Novel CD4-Based Bispecific Chimeric Antigen Receptor Designed for Enhanced Anti-HIV Potency and Absence of HIV Entry Receptor Activity

J Virol. 2015 Jul;89(13):6685-94. doi: 10.1128/JVI.00474-15. Epub 2015 Apr 15.

Abstract

Adoptive transfer of CD8 T cells genetically engineered to express "chimeric antigen receptors" (CARs) represents a potential approach toward an HIV infection "functional cure" whereby durable virologic suppression is sustained after discontinuation of antiretroviral therapy. We describe a novel bispecific CAR in which a CD4 segment is linked to a single-chain variable fragment of the 17b human monoclonal antibody recognizing a highly conserved CD4-induced epitope on gp120 involved in coreceptor binding. We compared a standard CD4 CAR with CD4-17b CARs where the polypeptide linker between the CD4 and 17b moieties is sufficiently long (CD4-35-17b CAR) versus too short (CD4-10-17b) to permit simultaneous binding of the two moieties to a single gp120 subunit. When transduced into a peripheral blood mononuclear cell (PBMC) or T cells thereof, all three CD4-based CARs displayed specific functional activities against HIV-1 Env-expressing target cells, including stimulation of gamma interferon (IFN-γ) release, specific target cell killing, and suppression of HIV-1 pseudovirus production. In assays of spreading infection of PBMCs with genetically diverse HIV-1 primary isolates, the CD4-10-17b CAR displayed enhanced potency compared to the CD4 CAR whereas the CD4-35-17b CAR displayed diminished potency. Importantly, both CD4-17b CARs were devoid of a major undesired activity observed with the CD4 CAR, namely, rendering the transduced CD8(+) T cells susceptible to HIV-1 infection. Likely mechanisms for the superior potency of the CD4-10-17b CAR over the CD4-35-17b CAR include the greater potential of the former to engage in the serial antigen binding required for efficient T cell activation and the ability of two CD4-10-17b molecules to simultaneously bind a single gp120 subunit.

Importance: HIV research has been energized by prospects for a cure for HIV infection or, at least, for a "functional cure" whereby antiretroviral therapy can be discontinued without virus rebound. This report describes a novel CD4-based "chimeric antigen receptor" (CAR) which, when genetically engineered into T cells, gives them the capability to selectively respond to and kill HIV-infected cells. This CAR displays enhanced features compared to previously described CD4-based CARs, namely, increased potency and avoidance of the undesired rendering of the genetically modified CD8 T cells susceptible to HIV infection. When adoptively transferred back to the individual, the genetically modified T cells will hopefully provide durable killing of infected cells and sustained virus suppression without continued antiretroviral therapy, i.e., a functional cure.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Anti-HIV Agents / metabolism*
  • Antibodies, Monoclonal / genetics
  • Antibodies, Monoclonal / metabolism
  • CD4 Antigens / genetics
  • CD4 Antigens / metabolism
  • HIV Antibodies / genetics
  • HIV Antibodies / metabolism
  • HIV Envelope Protein gp120 / metabolism
  • HIV-1 / immunology*
  • Humans
  • Leukocytes, Mononuclear / immunology*
  • Leukocytes, Mononuclear / virology*
  • Protein Binding
  • Receptors, Antigen / genetics
  • Receptors, Antigen / metabolism*
  • Receptors, HIV / genetics
  • Receptors, HIV / metabolism*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Single-Chain Antibodies / genetics
  • Single-Chain Antibodies / metabolism
  • Transduction, Genetic

Substances

  • Anti-HIV Agents
  • Antibodies, Monoclonal
  • CD4 Antigens
  • HIV Antibodies
  • HIV Envelope Protein gp120
  • Receptors, Antigen
  • Receptors, HIV
  • Recombinant Fusion Proteins
  • Single-Chain Antibodies
  • gp120 protein, Human immunodeficiency virus 1