Species-specific, postentry barriers to primate immunodeficiency virus infection

Abstract

By using replication-defective vectors derived from human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency virus (SIV(mac)), and murine leukemia virus (MuLV), all of which were pseudotyped with the vesicular stomatitis virus (VSV) G glycoprotein, the efficiency of postentry, early infection events was examined in target cells of several mammalian species. Titers of HIV-1 vectors were significantly lower than those of SIV(mac) and MuLV vectors in most cell lines and primary cells from Old World monkeys. By contrast, most New World monkey cells exhibited much lower titers for the SIV(mac) vector compared with those of the HIV-1 vector. Prosimian cells were resistant to both HIV-1 and SIV(mac) vectors, although the MuLV vector was able to infect these cells. Cells from other mammalian species were roughly equivalent in susceptibility to the three vectors, with the exception of rabbit cells, which were specifically resistant to the HIV-1 vector. The level of HIV-1 vector expression was very low in transduced cells of rodent, rabbit, cow, and pig origin. Early postentry restriction of primate immunodeficiency virus infection exhibits patterns largely coincident with species borders and applies to diverse cell types within an individual host, suggesting the involvement of species-specific, widely expressed cellular factors.

FIG. 1

Vectors used in the study. The HIV-1, SIV_mac, and MuLV vectors used in the study are shown. The construction of the vectors is described in Materials and Methods.

FIG. 2

Infection of cells from different mammals with HIV-1 and SIV_mac vectors. (A) Medium containing recombinant HIV-1 or SIV_mac vectors was normalized according to reverse transcriptase and added in serial dilutions to the indicated cells, which were incubated for 5 days. Cells were then trypsinized if necessary, fixed in 3.7% formaldehyde, and analyzed by FACS (Becton Dickinson FACscan). The average IR_H/S ratio and standard deviation derived from at least two independent experiments are shown. (B) An example of the data used to generate Fig. 2A is shown. Human (HEK293), owl monkey (OMK), and squirrel monkey (Pindak) cells were infected with replication-defective HIV-1, SIV_mac, and MuLV vectors expressing GFP. Five days later, fluorescence microscopy was performed.

FIG. 3

Infectibility of primary cells by HIV-1, SIV_mac, and MuLV vectors. Primary cells from rhesus monkeys (A), tree shrews (B), and squirrel monkeys (C) were infected with HIV-1, SIV_mac, and MuLV vectors as described in Materials and Methods, alongside control cell lines (HEK293, OMK, and Pindak). The infectious titer of each vector in a typical experiment is shown. Although the absolute values of infectivity varied between experiments, the relative infectivity of the vectors was comparable in different experiments.

FIG. 4

Fluorescence intensity of GFP in HIV-1 vector-infected cells. The indicated cells were infected with the HIV-1 vector as described in Materials and Methods. GFP-positive and -negative cells were gated separately, and positive values were normalized for background fluorescence. The values shown represent the geometric mean (fold above background).

FIG. 5

Effect of multiplicity of infection on the infectibility of cells. Cells were infected, as described in Materials and Methods, with various dilutions of the HIV-1 and SIV_mac vectors. The infectious titer of each vector is indicated (HIV-1, solid lines and datum points; SIV_mac, broken lines and open datum points).