Vitamin D status and immune function reconstitution in HIV-infected men initiating therapy

Objective: Despite effective antiretroviral therapy (HAART) and durable viral suppression, many HIV-infected individuals still do not achieve CD4⁺cell count (CD4 +) normalization. Vitamin D has immunoregulatory functions, including inducing the development of T cells and higher levels may improve CD4⁺rebound. Design: Longitudinal study of men from the Multicenter AIDS Cohort Study who virally suppressed following HAART initiation and had pre-HAART and post-HAART 25(OH)D and 1,25(OH) 2 D measurements and repeated measures of CD4 +. Methods: CD4⁺rebound was modeled using a nonlinear mixed effects model. We estimated the adjusted effect (adjusted for pre-HAART antiretroviral exposure, black race, age and CD4⁺at HAART initiation) of pre-HAART and post-HAART vitamin D metabolite levels on the rate of CD4⁺increase and final CD4⁺plateau. Results: Among the 263 HIV-infected HAART initiators with pre-HAART vitamin D measurements, a 1-SD higher pre-HAART 25(OH) 2 D level was associated with a 9% faster rate of rise (P = 0.02) but no gain in final CD4⁺plateau. In contrast, a 1-SD higher 1,25(OH) 2 D level was associated with a 43-cell lower final CD4⁺(P = 0.04). Among 560 men with post-HAART measurements, findings were similar to those for pre-HAART 25(OH) 2 D with 1-SD higher level associated with faster rate of rise but no improvement in final CD4 +. Conclusion: We found no evidence that higher vitamin D metabolite levels pre-HAART or post-HAART are associated with better CD4⁺outcomes among HIV-infected HAART initiators. However, the value of pre-HAART 1,25(OH) 2 D levels as an indicator of immune response dysregulation could be further explored.