A Valuable Antigen Detection Method for Diagnosis of Acute Hepatitis E

Abstract

Hepatitis E virus (HEV) is a serious public health problem. The commonly used tests that are specific for current HEV infection diagnosis include the detection of anti-HEV IgM and HEV RNA. Here, we report an improved enzyme-linked immunosorbent assay (ELISA) method for HEV antigen detection with a linear range equivalent to 6.3 ؋ 10 3 to 9.2 ؋ 10 5 RNA copies per ml. The monoclonal antibody (MAb) 12F12, a high-ability MAb that binds HEV virus, was selected as the capture antibody from a panel of 95 MAbs. The positive period of HEV antigenemia in infected monkeys using this test was, on average, 3 weeks longer than previously reported and covered the majority of the acute phase. The positive detection rates of IgM, RNA, and new antigen from the first serum samples collected from 16 confirmed acute hepatitis E patients were 81% (13/16), 81% (13/16), and 100% (16/16), respectively. In three patients, the initial serum specimens that tested negative for IgM, despite the presence of symptoms of acute hepatitis and elevated alanine aminotransferase (ALT) levels, were positive for HEV antigen and HEV RNA. In contrast, the serum samples of the three RNA-negative patients were antigen positive (and IgM positive), possibly due to the degradation of HEV nucleic acids. Our results suggest that this new antigen detection method has acceptable concordance with RNA detection and could serve as an important tool for diagnosing acute hepatitis E. H epatitis E is an enterically transmitted viral hepatitis caused by hepatitis E virus (HEV) infection (1). Hepatitis E is a serious public health problem in many countries (especially developing countries), with a mortality rate of approximately 20 to 25% among pregnant women (2). HEV is a 34-nm, nonenveloped, and icosahedral virus (3) with a 7.2-kb positive-sense single-stranded RNA genome containing three open reading frames. Open reading frame 2 (ORF2) (660 amino acids) encodes the major viral capsid (4). Mammalian HEV is divided into four genotypes with distinct geographic distributions and prevalences (5, 6).Most patients with acute hepatitis E infection present with typical acute hepatitis symptoms, such as jaundice and dark urine. Typical biochemical changes in acute HEV patients include increased serum levels of alanine aminotransferase and aspartate aminotransferase (ALT and AST, respectively) and bilirubin; however, these factors are not specific for hepatitis E, as increases also occur due to other viral and nonviral forms of liver injury. The most commonly used tests specific for diagnosing HEV infection detect anti-HEV IgM and HEV RNA. In acute hepatitis E patients, anti-HEV IgM can typically be detected within 3 to 4 days after the onset of jaundice and can persist for an average of 5 months (7). The presence of anti-HEV IgM provides evidence of recent HEV infection; however, its short detection period indicates that anti-HEV IgM is unsuitable as a single marker for current infection in acute hepatitis E patients. In contrast, the detection of HEV RNA provides a specific ...

Hepatitis E virus seroepidemiology: a post-earthquake study among blood donors in Nepal

“…This indicates HEV antigen is likely to persist for a short period, and is undetectable by the time of appearance of HEV IgM. A study has shown that 19% (3/16) of HEV antigen positive samples were HEV IgM negative [27]. Concurrent detection of HEV antigen and IgG in both our donors could indicate re-infection, however, non-specificity of the antigen assay cannot be ruled out.…”

Origin, antigenicity, and function of a secreted form of ORF2 in hepatitis E virus infection

“…A recombinant ORF2 dimer (rDimer) comprising amino acids 394-606 was also included (21). mAbs 12F12 and #4, which are used in the commercial HEV antigen ELISA (25), recognized all four forms of ORF2 (rVLP, rDimer, ORF2 S , and virions) of all genotypes tested (g1, g3, and g4), therefore were used to adjust the input amounts of different ORF2 forms.…”

Unexpected long‐lasting anti‐HEV IgM positivity: Is HEV antigen a better serological marker for hepatitis E infection diagnosis?

“…Recently, a test to detect HEV antigen (HEV‐Ag) has been developed and assessed for HEV diagnosis . A potential advantage of HEV‐Ag is that it is detectable prior to ALT elevation and development of anti‐HEV antibodies, although this finding is supported by only a few studies . The aims of our study were (a) to analyse the duration of two different anti‐HEV IgM assays (Mikrogen and Wantai) in patients with self‐limited acute hepatitis E and (b) to assess the performance of anti‐HEV IgM and HEV‐Ag in this cohort in comparison with a group of subjects with transient HEV infection, defined by HEV RNA positive.…”