Toll-like receptors: key players in antiviral immunity

TLRs are a family of innate receptors whose specificities are predetermined in the germline. Therefore, TLRs have evolved to recognize conserved features of microbes. Viruses typically lack the conserved features common to other pathogen classes, so the innate immune system has evolved to recognize viral nucleic acid as a hallmark of viral infection. In this review we discuss examples of TLR-mediated viral recognition and the functional consequences of this recognition for antiviral immunity.

► TLRs detect viral nucleic acid and envelope proteins.
► Defective viral particles that do not infect cells can also activate TLRs.
► TLRs can detect viral nucleic acid by engulfing infected apoptotic cells.
► TLR signaling upregulates costimulatory molecules for T cell activation.
► Selection of antigens for presentation is mediated by phagosomal TLR activation.