Hepatitis Viruses Case File

Hepatitis Viruses Case File

Eugene C.Toy, MD, Cynthia Debord, PHD, Audrey Wanger, PHD, Gilbert Castro, PHD, James D. Kettering, PHD, Donald Briscoe, MD

CASE 27

A 62-year-old male presents to your office for follow-up of some abnormal blood test results. You had seen him 2 weeks ago as a new patient for a routine physical examination. You ordered blood tests and found that his liver enzymes were elevated by approximately three times the upper limits of normal. The patient says that to his knowledge he’s never had abnormal liver tests before, although he has not been to a doctor in several years. He denies alcohol or drug use and is not taking any medications. He gives no history of jaundice. His past medical history is significant only for hospitalization at the age of 45 for a bleeding stomach ulcer. He required surgery and had transfusion of 4 units of blood. He recovered from this episode without further complication and has had no recurrences. Your complete physical examination 2 weeks ago was normal, and a focused physical examination today shows no signs of jaundice, no hepatosplenomegaly, and no physical exam findings suggestive of portal hypertension. You diagnose an infectious etiology for the laboratory findings (elevated liver enzymes).

◆ What is the most likely infectious cause of his abnormal liver function tests?

◆ How did he most likely acquire this infection?

ANSWERS TO CASE 27: HEPATITIS VIRUSES

Summary: A 62-year-old man with abnormal liver function tests who had a blood transfusion previously, likely caused by an infectious etiology.

◆ Most likely infectious etiology: Hepatitis C virus

◆ Most likely route of transmission: Blood transfusion

CLINICAL CORRELATION

Hepatitis C virus (HVC) is transmitted parenterally by blood transfusions or intravenous drug use and rarely by sexual contact. It is uncommonly diagnosed as a cause of acute hepatitis, often producing subclinical infection, but it is frequently diagnosed later as a cause of chronic hepatitis. The natural history of infection is not completely understood, but 50–85 percent of patients with hepatitis C will develop chronic infection.

On initial infection, approximately 15 percent of persons will develop an acute hepatitis syndrome and recover completely. However, most infected individuals will appear asymptomatic yet progress to chronic infection. This chronic infection may progress to cirrhosis, liver failure, or hepatocellular carcinoma. HCV is transmitted from person to person, primarily via contact with infected blood or sexual contact. Routine screening of the donated blood supply for HCV was started in 1992. Prior to this, HCV was the primary cause of posttransfusion hepatitis. The high percentage of infections that are asymptomatic contributes to the spread of the virus in the population. Diagnosis is made by the presence of circulating antibody to HCV. HCV-polymerase chain reaction is also used to quantitate the amount of circulating virus present in an infected person. This serves as a measure of disease activity and as a monitor of response to therapy. Recombinant interferon, which induces host antiviral and antiproliferative activity, is the most widely used therapy for HCV.

APPROACH TO VIRAL HEPATITIS

Objectives

1. Know the structure and characteristics of the viruses that cause hepatitis.
2. Know the specific diseases associated with and routes of transmission of the hepatitis viruses.
3. Understand the mechanisms of development of acute and chronic hepatitis infections.

Definitions

Hepatitis: Inflammation of the liver; viral causative agents include hepatitis viruses A, B, C, D, E, and G. The clinical presentation can include fever, nausea or vomiting, jaundice, dark urine, pale feces, and elevated liver enzymes (AST and ALT).

Dane particle: A 42-nm particle that is the hepatitis B virion.

Fulminant hepatitis: Severe acute hepatitis that causes rapid destruction of the liver.

