Feline leukemia virus infection requires a post-receptor binding envelope-dependent cellular component

Area of Science:

• Virology
• Cell Biology
• Molecular Biology

Background:

• Gammaretrovirus receptors are thought to mediate virus binding and entry.
• Feline leukemia viruses (FeLVs) are gammaretroviruses with specific host cell tropisms.

Purpose of the Study:

• To investigate the cellular determinants required for feline leukemia virus (FeLV) infection beyond receptor expression.
• To identify factors contributing to resistance or susceptibility of different cell lines to FeLV pseudotype viruses.

Main Methods:

• Overexpression of FeLV receptors in murine NIH 3T3 and baby hamster kidney (BHK) cells.
• Infection assays using FeLV pseudotype viruses with varying core and envelope proteins.
• Cell fusion experiments between susceptible and resistant cell lines.
• Analysis of conditioned media for secreted factors.

Main Results:

• NIH 3T3 and BHK cells expressing FeLV receptors showed weak susceptibility to FeLV pseudotype viruses, unlike Mus dunni tail fibroblast (MDTF) cells.
• Resistance was not due to envelope binding defects, low receptor levels, or glycosylation.
• Fusion with susceptible cells (MDTF, TE671) alleviated FeLV resistance in NIH 3T3 and BHK cells.
• A cell-associated, envelope-dependent factor, not a secreted one, is implicated in FeLV infection.

Conclusions:

• FeLV infection necessitates an additional cellular component, distinct from the viral receptor.
• This component is envelope-dependent and its absence in certain cell lines confers resistance to FeLV.
• Susceptibility to FeLV is determined by both receptor expression and the presence of this additional cellular factor.