Summary auto-generated
This study addresses a significant problem in diagnosing acute viral infections: non-specific binding of human IgM antibodies to cytoplasmic structures in virus-infected cells, which creates false positive results in immunofluorescence and enzyme immunoassays. The researchers identified that formaldehyde selectively inactivates cytoplasmic receptors for human IgM without affecting viral antigens, thereby reducing background interference. They tested this approach on Epstein-Barr virus (EBV), cytomegalovirus (CMV), and central European encephalitis virus antigens. For EBV detection using immunofluorescence, formaldehyde treatment eliminated non-specific staining while preserving antibody detection sensitivity, allowing use of lower serum dilutions. Alternatively, using isolated nuclei from infected cells provided receptor-free antigens, which proved particularly effective for CMV. The researchers demonstrated through enzyme immunoassays that formaldehyde treatment reduced non-specific IgM binding to CEE virus antigen while maintaining specific antibody titers. These improvements enhance both specificity and sensitivity of IgM antibody detection for diagnosing acute viral infections.
Key findings
- Formaldehyde treatment selectively inactivates cytoplasmic IgM receptors on virus-infected cells while preserving viral antigen integrity and immunogenicity
- Using isolated nuclei instead of whole cell extracts as antigen eliminates non-specific IgM binding, as immunoglobulin receptors are located only in the cytoplasm
- Formaldehyde-treated cell preparations allow detection of virus-specific IgM at lower serum dilutions, increasing assay sensitivity for EBV, CMV, and CEE virus
- The anti-complement immunofluorescence (ACIF) technique successfully differentiates specific from non-specific IgM binding by detecting only complement-fixing antibodies
- Serum specimens containing high IgM concentrations without specific antibody activity should be included as negative controls to identify non-specific reactions
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Abstract
A non-specific reaction between human IgM and cytoplasmic structures of virus infected cells can often be observed if IgM antibodies to virus antigens are detected by indirect immunofluorescence or by immuno enzyme assays. Formaldehyde selectively inactivates the cytoplasmic receptors for human IgM without affecting the virus structural proteins. Alternatively, receptor-free antigens can be obtained by isolation of nuclei from virus infected cells. Due to reduced back-ground, a more specific and more sensitive detection of IgM antibodies to Epstein-Barr virus, cytomegalovirus or central European encephalitis virus is possible.