Enteric and Respiratory Viruses Flashcards
viruses that enter through the respiratory tract
adenovirus
herpesvirus
poxvirus
picornavicrus
togavirus
orthomyxovirus
paramyxovirus
coronavirus
viruses that enter through the mouth, intestinal tract
adenovirus
herpesvirus
picornavirus
reovirus
viruses that enter through the skin and mucosa, including sexual transmission
papovavirus
herpesvirus
poxvirus
retrovirus
viruses that enter through injection
herpesvirus
hepadnavirus
flavivirus
retrovirus
viruses that enter through bites
rhabdovirus
togavirus
flavivirus
enteroviruses
picorna family
small RNA viruses
many different viruses in the family
most cause mild self-limiting diseases in the gut
includes poliovirus and enterovirus 71
plaque assay
used to detect viruses, titer viral stocks, and isolate viruses by limiting dilution
two vaccines for the treatment of polio
inactivated polio vaccine (IPV) - invented by Salk, required inactivation with formaldehyde, and poor control resulted in infection with activated virus
oral polio vaccine (OPV) - Sabin, live virus that has been attenuated, produced better immunity because it could enter cells and replicate to an extent
triggering of picornaviruses
triggered by binding to receptors, and then VPs 1,2, and 3 allow insertion of internal contents
picornavirus genome
only one protein is made called the polyprotein, which is then cleaved into little peptides through autocatalytic means
flaviviruses have the same processes
2BC and 3AB fragments of the picornavirus polyprotein
proteins that disrupt the golgi complex and induce production of membranous vesicles
cytopathic effect (CPE)
gross changes that occur to cells that include the disruption of the Golgi complex and a dramatic accumulation of cytoplasmic vesicles
also the nucleus is poisoned and cellular gene expression is shut down
viral infection and rate of host cell proteins synthesis
there is an initial drop in the rate of protein synthesis followed by a gradual increase as the viral mecnahisms restarts the machinery, which overrides the host cell safety mechanisms
eIF2B and viral particle response
eIF2B regulates translation by allowing for activation of eIF2 and loading of the methionine amino acid at the start site
when there are high levels of dsRNAs, protein kinase R activates and phosphorylates eIF2, which binds to eIF2B and inactivates the compound, therefore stalling translation
methods that viruses can use to stop cell translation
cleavage of the cap proteins
dephosphorylation of the cap proteins
poliovirus can also degrade protein kinase R to ensure that its own genes can be replicated
internal ribosome entry sequence
particular sequences on viral RNAs that allow for translation to begin in the middle of an RNA strand and is cap-independent
viruses can use inactivated protein machinery to make its own proteins
picornavirus 2A protein
cleaves eIF4G and prevents cells from responding to infection
picornavirus 3CD
enters nucleus and cleaves TATA binding protein
ensures that minimal amounts of endogenous RNA are being transcribed or translated
astroviruses
calici family
naked, +ss
no viral polymerase
virion diameter is 35-49 nm
genome size is 8 kb
RNA virus, naked
rotavirus
reo family
rare dsRNA genome, 10-18 segments
virion polymerase present
viron diameter 60-80nm
22-27kb genome size
RNA virus
norovirus
calici family (see astrovirus)
+ssRNA genome
highly contagious and highly stable, not inactivated by alcohol or mild detergents
most common cause of gastroenteritis and foodborne disease outbreaks
no good protective immunity, high mutation rate
rotavirus infection
transmission is by fecal-oral route
infections can occur at any age but diarrheal disease occurs mostly in infants and children
high incidence of infection
immunity becomes more protective with every infection (disease attenuates with each infection)
major cause of gastroenteritis requiring hospitalization
structure of the rotavirus
three shells
third outer layer is a membrane without lipids
when the virus fuses, left with inner two shells as the outer membrane disappears
dsRNA is the minus strand of the RNA that the polymerase is going to transcribe
How does the rotavirus survive with a dsRNA genome?
It synthesizes RNA inside the shell that gets into the cell and shoots out single-stranded RNA, avoiding cell dsRNA sensors
viroplasm
a designated area of the cytoplasm of the cell where the assembly of new virions occurs
VP4
a rotavirus protein that is activated by low pH to enhance infection of villi in the small intestine
NSP4
an enterotoxin secreted by rotaviruses that promotes diahhrea
functions as an integral membrane protein, required for envelopment of the double-layered virus particles but is then removed concomitant with the removal of the envelope and addition of the outer later
a secreted fragment can bind to cell receptors that trigger the mobilization of intracellular calcium, stimulating anion movement across membranes, and causes fluid secretion into the intestinal lumen
typical viruses that cause the common cold
adenoviruses
coronaviruses
respiratory syncytial virus
rhinoviruses
rhinoviruses
more than 100 serotypes known, accounts for half of all colds
Respiratory Syncytial Virus (RSV)
doe snot induce durable protective immunity, can keep infecting the same host
leading cause of bronchiolitis
parainfluenza
causes croup, bronchiolitis, pneumonia
only four serotypes and all produce protective immunity, generally limited to children
parovirus B19
causes fifth disease
bable to invade RBC precursors in the bone marrow
most common infectious disease that causes miscarriage due to loss of RBC production resulting in fetal anemia
no recurrent infections
non-enveloped, small single-stranded linear DNA genome
spread by respiratory droplets
may cause arthritis
Human Bocavirus 1 (HBoV1)
causes acute respiratory tract infection
one of the leading causes of hospitalization of young children
commonly detected in association with other respiratory viruses
causes lower respiratory infections associated with wheezing
can be life-threatening in pediatric patients
SARS (Severe Acute Respiratory Syndrome)
coronavirus, enveloped, +ssRNA, 9 protein derived from a single polyprotein
caused by coronavirus that crossed into humans from civets
contagious and fatal in 6% of cases
spread by respiratory droplets and fecal matter
10-20% of infected individuals require intensive care
measles
paramyxovirus, -ssRNA, 15-19kb, encodes 6-10 genes
highly contagious
spread by respiratory droplets
causes fever with cough, coryza, and conjunctivitis (3 C’s)
rash appears several days later
complications common and severe in adults (diarrhea, pneumonia, encephalitis, corneal ulceration and scarring)
mumps
paramyxovirus (related to measles)
painful swelling of salivary glands, and less commonly the testicles
can cuase sterility in men
no antiviral treatment
rubella
