Morphologic heterogeneity of a strain of swine influenza virus (A/swine/Wisconsin/1/68, Hsw1N1) propagated at different temperatures
Pirtle, E.C.; Ritchie, A.E.
American Journal of Veterinary Research 36(12): 1783-1787
1975
ISSN/ISBN: 0002-9645 PMID: 1200448 Document Number: 95011
Strain A/swine/Wisconsin/1/68 (WI/68) swine influenza virus (SIV) was propagated in embryonating chicken eggs at 33, 35, or 37 C. The SIV harvested from eggs incubated at 33 C invariably had higher hemagglutination (HA) and egg infectivity titers than did SIV propagated in eggs at the 2 higher temperatures. When SIV inoculum propagated at 33 C was inoculated into separate groups of eggs and incubated at 33, 35, and 37 C, the SIV harvested from inoculum incubated at the 2 higher temperatures had significantly lower infectivity and HA titers than did that propagated at 33 C. By electron microscopy (EM), viral particles of Wi/68 were of various sizes and shapes regardless of the temperature used to propagate the virus. However, in contrast to what was seen in SIV harvested from innoculum incubated at 33 C incubation, pleomorphic shapes and particles with surface abnormalities were much more frequent in SIV harvested from inoculums kept at the 2 higher temperatures. Approximately one-third of the particles from 35 and 37 C incubation either were spikeless or were relatively deficient in surface spikes.