Abstract
It is generally accepted that all primary isolates of feline leukemia virus (FeLV) contain a subgroup A virus (FeLV-A) that is essential for transmission. In contrast, FeLV-B is thought to arise de novo in the infected animal through RNA recombination events with endogenous FeLV transcripts, presumably through copackaging of RNA from endogenous FeLV and exogenous FeLV-A. Here, we report the complete genome sequences of two novel strains of FeLV-B (FeLV-2518 and FeLV-4314) that were isolated in the absence of FeLV-A. The env genes of these isolates have been characterized previously, and the 3′ recombination sites have been identified. We describe herein the 5′ recombination breakpoints of each virus. These breakpoints were found to be within the signal peptide of the env gene and the reverse transcriptase-coding region, respectively. This is the first report of a recombination site within the pol gene of an FeLV-B genome and the first genetic characterization of multiple independently arising FeLV-B isolates that have been identified without a functional FeLV-A ancestral virus.
Highlights
It is generally accepted that all primary isolates of feline leukemia virus (FeLV) contain a subgroup A virus (FeLV-A) that is essential for transmission
We recently reported the first known identification of feline leukemia virus subgroup B (FeLV-B) strains isolated without an accompanying subgroup A virus [1]
As full-length, putatively functional, endogenous FeLV proviruses have been described [3], and other enFeLV loci are known to be transcriptionally active [4,5,6], it is possible that the genomically intact enFeLV elements are transmitted in a horizontal manner between hosts
Summary
It is generally accepted that all primary isolates of feline leukemia virus (FeLV) contain a subgroup A virus (FeLV-A) that is essential for transmission. As full-length, putatively functional, endogenous FeLV (enFeLV) proviruses have been described [3], and other enFeLV loci are known to be transcriptionally active [4,5,6], it is possible that the genomically intact enFeLV elements are transmitted in a horizontal manner between hosts. Such viruses would present as comprising FeLV-B only in subgroup analyses due to the shared receptor-binding properties of FeLV-B and enFeLV Env proteins [7, 8].
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