1 What are Viruses? Obligate intracellular parasites Viral components –Nucleic acids –Capsid –Envelope

2 Viral Shapes and Sizes Helical Icosahedral

3 Infectious Properties Viral Host range Viral specificity Viral Origins

4 RNA Viruses Chromosomal Arrangements –+ (sense) strand –– (antisense) strand –Double + strand

5 11 RNA virus families - *viridae Picornaviridae - + strand RNA virus –3 Genera: –Enterovirus –Hepatovirus –Rhinovirus

6 RNA Virus Families (cont.) Retroviridae (Two + RNA strands) –uses ____________________ –ds DNA ____________ –Inserted into host DNA Include many tumor viruses HIV –Enveloped viruses

7 RNA Virus Families (cont.) Rhabdoviridae - strand RNA virus –RNA dependent RNA polymerase makes a sense strand for mRNA –Includes _________ virus Reoviridae –ds RNA –Non-enveloped –Cause respiratory and intestinal infections in adults –Severe diarrhea in infants caused by Rotavirus –Animals may be affected by some members

8 DNA Virus Families Adenoviridae –Cause many “colds” –Highly stable over pH and temperature changes –10-30% of infant diarrhea –Infection may be associated with a rash Herpesviridae –ds DNA virus – > 100 species –Latent viruses

9 DNA Virus Families (cont.) Papovaviridae –Cause skin and genital warts –13 papilloma viruses are associated with cervical cancer –____________ vaccine Parvoviridae –Ss DNA viruses –Unrelated viruses or host genes needed to allow replication –Human disease known as 5 th disease (Erythrovirus) –Canine Parvovirus gastroenteritis –Dependovirus genus must be assoc. with Adenovirus or Herpesvirus for replication, no human diseases

10 Emerging Viruses Considerations: –Reservoirs in animal populations –Vectors –Mutation/Recombination frequencies –Immunity vs. containment (after rapid air travel of incubating patients)

11 Viral Replication Activities –Adsorption –Penetration (virus or chromosome) –Synthesis –Maturation/Assembly –Release

12 Animal DNA Viruses Virus is adsorbed/fuses to plasma membrane Uncoated DNA travels to nucleus, replicated and transcribed mRNA translated in cytoplasm –Capsid proteins return to nucleus for assembly of virions –Envelope proteins travel to plasma membrane

13 Animal Viruses RNA viruses Retroviruses

14 Culturing Animal Viruses Live animals Eggs

15 Culturing Animal Viruses Cell Culture –Primary –Continuous

16 Viral Cytopathic Effects Cytopathy Teratogenic effects –CMV, HSV-1, Rubella –TORCH series (T_______, O________ like Chicken pox and Hepatitis B, R_______, C___, H_____

17 Viruses and Cancer Mechanism of cancer causation –Triggering of rapid uncontrolled cell division –Oncogenes (may be carried by DNA cancer viruses) –Proto-oncogenes (part of human genome)

18 Cancer causing viruses Adenoviridae Papovaviridae Hepadnaviridae Herpesviridae Retroviridae