation of lower, better-tolerated doses. In a study of six patients given daily (n = 2), alternate day (n = 1), or thrice weekly (n = 3) intramuscular injections of IFN at 7.5-10 million units/m2, we found that thrice weekly administration of IFN was as effective as daily injections in inhibiting HBV replication, were associated with fewer side effects, and could be continued for up to 3 months.3 The rationale for thrice weekly (Monday, Wednesday, and Friday) versus alternate day administration was simply a matter of convenience because alternate day would require working over the weekend. Until pegylated IFN became available, thrice weekly administration of IFN was the norm for hepatitis B. I have always wondered why no one questioned the irregular spacing. In hindsight, we would not be able to tell whether HBV DNA levels crept up during the weekend gap because the HBV DNA assay used was not sensitive enough to detect 50% mortality within 2-3 years of transplant. Although the findings of Didier Samuel and his colleagues in Europe showed that long-term intravenous infusion of hepatitis B immune globulin starting from the anhepatic phase significantly decreased the incidence of HBV reinfection and mortality from recurrent HBV,24 this approach was very expensive and ineffective in patients who were viremic (serum HBV DNA detected by hybridization assay, roughly >5 log10 IU/mL) at the time of transplant. This field changed so much in the last 15 years that my attempt in leading an NIDDK-funded multicenter study in early 2000 to examine the most cost-effective strategy to prevent recurrent hepatitis B after liver transplantation was repeatedly derailed when successive new antiviral drugs and more sensitive HBV DNA assays became available during the course of the study. We ended up abandoning the notion of completing the planned randomized trials for a pragmatic study which showed that when appropriate oral antiviral drugs were administered before and after liver transplantation and rescue therapy was available for virologic breakthrough, HBV recurrence can be kept below 10% regardless of the dose and duration of hepatitis B immune globulin used.25 Implementation of HBV vaccination programs and universal precautions in healthcare settings have resulted in a marked decline in the incidence of acute HBV infection as well as a decrease in the prevalence of chronic HBV infection in children and adolescents in the U.S.; however, the prevalence of chronic HBV infection in adults has remained relatively stable because of the immigration of chronically infected persons from endemic countries. The U.S. is known to be a melting pot. In the case of hepatitis B, it is not just a mix of persons of different races and ethnicities but also a mix of HBV genotypes (A-H), age at infection (perinatal, childhood, and adult), and lifestyle and environmental factors (alcohol, smoking, obesity, etc.). Thus, data on the natural history of HBV infection from studies conducted in other countries may not be applied in the U.S. Similarly, because of changes in immigration pattern over the years, epidemiological data of HBV infection in the U.S. in the past may not apply to the present. In early 2000, with the recognition that responses to antiviral treatment of HBeAg-negative chronic hepatitis differ from that of HBeAg-positive chronic hepatitis, pharmaceutical sponsors began to have separate protocols for treatment of HBeAg-positive and HBeAg-negative chronic hepatitis B. In several instances, U.S. sites were excluded from the trials for HBeAg-negative chronic hepatitis because it was thought that HBV genotype A predominated and HBeAg-negative chronic hepatitis is rarely seen in the U.S. As a physician who sees patients in the clinic, it was obvious that these dogmas were incorrect. To rectify these myths, I led a 17-center study in 2002 to determine the prevalence of HBV genotypes, precore and basal core promoter variants in the U.S. This study showed that genotype A was present in 35% of patients and genotypes B and C (that predominate in Asian countries) in 53% of patients, supporting data from other studies that 50-70% of patients with chronic HBV infection in the U.S. are Asians.26 This study also showed that precore variants were present in 27% and basal core promoter variants in 44% of patients, confirming that HBeAg-negative chronic hepatitis was not a rare entity in the U.S. Twenty years after I moved to the U.S. and was told that hepatitis B will soon be eradicated, it is estimated as many as 2.2 million persons living in the U.S. have chronic HBV infection,27 and many questions regarding immunopathogenesis, natural history, and optimal treatment of hepatitis B remain. It was very gratifying that in 2008 NIDDK established the Hepatitis B Research Network (HBRN) which includes 21 adult and 7 pediatric clinical sites in the U.S. and in Toronto, Canada. The HBRN has enrolled more than 2,000 adults and children with chronic HBV infection in the observational cohort studies and launched three clinical trials of antiviral therapy. The diverse race/ethnicity of the patients and entire spectrum of HBV genotypes from A to H provide a unique opportunity to examine the impact of host, virus, and environmental factors on the outcomes of HBV infection that is not possible with studies in countries where most patients are of the same race and only one or two HBV genotypes prevail. It has been an honor and a privilege to chair the HBRN Steering Committee. Data from the HBRN are beginning to emerge and we expect these data will improve our understanding of the epidemiology and natural history of HBV infection not only in the U.S. but worldwide because ∼80% of the participants were foreign-born. As the first and only (so far) physician in the family, this has been a remarkable journey. There were many hurdles along the way but also a lot of triumphs personally and professionally. Over the years, I have made many friends, traveled to many parts of the world, and experienced many cultures. Through participation at hundreds of meetings and collaboration on multiple projects, I got to know many iconic figures in hepatology who have inspired and helped me in my professional development and made many friends who share not just research ideas and data but also life experiences and lasting friendship. I have also mentored many fellows and junior faculty, many of whom have risen through the ranks and have become internationally recognized leaders: Bob Fontana, Jorge Marrero, Henry Chan, just to name a few. My proudest accomplishment is being the matriarch of the Lok Hepatology Family witnessing the growth and success of the kids who stay in touch through an annual family reunion during The Liver Meeting. I have been fortunate to be recognized by my peers and to have received many awards including a Distinguished Scientist Award and an autographed book "Hepatitis B: The Hunt for a Killer Virus" by the late Nobel laureate Baruch Blumberg from the Hepatitis B Foundation in 2008, and a Distinguished Service Award from AASLD in 2011—it meant a lot to be recognized by the society that I am most closely affiliated with and to be placed among other giants in hepatology whom I admire and respect. After serving as Councilor at Large of AASLD in 2001-2003, I was honored to be selected as Councilor again in 2013 and will serve as President in 2017. I look forward to the challenges and opportunities of leading the premier society of our specialty. As a researcher, being part of the growth of the field of hepatology and hepatitis B has been an amazing journey. Table 1 shows the major milestone in HBV progress and Table 2 shows how far we have come in the last three decades. As a co-author of the AASLD guidelines on HBV (with Brian McMahon) for a decade, I appreciate the opportunity to shape the care of hepatitis B worldwide. During the last 30 years, there have been drifts of investigators and funding from HBV to HIV and then HCV. With the imminent prospect of HCV cure, it is gratifying to see a shift back to HBV and a commitment from the scientific community and the pharmaceutical industry to find a "cure" for HBV. In closing, I want to thank the Hepatology editors for the honor to contribute this Master's Perspective. Many important milestones in HBV progress and many people who have contributed to the progress and who have helped me along the way could not be included due to space constraints. There are a few people I must acknowledge: my mother, who believed girls can be doctors, my father, who told me I need to work harder (when I was 9), and my brothers, who bear the brunt of taking care of our elderly parents allowing me to pursue my dreams guiltlessly. Professionally, I would not be where I am without the inspirations and support from Sir David Todd and Rosie Young in Hong Kong, the late Dame Sheila Sherlock in London, and Jay Hoofnagle in the U.S.