Flashcards in Microbiology III Deck (177):
How does the cell produce an immune response toward virus?
Viral proteins cut up
Class I HLA presents
Cytotoxic T-cells destroy
All known life has viruses
What does a fast mutation of "spikes" mean?
Epitopes change and Antibody can't recognize
What are 4 possible genome categories for viruses?
What surrounds the genetic material in a virus?
What shape is it?
icosahedral or helical
After replicating, what are the 2 ways a virus leaves a cell?
Budding (envelope with spikes)
Lytic viruses are...
Non-lytic viruses are...
A Latent virus, like Herpes, can be...
HPV cause cancer because they...
*hyperproliferation causes the cell to divide, thereby replicating the virus that is part of the genome
Aside from being enveloped or non-enveloped, a virus can be...
(characteristics of both)
Define sense and antisense:
sense (+): same as mRNA
antisense (-): same as template DNA
What are the 4 structural possibilities for a virus?
Icosahedral (naked or enveloped)
Helical (naked or enveloped)
plus(+) sense ssRNA viruses must bring what with it?
RNA-dependent RNA polymerase
makes template strand for ssRNA sequence for every replicated virus
*sense strand directly codes for proteins
**type I virus
anti-sense(-) ssRNA viruses must bring what with it?
RNA-dependent RNA polymerase
anti-sense(-) to sense(+)
*sense strand codes for proteins AND (-)ssRNA
**type II virus
Upon entering the cell, what does dsRNA need to replicate?
RNA-dependent RNA polymerase to make sense(+) strand from DNA template.
AND to make dsDNA from (+)sense strands
*sense strand makes mRNA's and viral proteins
**type III virus
Describe the replication of Type IV (+)ssRNA.
sense strand enters
Viral RNA-dependent DNA polymerase creates (-)DNA
Viral RNA-dependent DNA polymerase creates (+)DNA
host cell integration
all host machinery from here
*aka Reverse Transcriptase
RNA viruses need their own polymerase at some step, while DNA viruses do not.
(+)ssRNA are the only viruses that don't need to bring a polymerase with them into the cell.
they are already mRNA, so code for needed proteins
What are viruses that lack capsids?
What do they infect?
(free nucleic acids)
Infect only plants
What are infectious proteins?
Infections are spread:
person to person
mother to neonate
What is the low profile of an infectious agent called?
What is required for a pathogen to have a big iceberg effect?
Many carriers (infectious, no symptoms)
Name two diseases that exhibit large iceberg effects?
How does antigen at one mucosal site stimulate antibody protection at all others?
IgA reacts with Ag at all sites
APC's cause T and B to react and clone
Daughter B cells migrate to other mucosal sites
What receptor is integral in moving new IgA from B-emmigrant cells onto mucosal surface?
poly-lg Fc receptors
(takes off B cells)
What protects sIgA dimers from proteases on the mucosal surface?
Where does this come from?
protease that cleaved sIgA from poly-lg Fc receptor
How does sIgA protect neonates?
Through mother's milk
Stays in intestinal lumen
What 2 places does a baby's passive immunity come from?
sIgA in gut through milk
IgG through placental transfer
IgA found outside the body is _____, while IgA found inside the body is typically ______.
sIgA is a poor activator of Complement and an inconsistent opsonizer.
What does anergy refer to in oral tolerance?
What is the main inhibitory cytokine involved?
High Ag feeding induces tolerance
What is the immunoglobulin complex that sticks to mucins?
What is this resistant to?
What does it block?
What are the specialized APC's found in the mucosa?
What does sIgA stick to on mucosal surfaces?
What type of virus is Polio?
Polio is enveloped/naked
is a (what stranded) RNA
usually found what part of body
Where does Polio bind in the body and replicate?
How is Polio transmitted?
What are its viremic effects?
What prevents initial colonization of the Polio virus?
What prevents viremia?
What Polio vaccine is killed and induces IgG?
Which one is attenuated-live and induces sIgA and IgG?
What are the Oro-Fecal considerations of the Polio vaccines?
Salk - 2 month window of continued fecal Polio excretion
Sabin - Fecal sIgA will confer bystander immunity
Even though it confers IgG, sIgA, and bystander immunity, what is a downside to the Sabin vaccine?
Can infect immunocompromised
Because Polio is a non-enveloped virus, it is very...
Poliomyelitis causes permanent damage.
*destroys motor neurons in the spinal cord
How big is the iceberg effect in Polio?
How many infected are paralyzed?
Where is the reservoir for Polio?
*only infects humans
How long is the Polio virus present in stool?
*long infective period
When was the "last case" of Polio in US?
*Global eradication goal of year 2000 not met
What type of virus is Influenza?
