Niacin ( vitamin B3 ) is able to control the excess tryptophan oxidation , correcting tryptophan depletion , and therefore represents an interesting strategy to improve CD4 recovery.We aim to design a crossover proof-of-concept study to assess supplementation with an extended-release form of niacin ( Niaspan FCT ) in combination with antiretroviral therapy , compared to antiretroviral therapy alone , on T-cell immune activation as defined by changes in the percentage of CD8 + CD38 + HLA-DR + T-cells .