Low Cd4(+) Cell Count Nadir Exacerbates The Impacts Of Apoe Epsilon 4 On Functional Connectivity And Memory In Adults With Hiv

Objective: Nearly half of individuals living with HIV in the USA are now 50 or older. This rapidly ageing populace may be at an increasingly greater risk of Alzheimer's disease. However, the potential interaction between HIV-disease and Alzheimer's disease pathogenesis (i.e. Alzheimer's disease genetic risk factors) on brain function remains an open question. The present study aimed to investigate the impact of APOE epsilon 4 on brain function in middle-aged to older people with HIV (PWH), as well as the putative interaction between epsilon 4 and HIV disease severity. Methods: Ninety-nine PWH participated in a cross-sectional study (56.3 +/- 6.5 years, range 41-70 years, 27 women, 26 epsilon 4 carriers and 73 noncarriers). Structural MRI and resting-state functional MRI were collected to assess alterations in brain structure and functional connectivity, respectively. Results: APOE epsilon 4 was associated with worse memory performance and reduced functional connectivity in the memory network. The functional connectivity reduction was centred at the caudate nucleus rather than hippocampus and correlated with worse memory performance. In epsilon 4 carriers, low CD4(+) cell count nadir was associated with reduced functional connectivity in the memory network, but this association was absent in noncarriers. Furthermore, there was an indirect detrimental impact of epsilon 4 on memory performance through memory network functional connectivity. However, this indirect effect was contingent on CD4(+) cell count nadir, that is the indirect effect of epsilon 4 on memory was only significant when CD4(+) cell count nadir was low. Interpretation: APOE epsilon 4 is associated with reduced memory and reduced functional connectivity within the memory network, and low CD4(+) cell count nadir -- indicating a history of severe immunosuppression -- may exacerbate the effects of epsilon 4.