Flashcards in MCM 2-24 Viral Pathogenesis Deck (44)
difference between +ssRNA and mRNA
sometimes they are the same. mRNA needs cap and poly-A tail to be recognized by a ribosome
sometimes a +RNA must get changed to -RNA first by RDRP, then trascribed into mRNA for the ribosomes
inanimate objects that have pathogens on them (counters, handles)
susceptibility and severity of viral disease depends on
if it is the correct
the status of the person
virus-host interaction - unique genetic features of the person and that viral strain
two viruses that can enter the body through a scratch
HSV1/2 and HPV
describe the epithelial anatomy of the respiratory tract
covered in mucus, ciliated cells and goblet cells with basement membrane (barrier to some viruses). Polarized - the apical is unlike the basal
some viruses enter/leave through the apical (flu)
other enter apical and can pass through the basal membrane
What do M-cells do? How are they effected by some viruses?
M-cells sample the gut contents and present to underlying immune cells.
Some viruses can infect M-cells and easily reach the blood stream.
describe the common features of Reo and Roto-virus
both unenveloped, get sampled by M-cell and can make it across into the blood stream quickly.
Immunity is mediated by?
tranmission is fecal oral
virulence - nonstructure protein 4 (toxin) nsp4 - effects enterocytes causing massive diarreah
immunity is mediated by IgA by prior exposure OR oral vaccine
Important features - there is a vaccine, this is not a summer disease, very little dissemination - "straight shot through"
type a - under 2 years
type b - over 2 years
what is "dissemination" of a virus?
when the virus crosses the basement membrane of the body
describe primary viremia
"viruses may spread form the surface of the body to lymph nodes and blood stream"
"primary viremia leads to replication in internal organs, may occur without symptoms (incubation stage)
first appearance of virions in blood. May not be replicationg, but ability to detect virus in blood at low levels.
any virus that interacts with the respiratory or gut epithelium requires
attatchment and receptor engagement
(recognition and attachment)
What is secondary Viremia?
the virus disseminates to the virus to organs where it is shed
-trasmission may be by direct contact or through environment
-exposure to infected blood is now a common route of transmission
describe chicken pox
very contagious via respiratory and eyes
replicates in upper airway, travels to lymph nodes and infects T-cells to spread throughout body
-maintained in dorsal root ganglia for life
-virus always detectable in the blood
vaccines for zoster and varicella, some antivrials but they are not very effective
where are the highest levels of HIV found an in infected person?
blood plasma, lymphocytes, CSF, ear secretions
virus infection may be...(5)
unnotticed, cause illness, induce autoimmunity, be persistent, or be lethal
a successful virus will..
avoid destruction by the immune system and avoid destroying the host before replication is complete
Persistent Vs Latent
Persistent - you are able to culture virus in the absense of disease
latent - cannot culture virus in absence of disease
acute - virus goes away
5 patterns of viral infection
Acute, Chronic (persistent, latent, slow), transforming
infection pattern of
cold = acute
measles = acute infection with rare late complications
zoster - latent
hep-b = chronic with early disease episode
HIV=chronic infection with late disease episode, different acute episode
slow infection - general increase to a disease episode
Symptoms of viral disease includes
fever, tissue damage, rash, aches, pains, nausea = mainly caused by the HOST response to infection (mainly interleuken)
cell injury is caused by
directly by viruses, indirectly by host reaction
fecal oral form contaminated water/food
no seasonal incidence
children, schools, resorts, cruise ships
treat with hydration
prevention = handwashing
A direct effect causing cell damage induced by virus
cell inactivation by a virus causing cells to fuse together and lose function
infected cells susceptible to apoptosis
caused by RSV in respiratory tract (Respiratory Syncytial Virus)
Indirect response, Host immune response to virus may cause the disease/injury
-ussually caused by T-cells and immune complexes
-May be made worse with vaccination
ex) herpes stromal keratitis - cause by effect of t-cell intervention of a frequent herpes reactivation in the eye
common routes of viral entry
mainy viruses enter through facial passageways including conjunctiva (eye membrane), mouth, and mucous membranes.
in the respiratory tract, viruses attatch to the...
mucous layer, from there they interact with the ciliated epithelial cells of the brush border and remain there to either
cross the basement membrane and penetrate the lymph and blood systems
Viruses may spread from the surface of the body to lymph nodes via an immune cell. From there, it can reach the bloodstream for the first time. This is referred to as primary viremia (first appearance of virus in the blood…usually at a very low level
fter replication in internal organs occurs, the virus can reenter the bloodstream (secondary viremia). During secondary viremia, the level of circulating virus is much higher, and symptoms usually emerge (end of incubation phase). From secondary viremia, the virus disseminates to the organs where it is shed.
After secondary viremia, the virus may be transmitted by direct contact, the environment, or the blood.