Organisms have a number of mechanisms which defend them from different pathogens. Higher eukaryotes have the immune system, as a complex network of organs and biological processes that protect the organism. Immune response can be innate or nonspecific and adaptive, or specific. Innate immune system exerts the first steps of defense against microorganisms, before the contact with them. Cells have specific receptors which are activated by microbe's antigen recognition. Pattern recognition receptors (PRR) recognize molecular patterns of proteins, nucleic acids and lipids characteristic for pathogens (PAMP) and initialize a number of signaling processes to protect the cell from the microbes. Receptors are located on the surface of cell membranes, membrane systems of organelles inside the cell and in the cytosol. Molecules that recognize viral nucleic acids are classified into: TLR receptors, RLR receptors, NLR receptors, ALR receptors and cGAMP synthase. The binding of the ligand, viral DNA or RNA, to the receptors initiates inflammatory signaling cascades of reactions, which ultimately results in the production of soluble mediators of the inflammatory response, cytokines and chemokines. The progressive action of activated cells and their soluble products is a key element of effective host defense against viral infection