Enhancement of hemagglutinating activity of Haemophilus gallinarum by trypsin.

Strain used. HG, strain 221, obtained from the National Institute of Animal Health, Tokyo, was passaged twice in egg yolk after receipt, lyophilized, and stored under refrigeration. This strain was used as seed culture for antigen preparation. Broth. Kato's broth was used for HG cell preparation (4). The medium contained 0.5% polypeptone, 0.5% NaCl, 0.1% casamino acid (vitamin free), 0.5% sodium glutamate, 0.1% glucose, 0.2% potassium phosphate, 1% yeast extract, and 0.5% chicken serum. Antigen preparation. The seed culture was prepared in yolk sac inoculation of 6-days-embryonating chicken eggs and inoculated onto 10% rabbit blood agar, which was cultured for 18 to 24 hours at 37 C in C02 incubators providing a 5% C02 atmosphere. Initially, the HG culture was incubated in 10 ml of chicken meat infusion broth supplemented with 0.5% chicken serum at 37 C for 18 to 24