Ch 22 Exam 4 Flashcards
introduced species
species released into a non-native environment
What must all viral cells do within host cells?
They must replicate WITHIN host cells
productive infection
new infectious viruses made after virus entry into host
abortive infection
a few, if any viruses are made after virus entry into host
what type of infection results in infectious disease?
productive infection
What does the overall outcome of viral infection depend on?
the replication of a virus
the immune response of the host
acute infections
(give an example)
viral infections that occur suddenly (most of viral infections we experience)
(rhinovirus infection)
latent infection
(give an example of a virus that exhibits latency)
virus remains in the host and replicates over the course of a long time (genome remains in infected cells)
herpesvirus
episome
LATs
circular genome of viral DNA separate from the host genome (affiliated with latent infection)
(latency-associated transcripts) transcribed during latency
What is the relationship between LAT expression and viral gene expression
During reactivation, an increase in VIRAL gene expression results in a decrease in LAT
What can cause viruses to switch from latency
stress events, UV light, studying for exams, menstruation (women) (basically depends on the health of the host)
persistent/ chronic infections
the continuous production of viruses
unlike acute where there is RAPID recovery, host does not clear the virus in a reasonable amount of time
For persistent/chronic infections to occur, what must happen?
How may a virus do this?
virus must be able to replicate in the presence of host innate/ adaptive immune responses
weakening immune response
mutation that alters replication (altering cathepsin B)
How must a virus be transmitted?
must be expelled from original host
must be infectious until new host is found
mast have access to cells within new host
Give examples of common horizontal transmission strategies
zoonotic?
respiratory (rhinoviruses, influenza)
fecal-oral (polioviruses, hepatitis A)
sexual(HIV, human papillomaviruses
Ebola
how may vertical gene transfer occur? Give an example.
blood may be transferred from mother to child, or milk form mother to child (rubella, HIV, hepatitis B and C)
also may be through germ cells that make sperm/ egg (like mammary tumor virus of mice)
endogenous retrovirus
(why is this important)
when a retrovirus inserts itself in sperm or egg, combining with the DNA of the gametes
viruses can be inherited through generations
What is zoonosis (don’t overthink it bud)
a disease resulting from the zoonotic transfer of viruses
True or False: Humans are typically dead-end hosts
True
how may viruses indirectly/directly lead to auto-immunity
a viral infection may cause the immune system to attack itself
molecular mimicry (immune response for virus attacks host)
transformation
tumorigenesis
changes within a cell that cause it to be out of control
formation of a tumor (not normal growth of tissue)
oncogenes
genes capable of causing animal cell transformation
Are viral oncogenes needed for cell replication?
Yes
papillomas
how does it cause tumor formation
skin tumors/ warts
stimulates the S phase of quiescent cells (cells that don’t actively divide) which are keratinocytes
What proteins do papillomas affect?
What do these proteins do?
tumor suppressors Rb (binds to E2fs stopping S phase) and p53 (makes p21, which induces apoptosis)
How do papillomas specifically prevent tumor suppressor proteins?
What technique (using an antibody to precipitate antigen) can be used to detect this?
HPV proteins E6 binds Rb and E7 binds p53 (therefore preventing p21 production)
immunoprecipitation (IP)
Why is cancer associated with certain strains of HPV?
proteins of oncogenic strains bind to tumor suppressor proteins with greater affinity than non-onco.
oncogenic strains target effectively
True or False: Many human cancers have been associated with adenovirus infections
False (they usually lead to apoptosis)
For tumorigenesis to occur, what proteins must be inactivated?
Rb and p53
how may hepatitis c virus cause cancer?
most likely a byproduct of chronic inflammation rather than directly from the RNA-containing virus
protooncogenes
genes that code for proteins involved in cell growth
how may protooncogenes convert to oncogenes?
viral DNA inserts near protooncogene, causing a change
retroviruses introduce oncogenes to normal cells
(cis-acting retroviruses)
cis-acting retroviruses type 7
transducing retroviruses
retroviruses that change oncogene when integrated
retroviruses that introduce oncogenes to other cells
