Antibody and Antigen Detection Assays Hepatitis B (HBV)
Hepatitis B (HBV) is virus that infects the liver and most adults (95%) who are infected are able to quickly recover. In babies and young children, HBV can develop into a chronic infection leading to liver cirrhosis or liver cancer later in life. 350 million people worldwide are infected with HBV and it is the cause of 620,000 deaths each year. The likelihood of an infected individual resolving an acute HBV infection depends on their age and the strength of their initial immune response. Infection around the time of birth is the most frequent way HBV is acquired in areas of the world where the disease is common, as mothers pass the infection to their babies during childbirth. East Asia and Sub-Saharan Africa have the highest rates of infection which can be as high as 15% of the adult population. In contrast, rates in Europe and North America are less than 1%. Since 1982 the World Health Organization (WHO) has recommended vaccination on the first day of life. HBV testing of donated blood began in the United States in 1971, and since 2006, over 180 countries give the vaccine as part of a national program.
The virus is divided into four major serotypes (adr, adw, ayr, ayw) based on antigenic epitopes presented on its envelope proteins, and into eight genotypes (A-H) according to overall nucleotide sequence variation of the genome. The genotypes have a distinct geographical distribution and properties including disease severity, course and likelihood of complications, and response to treatment.
SEROLOGICAL TIMECOURSE OF HEPATITIS B INFECTION
Weeks after exposure
SOURCE: Adapted from CDC.gov
DIAGNOSIS Serologic testing of HBV involves a panel of several HBV-specific markers: • HBV surface antigen (HBsAg)
• HBV core antigen (HBcAg) • HBV “e” antigen (HBeAg) These markers help distinguish whether a patient is susceptible to primary infection, immune as a result of a resolved infection, immune as a result of vaccination, acutely infected, or chronically infected. During acute infection, the appearance of virologic markers develop in a typical pattern. The first serologic marker to appear within 1-12 weeks of an acute infection is HBsAg, along with pre-S1 and pre-S2 antigens. Then, HBeAg becomes detectable which indicates that a person is highly infectious and clinical symptoms begin to develop. IgM antibody to HBcAg (anti-HBc) appears and remains present in high titer for up to 4 months, after which only IgG antibody to HBcAg remains and persists indefinitely. Anti-HBe appears after anti-HBc and its presence correlates to a decreased infectivity. Acute hepatitis patients who maintain a constant serum HBsAg concentration or whose serum HBeAg persists for 8-10 weeks after symptoms have resolved, are at risk of developing chronic liver disease.
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Hepatitis- Reagents for Assay Development
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