DISCUSSION

Characteristics of Hepatitis Viruses

Because of its rich vascular supply, the liver may be involved in any systemic blood-borne infection, but the most common and clinically significant infections are those with one of five hepatotropic viruses: Hepatitis A, B, C, D, or E. They can produce virtually indistinguishable clinical syndromes. Affected individuals often complain of a prodrome of nonspecific constitutional symptoms including fever, nausea, fatigue, arthralgias, myalgias, headache, and sometimes pharyngitis and coryza. This is followed by the onset of visible jaundice as a result of hyperbilirubinemia, with tenderness and enlargement of the liver, and dark urine caused by bilirubinuria. The clinical course, outcomes, and possible complications then vary depending on the type of virus causing the hepatitis. A comparison of features of these five viruses is shown in Table 27–1.

Hepatitis A

Hepatitis A and E are both very contagious and transmitted by fecal-oral route, usually by contaminated food or water where sanitation is poor and in day care by children. Hepatitis A virus (HAV) is found worldwide, and is the most common cause of acute viral hepatitis in the United States. Hepatitis E is much less common, and it is found in Asia, Africa, and Central America. Both hepatitis A and E infections usually lead to self-limited illnesses and generally resolve within weeks. Almost all patients with hepatitis A recover completely and have no long-term complications.

HAV is a member of the Picornaviridae family. It is a nonenveloped, linear, positive-sense, single-stranded RNA virus with only one serotype. Its average incubation period is approximately 30 days, and it results in 25,000 symptomatic cases in the United States annually. However, nearly 90 percent of HAV infections in children and 30–50 percent in adults are asymptomatic. Clinical symptoms vary according to the age of the patient; infections in children are mostly asymptomatic or present with nonspecific symptoms, whereas adults generally have a more severe clinical course. Only 1–4 percent of patients develop fulminant liver failure, and there is 1 percent mortality from HAV infection. It is not known to cause chronic infection. The virus is contagious before symptoms appear. Serologically, HAV infection can be diagnosed as ALT level rise initially with the appearance of symptoms. Then, anti-HAV IgM antibodies are produced and can be detected by enzymelinked immunoassay. Then 1–3 weeks later, anti-HAV IgG antibodies are made, providing lifelong immunity to the host.

Table 27-1

COMPARISON OF HEPATITIS VIRUS

Proper hand washing, avoidance of contaminated food and water, and the administration of a vaccine for travelers are all methods for prevention of HAV infection. The CDC now recommends universal vaccination against HAV for all children 1 year and older. Alternatively, exposed persons can be treated with HAV immunoglobulin intramuscularly within 14 days of exposure. Additional treatment for infected patients is supportive.

Hepatitis B

Hepatitis B virus (HBV) is a member of the Hepadnavirus family and has a DNA genome, making it unique among the hepatitis viruses. It is an enveloped virus with a circular and partially double-stranded DNA genome. The HBV virion, known as the Dane particle, consists of the genome, a viral DNA polymerase, and P protein, which is attached to the genome. The DNA polymerase also contains reverse transcriptase and ribonuclease H activity, allowing HBV to use an RNA intermediate during replication.

HBV has a specific affinity for liver cells, with attachment to these cells being mediated by viral glycoproteins. Once attached, HBV is taken up by the hepatocytes and the genome is converted into fully double-stranded DNA which is then delivered to the nucleus. The host cell’s transcription and translation machinery are then used to make new HBV virions. These virions are then released from the hepatocyte via exocytosis.

Several viral proteins can be detected during HBV infection and are useful in diagnosis and monitoring of disease. The virion is surrounded by a core protein antigen (HBcAg), and the presence of HBcAg in a patient’s serum indicates that the patient has been exposed to HBV. Other HBV antigens include surface antigen (HBsAg) and the “e” antigen (HBeAg). HBsAg can be detected when live virions are present in an infection, and HBeAg is a glycoprotein cleavage product of the core which is shed into the serum. The presence of HBeAg and HBsAg correlate with active HBV infection and thus, active disease. Antibodies to these viral antigens can help to determine whether infection is recent or not. IgM anti-HBc indicates a new infection, whereas IgG anti-HBc indicates past infection. Figure 27-1 shows a hepatitis B serology diagram.

