Human pDCs preferentially sense enveloped hepatitis A virions
Zongdi Feng, You Li, Kevin L. McKnight, Lucinda Hensley, Robert E. Lanford, Christopher M. Walker, Stanley M. Lemon
Zongdi Feng, You Li, Kevin L. McKnight, Lucinda Hensley, Robert E. Lanford, Christopher M. Walker, Stanley M. Lemon
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Research Article Virology

Human pDCs preferentially sense enveloped hepatitis A virions

Abstract

Unlike other picornaviruses, hepatitis A virus (HAV) is cloaked in host membranes when released from cells, providing protection from neutralizing antibodies and facilitating spread in the liver. Acute HAV infection is typified by minimal type I IFN responses; therefore, we questioned whether plasmacytoid dendritic cells (pDCs), which produce IFN when activated, are capable of sensing enveloped virions (eHAV). Although concentrated nonenveloped virus failed to activate freshly isolated human pDCs, these cells produced substantial amounts of IFN-α via TLR7 signaling when cocultured with infected cells. pDCs required either close contact with infected cells or exposure to concentrated culture supernatants for IFN-α production. In isopycnic and rate-zonal gradients, pDC-activating material cosedimented with eHAV but not membrane-bound acetylcholinesterase, suggesting that eHAV, and not viral RNA exosomes, is responsible for IFN-α induction. pDC activation did not require virus replication and was associated with efficient eHAV uptake, which was facilitated by phosphatidylserine receptors on pDCs. In chimpanzees, pDCs were transiently recruited to the liver early in infection, during or shortly before maximal intrahepatic IFN-stimulated gene expression, but disappeared prior to inflammation onset. Our data reveal that, while membrane envelopment protects HAV against neutralizing antibody, it also facilitates an early but limited detection of HAV infection by pDCs.

Authors

Zongdi Feng, You Li, Kevin L. McKnight, Lucinda Hensley, Robert E. Lanford, Christopher M. Walker, Stanley M. Lemon

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Figure 1

Coculturing with HAV-infected cells induces IFN-α production by pDCs.

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Coculturing with HAV-infected cells induces IFN-α production by pDCs. (A...
(A) pDCs (4 × 105/ml) were exposed to nonenveloped HAV (MOI = 20), either with or without anti-HAV antibody, or cocultured with HM175/p16 virus-infected cells (1 × 106/ml). Supernatant IFN-α was measured at 20 hours by ELISA. CpG DNA (ODN2216, 1 μM) was used as a positive control. LOD, limit of detection. (B) pDCs were exposed to influenza A virus (IAV, 6 HA units/ml), R848 (1 μM), or CpG in the presence or absence of HAV. (C) pDCs from multiple donors were exposed to CpG or HAV or cocultured with mock or HAV-infected Huh-7.5 cells or FRhK-4 cells for 20 hours. Red bars indicate median. (D) pDCs and HAV-infected cells were cocultured in the presence of monoclonal anti-HAV antibody or control IgG, following treatment with either bafilomycin A (BAF, 50 nM) or chloroquine (CLQ, 50 μM) or 1 μM TLR7 antagonist IRS-661 or control IRS. Results are representative of 2 independent experiments. (E) Total or pDC-depleted PBMCs (-pDC) were exposed to 1 μM CpG A or cocultured with mock or HAV-infected Huh-7.5 cells. (F) pDCs were cocultured with cells infected for increasing numbers of days. Supernatant IFN-α (bars) and intracellular HAV RNA (red line) are shown. GE, genome equivalents. (G) pDCs and HAV-infected cells were cocultured with or without separation by a permeable membrane (pore size = 1 μm). Data represent mean ± SEM in A, B, and D–G.