Exam 2 Flashcards
What kind of genome does Hepatitis A have?
+ssRNA
What kind of genome does Hepatitis B have?
Partially dsDNA
What kind of genome does Hepatitis C have?
+ssRNA
Hepatitis A is a (naked/enveloped) virus
Naked
Hepatitis B is a (naked/enveloped) virus
Enveloped
Hepatitis C is a (naked/enveloped) virus
Enveloped
What family does Hepatitis A belong to?
Picornavirus
What family does Hepatitis B belong to?
Hepadnavirus
What family does Hepatitis C belong to?
Flavivirus
What is the mode of transmission for Hepatitis A?
Fecal-oral
What is the mode of transmission for Hepatitis B?
Blood, sexual contact
What is the mode of transmission for Hepatitis C?
Blood, sexual contact
Is there a vaccine available for Hepatitis A?
Yes!
Is there a vaccine available for Hepatitis B?
Yes!
Is there a vaccine available for Hepatitis C?
No!
In Hepatitis A, ___ is covalently linked to the 5’ end of the viral genome and a _____ is at the 3’ end.
VPg, polyA tail
Hepatitis A is cap (dependent/independent).
Independent
What feature of Hepatitis A allows for cap-independent translation of viral mRNA?
IRES sequence
Hepatitis A binds to ______ located on ______.
Mucin-like glycoprotein hepatitis A virus cellular receptor (huHAVcr-1), hepatocytes
(T/F) Hepatitis A synthesizes a polyprotein.
True
What is the protease encoded by Hepatitis A that cleaves the polyprotein?
Viral 3C
Viral 3D in Hepatitis A encodes _____________.
RNA-dependent RNA polymerase
What is the role of RNA-dependent RNA polymerase in Hepatitis A?
To synthesize –ssRNA and then genomic +ssRNA
(T/F) There is a specific treatment available for HAV infection.
False
What is the best way to protect oneself against HAV?
Handwashing and proper sanitary disposal of human feces
HAV Immunization is _______, and is 85% effective in preventing HAV infection.
Passive
HAV vaccines are inactivated by ______, produced from _____ ______, and are _______ ______ vaccines.
Formalin
Cell culture
Whole virus
(T/F) HAV Vaccines are effective and given to people who travel to areas where HAV infections are prevalent.
True
Which 5 regions of the world have prevalent HAV?
Mexico, central America, Asia, Africa, & Eastern Europe
HBV is fascinating for 2 reasons. What are they?
1) Have very small genomes
2) DNA genomes are replicated via an RNA intermediate
The discovery of HBV led to the creation of Baltimore class ____.
VII
The HBV capsid has ________ symmetry.
Icosahedral
How is HBV vaccine produced?
Recombinant HBsAg is used. Use yeast cells which contain HBV S protein
Is HBV vaccine safe for newborns? Why?
Yes. The virus is a recombinant virus. Since it uses just pieces of the virus, there is no risk of contracting HBV
In addition to producing infectious particles, HBV also produces a number of __________. Why do scientists think they exist?
Non-infectious particles. Possible decoys for antibodies.
The 2 kinds of non-infectious particles produced by HBV are ______ & _____.
Spheres & filaments.
The non-infectious particles produced by HBV are mainly found in the (blood/liver)
Blood
The non-infectious particles produced by HBV are mainly found in the (blood/liver)
Blood
HBV has __ ORF(s) and produces ___ protein(s)
4 ORFs, 7 proteins
The HBV genome is converted into a _______ molecule upon transportation into the nucleus
Circular DNA molecule. cccDNA
(T/F) HBV viral DNA replicates in the nucleus.
False. More copies are brought into the nucleus later in infection.
Where does replication take place for HBV?
In the cytoplasm inside the nucleocapsid
(T/F) While replication is ongoing, the virus is incapable of undergoing maturation and budding from the cell.
False. The DNA strand is incomplete.
Through which membranes does budding occur for HBV?
A compartment between ER and Golgi
Is the host hepatocyte killed by HBV infection?
No. The cell survives for months releasing large quantities of virus and non-infectious particles
Antivirals that treat HBV target which step in replication?
Genome replication. Lamivudine (don’t have to know name) is a nucleoside analog.
Is a vaccine available for Hepatitis C?
