Transcript VIRUSES - Antelope Valley College

What are Viruses?

Obligate intracellular parasites

Viral components
– Nucleic acids
– Capsid
– Envelope
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Viral Shapes and Sizes
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Helical
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Icosahedral
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Infectious Properties
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Viral Host range
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Viral specificity
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Viral Origins
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RNA Viruses
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Chromosomal Arrangements
– + (sense) strand
– – (antisense) strand
– Double + strand
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11 RNA virus families - *viridae
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Picornaviridae + strand RNA virus
– 3 Genera:
– Enterovirus
– Hepatovirus
– Rhinovirus
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RNA Virus Families (cont.)
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Retroviridae (Two + RNA strands)
– uses ____________________
– ds DNA ____________
– Inserted into host DNA
• Include many tumor viruses
• HIV
– Enveloped viruses
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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
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DNA Virus Families
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Adenoviridae
– Cause many “colds”
– Highly stable over pH
and temperature
changes
– 10-30% of infant
diarrhea
– Infection may be
associated with a rash
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Herpesviridae
– ds DNA virus
– > 100 species
– Latent viruses
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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
5th disease (Erythrovirus)
– Canine Parvovirus
gastroenteritis
– Dependovirus genus must
be assoc. with Adenovirus
or Herpesvirus for
replication, no human
diseases
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Emerging Viruses
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Considerations:
–
–
–
–
Reservoirs in animal populations
Vectors
Mutation/Recombination frequencies
Immunity vs. containment (after rapid air travel
of incubating patients)
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Viral Replication

Activities
– Adsorption
– Penetration (virus or chromosome)
– Synthesis
– Maturation/Assembly
– Release
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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
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Animal Viruses
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RNA viruses
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Retroviruses
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Culturing Animal Viruses
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Live animals
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Eggs
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Culturing Animal Viruses
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Cell Culture
– Primary
– Continuous
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Viral Cytopathic Effects
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Cytopathy
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Teratogenic effects
– CMV, HSV-1, Rubella
– TORCH series (T_______, O________ like
Chicken pox and Hepatitis B, R_______, C___,
H_____
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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)
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Cancer causing viruses
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Adenoviridae
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Papovaviridae
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Hepadnaviridae
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Herpesviridae
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Retroviridae
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