title: Verotoxin A subunit protects lymphocytes and T cell lines against X4 HIV infection in vitro.
abstract: Our previous genetic, pharmacological and analogue protection studies identified the glycosphingolipid, Gb(3) (globotriaosylceramide, Pk blood group antigen) as a natural resistance factor for HIV infection. Gb(3) is a B cell marker (CD77), but a fraction of activated peripheral blood mononuclear cells (PBMCs) can also express Gb(3). Activated PBMCs predominantly comprise CD4+ T-cells, the primary HIV infection target. Gb(3) is the sole receptor for Escherichia coli verotoxins (VTs, Shiga toxins). VT1 contains a ribosome inactivating A subunit (VT1A) non-covalently associated with five smaller  receptor-binding B subunits. The effect of VT on PHA/IL2-activated PBMC HIV susceptibility was determined. Following VT1 (or VT2) PBMC treatment during IL2/PHA activation, the small Gb(3)+/CD4+ T-cell subset was eliminated but, surprisingly, remaining CD4+ T-cell HIV-1(IIIB) (and HIV-1(Ba-L)) susceptibility was significantly reduced. The  Gb(3)-Jurkat T-cell line was similarly protected by brief VT exposure prior to HIV-1(IIIB) infection. The efficacy of the VT1A subunit alone confirmed receptor independent protection. VT1 showed no binding or obvious Jurkat cell/PBMC effect. Protective VT1 concentrations reduced PBMC (but not Jurkat cell) proliferation by 50%. This may relate to the mechanism of action since HIV replication requires primary T-cell proliferation. Microarray analysis of VT1A-treated PBMCs indicated up regulation of 30 genes. Three of the top four were histone genes, suggesting HIV protection via reduced gene activation. VT blocked HDAC inhibitor enhancement of HIV infection, consistent with a  histone-mediated mechanism. We speculate that VT1A may provide a benign approach to reduction of (X4 or R5) HIV cell susceptibility.
authors.affiliation: Department of Biochemistry, University of Toronto, Ontario M5G 1X8, Canada. peilinss@yahoo.ca
authors.forename: Pei Lin
authors.initials: PL
authors.lastname: Shi
authors.forename: Beth
authors.initials: B
authors.lastname: Binnington
authors.forename: Darinka
authors.initials: D
authors.lastname: Sakac
authors.forename: Yulia
authors.initials: Y
authors.lastname: Katsman
authors.forename: Stephanie
authors.initials: S
authors.lastname: Ramkumar
authors.forename: Jean
authors.initials: J
authors.lastname: Gariepy
authors.forename: Minji
authors.initials: M
authors.lastname: Kim
authors.forename: Donald R
authors.initials: DR
authors.lastname: Branch
authors.forename: Clifford
authors.initials: C
authors.lastname: Lingwood
mesh_terms: D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D020869:Gene Expression Profiling; D015658:HIV Infections / Q000517:prevention & control*; D015497:HIV-1 / Q000187:drug effects / Q000472:pathogenicity; D006801:Humans; D019169:Jurkat Cells; D007963:Leukocytes, Mononuclear; D020411:Oligonucleotide Array Sequence Analysis; D021122:Protein Subunits / Q000494:pharmacology*; D022622:Shiga Toxin 1 / Q000494:pharmacology*; D022641:Shiga Toxin 2 / Q000494:pharmacology*; D013601:T-Lymphocytes / Q000187:drug effects*
chemical_list: D021122:Protein Subunits; D022622:Shiga Toxin 1; D022641:Shiga Toxin 2