HBV is the second most common type of viral hepatitis in the United States, and it is usually sexually transmitted. It may also be acquired parenterally, such as from intravenous drug use, or during birth, from chronically infected mothers. The outcome then depends on the age at which the infection was acquired. Up to 90 percent of infected newborns develop chronic hepatitis B infection, which places the affected infant at significant risk of hepatocellular carcinoma later in adulthood. For those individuals infected later in life, approximately 95 percent of patients will recover completely without sequelae. Between 5 and 10 percent of patients will develop chronic hepatitis, which may progress to cirrhosis. Also, a chronic carrier state may be seen in which the virus continues to replicate but does not cause hepatic damage in the host.

Figure 27-1. Clinical and laboratory features of acute viral hepatitis B infection.

A vaccine consisting of recombinant HBsAg is available and is a scheduled immunization given to all infants and adolescents, as well as to persons with increased risk of exposure (i.e., health-care workers and IV drug users). The incidence of HBV infection has decreased with the onset of the HBV vaccine and the screening of pregnant women prior to delivery. Yet, HBV remains in high rates in Southeast Asia and the Mediterranean areas. Nonimmunized persons exposed to HBV can be treated with immunoglobulin within 1 week of exposure. HBV infection can be treated with reverse transcriptase inhibitors or α-interferon.

Hepatitis C

Hepatitis C virus (HCV) is a member of the Flaviviridae family. It is a lipoprotein-enveloped virus with a positive-sense RNA genome. There are hundreds of HCV genotypes as a result of a hypervariable region in the envelope region. The virus is more or less virulent depending on the hypervariable region, thus making it very difficult to produce an effective vaccine against HCV. The virus enters cells through endocytosis after binding to the CD81 surface receptor. The acidity of the endosome causes fusion of the viral envelope with the endosomal membrane and results in release of the viral RNA into the host cytoplasm. The viral RNA acts as messenger RNA, directing the production of the viral polyprotein. The polyprotein anchors to the host cell endoplasmic reticulum and the virus remains cell-associated. The HCV proteins inhibit apoptosis and the action of interferon-α. By remaining associated with the cell and inhibiting apoptosis, HCV can cause chronic infection and persistent liver disease. The incubation period for infection can vary from 2 to 26 weeks, with an average of 6–7 weeks.

Most initial HCV infections are asymptomatic or result in mild nonspecific symptoms such as malaise or abdominal pain. On initial infection, approximately 15 percent of persons will develop an acute hepatitis syndrome and recover completely. More than 70 percent of infected patients will be asymptomatic, yet many will progress to chronic hepatitis. Yet, another 15 percent of infected patients rapidly develop cirrhosis. Chronic infection can also progress to more serious disease including: cirrhosis, liver failure, or hepatocellular carcinoma. The high percentage of infections that are asymptomatic also contributes to the spread of the virus in the population.

HCV infection is diagnosed by demonstrating the presence of circulating IgG antibodies to HCV antigens through enzyme immunoassay. Unfortunately, these antibodies may not be detected until up to 4 months postinfection, making it difficult to diagnose an acute HCV infection. Additionally, such tests cannot distinguish between acute, chronic, or resolved HCV infections. Alternatively, reverse transcriptase polymerase chain reaction (RT-PCR) testing can be used to diagnose infection and to quantitate the amount of circulating HCV RNA in an infected person. This assay serves as both a measure of HCV disease activity and as a monitor of response to therapy.

Numerous antiviral agents are used as therapy for HCV infection, including recombinant interferon-α, which helps to induce host antiviral and antiproliferative activity. End-stage chronic HCV hepatitis may require liver transplantation; however, the risk of graft reinfection is 50 percent for HCV. Currently, there is no effective vaccine to prevent HCV infection. However, the establishment of routine screening of donated blood and organs has reduced the spread of HCV via these modes of transfer.

