A sample of aphthovirus type C3 strain Resende carrying two polyribocytidilic
acid [
poly(C)] tracts was cloned in tissue culture. One clone with a
poly(C)-rich tract of about 145
nucleotides long (clone 3B) and another with a
poly(C)-rich tract of about 230
nucleotides long (clone 12) and a mixture of both were injected intralingually into three steers. Samples from all three animals were recovered during the acute phase of the disease, from the blood and from the feet, and at various days after inoculation from the oesophageal-pharyngeal (OP) fluids. Analysis of the viral RNAs of the positive samples by means of
RNase T1 maps on one- and two-dimensional
gels showed (1) changes in the electrophoretic mobility of the
poly(C)-rich tracts of viruses recovered from the OP fluids at various times after
infection; (2) selection of virus populations with
poly(C)-rich tracts of increased size; (3) later on, changes in the patterns of
oligonucleotides of persistent viruses. These variations may lead to the production of new strains with altered
biological properties that may contribute to the maintenance and spread of these viruses in the field.