Relative functional affinity of specific anti-core IgG in different categories of hepatitis B virus infection

Abstract

While resolution of hepatitis B virus (HBV) infection occurs in most cases, a carrier state can exist in which the HBV surface antigen (HBsAg) persists. Some carriers are also positive for the HBV "e" antigen (HBeAg), indicative of high viral replication. Others are HBV "e" antibody (anti-HBe)-positive carriers in whom there appears to be a fall in the level of viral replication with the appearance of antibodies against the "e" antigen. The former group of carrier is considered to be at a higher risk of transmitting HBV infection than the latter. In order that a carrier state may occur, some degree of tolerance to the infectious agent must exist. A study of the rate of increase of specific antibody avidity following infection provides a means of assessing the maturity of the immune response to an infectious agent. Since antibodies specific for the HBV core antigen (HBcAg) are produced in almost all cases of HBV infection and the HBeAg and HBcAg share a large number of amino acids and some B- and T-cell epitopes, the increase in the avidity of antibodies against the HBV core antigen (anti-HBc) in cases of acute, resolving HBV infection and in HBV carriers has, therefore, been studied. An increase in the avidity of specific antibody, similar to that seen in other viral infections, was observed following acute, resolving infection. However, low avidity antibody persisted longer in carriers who remained positive for HBeAg, whereas in cases where there were antibodies specific for HBeAg, the anti-HBc antibody was of high avidity. Analysis of sequential sera from carriers who seroconverted from HBeAg-positive to anti-HBe-positive showed that an increase in anti-core avidity could predate seroconversion from HBeAg-positive to anti-HBe-positive status. Thus, anti-HBc avidity studies may be of diagnostic and prognostic significance.

Anti-HCV IgG avidity index in acute hepatitis C

“…A progressive increase in antibody avidity after exposure to an immunogen has been demonstrated in several other infectious diseases (Eggers et al, 2000;Jenum et al, 1997;Kangro et al, 1991;Puchhammer-Stockl et al, 2005;Rodella et al, 2006;Suligoi et al, 2002Suligoi et al, , 2003Thomas, 1997;Ward et al, 2001). The HCV-AI values observed on admission in our AHC patients were clearly lower than those found in the CHC group, confirming the data from two pilot studies (Kanno et al, 2002;Ward et al, 1994).…”

Quantitative analysis of HBsAg, IgM anti-HBc and anti-HBc avidity in acute and chronic hepatitis B

“…We assayed the anti-HBc avidity by an experimental procedure requiring only a 1:10 predilution of the specimens in a chaotropic agent and in neutral buffer before anti-HBc testing, thus minimizing pre-analytical variations (Suligoi et al, 2002). In the only systematic experience published so far (Thomas, 1997) an increase in the avidity of this specific antibody, similarly to what happens in other viral infections, has been observed in patients with an acute, resolving infection, while low avidity antibodies persisted in HBeAg-positive patients who progressed towards chronicity. The possibile occurrence of an increase of anti-HBc avidity in acute cases before seroconversion from HBeAg to anti-HBe is consistent with our data obtained on convalescent specimens, mostly HBeAgnegative, who had an average AI close to 1 (0.91 ± 0.14) and only one result below the proposed threshold of 0.70.…”

“…To do that, the measurement of the avidity index of anti-HBc antibodies, that are detectable in all phases of HBV infection, may represent an interesting tool (Thomas, 1997), but no assay is currently available. Another diagnostic dilemma is the differentiation between inactive carriers and chronic hepatitis cases, since both forms are asymptomatic for long periods of time.…”

Development of Fully Automated Determination of Marker-Specific Immunoglobulin G (IgG) Avidity Based on the Avidity Competition Assay Format: Application for Abbott Architect Cytomegalovirus and Toxo IgG Avidity Assays

“…Avidity tests have been developed for rubella virus (17), Toxoplasma gondii (5,8,18), cytomegalovirus (CMV) (1), varicella-zoster virus (11), human immunodeficiency virus (25), hepatitis viruses (22,26,27,29), Epstein-Barr virus (28), and others. For immunocompetent, untreated individuals, the presence of low-avidity IgG directed against pathogens may indicate a recent infection, whereas the presence of high-avidity IgG excludes a primary infection (13,14).…”