RNA Viruses -Saviola Flashcards
Do DNA or RNA viruses mutate faster?
RNA viruses
What are some commonalities between the RNA viruses?
replicate in the cytoplasm
require as RNA-dependent RNA polymerases
viruses show a high mutation frequency
Their genetic material replicates by synthesis of complementary RNA, and DNA is not involved
What kind of virus is rotavirus? How is it transmitted?
naked
double stranded RNA virus
fecal-oral
*story about school getting sick because cooks not washing hands properly
What do retroviruses require?
RNA dependent DNA polymerase
Reverse transcriptase
What are the 3 groups of picornaviridae? What are common characteristics of these groups?
enteroviruses, hepA, rhinovirus
cytolytic and naked
transmitted fecal-oral (except for rhinovirus)
What are some characteristics of poliomyelitis?
polio is an enterovirus
replicates in the motor neurons of the anterior horn of the spinal cord and brain stem. May involve meninges and produce permanent paralysis (flaccid paralysis)
Virus multiplies in neurons and kills them
fecal-oral transmission. used to be more prevalent in summer and early fall–> swimming pools** can transmit fecal-oral if not properly chlorinated (story about Roman baths)
hearty because it is naked
live attenuated vaccine more effective but can revert back to a virulent form and cause polio –> use the enhanced inactivated vaccine normally
What percentage of people with poliovirus get non paralytic aseptic meningitis? flaccid paralysis?
in 1-2 % of people it causes nonparylytic aseptic meningitis, and in less than 1% of people it results in flaccid paralysis.
What are some characteristics of Hep A?
lives in the liver –> acute hepatitis
not cytolytic and doesn’t release by budding
transmitted fecal oral
How is Hep A different from Hep B?
Hep B causes chronic hepatitis (and Hep C)
Hep A only causes acute hepatitis
Hep A is also fecal oral while Hep B is blood or sexually transmitted (*story about LA restaurant giving people Hep A because not proper hand washing)
Why is rhinovirus different from the other picorna viruses?
it is acid labile–> can’t live in gut
likes to live in the nose because also temperature sensitive.
200+ serotypes–> can’t have vaccine
What are 3 causes of the common cold?
rhinovirus and adenovirus and coronaviridae
What are characteristics of caliciviridae (calix-cup) viruses? What are the 2 viruses in this category?
naked icosahedral nucleocapsids, slightly larger than picornaviruses, and differ in macromolecule synthesis
- Norovirus- fecal-oral transmission, 60% of non bacterial gastroenteritis can be attributed to Norwalk like viruses. (*story about cruise ships –>norovirus outbreak–> very transmissible via improper hand washing)
- Hepatitis E virus: fecal-oral fairly similar to the calciviruses. It causes epidemic outbreaks of acute hepatitis in parts of the world with poor sanitation. Deadly for pregnant women (similar to Hep A)
Which other Hepatitis is Hep E similar to? How are they similar?
Hep A
fecal oral transmission
cause acute hepatitis (not chronic)
what families have arboviruses in within them?
Togaviridae and flaviviridae
arbovirus=arthropod virus (can be transmitted by mosquitos)
What are some characteristics of Rubella?
togoviridae
spreads through respiratory and can can get into blood and affect the fetus of pregnant women
(cause cataracts, deafness, congenital heart disease, developmental defect, rubella rash)
if woman vaccinated or exposed to rubella previously, fetus will not be affected
there is a good live attenuated vaccine (MMR vaccine) that is given to children and women of child bearing age
what are some characteristics of Hepatitis C virus?
flavivirus
sexually transmitted or through blood
enveloped –> bud off hepatocytes
cause chronic hepatitis (70% cases are chronic)
what are some characteristics of Coronaviridae virus? What does this virus cause?
Enveloped helical nucleocapsids–> looks like a crown (glycoproteins embedded in the envelope causing crown shape)
Cause some mild upper respiratory infections including about 15 % of common colds.
Some cause enteric disease
SARS: severe acute respiratory syndrome
What is MERS (Middle East Respiratory Syndrome)? Where is it thought to have come from?
coronavirus called MERS-CoV. first reported in Saudi Arabia in 2012
Most people who have been confirmed to have MERS-CoV infection developed severe acute respiratory illness.
fever, cough, and shortness of breath.
50% mortality rate but not very transmissible
-bats=animal source into humans
What are the characteristic of retroviridae?
two identical copies of +SSRNA per virus particle
enveloped
make a DNA intermediate: must use reverse transcriptase (more error prone than RNA dependent RNA polymerase–> no editing function)
double stranded DNA intermediate circularizes and integrates into a host chromosome
what are some characteristics of HTLV-1 and HTLV-2? what disease is HTLV-1 associated with?
enveloped
Infect helper T lymphocytes (lymphocytes with the CD4 marker)
nondefective exogenous viruses which cause cell proliferation.
