Nineteen isolants of infectious bronchitis virus (IBV), including most of the recently reported new isolants, were adapted to chick kidney cell cultures. After plaque purification and the preparation of antiserums against purified strains, antigen interrelatedness was evaluated with cross-neutralization tests by the plaque-reduction technique. The results indicated that there are 7 serotypes current in the United States and that the Australian "T" strain is distinct from each of these. Antigenic variants occurred within some of these serotypes.
An infectious bronchitis virus (IBV) hemagglutination-inhibition (HI) test was used to assay serum-antibody titers after IBV vaccination of IBV-susceptible specific-pathogen-free broilers and commercial layers. Three-week-old broilers were vaccinated via eye-drop with IBV strains that represent the antigenic spectrum of commercial vaccines--Holland, Massachusetts 41 (41 Ms), Connecticut 46, Florida 18288, or JMK strain--and revaccinated 3 weeks later with either the same or a heterologous strain. Weekly serum samples were tested by IBV HI with homologous and heterologous antigens. Vaccinates, except for those vaccinated with the Holland strain, were HI-positive with homologous but not heterologous antigens by 1 to 2 weeks postvaccination. Sixteen-week-old IBV-vaccinated commercial layers were revaccinated with IBV Holland 52 (H 52) strain and subsequently infected with Arkansas 99 (Ark 99) and SE 17 strains. In contrast to the limited HI cross-reactivity of serum from IBV-vaccinated broilers, there were extensive cross-reactions in HI tests with 41 Ms, H 52, Ark 99, and SE 17 antigens of revaccinated layers. These results demonstrate that the IBV HI test is more strain-specific than previous reports indicate, especially when the test samples are from early postvaccination.
The influence of the composition of water-in-oil emulsions on their physical characteristics was determined by preparing experimental emulsions with various water-to-oil ratios and various emulsifiers. Emulsions containing Tween 80 in the aqueous phase and Arlacel A or Arlacel 80 in the oil phase were lower in viscosity than emulsions containing only an oil-phase emulsifier. Viscosity decreased as the concentration of oil increased. Oil-emulsion vaccines prepared with aqueous- and oil-phase emulsifiers had low viscosity, were stable for more than 12 weeks at 37 C, and induced a marked primary antibody response in chickens.
Mycoplasma synoviae (MS) obtained from broiler chickens condemned for airsacculitis was used to determine the influence of air temperature and relative humidity on the severity of airsacculitis produced experimentally. Infectious bronchitis virus was administered to 3-week-old broilers 5 days before aerosol exposure to MS broth cultures, producing extensive airsacculitis within 21-day study periods. High (31-32 C), medium (19-24 C), and low (7-10 C) air temperatures were studied in conjection with high (75-90%), medium (38-56%), and low (23-26%) relative humidities. Airsacculitis was most extensive (45%) at low temperatures regradless of high or medium humidity. The incidence of airsacculitis was greater (39%) at low humidity than at high humidity (17%) when air temperatures were medium. At high temperature, the trend was toward more airsacculitis (12%) at high humidity than (5%) at low humidity. However, the effect of cold air temperature was more dominant than the effect of relative humidity.
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