Serological approaches to distinguish immune response to hepatitis A vaccine and natural infection

Characteristics of acute hepatitis A virus infection before and after 2001: A hospital-based study in Tokyo, Japan

BACKGROUND AND AIM

The incidence of acute hepatitis A [AH (A)] is decreasing because of improvements in hygiene; however, cases of sporadic severe hepatitis are still being reported. We assessed the epidemiology of AH (A) in Japan.

METHODS

This was a hospital-based retrospective study, in which 126 AH (A) patients (96 men [76%], median age 39 [range, 19-66] years) were enrolled. Patients diagnosed with AH (A) before 2001 (n = 79) and after 2001 (n = 47) were compared.

RESULTS

The incidence of AH (A) showed peaks in 1990, 1999, and 2018. After 2001, one patient had hepatitis B virus, four had human immunodeficiency virus, and three had syphilis coinfections. Before and after 2001, HAV was transmitted, respectively, by raw oysters (28% and 26%), overseas travel (19% and 28%), and sexual contact (0% and 19%) (P < 0.01). The frequencies of symptoms were appetite loss (51% and 32%), fever (63% and 81%), and diarrhea (3% and 13%) (all P < 0.05), respectively. On admission, the median levels of alanine aminotransferase (1455 and 3069 U/L) and γ-glutamyl transpeptidase (221 and 345 U/L) were significantly higher (P < 0.01), and the prothrombin time (77.5% and 65.9%) and platelet count (22.7 and 16.4 × 10/μL) were significantly lower after 2001 (P < 0.05). A time to normalization of the bilirubin level ≥ 30 days was associated with older age and a diagnosis of AH (A) after 2001.

CONCLUSIONS

Outbreaks and severe AH (A) cases due to sexual transmission have been reported recently. It is necessary to examine their sexual behavior and other sexual infection.

Development of a peptide ELISA to discriminate vaccine-induced immunity from natural infection of hepatitis A virus in a phase IV study

Hepatitis A virus (HAV) is a highly infectious agent that causes acute liver disease. The infection can trigger the production of antibodies against the structural and non-structural proteins of HAV. Nonetheless, vaccination with an HAV vaccine leads to the production of a primary antibody against the structural proteins. Because the non-structural proteins are only produced during active virus replication, there is no or very little antibody production against the non-structural proteins. However, the current commercial immunoassay cannot distinguish between antibodies produced during natural infection and those from vaccination against HAV. In our study, six immune-dominant epitopes from the non-structural proteins were designed, synthesized, linked together and cloned into pGEX-5X-1 plasmid. The recombinant protein was expressed in E. coli and purified by Ni²⁺-coated magnetic agarose beads. Then the purified recombinant protein was used as an ELISA antigen to detect antibodies for HAV non-structural proteins in serum samples. Seventy-seven attenuated and 89 inactivated vaccinated samples collected from our previous phase IV study of HAV vaccines were detected by peptide ELISA developed in this study. The mean OD₄₅₀ value for the vaccination samples and acute infection samples were 0.529 (0.486 for the attenuated group and 0.567 for the inactivated group) and 1.187, respectively. According to the receiver operating characteristic (ROC) curve, the sensitivity and specificity of the peptide ELISA were 93.80% and 91.00%, respectively. This peptide ELISA was confirmed to discriminate vaccine-induced immunity from natural infection of HAV in a phase IV study with high sensitivity and specificity.

Epitope-based recombinant diagnostic antigen to distinguish natural infection from vaccination with hepatitis A virus vaccines

Hepatitis A virus (HAV) infection can stimulate the production of antibodies to structural and non-structural proteins of the virus. However, vaccination with an inactivated or attenuated HAV vaccine produces antibodies mainly against structural proteins, whereas no or very limited antibodies are produced against the non-structural proteins. Current diagnostic assays to determine exposure to HAV, such as the Abbott HAV AB test, detect antibodies only to the structural proteins and so are not able to distinguish a natural infection from vaccination with an inactivated or attenuated virus. Here, we constructed a recombinant tandem multi-epitope diagnostic antigen (designated 'H1') based on the immune-dominant epitopes of the non-structural proteins of HAV to distinguish the two situations. H1 protein expressed in Escherichia coli and purified by affinity and anion exchange chromatography was applied in a double-antigen sandwich ELISA for the detection of anti-non-structural HAV proteins, which was confirmed to distinguish a natural infection from vaccination with an inactivated or attenuated HAV vaccine.