Hepatitis D

Hepatitis D virus (HDV) is a defective RNA virus that requires the presence of the hepatitis B virus to replicate. Specifically, it lacks genes for envelope proteins, and thus to replicate it requires infection with HBV. It then consists of an envelope (provided by HBV) with HBsAg, delta antigen, and single-stranded, circular RNA. If infection with HDV occurs during a superinfection of preexisting HBV, there is a higher risk of chronic liver infection and chronic HDV infection. This type of superinfection is also more likely to lead to fulminant hepatitis and has a 5–15 percent mortality rate. However, when HDV coinfects a person simultaneously with HBV, it typically presents as severe acute disease with a low risk of developing chronic liver infection or mortality. HDV is spread similarly to HBV, via percutaneously, mucosally, or through sexual contact.

Laboratory diagnosis of HDV is made by detection of the RNA genome (via RT-PCR) or the delta antigen (via enzyme-linked immunosorbent assay, ELISA) from blood samples. Additionally, anti-HDV antibodies can also be detected by ELISA; however, antibodies are present only transiently. To prevent coinfection with HBV, prophylaxis to HBV can be administered. To prevent a HDV superinfection, it is important to educate HBV-positive patients about reducing risk factors for infection. The only treatment available for HDV infection is α-interferon, which lessens clinical symptoms.

Hepatitis E

Hepatitis E virus (HEV), also called “enteric non-A, non-B hepatitis,” is a member of the Caliciviridae family. It is nonenveloped, and its genome consists of linear, positive-sense, single-stranded RNA. HEV is similar in many ways to HAV. Both are transmitted by the fecal-oral route, most frequently through contaminated water sources. It is not endemic to the United States and is therefore seen most often in travelers. The average incubation period is 40 days. HEV infection is most often diagnosed by exclusion, because laboratory testing is not available.

Like HAV, it has a low mortality rate (1–2 percent), except for infection in pregnancy where a 15–25 percent mortality rate is noted, and there is no chronic stage. Like all of the hepatitis viruses, the clinical severity of infection increases with the age of the patient. The immunological response is also similar to that of HAV. To protect from HEV infection while traveling to endemic areas, travelers are advised not to drink the water (or ice) and not to eat unpeeled fruits or vegetables. There is no vaccine available, and immunoglobulin does not prevent infection with HEV.

Hepatitis G

The hepatitis G virus (HGV), has been more recently identified. As a member of the Flavivirus family it resembles HCV in its viral structure (positivesense RNA genome), transmission (blood-borne) and in its high production of chronic hepatitis disease. Lab diagnosis involves identifying the HGV genome via RNA detection methods (i.e., RT-PCR).

Hepatitis Serologies

Clinical presentation does not reliably establish the viral etiology, so serologic studies are used to establish a diagnosis. Antihepatitis A IgM establishes an acute hepatitis A infection. If Antihepatitis C antibody is present, an acute hepatitis C is diagnosed, but it may be negative for several months. The hepatitis C PCR assay, which becomes positive earlier in the disease course, often aids in the diagnosis. Acute hepatitis B infection is diagnosed by the presence of hepatitis B surface antigen (HBsAg) in the clinical context of elevated serum transaminase levels and jaundice. HBsAg later disappears when the antibody (anti-HBs) is produced.

There is often an interval of a few weeks between the disappearance of HBsAg and the appearance of anti-HBsAb, which is referred to as the “window period.” During this interval, the presence of antihepatitis B core antigen IgM (anti-HBc IgM ), will prove indicate an acute hepatitis B infection. Hepatitis B precore antigen (HBeAg) represents a high level of viral replication. It is almost always present during acute infection, but its persistence after 6 weeks of illness is a sign of chronic infection and high infectivity. Persistence of HBsAg or HBeAg are markers for chronic hepatitis or a chronic carrier state; elevated or normal serum transaminase levels distinguish between these two entities, respectively.

