Unit 3 Viral Pathogenesis Flashcards
For viruses, infection simply means entry of a virus into a host cell
This type of infection has new infectious particles produced inside the host cell
For this type, few, if any new viral particles are produced inside the host cell. Not good for the virus.
Productive Infections
Abortive Infections
Abortive infection is sometimes due to 2 things:
Mutation (of the virus)
Protective mechanisms of the host
This type of infection is of short duration, signs/symptoms observed, and then infection is cleared (immunity results)
Prime example is the
Acute infections
(rapid in rapid done)
Rhinovirus
This type of infection is not completely eliminated after primary infection
What is the example of this
Latent Infections
Herpesviruses (there are 8)
This herpes virus is primarily responsible for cold sores but it could also be
Genital ulcers are usually this herpes virus but can also be
HHV-1 is primarily responsible, can also be HHV2 (genital ulcers is a symptom too)
HHV-2 is primarily responsible, HHV-1 can cause them as well
Chickenpox and shingles are this herpes virus
HHV-3 (varicella zoster)
This term means virus is in the blood, and applies to chickenpox before rashes emerges. Explains why rashes appear all over body
Viremia
This is the reactivated form of chickenpox and is more localized, can be activated by stress. A vaccine is out there to keep our immune system in check for it.
Shingles
This herpes virus causes mononucleosis (sick and tired all the time) and Burkitt lymphoma, a reactivated version of it, especially common in HIV positive individuals
It likes to reproduce inside of ____ cells
HHV-4
B cells
This herpes virus is associated with Kaposi Sarcomi, also associated with HIV positive status. Causes an overgrowth of blood vessels underneath the skin.
HHV-8
Latency is maintained inside ___ cells, by maintaining a circular ___ during latency
These help maintain latency
Nerve cells
Circular Episome
Latency associated transcripts (LATs)
Stress, UV light, hormonal changes, and getting over other sicknesses may cause reactivationcc
!
This is the term for chronic infections, where new viral particles are continuously produced. The host doesn’t clear the virus even though signs and symptoms may cease
Persistent Infections
Persistent infections may be a result of a targeted weakening of the immune system or mutational changes in the virus and/or changes in the virus and/or changes in host target cells
!
Examples of persistent infection include
Do these illnesses always become persistent in individuals?
HIV, hepatitis B and C
No, but they can in some individuals and do.
Viruses must be able to leave one host and enter another. What are the 4 basic types of transmission
Horizontal Transmission
Vertical Transmission
Zoonotic Transmission
Vector Transmission
This type of transmission is due to an animal passing it onto a human
This is more specific, is flea or blood sucking animal
Zoonotic Transmission
Vector Transmission
Which type of viral transmission passes between friends, or from individual from individual within the same species. Includes respitory, fecal oral, and sexual transmission
Which can be passed through mother to offspring in unborn children
Horizontal Transmission
Vertical Transmission
Rhinovirus, influenza, poliovirus, hepatitis A, HIV and HPV are what type of transmission?
Horizontal Transmission
This type of transmission occurs within the same species but from mother to fetus or newborn. Can be transmitted through the ____ or during birth via blood.
The virus can also be transmitted by bodily secretions like
A few viruses can even be transmitted via these type of cells, spermatocytes/oocytes infected with mouse mammary tumor virus
Vertical Transmission, placenta (rubella aka German measles, Hep B and C, HIV)
Breastmilk (HIV)
Germ line cells (reproductive cells)
Facilitated transfer of virus from host to host via another vector, like yellow fever or the myxoma virus
How is it different from zoonotic?
Vector Transmission
Animal isn’t affected by pathogen, it’s more specific (blood sucking insect passes it from one organism to another)
What are the two ways a virus can kill a body cell
What is the other way body cells can die?
Necrosis and Apoptosis
The immune system (kills infected body cells)
This type of viral induced cell death causes the cell to burst
Is this usually naked or enveloped virion?
What are three mechanisms that cause the cell to burst?
Necrosis
Naked (only way to get out, no spike protein)
Overfilling cell with new viruses
Viral impairment of normal cell function
Additionally, the virus produces particles that weaken the membrane (some)
What symptom is necrosis associated with?
What is inflammation caused by?
Inflammation
Tissue damage that releases chemicals that trigger immune response (chemicals inside cells, like via process of necrosis)
This is the more subtle death of cells that is safer for surrounding cells. The cell commits suicide, sometimes as ordered by the immune system to safely kill virally infected cells.
Apoptosis
During apoptosis, internal events occur that degrade DNA into small fragments, bits of cell are released as ______
Does this induce inflammation?
Blebs
No, not rupturing/leaking the cell contents out
Some viruses can fuse host cells together, forming ___ that often kill the cells
What virus is well known for doing this?
Synctia
HIV
By doing syncytia, what does the virus avoid? Intracellular or extracellular immune responses
Extracellular Immune responses
In HIV, syncytia occurs via spike proteins injected into a CD4 cell membrane, where they can bind to the other CD4 cell because the spike proteins have gp120. The newly infected CD4 cells can’t function.
!
Can a virus move between different cells when synctia occurs?
How is this benefecial
Yes it can move between the cells that are involved in a synctia
Avoid extracellular immune responses
Other viruses may form clumps of virus or proteins inside host cells that often kill cells by interfering with cell function, these clumps are called
Inclusion bodies
What are inclusion bodies helpful for?
Example?
