Arbovirus An insect vector for transmission Serotype Different types of immune response; multiple viruses may share a single serotype in the immune system. Infection rate for West Nile Virus 1 in 150, 12% fatality When disease caused by viruses Pathogenesis Virus Biology at the organism level Pathogenesis; Immunity Virus Biology at the environmental level Effects on population; response of society Basic thing we're doing in this class' lab Cloning fragments of lambdaphage DNA into M13 phage: prepare vector DNA, prepare insert DNA, ligate insert into vector and characterize Virus in greek means... slimy liquid, stench, poison Cellular def'n of virus parasitic genome Viral functions one function: enter host, direct multiplication, escape Why are viruses non-living They do not metabolize or synthesize own proteins Virion Extracellular infectious particle: protein capsid + nucleic acid genome Features of more complex viruses Membrane envelope around capsid (now called nucleocapsid), envelope glycoproteins Peplomer Envelope glycoprotein An icosahedron has this type of symmetry 2, 3, and 5 fold symmetry Types of viral morphologies (and example viruses) Roughly spherical (herpesvirus), filamentous (M13), complex (T4 bacteriophage) Size of viruses Can be very small (20 nm, about the size of a ribosome) Size of viral genomes As low as 2.5 kb (2.5 genes) Minimal virus has these genes Capsid protein, polymerase protein, attachment protein (pilate) Viral characteristics to consider Morphology, molecular organization; infection mechanism; replication mechanism; mechanism to express and regulate genes; mechanism to assemble and escape; consequences of infection. Dormant phase free virion, no multiplication - extracellular Vegetative phase Productive multiplication - intracellular Infection cycle adsorption; penetration; gene expression; produce virion components (replication of genome, synthesize capsid components); virion assembly (build capsid around genome); escape Summary of steps for one-step growth curve Add Virus to Host (Host cells must be in one metabolic state and be the same cell type; Use excess virus; Remove uninfecting virus) Eclipse Phase after infection and before propagation Latent Phase Time it takes to produce first extracellular virion from time of detected intracellular viral activity MOI multiplicity of infection; MOI = 1 ==> 1 virus from 1 cell