Host range and receptor binding properties of vectors bearing feline leukemia virus subgroup B envelopes can be modulated by envelope sequences outside of the receptor binding domain

Abstract

To evaluate host range differences between two different strains of feline leukemia virus subgroup B (FeLV-B), we compared the binding and infectivity patterns of retrovirus vectors bearing either FeLV-B-90Z or FeLV-B-GA envelopes. We report here that the ability of these envelopes to utilize different Pit1 orthologs is mediated primarily by the receptor binding domain; however, in the case of FeLV-B-90Z, the C terminus also contributes to the recognition of certain Pit1 orthologs.

FIG. 1.

Susceptibility of various cell lines to infection by FeLV-B correlates with cell surface binding. (A) Cells were infected with retrovirus vectors packaging a genome containing the lacZ gene and bearing either FeLV-B-90Z (solid bars) or FeLV-B-GA (open bars) envelopes. Titers are expressed as the mean numbers of bfu per milliliter ± the standard errors of the means and are based on the results of experiments done in triplicate; asterisks indicate a titer of <10 bfu/ml. (B to D) Histograms from flow cytometric analysis of cells stained with fluorescein-conjugated monoclonal antibody HA.11, recognizing soluble HA-tagged FeLV-B-90Z and FeLV-B-GA SU. For each panel, the x axis represents fluorescence intensity (log scale) and the y axis represents cell number. Areas under bold black lines represent negative control cells which were incubated with medium only, followed by addition of fluorescein-conjugated HA.11 antibody. Gray-shaded areas correspond to MDTF-Pit1 (B), SIRC (C), or NRK 6509 (D) cells exposed to either FeLV-B-90Z SU or FeLV-B-GA SU.

FIG. 2.

Histograms of flow cytometric analyses showing binding of FeLV-B-90Z_RBD or FeLV-B-90Z SU to cells. Binding was detected by staining cells with fluorescein-conjugated monoclonal antibody HA.11, which recognizes soluble HA-tagged SU. The x axis represents fluorescence intensity (log scale), and the y axis represents cell number. Areas under bold black lines represent negative control cells which were exposed to medium only, followed by incubation with fluorescein-conjugated HA.11 antibody. Gray-shaded areas correspond to MDTF-Pit1 or mink CCL 64 cells binding to either FeLV-B-90Z_RBD SU (A and C) or FeLV-B-90Z SU (B and D).