No
How does the treatment Sofosbuvir help HCV infection?
Inhibits HCV RNA polymerase. Major improvement over interferon treatment
Does HCV cause cancer?
Yes. Liver cancer. Hepatocellular carcinoma.
Smallpox had a (high/low) mortality and occurred in (1/2/3) forms.
High, 2
What are the 2 forms of poxviruses associated with smallpox?
Variola major and Variola minor
Variola major had a mortality rate greater than __%, and Variola minor had a (higher/lower) mortality rate of ___%.
20%
Lower, 2-5%
In humans, smallpox is spread via _________.
Inhalation
In humans, the primary site of infection for smallpox is _______.
The lungs
Smallpox travels through the host via ______, leading to secondary ________ infections.
Viremia, epidermal
In smallpox, secondary epidermal infections result in _____ ________, making it easier for further spread of the virus.
Skin eruptions
(T/F) Pox virions are not resistant to inactivation by desiccation.
False. Poxviruses are VERY resistant to inactivation
(T/F) Infectious smallpox virus can be recovered from infected bedding, clothing, house wares, and soil for a significant length of time
True
Which factors contributed to a successful elimination of smallpox?
No latency, no persistent infection, do not make themselves invisible to the immune system. DO NOT remain associated with the host after infection has cleared; host survives with permanent immunity
Where is smallpox virus safely stored today?
In public health labs in Russia & US
Most of the knowledge on smallpox comes from the study of _______ virus.
Vaccinia
(T/F) A cell culture system is possible for vaccinia virus.
True
Smallpox virions are incredibly (small/large).
Large (can be visualized by a light microscope)
Describe the shape of a smallpox virion (envelope vs. non-envelope, spherical vs. icosahedral, etc.)
Complex. Enveloped, brick shaped
The smallpox genome is composed of _____.
Linear dsDNA
The smallpox genome has ______ ______ at the terminals.
Closed ends
The ends of the smallpox genome have terminal _______ _______.
Inverted repeats
Internally, poxviruses have a ______-______ core and (1/2/3) _______ _______ surrounded by outer membrane
Dumbbell-shaped core
2 later bodies
What is the function of the 2 lateral bodies in smallpox?
Contain various enzymes for viral replication
The core of smallpox contains ______ _______needed for ________ of virions and also for _______ of genome.
Essential proteins
Morphogenesis
Transcription
Entry of smallpox is (easy/complicated)
Complicated
Why is entry of smallpox complicated?
Many forms of the virion exist
What are the 2 forms of the virion in smallpox?
Mature virion (MV) and extracellular virion (EV)
The mature virion of smallpox contains (1/2) envelopes derived from _______. It is released due to _______.
2 envelopes
Golgi and endosome
Cell lysis
The extracellular virion of smallpox contains (1/2) membrane(s) derived from _______. It is released by ________.
1 membrane
Golgi
Budding
(T/F) Each form of the smallpox virion enters by a different mechanism.
True
What are the cell surface glycosaminoglycans conserved in every cell type in smallpox infection?
Receptors
In smallpox, uncoating happens in the _______ and the viral core is released into the _______.
Cytoplasm, cytoplasm
For smallpox virus, where does replication occur?
In the cytoplasm. Unusual for a DNA virus.
(T/F) Poxviruses encode most but not all the enzymes needed for replication.
False. Encode all enzymes needed for replication in cytoplasm. Can replicate in enucleated cells
(T/F) Smallpox virions do not carry their complete transcription systems.
False.
Smallpox gene expression occurs in 3 phases. What are they?
Early, intermediate, and late
Smallpox evades the immune system in several ways. What are they?
Encode a variety of proteins. Viroceptors – Secreted from infected cells and sequester ligands that would target infected cells for destruction
Virokines – Secreted viral proteins that resemble host cell’s cytokines. Bind to interferons, interleukins, and Tumor necrosis factor.
Inhibit PKR
Serpin (protease) inhibitors
What poxvirus was used to control the wild rabbit population in Australia?
Myxomavirus
Why is smallpox a potential biological terror weapon?
Active vaccination has been discontinued. Susceptibility to the disease is now worldwide. Mass vaccination would require large stocks of vaccine, which we don’t have.
What are the pro-retention arguments for keeping smallpox safely stored?