What must Influenza bring with it into the cell?
Functional RNA polymerase
What allows the Influenza virus to so effectively mutate?
It is a segmented virus
*allows for genome mixing
What are the 2 important spike proteins of influenza?
Why are they important?
N - neuraminidase
H - hemagglutinin
complete segments are exchanged with other viruses in the cell.
What is the mixing of different expressions of the N and H protein called?
*can cause Pandemics
What is a viral point mutation causing new epitope expression called?
H and N of the following:
2009 swine flue
Why are RNA viruses more mutagenic than DNA?
lacks "spell check" mechanism
When influenza infects a cell
__ gets in
__ gets out
*these are both Spike proteins
Where does influenza replicate in the cell?
Hemagglutin facilitates viral attachment
Nuraminidase helps viral release
What is a fast way to determine if someone is carrying antibodies to a specific influenza strain?
Hemagluttination Inhibition Assay
What causes many deaths from Influenza?
Lung becomes "denuded" and susceptible to secondary opportunists (staph and strep)
What identifies the 3 Influenza types?
What are they?
Which cause human disease?
A and B
What does it mean that flu vaccines are usually "trivalent?"
They have 2 A and 1 B component
What do the following Antiviral Drugs do?
Amantadine and Rimantadine
Oseltamivir (Tamiflu) and Zanamivir (Relenza)
Blocks viral uncoating
Inhibits neuramidase viral release from cell
Influenza Pandemics most often come from _____ and epidemics most often come from _____.
A and B
What determines the subtypes of the A influenza virus?
How many types of Hemagglutinin are there?
What is the reservoir for Type A influenza?
*we can't vaccinate ourselves out of the disease
What does Type A influenza cause?
Epidemics and Pandemics
What is the reservoir for Type B influenza?
(milder, mostly young and old are infected)
With influenza, what type of mutation is major?
*this causes new subtypes of H and N
What causes minor mutations in influenza?
How is the inactivated flu vaccine administered?
How does the Quadravalent flu vaccine differ from the Trivalent?
Quad - 2 most probable A and B types
What is the average efficacy of the influenza vaccine?
*depends on age, works poorly with elderly
What are the normal animal vector pathways used by the Influenza virus?
Fowl to Pig to Human
(or vice versa)
What does Hepatitis mean?
Inflammation of the Liver
There is no cross immunity of the Hepatitis viruses with what exception?
HBV and HDV
What is the viral load in the blood with both HBV and HCV?
With so many viruses that damage the liver, how do we determine a Hep virus?
If it lives in and damages hepatocytes
What blood factor is increased by Hep virus liver damage?
Which Hepatitis viruses are non-enveloped?
How are they transmitted?
HAV and HEV
Which Hep viruses are enveloped?
How are they transmitted?
HBV, HCV, HDV
vertical, sex, droplets
Which Hep viruses have no chronic condition?
Hep A and Hep E
*either live or die, Acute Only
What 2 ways can we prevent Hep A infection?
HAIG (immune globulin) - can be used pre or post infection
Hep B has immunoglobulin therapy and available vaccine.
HBIG and vaccine
There are no products that prevent HepC
*although there is now an expensive $84k cure
What does HBV prevention also affect?
There are no prevention measures for HEV other than sanitation measures
What demographic is susceptible to HEV?
Women 3rd Trimester
What Hep causes most deaths/yr in the US?
Fulminant (acute) Hep death is rare.
*sturdy and acute
HAV has a single serotype worldwide
HAV can be asymptomatic
HAV vaccine has been available since the 1960's
Does HAV have carriers?
Acute (or asymptomatic) infection only
*after which immune
There is single worldwide serotype for HBV
There can be an acute, asymptomatic, or chronic infection with HBV.
If exposed to HBV, what is the rate of developing a chronic infection for an adult?
For a baby?
10% (90% resolution)
90% (25% go on to major consequences)
HBV vaccine has been available since 1981
What is the primary component of the Hepatitis B vaccine?
*this is a Spike Protein
Why are health care personnel so at risk for HBV?
very big viral loads among chronically infected
What are the 2 major consequences of chronic HBV?
What is responsible for the pathology surrounding HBV?
Cell-mediated immunity and inflammation
*this also eliminated HBV infection
HBV is double-stranded DNS virus
What 3 immune components eliminate HBV in 90% of adult cases?
B, Th, and Tc
dsDNA virus in HBV goes DNA RNA RNA DNA
There is no treatment for Chronic HBV
*unlike HCV (new)
How do retroviruses reverse the process of the host cell?
Enter as (+)ssRNA
converted to dsDNA
HIV is a diploid virus.
HIV frequently changes host range and causes tumors inhumans
What is the enzyme in retroviruses that transcribes RNA to DNA?
