Electronic Poster | Session 1

030 – Diurnal Variations in Circulating T-Cell Counts and Phenotype in HIV-Infected Individuals Receiving Viral Suppressive Antiretroviral Therapy

Debashree Chatterjee (1, 2) – Tomas Raul Wiche Salinas (1, 2) – Delphine Planas (1, 2) – Laurence Raymond Marchand (1, 2) – Amelie Cattin (1, 2) – Augustine Fert (1, 2) – Etiene Moreira Gabriel (1, 2) – Yuwei Zhang (1, 2) – Daniel Kaufmann (1, 2) – Jean-Pierre Routy (3) – Petronela Ancuta (1, 2)
Université de Montréal, Faculté de médecine, Départment de microbiologie, infectiologie et immunologie (1) – CHUM-Reseach Centre, Montréal, Québec, Canada (2) – McGill University Health Centre-Glen site, Montreal, QC, Canada (3)

Objective: Previous studies reported diurnal variations in T-cell trafficking through the blood of healthy individuals, with nadir CD4 counts observed in the morning. Human immunodeficiency virus type 1 (HIV-1) infection is associated with profound alterations in hematopoiesis, including the depletion of CD4+ T-cells. Here, we investigated diurnal variations in peripheral blood T-cell counts and phenotype in a cohort of HIV-infected individuals receiving viral-suppressive antiretroviral therapy (HIV+ART).Methods: Eleven HIV+ART individuals were hospitalized a Friday afternoon for 40 hours. The next morning, blood was collected every 4 hours for 24 hours (6am, 10am, 2pm, 6pm, 10pm, 2am, 6am) before food intake. Polychromatic flow cytometry was used for cell counting and phenotypic analysis. Results: The CD4 and CD8 T-cell counts showed pronounced diurnal rhythmicity, with maximal cell counts observed between 8pm-4am. Interestingly, the HIV co-receptors CCR5/CXCR4, the gut-homing molecule integrin ß7, and the negative regulator PD-1 also showed maximal expression during the same time zones. The circadian pattern was consistent among individuals. Conclusion: Our study reveals robust diurnal variation in T-cell counts and rhythmic expression of key molecules involved in HIV pathogenesis, with relevance for therapeutic interventions in HIV cure/remission strategies (e.g., time of drug administration, time of immune monitoring). Studies are in progress to understand molecular mechanisms underlying these differences and the consequences on the residual HIV replication during ART.