It is possible that undisclosed or forgotten stocks of smallpox exist. Genetic information of virus is online, technology exists to create a new smallpox virus. Destroying virus is merely symbolic. Virus is needed to synthesize more vaccine
What is the definition of an emerging virus?
New or recently identified viruses that are affecting human health. A majority are of zoonotic origin
What is the definition of a reemerging virus?
Viruses that were once thought to be under control from a public health perspective but are making a “comeback” and causing increased incidence or geographic range of infections in humans
What are the factors that influence emergence or reemergence of viruses? KNOW THESE
Changes in viral pathogen Changes in human host Changes in environment Changes in ecological niche Human behavior Environmental disruptions
There are 4 viruses in new host species that we studied. Name them.
Hanta, Sin Nombre, Hendra, & Nipah
What might cause a virus to emerge in a new host species?
Travel/trade, close contact with animals (hunting and killing non-human primates for bushmeat), virus may undergo changes in the new host resulting in a new virus (HIV-1 & HIV-2 derived from SIV)
How did Hantavirus/Sin Nombre virus emerge?
Deer mouse population exploded after Four Corners region of US received more rainfall than usual. Mice were persistently infected with a virus excreted in their urine, droppings, and saliva. Humans exposed to these materials developed respiratory illness.
How did the Hendra virus emerge?
Horses had acquired virus from fruit-eating bats, which had emerged after deforestation. Humans acquired the virus from the horses. No disease is caused in bats.
How did the Nipah virus emerge?
Deforestation drove fruit-eating bats out of forests. Pigs came into contact with infected bat droppings. Spread by aerosol and close contact with sick pigs to humans.
The Nipah virus emerged as a result of _________ activity.
Deforestation
What is a spillover host? How does it get infected?
Spillover infection occurs when a reservoir population with a high pathogen prevalence comes into contact with a novel host population. The infection is transmitted from the reservoir population and may or may not be transmitted within the host population
There are 4 examples of viruses that emerged in new areas that we discussed. Name them.
WNV, Zika, Marburg, & Ebola.
What is the vector for West Nile Virus?
Mosquitos
What is the leading theory as to how WNV came to the US?
Airplanes carrying infected mosquitos flew across the Atlantic Ocean from Israel at a time when airplane cabins were not sprayed with insecticides
WNV is mostly (symptomatic/asymptomatic) in humans.
Asymptomatic
WNV can cause a range of symptoms. Name them.
Feber, aching muscles, in less than 1% of cases virus spreads to CNS and causes encephalitis and death.
Describe the transmission cycle for WNV.
Main reservoir of WNV is birds and mosquitos pick up WNV while taking a blood meal from infected birds. From there, WNV moves to horses and humans via mosquito bite. Humans and horses are dead end hosts. Stable flies have also been found to be a new reservoir for WNV
Why did the Zika virus emerge?
Mosquitos Aedes aegypti and albopictus transmitted the virus. Pathogens introduced in new areas caused explosive epidemics as the population lacks immunity.
Zika virus causes _______ in newborns.
Microcephaly
______ virus and _____ virus are examples of viruses in new host species AND new areas.
Marburg and Ebola
What is the natural reservoir for Marburg virus?
African Green Monkeys
Researchers believe that ____ are the most likely natural reservoir for Ebola
Bats
How did Monkeypox emerge?
Monkeypox entered the US in pouched rats imported from Ghana. Infected pet prairie dogs that were housed next to the imported rats and then to humans.
What are the new viruses we discussed?
SARS-CoV and new strains of influenza (H5N1 & H9N2)
What does evidence suggest is the natural reservoir for SARS-CoV?
Chinese horseshoe bat
How did the human pathogen of SARS-CoV evolve?
It’s possible that SARS-CoV evolved from a rare virus that had this human to human transmission ability.
How did H5N1 and H9N2 emerge?
An influenza virus emerged with a novel combination of N and H genes formed by reassortment. Aquatic birds acquired the virus by inhalation or ingestion.
How can humans become infected with flu not H type 1, 2, or 3 and N type 1 or 2?
Some avian strains are highly pathogenic in birds and can be transmitted to domestic poultry and then to humans
What are the 3 kinds of reemerging viruses we discussed in class?
Polio, Mumps, and Measles
Why are measles, mumps, and polio reemerging?
