F8701: a FeLV-A variant with a broader cellular host range in culture

The Journal of general virology · 2026

In plain language

This study used cells grown in the laboratory, not live animals. The F8701 variant multiplied in cat cells comparably to other FeLV-A strains and in one dog cell line more efficiently than the reference strains tested. The assays also showed greater entry into several cell lines from other mammals, but this does not demonstrate that the virus multiplies in all of them. These findings do not establish how it behaves in live cats, whether it infects or spreads between dogs, or any clinical intervention.

Scientific detail

The in vitro study published in The Journal of general virology in 2026 (doi: 10.1099/jgv.0.002316) examined the cellular host range and subgroup identity of the naturally occurring FeLV-A variant F8701. Clone-derived F8701 was replication-competent in feline cells and grew comparably to established FeLV-A strains. Controlled interference assays in feline FEA cells supported retention of the FeLV-A subgroup phenotype despite its broader cellular host range. These findings are not evidence of clinical behavior, replication or transmission in live cats.

F8701 Env mediated greater pseudotype infectivity than Glasgow-1 Env in several non-feline mammalian cell lines. This finding describes cellular entry and does not establish productive infection in every cell type tested or infection of humans or other animals in vivo. In cultured canine D17 cells, F8701 did undergo productive replication more efficiently than the reference FeLV-A strains tested. The article title also identifies this variant's use of canine thiamine transporter 1.

The four experimental findings are assigned evidence level D in the knowledge object. The qPCR measurements included n = 3 technical replicates from a single infection experiment. Focus, entry, host-range and growth-kinetics titre assays reported n = 4 technical replicate wells. Feline and canine growth kinetics each came from a single experiment; several other assays were described as representative without reporting the total number of independent biological experiments. Technical replicates are not independent biological repetitions, and the non-feline findings are subject to the level D cap specified in the object.

Receptor abundance was not measured quantitatively, so differences in transfection efficiency or receptor expression could have influenced comparisons between receptor assays. No site-directed mutagenesis was performed to establish a causal contribution of the Env 105 N residue to F8701's broad cellular tropism; the data should not be interpreted as demonstrating causality. Receptor determinants in other non-feline cell types remain undefined.

Replication in cultured canine cells does not establish organism-level susceptibility, persistent infection, disease or transmission in dogs in vivo. Whether F8701 can establish productive infection or transmission in live dogs remains unknown. The study provides findings on FeLV entry and replication but does not establish infection of non-feline animals in vivo or any clinical intervention.

What we know

With level D evidence, clone-derived F8701 replicated in feline cells with growth comparable to established FeLV-A strains, retained the subgroup A interference phenotype, showed greater Env-mediated pseudotype infectivity than Glasgow-1 in several non-feline cell lines, and replicated productively in canine D17 cells more efficiently than the reference strains tested. These are cell-culture findings; the growth kinetics come from single experiments with technical replicates.

What we don't know

Whether the Env 105 N residue causally contributes to F8701's broad cellular tropism remains unresolved, as do receptor determinants in other non-feline cell types. The extent to which transfection efficiency or receptor expression may have influenced comparisons was not quantified either. The findings do not establish productive infection in every cell type tested, clinical behavior in cats, or infection of humans or other non-feline animals in vivo. Productive or persistent infection, disease and transmission in dogs remain unestablished. No clinical intervention has been established.

Evidence

Provenance

This project does not diagnose or prescribe. Always consult your veterinarian.