Heat-Labile Factor Necessary for Hemagglutination-Inhibition Testing of Horse Sera

Abstract

Normal and immune sera were obtained from horses immunized with either aqueous, alum, or adjuvant bivalent vaccines containing Milford equine 2 virus. Upon heating at 56 C for 30 min, a factor, required for hemagglutinationinhibition but not complement fixation or neutralization testing, was destroyed. This factor which is present in normal sera does not appear to be complement.

Comparison of Immunization Methods for Producing Reference Adenovirus Antisera in Horses

“…This supports our extensive observations that equine antisera do not contain nonspecific inhibitors or complement components in sufficient levels to affect HI or SN antibody titers. Hence heat-inactivation of equine antisera for AV serology appears to serve no useful purpose, and may in fact destroy heat-labile factors that could be essential (4,23).…”

Comparison of serum treatments to remove nonspecific inhibitors from chicken sera for the hemagglutination inhibition test with inactivated H5N1 and H9N2 avianInfluenza A virussubtypes

“…The heat-labile factor, one of the NSIs in serum, is known to be destroyed by heating at 56°C for 30 min. 7 Nonspecific agglutination of the chicken erythrocytes used in the HI test can be removed by pretreatment of the serum with chicken erythrocytes. 15 Kaolin adsorbs NSIs but may not completely inactivate them.…”