Human immunodeficiency virus type 1 (HIV-1) is a tricky bug. Our bodies use a barrage of immune mechanisms to combat bacteria, viruses and the like, but HIV-1 just happens to target one of the primary immune modulators – the CD4+ T cell. By eliminating this “helper” cell, the body’s overall immune response becomes severely compromised and is at risk for opportunistic infections.
We’ve studied HIV-1 from every conceivable angle and produced a highly active antiretroviral therapy (HAART) for infected patients. This therapy blocks essential steps in HIV-1’s invasion/replication process, but still requires exogenous drug(s) to be administered in a timely manner. So let’s consider a scenario – is it possible to prevent HIV-1 from actually infecting CD4+ T cells in the first place? How does the virus even know which cells to infect? HIV-1 uses its surface proteins to bind to a very specific receptor on the CD4+ T cell known as CCR5. So what if our T cells didn’t have CCR5?
No CCR5 -> no HIV attachment -> no HIV invasion/latency -> no HIV proliferation -> immune system remains happy
Researchers at USC’s Keck School of Medicine transplanted modified (no CCR5) human immune cells into HIV-infected mice. These mice successfully maintained a healthy level of human T cells which consequently suppressed the HIV virus. Clinically, it’s possible to extract hematopoetic stem cells from a patient’s bone marrow, use enzymes to eliminate the CCR5 gene, and reintroduce the modified cells back into the patient. This therapy would make antiretroviral drugs a thing of the past and significantly reduce the risk of opportunistic infections typically associated with an HIV patient’s fluctuating white blood cell count.
Pretty neat combination of stem cell and gene therapy! 🙂