title: Endocytosis and a low-pH step are required for productive entry of equine infectious anemia virus.
abstract: Recently, it has become evident that entry of some retroviruses into host cells is dependent upon a vesicle-localized, low-pH step. The entry mechanism of equine infectious anemia virus (EIAV) has yet to be examined. Here, we demonstrate that wild-type strains of EIAV require a low-pH step for productive entry. Lysosomotropic agents that inhibit the acidification of internal vesicles inhibited productive entry of EIAV. The presence of ammonium chloride (30 mM), monensin (30 microM), or bafilomycin A (50 nM) in the medium dramatically decreased the number of EIAV antigen-positive cells. We found that a low-pH step was required for EIAV infection of tissue culture cell lines as well as primary cells, such as endothelial cells and monocyte-derived macrophages. The ammonium chloride treatment did not reduce virion stability, nor did the treatment prevent virion binding to cells. Consistent with a requirement for a low-pH step, virion infectivity was enhanced more than threefold by brief low-pH treatment following binding of viral particles to permissive cells. A superinfecting variant strain of EIAV, vMA-1c, did not require a low-pH step for productive infection of fibroblasts. However, lysosomotropic agents were inhibitory to vMA-1c infection in the other cell types that vMA-1c infected but did not superinfect, indicating that the entry pathway used by vMA-1c for superinfection abrogates the need for the low-pH step.
authors.affiliation: Dept. Microbiology, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Melinda A
authors.initials: MA
authors.lastname: Brindley
authors.forename: Wendy
authors.initials: W
authors.lastname: Maury
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D004859:Equine Infectious Anemia / Q000209:etiology / Q000821:virology*; D006736:Horses; D006863:Hydrogen-Ion Concentration; D004860:Infectious Anemia Virus, Equine / Q000187:drug effects / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D014771:Virion / Q000502:physiology
chemical_list: D000643:Ammonium Chloride