Diagnosis of hepatitis a virus infection: a molecular approach

Current serologic tests provide the foundation for diagnosis of hepatitis A and hepatitis A virus (HAV) infection. Recent advances in methods to identify and characterize nucleic acid markers of viral infections have provided the foundation for the field of molecular epidemiology and increased our knowledge of the molecular biology and epidemiology of HAV. Although HAV is primarily shed in feces, there is a strong viremic phase during infection which has allowed easy access to virus isolates and the use of molecular markers to determine their genetic relatedness. Molecular epidemiologic studies have provided new information on the types and extent of HAV infection and transmission in the United States. In addition, these new diagnostic methods have provided tools for the rapid detection of food-borne HAV transmission and identification of the potential source of the food contamination.

Immune responses of anti-HAV in children vaccinated with live attenuated and inactivated hepatitis A vaccines

The immunogenicity of a live attenuated HAV vaccine and an inactivated HAV vaccine was compared. Altogether 117 children were vaccinated with either the inactivated or the live attenuated vaccine. Children were bled at months 1, 6, 7, 12 and 24, and the anti-HAV total IgG antibody and IgG subclass profile were assessed. In both vaccinated groups, the geometric mean titer (GMT) of anti-HAV peaked 7 months after the initial dose and declined during the following months. The IgG subclass profiles in both vaccinated groups were highly restricted to IgG1 and IgG3. Both vaccines have been shown highly effective in preventing viral hepatitis A in former studies.

Antigenic epitopes of the hepatitis A virus polyprotein

Forty-two antigenic domains were identified across the hepatitis A virus (HAV) polyprotein by using a set of 237 overlapping 20-mer synthetic peptides spanning the entire HAV polyprotein and a panel of serum samples from acutely HAV-infected patients. The term "antigenic domain" is used in this study to define a protein region spanned with consecutive overlapping immunoreactive peptides. Nineteen antigenic domains were found within the structural proteins, and 22 were found within the nonstructural proteins, with 1 domain spanning the junction of VP1 and P2A proteins. Five of these domains were considered immunodominant, as judged by both the breadth and the strength of their immunoreactivity. One domain is located within the VP2 protein at position 57-90 aa. A second domain, located at position 767-842 aa, contains the C-terminal part of the VP1 protein and the entire P2A protein. A third domain, located at position 1403-1456 aa, comprises the C-terminal part of the P2C protein and the N-terminal half of the P3A protein. The fourth domain, located at position 1500-1519 aa, includes almost the entire P3B, and the last domain, located at position 1719-1764 aa, contains the C-terminal region of the P3C protein and the N-terminal region of the P3D protein. It is interesting to note that four of the five most immunoreactive domains are derived from small HAV proteins and/or encompass protein cleavage sites separating different HAV proteins. The HAV-specific immunoreactivity of each antigenically reactive peptide was confirmed by using seven HAV seroconversion panels. Collectively, these data demonstrate that HAV structural and nonstructural proteins contain antigenic epitopes that can be efficiently modeled with short synthetic peptides.

Recombinant hepatitis A virus antigen: improved production and utility in diagnostic immunoassays

