Bovine serum albumin antibodies as a disease marker for hepatitis E virus infection

Abstract

This report evaluates the significance of antibody/bovine serum albumin (BSA) interactions as a risk factor for the diagnosis of acute hepatitis E. Serum samples from 40 patients with acute hepatitis E and from 40 age/sex matched healthy adult subjects were tested for IgA, IgG, and IgM by ELISA and by turbidimetric assay. BSA was used as a target to characterize changes in levels of interacting immunoglobulins. Initial results obtained before removal of antibodies that interacted with BSA suggested that HEV patients had increased levels of IgM in their sera. It was found that normal individuals had mean IgA, IgG, and IgM levels of 2.55 mg/mL, 9.80 mg/mL, and 1.73 mg/mL, respectively while HEV patients had mean levels of 2.66 mg/mL, 10.04 mg/mL, and 2.01 mg/mL ($P < .26$ , $P < .32$, and $P < .0004$). However, the mean level of IgM in HEV-infected sera after purification from antibodies that interacted with BSA was determined to be 1.72 mg/mL indicating that there was no significant difference in IgM level in HEV patients compared to normal individuals ($P < .6$). The presence of antibodies that interact with BSA might serve as a diagnostic tool for detection of high-risk patients.

Figure 1

Immuno-precipitation and polyacrylamide gel electrophoresis of human serum samples with anti-human IgM. Three HEV-infected serum samples were immuno-precipitated with anti-IgM antiserum developed in rabbit in the absence (lanes A, B, and C resp) or presence of BSA (lanes F, E, and D resp). Lane H contained one normal serum sample in the absence of BSA and Lane G contained the same normal serum sample in the presence of BSA. Lane I represents standard human IgM. H indicates positions of immunoglobulin heavy chains. The precipitates were washed, dissolved in Laemmli sample buffer, and analyzed by polyacrylamide gel electrophoresis.

Figure 2

Serum IgM levels in groups of HEV-infected sera and unaffected control measured by ELISA. Comparison of average serum IgM (mean ± SD).