Exogenous viruses are transferred...
Endogenous viruses are transferred...
Vertically (these are integrated into germ line)
What is a sexually transmitted human leukemia?
Where is it endemic?
Japan, SE asia
HIV-1 and HIV-2 are what type of Retrovirus?
What percentage of the human genome is made of past retrovirus?
(almost all turned off)
What are the 3 Exogenous retrovirus families?
*spuma has to overt pathology
Why are STI's a major risk factor in contracting HIV?
Some cause ulcers, and any breach in mucosa greatly increases risk
*Chlamydia type in Africa causes ulcers
Babies born to mothers with HIV generally carry the disease
If Mother is on anti-retrovirals good chance child HIV free
How many people have HIV worldwide?
How many deaths are there from HIV worldwide per year?
What type of HIV causes the preponderance of infection?
Why do Anti-HIV drugs eventually stop working?
What is generally the 1st symptom of crisis phase?
What makes up the ends of HIV?
What makes up the spike complex?
LTR - long terminal repeat
GP120 and GP41
What protein in HIV is targeted by a number of protease drugs?
Describe how HIV enters a cell.
GP120 binds first to CD4
GP41 binds and activates Chemokines
What is the receptor for GP120?
What is the receptor for GP41?
What cells have CD4 and CCR5 receptors?
What are the 6 steps of HIV replication?
Assembly of new HIV
What base deletion is responsible for HIV resistance?
What percentage has this in both alleles?
1% northern europeans
*CCR5 removal VERY promising HIV therapy
What is the current treatment for HIV?
HAART - Highly active anti retroviral therapy
Why is a dentist often the first to notice AIDS?
Oral diseases appear first as Th cells fall below 200.
What is the most communicable disease?
*300k keeps infection going
There is no iceberg effect with measles
*because of its communicability
What class of virus causes Measles?
How is measles transmitted?
What causes the characteristic Measles rash?
Tc cells targeting infected capillary endothelium
Cytotoxic T-cells (Tc) and Immunoglobulins usually completely eliminate measles.
What feature in Measles infection synergizes with poverty and malnourishment?
*Measles targets memory cells causing window of immunosuppression
What 2 diseases are caused by (-)ssRNA Paramyxovirus?
Measles and Mumps
What is the main difference between Measles and Mumps?
Mumps has an iceberg effect
*Measles has no asymptomatic carriers
What is the characteristic symptom of Mumps?
(painful swelling of salivary glands)
*can also infect testicular ducts
What is German Measles?
Rubella is comparatively benign
When would a fetus be at risk for Rubella?
*leads to birth defects
When is the Measles Mumps Rubella vaccine generally given?
booster before school
What is the reservoir for the MMR viruses?
What is by far the most important of the MMR diseases?
*because drop in vaccinations/loss of Herd Immunity
MMR are all ssRNA and enveloped
What white spots associated with Measles used to be diagnostic?
What can Mumps viremia cause in the 1st trimester?
Why are ssRNA, enveloped, zoonotic infections on the rise?
Encroachment into reservoirs
Novel, vector borne viruses can either be _____ or _____.
*often very virulent
Why is zoonotic infection more common outside Hunter/Gatherer societies?
Diseases tend to Burn Out in Hunter/Gatherer
What is a novel virus from an insect?
Arbovirus and Robovirus often cause what 2 conditions in humans?
All vector borne viruses are enveloped and ssRNA
What type of pathology is induced by the Togaviruses (Rubella) and Flaviviruses (West Nile, Dengue)?
these are Arboviruses
Encephalatic: Rubella, West Nile
*Rubella exception, was once vector born Arbovirus but now its ours and is spread via respiratory aerosols
What is the reservoir for Hanta?
What kind of virus is it?
Desert Mous rat
*causes hemorrhagic fever (capillaries collapse)
How are roboviruses transmitted?
Fecally by rodents
(including bats, etc)
Why do vector-borne zoonotics often jump species?
ssRNA enveloped viruses have very high mutation rate
What do Prions cause?
Transmissible Spongiform Encephalopathies
Name 5 Prion diseases.
Prions are larger than bacteria
Do Prions elicit an immune response?
Describe a PrP
What is an accumulation of PrP's in the CNS called?
Prions were once called...
How are new Prions formed?
What is the disease progression?
Contact existing Prion causes folding
Prions > Ameloid > disease
If infected with smallpox, what were the chances of dying?
What is the 1st and only infectious disease eliminated worldwide?
nucleic acid type?
Complex (both enveloped and naked)
The Middle Age technique of harvesting scabs at the end of a smallpox outbreak and applying it to cuts on the forehead after a time is called?