Baseline naïve CD4 T cell numbers predict the immunological response to ART
2 April 2010. Related: Basic science.
Richard Jefferys, TAG
The loss of naïveté that comes with getting older is familiar to just about everyone. Somewhat less familiar is the fact that this is also true immunologically; our repertoire of naïve T cells and B cells – vital to responding to pathogens that have not previously been encountered, and keeping up with evolving chronic infections – steadily diminishes. For T cells, the loss is associated with declining output from the thymus, which also shrinks in size over time. It has been appreciated for many years that chronic infections can accelerate the pace of naïve T cell decline, but the effects of HIV far exceed those of any other chronic virus; progression to AIDS is typically associated with an almost complete loss of naïve CD4 and CD8 T cells.
Recent studies of long-term immune reconstitution on antiretroviral therapy (ART) have identified the ratio of naïve T cells to memory T cells as an important factor predicting the extent of CD4 T cell repopulation after 7+ years of treatment. 
A study from Timothy Schacker at the University of Minnesota now addresses the question of whether baseline measures of naïve CD4 T cell numbers can predict the potential for immune reconstitution on ART. 
The results of an analysis of 348 participants in AIDS Clinical Trials Group (ACTG) trials show that, indeed, baseline naive but not total CD4 T cell counts strongly predicted the magnitude of CD4 T cell increases after ART initiation. Lower naïve CD4 T cell levels at baseline were also associated with greater time spent with low CD4 T cell counts on ART, which is known to be associated with a greater risk of clinical events. The study findings suggest that measurements of naïve CD4 T cells could help optimize timing of ART initiation and lessen the incidence of poor immune reconstitution despite HIV suppression.
Source: TAG Basic Science Blog (01 March 2010)
1. Immune recovery on antiretroviral therapy. TAG Basic Science Blog (04 February 2009).
2. Schacker TW et al. Measurement of naive CD4 cells reliably predicts potential for immune reconstitution in HIV. J Acquir Immune Defic Syndr. 2010 Feb 24. [Epub ahead of print]