Viral identification
Niger bodies in detection of rabies
The signs and symptoms of viral infection may be a result of our own immune responses
What causes the symptoms in the common cold this way?
Inflammatory cytokines (chemicals involved in communication, stimulates other immune cells) -causes tired/aching/fever/mucous production etc
What does the mucous do in the common cold?
Prevents virus particles from attaching to host tissues (too much cold medicine can be bad)
Another example of inflammatory cytokines in viruses, cold sores/red blisters
Decline in CD4 cells leading to opportunistic pathogens taking over part of your body is
Herpes
HIV
The impact of the hepatitis B virus on liver function is a result of immune responses killing off infected _______, aka liver cells
What type of infection is can hep B be??
Hepatocytes
Acute (not bad) Chronic/persistent infection (bad)
Chronic hep B can cause liver disease, which is _______________ mediated
Liver disease can lead to _____ when coupled with Hep D infection
It can also cause kidney disease, which is ___ mediated (humoral/autoimmune response), they attack our tissues causing damage
reCytotoxic lymphocyte mediated
Liver Cancer
Antibody-mediated
The signs/symptoms of autoimmune diseases may be a result of our own immune response against viruses. If molecular ____ occurs, an antiviral response accidentally views self structures as foreign
Molecular Mimicry (cross re-activity of antibodies)
It’s not the same surface chemical on the host cell as the virus that activates white blood cells but they look close enough in molecular mimicry. Killer Ts make the mistake this way (ex: multiple sclerosis)
!
In autoimmune disease ____ cells attack healthy body cells that have similar proteins that are on pathogens
Killer T cells (CD8)
In MS, it targets dendritic cells that make myelin sheath
MS is marked by a rapid deterioration in
Vision
Also uncoordinated movement
Also pins and needles
Do all people with MS die?
No, some have one episode, some it progresses quickly, some progress slowly
Tranformation events produce changes in a cell that make it cancer like
Some viruses possess _____, genetic material capable of inducing tranformation events in host cells
Oncogenes
In cancer, oncogenes go what?
Turn off tumor suppressor genes
This may result from a viral protein inducing a normally quiescent (or not dividing, in a G0 phase) cell to enter the cell cycle
Tumorigenesis
leads to warts, etc.
This disease is associated with warts, especially genital , does give rise to others.
Are the warts always visible?
Does every strain have oncogenes?
If you do have the oncogenes, you have an increased chance of
HPV (Papillomaviridae family)
No.
No.
Cancer developing (penile/scrotal or cervical)
HPV has a vaccine for both men and women.
!
This disease is associated with the herpesviridae virus family and it transforms endothelial blood vessel cells, a defining cancer of people with HIV/AIDS
Kaposi Sarcoma
This disease is associated with herpesviridae and causes infectious mononucleosis more commonly
Burkitt Lymphoma
Why is it beneficial for viruses to up the cell cycle?
It gives them more hosts to infect (leads to warts)
The virus cells, like the dead epithelial cells, are at the surface and can infect other people when they shed
! Scary.
There are events at the genomic level that can occur as viruses reproduce that can alter there virulence. What are the 3 things?
Mutations
Recombinations
Reassortments
This type of event produces changes in the genome directly
Viral Mutation
Eukaryotic/prokaryotic cells have many ways of preventing mutations. The proofreading activity of ____ is one. It lowers the amount in this type of virus
Some viruses lack these capabilities, like viruses that have _____
DNA polymerase used by DNA polymerase
RNA polymerase used by RNA viruses (including reverse transciptase!)
So which produce more viral mutations, DNA or RNA viruses?
RNA viruses, they don’t have proofreading capability (reverse transciptase or RNA polmerase
Viral mutations can lead to issues with treatments, and can change which cells are infected in a persistent infection
!
In one strain of HIV, the CD4 surface receptor and the _____ surface co-receptor on monocytes can be infected
In another strain, the helper T cells have CD4 and the _______ coreceptor, when this occurs in HIV its more dangerous.
CCR5
CXCR4
In many HIV cases, especially if it was contracted sexually, most people get exposed to which strain of HIV, CCR5 or CXCR4?
Over time what occurs?
CCR5. So the first wave of cells infected are the monocytes/macrophages.
Mutations, causing different strains to emerge like the strain that affects helper T cells (the generals of the immune system)
This type of event occurs during Prophase I, fusions of pieces of two separate viral genomes creates a new hybrid genome, can result in entirely new properties rapidly. Not always good for the virus.
Virus Recombination
As an example of virus recombination, this virus has two strains, the polymerase can create 4 different viruses
Coronavirus (2 strains, 4 possibilities)
1 all strain 1, 1 all strain 2, 2 recombinant viruses
This type of process can lead to antigenetic shift, multiple viruses with segmented genomes infect the same cell and can swap segments in a newly formed virus. This can lead to new or modified virulence traits
Viral Reassortment
A slight mutation giving a little change in a surface protein so the immune system doesn’t recognize it is defined as
Antigenetic Drift
This is a big change, the genome is re-assorted and a different strain occurs. Very low herd immunity results.
Antigenetic Shift
Viral reassortment occurs between these viruses
Swine flu , Avian Flu, Human flu
In order for something to be a pandemic flu, it everybody has t be susceptible, in other words, the virus must be
Transmissible
Note: antigenetic shift may occur but it isn’t very transmissible. What is an example of this?
Bird flu, spreads rapidly between birds but doesn’t spread between humans well. But it could become the next pandemic flu with a shift/drift
Additionally, H1N1
