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Updated: Jun 14, 2026
An Optimized Hemagglutination Inhibition (HI) Assay to Quantify Influenza-specific Antibody Titers
Published on: December 1, 2017
Enhancement of neutralizing activity of influenza virus-specific antibodies by serum components
Krystyna Mozdzanowska1, Jingqi Feng, Mark Eid
1Immunology Program, The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104-4268, USA.
Abstract:
The role of serum components in enhancing virus neutralizing (VN) activity of influenza virus A/PR/8/34 hemagglutinin (HA)-specific MAbs in vitro was investigated. The degree of enhancement depended on the MAb's fine specificity and heavy chain isotype and on type of serum. Greatest enhancement (>100-fold) was seen with sera from immunodeficient mice that lacked serum immunoglobulin. At least two serum components were involved: C1q and a heat-resistant factor. C1q was mandatory for enhancement, and other components of the complement system were not required. C1q appeared to operate by improving MAb-mediated inhibition of virus attachment to host cells and was most effective with MAbs that inhibited virus attachment poorly on their own. The heat-resistant factor enhanced VN activity only in the presence of C1q and appeared to operate by enhancing VN activity at a post-attachment stage.
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