COMPREHENSION QUESTIONS

[27.1] A 33-year-old nurse suffered a needle stick injury. The patient used illicit intravenous drugs. One month later, the nurse develops jaundice. Which of the following findings would implicate hepatitis B as the etiology?

A. Positive antihepatitis B surface antibody

B. Positive antihepatitis B-core antibody

C. Positive hepatitis B surface antigen

D. Positive antihepatitis A antibody

[27.2] A 25-year-old male tests positive for a hepatitis C infection. Which of the following is the most likely method of transmission?

A. Fecal-oral

B. Fomite

C. Intravenous drug (needles)

D. Sexual transmission

[27.3] A 12-year-old teenager is brought into the emergency room with skin “turning yellow” and abdominal discomfort. The liver function tests reveal serum transaminase levels in the 2000 IU/L range. Which of the following is the most accurate statement about probable complications?

A. Significant likelihood of hepatocellular carcinoma

B. Almost no chance of long-term sequelae

C. About a 10 percent chance of a chronic carrier state

D. Long-term complications usually respond to α-interferon therapy

[27.4] A 28-year-old woman presents with symptoms of jaundice, right upper quadrant pain, and vomiting. She also has elevated ALT. It is determined that she acquired hepatitis A from a church picnic where several other adults also became infected. What should be done to protect the family members?

A. One dose of HAV immunoglobulin should be administered intramuscularly.

B. No treatment is necessary.

C. A series of three vaccinations should be administered at 0, 1, and 6 months.

D. α-Interferon should be administered.

E. Household contacts should be quarantined and observed.

Answers

[27.1] C. The presence of hepatitis B surface antigen means actively replicating virus, and in the context of the recent needle stick injury, this likely represents a hepatitis B infection. The presence of HBeAg is a marker of active disease and infectivity. For example, pregnant mothers infected with HBV who have the absence of serum HBeAg, there is a greater than 10 percent transmission rate to the fetus, whereas in pregnant mothers with HBeAg in their serum, there is a greater than 90 percent transmission rate to the fetus.

[27.2] C. Intravenous drug use is the primary method of transmission of hepatitis C virus.

[27.3] B. This is most likely hepatitis A infection, which carries a very low chance of long-term sequelae.

[27.4] A. HAV immunoglobulin should be given to household contacts in one IM dose. This must be done within 14 days of exposure to the index patient as prophylaxis against hepatitis A. Answer (C), the series of three vaccinations at time 0, 1, and 6 months, refers to the immunization schedule for hepatitis B, not hepatitis A. This would not be protective for those exposed to HAV. (D) α-Interferon is used to treat symptomatic patients with HBV and HCV, not prophylaxis of family members of patients with HAV. (E) Quarantining the household contacts of the patient is not the appropriate treatment.

MICROBIOLOGY PEARLS ❖ HCV is an enveloped virus with a positive-sense RNA genome. ❖ HCV transmission occurs primarily via infected blood/parenteral transmission. ❖ Although most acute infections are asymptomatic, HCV produces high rates of chronic infection and mortality. ❖ Treatment of HCV infection includes recombinant interferon-á. ❖ No vaccine is available for HCV.

REFERENCES

Brooks GF, Butel JS, Morse SA. Jawetz, Melnick, & Adelberg’s Medical Microbiology, 23rd ed. New York: McGraw-Hill, 2004:466–86. 

Howley PM, Knipe DM. Fields Virology, 4th ed. Philadelphia, PA:Lippincott Williams & Wilkins, 2001. 

Murray PR, Rosenthal KS, Pfaller MA. Medical Microbiology, 5th ed. St. Louis, MO: Mosby, 2005:675–90. 

Ryan JR, Ray CG. Sherris Medical Microbiology, 4th ed. New York: McGraw-Hill, 2004:541–53. 

National Institute of Allergy and Infectious Disease. Hepatitis. www.niaid.nih.gov/ publications/hepatitis.htm

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