HTLV-1 sexually transmitted
HTLV-I infection can lead to adult T cell leukemia/lymphoma (ATL) in humans (50-70%)
What are some characteristics of HIV?
cytopathic nontransforming viruses which cause death in infected cells T lymphocytes (T4), monocytes and macrophages
Cells in which the virus is latent may be activated to produce virus gene products and viral particles
cause persistent and debilitating disease in animals, often preceded by a long incubation period
very mutable envelope gene, and show very rapid antigenic drift–> change quickly
causes AIDS
HIV becomes latent in unactivated CD4+ helper T cells and can be reactivated when the immune system is activated
spread through sexual contact or blood
Where is HIV thought to have originated?
HIV-2 is very similar to SIV (simian immunodeficiency viruses) virus found in sooty mangabeys (primates) found in West Africa
close contact between humans and these animals through hunting them (blood exposure) and keeping them as pets
HIV-1 similar to SIV in chimp (Pan t. troglodytes) ==> humans hunted these chimps for for
How are integrate and protease important in HIV?
Integrase integrates the viral DNA into the host chromosome
Protease takes long polypeptides that are produced and cleaves it into 2 functional proteins
without functional protease–> no functional proteins produced
What proteins determine the specificity of HIV?
Virus has a tropism for CD-4 expressing T cells and macrophages.
Gp 41 (fusion protein–> allows membranes to fuse) forms stick of lollipop, gp120 is associated with gp41
Gp120 binds to CD4 containing cells and a coreceptor:
- CXCR4- present on T- cells OR
- CCR5- present on macrophages and some T-cells
Gp120 is extensively glycosylated and its antigenicity and receptor specificity can drift during the course of a chronic HIV infection
what strains of HIV predominate early and late in infection?
initially macrophage (M-tropic) strains predominate CCR5
and then later T-tropic strains predominate (CXCR4)
What allows for resistance to HIV infection?
people lacking in CCR5–> unknown mechanism and no other symptoms found in these patients
How does HIV enter the cell?
Upon binding of gp120 with CD4 and a chemokine coreceptor (CXCR4 or CCR5), a conformational change takes place.
Gp41 (a fusion protein) inserts itself into the membrane of the host cell and catalyzes membrane fusion.
The nucleocapsid enters the cell cytoplasm.
What are the 3 major genes of HIV?
- GAG- group specific antigen–>capsid proteins
- POL- polymerase (RT), integrase, protease
- Env-envelope glycoproteins; SU(gp120), TM (gp41)
there are also genes encoding accessory proteins
What are some -ssRNA viruses?
Orthomyxoviridae (influenzaviridae)
What are some characteristics of Orthomyxoviridae (influenzaviridae)?
the real flu (influenza A, B and C)
-ssRNA
Helical nucleocapsids with an envelope.
Hemagglutinin (H) and neuraminidase (N) are on the outside of the envelope
*has 8 segments (C actually has 7)
What is the function of Hemagglutinin (H) and neuraminidase (N)?
H=spikes are important in binding the virus to the host cell
N=enzymes that help release the newly synthesized virus from the host cells
Which influenza Causes Worldwide Pandemics and infects many animal types?
Type A
What animals does type B influenza affect?
humans and seals
What animals does type C influenza affect?
humans, pigs, dogs
How does the Influenza virus evolve? (2)
- point mutations: single RNA residue changes. Antigenic drift –> slow change
- reassortment: whole segments substituted in viruses with segmented genomes (ie influenza) and in cells infected with more than 1 strain of the virus. Causes antigenic shift. Causes Pandemics
What factors of influenza allow for antigenic shift?
segmented DNA
many animals affected: ex: a pig can get the flu from humans or ducks–> if infected with both, can get segment reassortment between the two–> antigenic shift–> humans have no immunity to the new segments and can start a pandemic
What are some characteristics of Paramyxoviridae?
Enveloped
can produce syncytium (more so than other enveloped viruses) –> cytopathic
respiratory transmission
(respiratory tract infections, croup, common cold)
infects the upper respiratory tract and rarely causes viremia.
What are 3 diseases that can be caused by paramyxoviridae?
Mumps (parotitis,orchitis,menigoencephalitis,pancreatitis)
Route: upper respiratory tract to mucous membranes, then viremia, then to salivary glands.
Measles (rubeola)
route: upper respiratory tract, then viremia, then skin (rash of endothelial cells)
One of the most highly communicable of all infections. Maternal antibody protects the infant until age 6 months.
syncytium formation
Respiratory syncytial virus (RSV) (pneumonia and bronchitis in infants and young children and common cold) The major cytopathic effect is syncytia formation. It is the single most important lower respiratory tract pathogen of infants and young children, causing 20-30% of the illness of this type.
What are some characteristics of Rhabdoviridae?
Bullet shaped enveloped helical nucleocapsids,-ssRNA
Rabies virus- encephalitis, fatal except for 2 or 3 survivors
Route- inoculated through broken skin through bites usually, occasionally from aerosol from bats in caves.
Enters PNS then through CNS–> encephalitis
Reservoirs- in U.S. raccoons, skunks, foxes, and especially bats.
What are some characteristics of Hepatitis D?
Hepatitis D is a defective virus and can only replicate with the aid of HepB virus (for its life cycle and to replicate)
tiny circular –ssRNA
Its envelope protein is serologically indistinguishable from HBsAg (comes from HepB).
