title: Human immunodeficiency virus-1 tat- and tat/nef-defective genomes containing HIV-regulated diphtheria toxin A chain gene inhibit HIV replication.
abstract: OBJECTIVE
  To assess the ability of human immunodeficiency virus-1 (HIV-1) tat- and tat/nef-defective genomes containing diphtheria toxin A chain gene (DTA) to inhibit replication of HIV in human cells.
  
  
  METHODS
  Plasmids were constructed to contain the HIV-1 genome disabled by tat and tat/nef deletions, and sequences coding for the A subunit of diphtheria toxin gene were inserted into one of these deletions. An infectious clone of HIV-1 (pBRU-3) was cotransfected into HeLa-CD4 cells, together with plasmids carrying the modified DTA-containing genomes. Cell culture supernatants were collected and titrated for the virus by multinuclear activation of beta-galactosidase (MAGI) assay.
  
  
  RESULTS
  Each of the DTA-containing plasmids suppressed HIV production by no less than 96%, whereas the defective non-DTA containing plasmids did not interfere with the virus growth. Plasmids containing wild-type DTA inhibited HIV replication slightly more than its moderately attenuated mutant form, probably by limiting the synthesis of viral proteins. These modified DTA-containing HIV constructs gave no evidence of virus growth in HIV susceptible cells that supported the multiplication of the parent plasmid. None of the modified DTA-containing plasmids was toxic to cells cotransfected with a selectable marker, as shown by the ability of cotransfectants to multiply and form colonies at rates identical to controls exposed to non-specific DNA. This suggested that DTA was probably not expressed in the absence of activating wild-type HIV plasmid.
  
  
  CONCLUSIONS
  HIV-regulated DTA in the background of a HIV replication and expression of defective provirus may be taken into consideration as a therapy approach to the treatment of HIV infection, based on its selective and specific toxicity only to HIV infected CD4-positive cells.
authors.affiliation: Department of Molecular Genetics, Ruder Bosković Institute, Bijenicka c. 54, 10000 Zagreb, Croatia. brdar@rudjer.irb.hr
authors.forename: Branko
authors.initials: B
authors.lastname: Brdar
authors.forename: Maja
authors.initials: M
authors.lastname: Matulić
authors.forename: Ivica
authors.initials: I
authors.lastname: Rubelj
authors.forename: Milena
authors.initials: M
authors.lastname: Ivanković
authors.forename: Edward
authors.initials: E
authors.lastname: Reich
mesh_terms: D004167:Diphtheria Toxin / Q000235:genetics*; D015967:Gene Expression Regulation, Viral / Q000235:genetics*; D015693:Gene Products, nef / Q000235:genetics*; D015696:Gene Products, tat / Q000235:genetics*; D016679:Genome, Viral; D015497:HIV-1 / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D010446:Peptide Fragments / Q000235:genetics*; D010957:Plasmids; D011533:Proviruses; D014162:Transfection; D014779:Virus Replication / Q000235:genetics*; D054311:nef Gene Products, Human Immunodeficiency Virus; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: D004167:Diphtheria Toxin; D015693:Gene Products, nef; D015696:Gene Products, tat; D010446:Peptide Fragments; C029795:diphtheria toxin fragment A; D054311:nef Gene Products, Human Immunodeficiency Virus; D054322:tat Gene Products, Human Immunodeficiency Virus