Viral structure
- Naked virus
- Enveloped virus
*capsids are made out of capsomers
(Nucleocaspid)
-Caspid+nucleid acid
Naked virus
-only nucleocapsid
Enveloped
-nucleocapsid + viral envelope
Capsids
- helical
- icosahedral
Envelope
*both help viral RNA&DNA ito cell& protect nucleic acid when virus is outside of the host cell
CAPSIDS (helical) -proteins polymerize in helical form (icosahedral) -20 sided with 12 corners
ENVELOPE (fat+protein)
- exposed proteins on outside of the envelope (spikes) are essential for attachment of the virus to the host cell
- can be inactivated if dehydrated/disorganized
Complex viruses
- Poxvirsuses
- Bacteriophages
(Poxvirsuses)
- lack capsid
- covered by dense layer of lipoproteins
(Bacteriophages)
- polyhedra nucleocapsids
- helical tail
- attachment filters
- Modes of viral multiplication (Lytic Cycle)
- Adsorption (lock and key)
- Penetration
- Uncoating
- Synthesis
- Assembly
- Release
Note: Acute infections(only in lytic cycle)
-host cells do not survive lytic cycles
(Adsorption)
-binding on virus to specific molecules on the host cell
(Penetration)
-genome enters the cell
>Endocytosis-entire virus engulfed
>Fusion-envelope merges membrane»entry into cytoplasm
(Uncoating)
-viral nucleic acid is released from capsid
(Synthesis)
-viral components are produced
(Assembly)
-new viral particles are constructed
(Release)
-assembled viruses are released by budding
>Budding(endocytosins)
>Lysis(nonenveloped &complex viruses)
Cytopathic effects
- changes in size and shape
- cytoplasmic inclusion bodies
- inclusion bodies
- cells fuse to form multinucleated cells
- cell lysis
- Transform DNA
- transform cells into cancerous cells
- changes in size and shape
- cytoplasmic inclusion bodies
- inclusion bodies
- cells fuse to form multinucleated cells
- cell lysis
- Transform DNA
- transform cells into cancerous cells
Persistent infections
- chronic
- latent
- SLOW PROGRSSION
(Lytic and lysogenic)
cells harbor the virus and not immediately lysed.
can reactivate into chronic latent states
> HSV1,2
H ZS
Measles
Steps in Phage Replication-lytic
(some)>Temperate phages undergo lysogenic cycle
- Adsorption
- Penetration
- Replication
- Assembly
- Maturation
- Lysis & Release
Lysogeny
-spread of virus without killing host
(integration)
-with or without integration
(episomal)
-when virus does not enter host genome
(Lysogenic conversion)
- Viral genome inserts into bacterial genome and becomes an inactivated prophage
- the cell in not lysed
Prophage is retained and copied
-induction may occur
>reseulting in activation of lysogenic prophage followed by vial replication and lysis
(Lysogenic conversion)
-phage genes in the bacterial chromosome can cause production of toxins and enzymes t
Techniques in cultivating and ID Animal viruses
-Methods
Methods:
- cell tissue cultures
- bird embryos
- live animal innoculation
Prions
- misfolded proteins
- resistant to usual sterilization
- cause transmissible spongiform encephalopathies-fatal neurodegenertive disease
Prion Diseases
(Protichation infection agents)
-may occur throughorgan transplants
Treatment
DISEASES: (neurological) (animals) -scapies -bovine -wasting disease (humans) -Creuzfeldt-Jakob Syndrome NERVOUS
TREATMENT:
with growth hormone
Satellite viruses
Viroids
Satellite viruses
-dependant on other viruses for replication
>Delta agent(only with hepatitis B)
Viroids
- short pieces of RNA
- no protein coat
Baltimore viral taxonomy
transcription and translation relies heavily on mRNA
dsRNA>mRNA>proteins
(-)DNA>(+)DNA>mRNA>protein
(-)RNA>(+)RNA>mRNA>proteins
1L of sea water has 10^5 particles
-Viruses attack bacteria in the ocean
Viruses lack machinery to synthesize proteins
- they have no ribosomes!
- they must use host
-viruses in ocean will not infect you because they do not have the machinery to do so
