Exam 3 - Lecture 8 Flashcards
Do a quick review of DNA viruses genome types and their replication (slide 1 here)
genome:
- ssDNA or dsDNA
- can be linear/circular, one piece/segmented
replication: most replicate their genome in the nucleus of the host cell
Poxviruses
- What is unique about their capsid shape and genomic structure?
Brick shaped nucleocapsid
Linear dsDNA genome, with the two strands covalently bonded at each end to create hairpins
Poxviruses
- Know the other unique characteristics of its structure
- multiple envelopes
- surface viral tubules rather than normal glycoproteins
- multiple layers of matrix, some without a specific function
- a large number of replicative enzymes
Poxviruses
- Where does it replicate and why is that unique?
Poxviruses replicate in the cytosol rather than most DNA viruses which replicate in the nucleus in order to use the host cell’s machinery. Poxviruses must bring with them their own machinery to do this
Poxviruses
- What enzymes must it package into virions because it replicates there?
poxvirus must bring its own RNA polymerase, transcription factors, mRNA capping enzymes and mRNA polymerase
What two poxviruses can infect and cause significant disease in humans?
smallpox and monkeypox
What is variola?
The poxvirus that actually causes smallpox
How is smallpox spread, what cells does it infect, and what tissue does it target?
Spread through respiratory secretions, direct contact, and even indirect contact
Smallpox infects local immune cells, and then gets moved to the lymph nodes
What disease symptoms does smallpox produce?
Characteristic pustule rash, fever, muscle ache, and fatigue
This can progress into hemorrhage, shock, and death
What is vaccinia virus and how do we use it as a vector?
Vaccina virus a derivative of cowpox, and it’s used as our smallpox vaccines
Herpesviruses
- What is the tegument?
- What gives them the ability to infect multiple tissues?
tegument: a diverse matrix layer inside the herpesvirus
they contain many glycoproteins which enable them to infect a variety of tissues
Herpesviruses
- What is different about alpha, beta, and gammaherpesviruses?
The difference between these viruses is the type of cell that is secondarily infected by a herpesvirus:
- alpha: a neuron
- beta: leukocyte
- gamma: B/T cell
Herpesviruses
- What generally meant by latency?
After primary infection, some capsids take the genome and bring it into another cell, and inside that new cell the virus goes dormant, and will stay their for the remainder of the infected individual’s lifetime
Herpesviruses
- What are LATs and how do the mechanistically create a state of latency?
LATs (latency associated transcripts) are RNAs that shut down viral replication so that the herpes genome remains inactive
Herpesviruses
- What triggers reactivation and what determines the frequency of reactivations?
Reactivation usually occurs following a period of stress to the individual
Frequency of reactivation is directly proportional to the inoculum level of the initial infection
Know how herpesviruses express their genes. What types of genes are expressed as IE, E, and L?
Herpesviruses express their genes in waves, and there are typically three classes of genes:
- Immediate-early (IE) : right after entry, set up infection
- Early (E) - DNA replication, modulate cell metabolism
- Late (L) - structural proteins to be packaged into virions
What are some ways in which herpesviruses evade the immune response?
1) Disrupt cellular MHC expression
2) Make fake (homologs) cytokines and receptors
3) Prevent NK cell recognition
Know alphaherpesviruses and the diseases they cause (and who typically gets the diseases, etc.)
Herpes simplex virus (type 1 or 2, aka HHV-1 and HHV-2) and Varicella zoster virus (VZV, aka HHV-3)
Anyone can get HHV-1 and -2, spreads through any contact of mucous membranes
- Cause painful watery blisters on the mouth (1) or genitals (2)
HHV-3 causes chickenpox and later shingles
Know betaherpesviruses and the diseases they cause (and who typically gets the diseases, etc.)
Human cytomegalovirus (HCM, aka HHV-5)
Nearly ubiquitous in the population (immunocompromised are at special risk), and infects every tissue in the body
Usually asymptomatic
Know gammaherpesviruses and the diseases they cause (and who typically gets the diseases, etc.)
Epstein-Barr virus (EBV, aka HHV-4)
- Ubiquitous
- Infects epithelial cells and spreads to B cells
- Can cause mono, many forms of lymphoma, gastric cancer, and more
Kaposi-sarcoma herpesvirus (KSHV, aka HHV-8)
- causes SK, a skin cancer seen in HIV/AIDS patients
- most people harbor it asymptomatically, but immunosuppression allows for replication
Papillomaviruses (PV)
- What tissue type does it target?
epithelial tissue
Papillomaviruses (PV)
- What is a common property to all papillomaviruses in terms of tissue growth?
All >200 human papillomaviruses (HPV) cause excessive tissue growth
- Most present as benign warts, but some types cause cancerous lesions
Papillomaviruses
- How do we prevent PV infections?
Infection of the most prominent cancer-causing types of HPV can be prevented with the vaccine Gardasil
Papillomaviruses
- What do PV capsids look like and what is bound to the genome (and why)?
Icosahedral capsids
histones are bound to the genome to keep the genome organized like cellular chromatin
Know how PV replicate through a 3-D tissue. What is unique about how it works? How does the virus gain access to the tissue and what cell type does it initially infect? How do virions get released?
HPV must gain entry into the basal layer of the skin through a wound to infect an individual
- usually on hands or feet because these are high-touch areas of the body
Infects skin cells, and viruses get sloughed off with dried squams, although the genomes stay in the basal layer unless destroyed
