Human CD34⁺ progenitor-derived DC2 and DC3 subsets support CD169-mediated HIV-1 uptake

Dendritic cells (DCs) are central orchestrators of antiviral immunity but can be exploited by HIV-1 to facilitate systemic dissemination. HIV-1 recognition by CD169 triggers massive endocytosis (MEND)-related internalization of viral particles into sac-like compartments in monocyte-derived dendritic cells (MDDCs), thereby promoting trans-infection of CD4+ T cells. However, MDDCS represent only one DC subpopulation, and whether other physiologically relevant DC subsets exhibit similar behavior remains unclear. Moreover, endogenous CD169 expression and viral capture have not been fully characterized in cDC1, DC2, or pDCs, while remain unknown in DC3. We therefore investigated the contribution of these DC subsets to CD169-mediated HIV-1 capture and subsequent viral dissemination. We used flow cytometry to assess CD169 expression and viral capture across DC subsets differentiated from CD34 hematopoietic stem and progenitor cells (HSPC) obtained from bone marrow (BM) and cord blood (CB), two sources that differ in cellular maturity. Confocal microscopy was used to evaluate sac-like compartment formation following immune activation with IFN- or LPS and treatment with MEND inhibitors. Trans-infection capacity was quantified by measuring luciferase activity in TZM-bl reporter cells. We identified cDC1, DC2, DC3, moDC (similar to MDDCs), and pDC subsets following the differentiation of CD34 HSPC from both CB and BM. Among these populations, DC2, DC3, and moDC displayed high CD169 expression, which was significantly upregulated by IFN- or LPS stimulation. BM-derived DCs exhibited higher basal CD169 expression than CB-derived DCs, whereas stimulation induced greater CD169 upregulation in CB-derived DCs. DC2, DC3, and moDC efficiently captured HIV-1 particles in cultures derived from both sources, and viral uptake was further enhanced by immune activation. Viral internalization into sac-like compartments depended on CD169 binding and MEND-related mechanisms, ultimately facilitating HIV-1 transfer to target cells. DC2 and DC3 are key dendritic cell subsets that support CD169 dependent HIV-1 capture and are associated with MEND-driven internalization into sac-like compartments and subsequent viral transfer to target cells, as was previously described for moDCs. We further observed distinct basal and inducible CD169 expression profiles in BM- and CB-derived DCs, consistent with source-dependent maturation states. These results identify DC2 and DC3 as key cellular contributors to HIV-1 dissemination.