The Recoverability of Virus From Papillomas Produced Therewith in Domestic Rabbits

Abstract

By preliminary preparation of the skin in ways that render it hyperplastic the presence of infective virus can be demonstrated in extracts of domestic rabbit papillomas which yield no growths when inoculated by the ordinary methods and which for this reason have been supposed to contain no virus. The amount of virus recovered by the method outlined in the present work, however, is small when compared with the yield obtained in most instances from comparable cottontail rabbit papillomas. The yield is greatly influenced not only by the virus strain used to produce the growths but by the individual rabbit host. Although virus has been obtained from papillomas produced in domestic rabbits by all of the virus strains tested, a total of 21 thus far, only about one-fourth of these strains are readily to be procured again from the growths they cause and the others are demonstrable only in hosts in which the conditions are favorable for reasons unknown. An experimental comparison of the capacity of suspensions of papilloma tissue from domestic and cottontail rabbits to elicit specific antibodies has shown that the titers attained are approximately proportional to the amount of infective virus demonstrable in the suspensions. The findings as a whole indicate that far less virus exists in infective or antigenic form in the papillomas of domestic rabbits than in those of cottontail rabbits.

Variation in the Nucleotide Sequence of Cottontail Rabbit Papillomavirus a and b Subtypes Affects Wart Regression and Malignant Transformation and Level of Viral Replication in Domestic Rabbits

“…CRPV vegetative DNA replication, late transcripts, and capsid antigens are seldom detected in domestic rabbit warts (37,41,62). CRPV strains recoverable from domestic rabbit warts have been reported, however (18,50,52), suggesting a genetic heterogeneity of the virus. This prompted us to compare the FIG.…”

“…Warts of naturally infected cottontail rabbits usually contain large amounts of virions, in spite of a great variation in virus content observed among rabbits (3). In contrast, little, if any, infectious virus is recovered from domestic rabbit warts (3, 18, 51, 52), and vegetative viral DNA replication, late transcripts encoding L1 and L2 capsid proteins, and capsid antigens are seldom detected (35,37,41,62).The first evidence for a biological variation of CRPV has been the isolation of strains recoverable from domestic rabbit warts (18,50,52). The existence of cancer-producing variants was proposed to account for tumor progression (44) but could not be substantiated (43,45,53).…”

“…The first evidence for a biological variation of CRPV has been the isolation of strains recoverable from domestic rabbit warts (18,50,52). The existence of cancer-producing variants was proposed to account for tumor progression (44) but could not be substantiated (43,45,53).…”

“…This has provided a model system to demonstrate that the E5 and L2 ORFs are dispensable for papilloma induction (7,34). Both wart evolution and the level of CRPV replication in warts have been shown or were suspected to depend on the genetic constitution of the host (3,23,30,54) and on the genetic variability of the virus (18,44,46,48,52). Wart regression occurs in less than 10% of cottontail rabbits, and its frequency varies between 10 and 70% in domestic rabbits (9,54).…”

“…Warts of naturally infected cottontail rabbits usually contain large amounts of virions, in spite of a great variation in virus content observed among rabbits (3). In contrast, little, if any, infectious virus is recovered from domestic rabbit warts (3,18,51,52), and vegetative viral DNA replication, late transcripts encoding L1 and L2 capsid proteins, and capsid antigens are seldom detected (35,37,41,62).…”