IgG-Complexed Adenoviruses Induce Human Plasmacytoid Dendritic Cell Activation and Apoptosis

Area of Science:

• Immunology
• Virology
• Cell Biology

Background:

• Most adults develop long-lived B- and T-cell responses to human adenoviruses (HAdVs), conferring protection.
• Some HAdV types cause persistent, life-threatening infections, particularly in individuals with compromised T-cell immunity.
• Patients with B-cell deficiencies show no increased risk of HAdV disease, questioning the role of anti-HAdV antibodies.

Purpose of the Study:

• To investigate the interaction between IgG-complexed HAdV5 (IC-HAdV5) and primary human plasmacytoid dendritic cells (pDCs).
• To elucidate the mechanisms by which HAdVs might evade immune responses and establish persistence.

Main Methods:

• Incubation of primary human pDCs with IC-HAdV5.
• Assessment of IC-HAdV5 internalization by pDCs.
• Analysis of pDC activation and signaling pathways, including TLR9.
• Evaluation of pDC apoptosis following IC-HAdV5 exposure.

Main Results:

• IC-HAdV5 are efficiently internalized by pDCs.
• IC-HAdV5 stimulation activates pDCs through Toll-like receptor 9 (TLR9) signaling.
• IC-HAdV5 exposure leads to pDC apoptosis.

Conclusions:

• The interaction between IC-HAdV5 and pDCs, involving TLR9-mediated activation and subsequent apoptosis, offers a potential explanation for HAdV persistence despite strong host immune responses.
• These findings reconcile the dichotomy of robust immunity against HAdVs with their capacity for persistent infection.