People are refusing to vaccinate due to fears the vaccine causes autism.
Which scientist discovered that viruses can cause cancer?
Francis Peyton Rous (remember Rous)
Rous injected chickens with a cell-free, bacteria-free liquid filtrate of the sarcoma tissue. Chickens developed sarcoma at the site of injection. This was the first demonstration that a transmissible agent could cause cancers. The agent was a _______ and was later named _____ _____ virus.
Retrovirus, Rous Sarcoma Virus (RSV)
Which scientists discovered oncogenes and proto-oncogenes?
Bishop and Varmus.
What is an oncogene?
A gene that is nonessential for virus replication that causes cells to become transformed or cancerous
Cellular oncogenes are involved in the production of many things, including:
Cytokines, growth factors, protein kinase, G-proteins, transcription factors, and other proteins that regulate cell proliferation
RSV has a gene that is not essential for virus replication, but is required for cell transformation. This gene is called ____.
src
Which 6 viruses cause cancer in humans?
HBV, HCV, HPV, EBV, Kaposi’s Sarcoma Associated Herpesvirus, HTLV-1 and HTLV-2 (retroviruses)
In retroviruses, the pol gene encodes ______ _______.
Reverse transcriptase
After synthesis of DNA by reverse transcriptase, the DNA copy of the viral genome does what?
Integrates into the host genome
How does HTLV cause cancer?
Mechanisms of cell transformation are poorly understood. Adult T-cell leukemia patents express high levels of IL-2 receptors. HTLV-1 encodes for a small protein called tax. Tax binds to cellular transcription factors (c-mic) and activate certain oncogenes, which then express proteins in abundance
EBV is a ______virus that causes ______ ______.
Herpes, Burkitt’s Lymphoma
DNA tumor viruses target ___ and ____ tumor suppressor gene products
Rb and p53
Why does Burkitt’s Lymphoma only occur in some regions of Africa?
Burkitt’s Lymphoma happens in individuals with weakened immune system, such as AIDS patients. Children in central Africa often suffer from such infections
Kaposi’s sarcomas develop in ______ patients. Why?
AIDS. They are immunocompromised. Immune system is typically good at controlling this infection.
(HBV/HCV) integrates into the human genome.
HBV
HBV and HCV can lead to ______ _______ and _________ cancer.
Liver cirrhosis
Hepatocellular
HPV types are divided into 3 risk categories. What are they?
Low-risk, intermediate-risk, and high-risk.
High-risk HPV is responsible for (genital warts/cancers)
Cancers
(T/F) HPV types that cause genital warts are not the same as the types that will cause cancer.
True
(T/F) HPV can only be spread when an infected person begins showing symptoms.
False
Why is it difficult to know when you first became infected with HPV?
You can develop symptoms years after you have sex with an infected person
Does HPV go away on its own or does it require treatment?
Will go away on its own. When it doesn’t go away, it can cause health problems like genital warts and cancer.
Cancer often takes (days/months/years) to develop after a person gets HPV
Years
(T/F) There is no way to know which people who have HPV will develop cancer or other health problems.
True.
70% of cervical cancers are caused by types ___ and ___.
16 and 18
Why can HPV not infect the dermis?
All viruses only infect metabolically active cells
HPV-16 is implicated in cancers of the ____ _____, ________, and ______.
Oral cavity, oropharynx, and throat
___ is a protein produced by HPV that binds to p53 and promotes its degradation.
E6
___ is a protein produced by HPV that binds to Rb-E2F complex, causing its dissociation.
E7
(T/F) High-risk HPV types integrate into the host genome
True
There are ___ vaccine(s) currently available for HPV.
3
Gardasil is a quadrivalent HPV vaccine that is a non-infectious _________ vaccine.
Recombinant
Gardasil-9 is a nonavalent HPV vaccine that is a non-infectious _______ vaccine.
Recombinant
(T/F) The HPV vaccine is safe and effective.
True.
(T/F) The CDC does not advise children to get vaccinated against HPV.
False. The CDC recommends 11 to 12 year olds get two doses of HPV vaccine to protect against cancers caused by HPV
Which oncolytic virus was the first to receive FDA approval?
A treatment for melanoma known as talimogene laherparepvec, or T-VEC (Imlygic).
