An enzyme-linked immunosorbent assay for the detection of autoantibodies to albumin.

The development of an enzyme-linked immunosorbent assay (ELISA) for anti-albumin autoantibodies (AAA), using immobilized monomeric or glutaraldehyde-polymerized human, bovine or egg albumin, is described. Major problems in detection by the ELISA of AA against human albumin (HSA) were due to high 'non-specific' binding with the commercial anti-human immunoglobulin antisera used and to interference by IgM/HBs circulating complexes. However, it was found that AAA are not species-specific and that these problems may be overcome using immobilized bovine (BSA) or egg (EggA) albumin. AAA were found to have a similar affinity for BSA as for HSA but slightly lower for EggA, while AAA affinities for the monomeric forms were lower than for the corresponding polymeric albumins. All sera from the 28 normal subjects tested were found to contain both IgM- and IgG-AAA. Patients with acute hepatitis B (n = 23) had significantly lower titres of IgM-AAA than normal subjects, as did chronic HBV carriers with (n = 33) or without (= 17) underlying liver disease, while IgG-AAA titres were reduced only in the acute hepatitis patients. These findings support the concept that AAA have a normal physiological function (probably for removal of effete albumin molecules) and that, in HBV infection, there is a decrement in titres that may be related to the clearance of the virus

Binding and receptors for human albumin polymers and IgM/HBs circulating complex in HBsAg chronic carriers.

Binding activity for polymerized human serum albumin (pHSA-binding), studied in passive haemoagglutination, receptors for polymerized human serum albumin (pHSA-receptors), studied in ELISA, as well as the circulating IgM/HBs complex were tested in 71 chronic carriers of HBsAg with and without liver pathology. We found that 73.2% of the sera were reactive for pHSA-binding while 45% were reactive for pHSA-receptors and 42.2% for the circulating IgM/HBs complex. The distribution and mode of association of these 3 markers showed a close correlation with the e-antigen in circulation (HBeAg) and with liver disease (p less than 0.05). We further observed that pHSA-binding can be present in the absence of pHSA-receptors, suggesting the possible existence of further reactants in the serum-pHSA reaction. We did not observe any correlations between the circulating IgM/HBs complexes, pHSA-binding and pHSA-receptors. Blocking experiments, in fact, confirmed the non-involvement of polymerized human serum albumin in the formation of the circulating IgM/HBs complex. Elution experiments showed that, in addition to HBsAg, class-G immunoglobulins are also directly involved in the serum-pHSA reaction

Autoantibody to albumin of type G and M in acute and chronic viral hepatitis.

Autoantibodies to albumin (AAA) were tested by an ELISA method in patients with A, B and NANB acute and chronic hepatitis, and in a control group. AAA-IgM had a different behaviour in acute hepatitis type A, in which we observed a high average titre as compared with B, and NANB hepatitis, in which we observed a decrease in the average titre. In the chronic phase, we noted a decrement of the average titre in all the types of hepatitis. For AAA-IgG, in the acute phase the average titre in hepatitis A, B and NANB was lower than in the control group. In the chronic stage, only NANB hepatitis showed a decrement of the average titre of the antibody. On the base of these results, we can say that the involvement of AAA seems to be different in hepatitis A from the other two types, in which the decrement of average titre may be explained by the formation of immunocomplexes which are not detected by this test