A brief blog reviewing the Bernard Fields Lecture. Monday 22nd Feb.
T Cells Control of HIV: Implications for Vaccines and Cure.
Speaker: Dr Bruce D Walker (Harvard, MA, USA)
In summary CD8 T cell immunity is still undergoing vital research in assessing how it impacts on overall immunity specifically relating to HIV. Can it help us in a cure or vaccine development?
Known that CD8 T Cells can kill infected cells before progeny virions are produced. Yang 1997 showed that In vitro CD8 cells can kill HIV infected cells.
In order to assess T Cell response in initial pre peak viremia infection they are studying HIV infected babies in Durban, South Africa. FRESH program was implemented. It was noted within these patients that the rate of increase in viral load was similar across all new infection babies, but the actual peak viral load number and time to reach that in an individual varied. http://ragoninstitute.org/international/fresh/
From current findings they have found that CD8 cells increase their activity within the human body just after initial exposure to HIV, a substance known as PD-1 is expressed and the more of this that is expressed over time there appears to be some correlation with the immune system getting turned down in regards to response. This was apparently similar to what has been noticed with cancer modulating cells and immune response impact.
They have been able to show that HIV some how activates CD8 activity –they hypothesize that perhaps active CD8 T cells are HIV specific. It was noted that an increased level of CD8 cell activated initial stages of infection was linked with a lower viral load set point.
Two other markers noted to be of relevant were, BCL-2 and perforin. As BCL-2 was activated CD8 cells underwent increased apoptosis, and similarly as there was a loss in perforin there was a progressive decline in CD8 functionality.
Overall early treatment does impact the overall quality of the immune response. To further hypothesis but if CD8 cell functions were maintained by commencing treatment in the pre-viremia stages of infection exposure could this help in the development of a cure and it’s effectiveness.
At the conclusion of the talk, despite being moderately confused with the biochem aspects, I got the impression that for now in order to help the development of future effectiveness of a potential cure we need to maintain baseline immunity of newly diagnosed HIV positive patients as much as possible, and prevent the exhaustion or destruction of CD8 cells after peak viremia.
I’m not sure if I would use this particular pitch to promote early commencement of ARVs in patients or for increased testing programs to detect earlier, but it’s food for thought as to why there is a possible other reason to suppress viral loads as early as possible.