immunity to viruses Flashcards
what does the rhinovirus infect and what does it cause ?
the epithelial cells which cause the cold
what does hepatitis A-G infect and what does it cause ?
the liver cells , it infects the CD4+ T cells and causes aids
what is the capsid ?
this is the protein shell that of a virus that surrounds the genetic material
where is the genetic material contained ?
in the core of the virus surrounded by a protein coat
what does reverse transcriptase do and why ?
it is an enzyme that converts RNA into DNA as the virus lacks the machinery to self replicate and needs to infect a cell to replicate.
what is the epitope of the virus?
this is the part that is antigenic to us and binds to the T cell receptor
when a virus undergoes budding , what is this ?
this is when the virus releases it’s particles called virions
how does a virus enter a cell ?
by endocytosis
once in the cell what does the virus do ?
it un-coats and enters the nucleus so that replication can occur
what are the viral particles packaged into ?
the ribonucleic core where it is then released by budding
what is an obligate parasite ?
this is a parasite that cannot complete it’s life cycle without exploiting a suitable host.It causes damages to the host
what are these damages to the host called ?
cytopathic effects
how can a virus cause cytopathic effects ?
if it leaves without budding which causes inflammation
what does a virus normally cause the cell being infected to do ?
stop’s it completing it’s function as the virus hijacks the machinery in the cell to make more copies of the virus . this often kills the host cell as it ruptures and releases the new virions
what must an immune response to a virus do ?
Kill virus particles called virions
Clear the virus infected cell
Neutralise the viral toxins
how does the innate cells - non specific help to clear a virus ?
by type 1 IFN
NK cells
dendritic cells
how does the acquired antigen specific immune response help to clear a virus ?
the T cells - CD4+ helper and cytotoxic CD8+ cells
B cells will produce a specific antibody.
how does the IFN alpha and beta from the innate prevent the spread of the virus ?
they put the nearby cells on alert and prevent the virus from replicating as they interfere
what does the activation of the NK cells allow ?
direct killing of infected cells with modified proteins or reduced MHC class I
how are cytotoxic T lymphocytes activated ?
by dendritic cells
what do the activated CTL do ?
they kill the infected cells that are displaying the virus antigen in the MHC.
role of antibodies in fighting a viral infection ?
they neutralise the virus , its toxins and help the removal
what are the 2 different types of IFN ?
IFN alpha and IFN beta
are IFN alpha and IFN beta the same as IFN gamma ?
no they are different and distinct from it
how were the IFN discovered ?
Alick Isaacs recognized the ability of heat-killed influenza to interfere with growth of live virus in eggs. He isolated the protein responsible for interfering with virus replication = interferon
how can the IFN’s be used today ?
in some cancer and hepatitis B /C treatments
what do they IFN cause in a cell ?
cytokine production in a virus-infected cell. These can be produced by most cell types upon infection and they act to alert nearby cells to virus. They induce the cell to shutdown some of its protein-making functions , kill infected cells as lower MHC showing , activate immune cells
How can the IFN act as an early warning system for the immune system ?
- activates dendritic cells and macrophages (antigen-presenting cells)
- activates NK cells to start killing virus-infected cells.
how does the virus try to evade detection by the cytotoxic CD8+ cells ?
switching off MHC-I expression or inhibiting the processing pathway. This means that the cytotoxic CD8+ cells are not produced.
if the Cytotoxic cells cannot recognise them what else can ?
the NK cells
when is the activity of the NK cells increased ?
in the production of IFN alpha
once the NK cells are activated what do they produce and what does this cause ?
IFN gamma which helps to activate the macrophages to remove the virus and induces the naive T cell towards Th1.
the NK cells can be activated by altered self , what does this indicate ?
the altered surface proteins on the infected cell might suggest infection.
what does this cause ?
direct killing by NK cells
if the MHC class I on normal cells is expressed then what does this cause in the NK ?
inhibitory signals being released from the activating receptor so that the NK cells do not kill the normal cell.
if there is an altered or absent MHC class I then what occurs ?
an inhibitory signal is not released and the NK cells is triggered by signals from activating receptors that cause granule release and apoptosis occurs in the target cells.
how does the Herpes Simplex virus evade detection ?
the virus blocks the peptide entry to the ER which then alters the binding to TAP , this inhibits TAP ATPase activity and this in turn inhibits the TAP peptide transport
how does the adenovirus evade detection ?
they cause retention of the MHC class I in the ER and this blocks the competitive inhibitor and function of Tapasin
what are the intracellular virus broken down into by what and what are they loaded into?
endogenous peptides by the . protesome and loaded into the MHC class I
what are the extracellular viruses broken down into and what are they loaded into ?
into endogenous peptides and they are then loaded into the MHC class II
what are the cytotoxic T lymphocytes ?
these are the effector CD8+ T cells
how do the CTL recognise infection ?
by the MHC class I
what is the MHC class I expression increased by ?
IFN alpha
what does recognition of the virus by the CTL cause ?
release of the contents of the granules and apoptosis
what is a benefit to circulating antibodies ?
they can neutralise an infection
who was the pioneer of vaccines ?
Edward Jenner
what did he recognise ?
milk-maids became infected with cow-pox, but rarely became infected with related small-pox
what was his hypothesis ?
cow-pox was similar to small pox and generated immunity
what did he do next ?
. He isolated the virus from pus of a cow-pox infected milk-maid (caught from Blossom the cow). He then immunized James Phipps with the pus, and then 8 days later, challenged with live, virulent small pox. He survived because the cow-pox and generated memory T cells that also recognized small-pox.
