Infectious bronchitis agar-gel precipitin test--use of infected allantoic fluid as antigen.

The use of infected allantoic fluid (AF) as precipitating infectious bronchitis (IB) antigen was investigated. The results show that unconcentrated AF harvested at the right time can be a very satisfactory precipitating IB antigen. With the majority of the virus strains used, unconcentrated AF, harvested 68 hours postinoculation (PI), showed more precipitating activity than that harvested at 20 or 120 hours PI. If further antigen concentration is required, dialysis with polyethyleneglycol MW 20,000, freeze-drying, and precipitation with polyethyleneglycol 6,000 are satisfactory methods of concentration.