MuLV

MuLV, or murine leukemia virus, is a group of gammaretroviruses within the family Retroviridae. They are enveloped, single-stranded positive-sense RNA viruses with a genome about 7.5 to 8.5 kilobases in length. The genome is organized into long terminal repeats flanking the gag, pol, and env coding regions. As retroviruses, MuLVs replicate through reverse transcription and integration of the viral genome into the host DNA, with expression driven by promoter activity in the LTRs.

MuLVs are classified by their envelope glycoproteins into ecotropic, xenotropic, polytropic, and amphotropic groups, which determine the range of cells and species they can infect. Ecotropic MuLVs infect mouse cells; xenotropic and polytropic MuLVs can infect cells from other species, while amphotropic MuLVs have a relatively broad host range. Natural infection in mice can lead to various diseases, most notably leukemia or related neoplasms; disease outcomes depend on viral strain, host genetics, and insertional effects on host genes.

In addition to exogenous viruses, endogenous MuLV sequences are present in the mouse genome and can be reactivated or recombined under certain conditions. Some strains, such as those involved in the Friend virus complex, are associated with erythroleukemia in susceptible mice due to viral genes and accompanying viral factors.

MuLVs have been extensively used in molecular biology as vectors for gene delivery. Replication-incompetent MuLV-based vectors are produced in packaging cell lines that provide gag, pol, and env in trans. These vectors primarily transduce dividing cells, and their integration into the host genome poses a risk of insertional mutagenesis, necessitating careful biosafety considerations and adherence to guidelines appropriate to their use.