Regulation of antigen processing and presentation molecules in West Nile virus-infected human skin fibroblasts

Infection of humans with the West Nile flavivirus principally occurs via tick and mosquito bites. Here, we document the expression of antigen processing and presentation molecules in West Nile virus (WNV)-infected human skin fibroblast (HFF) cells. Using a new Flavivirus-specific antibody, 4G4, we have analyzed cell surface human leukocyte antigen (HLA) expression on virus-infected cells at a single cell level. Using this approach, we show that West Nile Virus infection alters surface HLA expression on both infected HFF and neighboring uninfected HFF cells. Interestingly, increased surface HLA evident on infected HFF cultures is almost entirely due to virus-induced interferon (IFN)alpha/beta because IFNalpha/beta-neutralizing antibodies completely prevent increased surface HLA expression. In contrast, RT-PCR analysis indicates that WNV infection results in increased mRNAs for HLA-A, -B, and -C genes, and HLA-associated molecules low molecular weight polypeptide-2 (LMP-2) and transporter associated with antigen presentation-1 (TAP-1), but induction of these mRNAs is not diminished in HFF cells cultured with IFNalpha/beta-neutralizing antibodies. Taken together, these data support the idea that that both cytokine-dependent and cytokine-independent mechanisms account for WNV-induced HLA expression in human skin fibroblasts.