Substitutions in the glycoprotein (GP) of the Candid#1 vaccine strain of Junin virus increase dependence on human transferrin receptor 1 for entry and destabilize the metastable conformation of GP.

Candid#1 (Cd1) is an attenuated vaccine strain of Junin virus, the causative agent of Argentine hemorrhagic fever. Although several substitutions are present in Cd1, their importance for attenuation has not been established. We functionally characterized the substitutions present in the Cd1 glycoprotein (GP) and identified F427I in the transmembrane domain of the GP2 subunit as reducing infectivity in a reconstituted viral system.

HIV-1 Vpu and HIV-2 Env counteract BST-2/tetherin by sequestration in a perinuclear compartment.

Background: In the absence of the Vpu protein, newly formed HIV-1 particles can remain attached to the surface of human cells due to the action of an interferon-inducible cellular restriction factor, BST-2/tetherin. Tetherin also restricts the release of other enveloped viral particles and is counteracted by a several viral anti-tetherin factors including the HIV-2 Env, SIV Nef and KSHV K5 proteins.

Results: We observed that a fraction of tetherin is located at the surface of restricting cells, and that co-expression of both HIV-1 Vpu and HIV-2 Env reduced this population.

Ebola virus glycoprotein counteracts BST-2/Tetherin restriction in a sequence-independent manner that does not require tetherin surface removal.

BST-2/tetherin is an interferon-inducible protein that restricts the release of enveloped viruses from the surface of infected cells by physically linking viral and cellular membranes. It is present at both the cell surface and in a perinuclear region, and viral anti-tetherin factors including HIV-1 Vpu and HIV-2 Env have been shown to decrease the cell surface population. To map the domains of human tetherin necessary for both virus restriction and sensitivity to viral anti-tetherin factors, we constructed a series of tetherin derivatives and assayed their activity.

Vpu-dependent block to incorporation of GaLV Env into lentiviral vectors.

Background: The gibbon ape leukemia virus (GaLV) Env protein mediates entry into a wide range of human cells and is frequently used to pseudotype retroviral vectors. However, an incompatibility exists between GaLV Env and lentiviral vectors that results in decreased steady-state levels of the mature GaLV Env in cells and prevents its incorporation into lentiviral vector particles.

Results: We identified the HIV-1 Vpu protein as the major cause of the depletion in GaLV Env levels that occurs when lentiviral vector components are present.

Investigation of clade B New World arenavirus tropism by using chimeric GP1 proteins.

Clade B of the New World arenaviruses contains both pathogenic and nonpathogenic members, whose surface glycoproteins (GPs) are characterized by different abilities to use the human transferrin receptor type 1 (hTfR1) protein as a receptor. Using closely related pairs of pathogenic and nonpathogenic viruses, we investigated the determinants of the GP1 subunit that confer these different characteristics. We identified a central region (residues 85 to 221) in the Guanarito virus GP1 that was sufficient to interact with hTfR1, with residues 159 to 221 being essential.

New world clade B arenaviruses can use transferrin receptor 1 (TfR1)-dependent and -independent entry pathways, and glycoproteins from human pathogenic strains are associated with the use of TfR1.

Arenaviruses are rodent-borne viruses, with five members of the family capable of causing severe hemorrhagic fevers if transmitted to humans. To date, two distinct cellular receptors have been identified that are used by different pathogenic viruses, alpha-dystroglycan by Lassa fever virus and transferrin receptor 1 (TfR1) by certain New World clade B viruses. Our previous studies have suggested that other, as-yet-unknown receptors are involved in arenavirus entry.

Receptor use by the Whitewater Arroyo virus glycoprotein.

Whitewater Arroyo virus (WWAV) is a North American New World arenavirus, first isolated from rats in New Mexico in 1993, and tentatively associated with three human fatalities in California in 1999-2000. However, it remains unclear whether WWAV was the cause of these, or any other, human infections. One important characteristic of viruses that influences pathogenic potential is the choice of cellular receptor and the corresponding tropism of the virus.

Differences in tropism and pH dependence for glycoproteins from the Clade B1 arenaviruses: implications for receptor usage and pathogenicity.

The Clade B lineage of the New World arenaviruses contains four viruses capable of causing severe hemorrhagic fevers in humans. Within this group, the B1 sub-lineage contains the pathogenic viruses Junin (JUNV) and Machupo (MACV), as well as the non-pathogenic Tacaribe virus (TCRV). In order to elucidate differences that may determine pathogenicity, we studied the entry pathways directed by the glycoproteins (GPs) from these related B1 viruses, using pseudotyped retroviral vectors and GP1 immunoadhesin constructs.

Receptor use by pathogenic arenaviruses.

The arenavirus family contains several important human pathogens including Lassa fever virus (LASV), lymphocytic choriomeningitis virus (LCMV) and the New World clade B viruses Junin (JUNV) and Machupo (MACV). Previously, alpha-dystroglycan (alpha-DG) was identified as a receptor recognized by LASV and certain strains of LCMV. However, other studies have suggested that alpha-DG is probably not used by the clade B viruses, and the receptor(s) for these pathogens is currently unknown.