An improved method for hemagglutinin extraction from feline herpesvirus type 1-infected cell line

Hemagglutination (HA) activity of feline herpesvirus type 1 (FHV-1) propagated in feline lung cell culture and two established feline cell lines, CRFK and fcwf-4, was investigated. Intra- and extracellular crude samples obtained from those infected cell cultures did not show HA activity. However, when treated with tween 80-ether, HA activity appeared. There was no correlation between virus infectivity titers and the HA titers at various harvesting times, and besides, hemagglutinins were found in intracellular samples at the early stage of infection. By ultrasonic destruction of the infected fcwf-4 cells, high titer hemagglutinins were obtained. High titer hemagglutinins were also extracted successfully from infected fcwf-4 cell membranes by solubilization with any of the three detergents: Triton X-100, DOC, and CHAPS. The optimal concentrations of each detergent for solubilizing hemagglutinin were 0.05 (v/v)%, 0.5 (w/v)%, and 0.1-0.2 (w/v)%, respectively. The HA activities of both the ultrasonic-treated hemagglutinin and the detergent-soluble hemagglutinin from infected fcwf-4 cells were inhibited specifically by anti-FHV-1 sera. Therefore, either hemagglutinin could be used as HA antigen for the hemagglutination-inhibition test.