Hepatitis A virus (HAV) immunoassays use cell culture-derived HAV antigen to detect HAV-specific antibodies. The current method of production of HAV antigen in tissue culture is time-consuming and expensive. We previously expressed the HAV open reading frame in recombinant vaccinia viruses (rV-ORF). The recombinant HAV polyprotein was accurately processed and was assembled into subviral particles. These particles were bound by HAV-neutralizing antibodies and were able to elicit antibodies which were detected by commercial immunoassays. The present investigation compared the production of HAV antigen by standard tissue culture methods to the production of HAV antigen with the recombinant vaccinia virus system. In addition, HAV and rV-ORF antigens were assessed for their utility in diagnostic immunoassays. Serum or plasma samples from HAV antibody-positive and antibody-negative individuals were evaluated by immunoassay that used either HAV or rV-ORF antigen. All samples (86 of 86) in which HAV antibody was detected by a commercial enzyme-linked immunosorbent assay (ELISA) also tested positive by the recombinant antigen-based immunoassay (VacRIA). Similarly, all samples (50 of 50) that were HAV antibody negative also tested negative by the VacRIA. The lower limit of detection of HAV antibody was similar among immunoassays with either HAV or rV-ORF antigen. Thus, in the population studied, the sensitivity and specificity of the VacRIA were equivalent to those of the commercial ELISA. Since production of recombinant antigen is faster and less expensive than production of traditional HAV antigen, the development of diagnostic HAV antibody tests with recombinant HAV antigen appears warranted.

Analysis of immunoassays to detect antibodies to hepatitis A virus (anti-HAV) and anti-HAV immunoglobulin M

Two newly developed anti-HAV tests were assessed, using a total of 1835 sera. These two tests are being distributed under the trademarks Enzymun-Test anti-HAV and Enzymun-Test IgM anti-HAV. The anti-HAV test was compared to anti-HAV tests from other manufacturers and featured a high sensitivity combined with a high level of reproducibility and specificity. In terms of sensitivity, reproducibility and specificity, the IgM test proved to be comparable to other IgM anti-HAV tests used for the diagnosis of acute type A hepatitis. Combining both tests was shown to be useful to recognize an acute or past hepatitis A virus infection. In addition, the high sensitivity of the anti-HAV test makes this test extremely useful to assess the immunoresponse to the hepatitis A vaccine.

Effect of postexposure vaccination in a chimpanzee model of hepatitis A virus infection

Passive transfer of antibodies to hepatitis A virus (HAV) in immune globulin (IG) effectively prevents hepatitis A when given after exposure, but does not provide lasting protection from infection. Hepatitis A vaccines have been shown to generate quickly levels of antibody equivalent to those found after IG administration. The effect of hepatitis A vaccine in preventing infection following fecal-oral exposure was evaluated in a chimpanzee model of HAV infection. Two animals were vaccinated 1 and 3 days, respectively following inoculation and two inoculated animals served as unprotected controls. Of the two immunized animals, one had no evidence of HAV infection, while the other had an attenuated infection with no evidence of virus shedding. These results suggest that while postexposure hepatitis A vaccination may be infection permissive, it attenuates disease expression and prevents virus shedding.

Rolling review--the pathogenesis, diagnosis and management of viral hepatitis

Five major hepatotrophic viruses have been identified. The pathogenesis, diagnosis and treatment of chronic viral hepatitis continues to be intensely researched. Experimental evidence suggests that HLA restricted virus-specific T cells play a role in hepatocellular injury in type A hepatitis. The absence of chronic infection indicates the effectiveness of the host immune response to hepatitis A virus (HAV). It is postulated that HAV may rarely trigger an autoimmune chronic hepatitis. Active prophylaxis of hepatitis A is possible. The elimination of hepatitis B is dependent on the recognition of viral determinants in association with HLA proteins on infected hepatocytes by cytotoxic T cells. The specific epitopes recognized by B and T cells are being mapped. Polymerase chain reaction (PCR) amplification and sequencing of genomic DNA in patients with chronic hepatitis B has indicated that nucleotide substitutions in the genome are not uncommon. Their pathogenicity is being explored. Antiviral therapy for hepatitis B remains difficult. Interferon is effective in a proportion of patients. Thymosin may prove to be more effective immunomodulatory therapy. New nucleoside analogues suppress HBV replication, but the safety of these drugs has been questioned after the appearance of severe liver toxicity with fialuridine. The data that hepatitis D virus is pathogenic has recently been challenged with the observation that HDV re-occurs in transplanted liver after engrafting, but without signs of HBV recurrence or evidence of liver damage. Treatment of hepatitis D virus remains difficult. Several isolates of hepatitis C virus have been cloned, and the sequence divergence of these isolates indicates that there are several major genotypes and component subtypes of this polymorphic virus.(ABSTRACT TRUNCATED AT 250 WORDS)