Mycobacterium tuberculosis infects human peripheral hematopoietic multipotent progenitors and promotes their myeloid differentiation in vitro.

Mycobacterium tuberculosis (Mtb) persists as a global health threat partly by establishing long-term reservoirs in myeloid cells. Although progenitors have been proposed as additional sites of persistence and immune reprogramming, it remains unclear whether circulating human hematopoietic stem/progenitor cells (HSPC) are permissive to Mtb infection. Here, we show that peripheral blood-derived CD34+ HSPC are permissive to Mtb, in vitro. Confocal microscopy showed Mtb cytoplasmic localization, while colony-forming unit (CFU) quantification demonstrated early intracellular Mtb growth. Flow cytometry revealed preferential Mtb infection of multipotent progenitors (MPP) with progressive enrichment of granulocyte-monocyte progenitors (GMP) and lineage-committed cells, indicating myeloid skewing. Infection drove early IL-8 and TNF-α release, followed by MIP-1α, MIP-1β, and IP-10, demonstrating a dynamic inflammatory response by CD34+ progenitors. Parallel infection experiments with Mycobacterium bovis BCG revealed that, despite lacking key virulence determinants, BCG infects CD34+ cells in vitro with a preference for MPP. Unlike Mtb, BCG infection did not promote expansion of more differentiated progenitor subsets, indicating that virulence-dependent mechanisms are required to drive progenitor differentiation and myeloid skewing. These findings identify CD34+ HSPC as a permissive niche for mycobacterial infection and suggest that Mtb-specific virulence factors contribute to the modulation of progenitor differentiation. Further studies are needed to fully assess the consequences of these events on the systemic immune modulation observed during tuberculosis infection.