Lec 20 Evasion/Subversion of Immune defenses Flashcards
improvements of host defenses and pathogen evasion is representative of ________
evolutionary battles
Herpes virus evades immunity by ________
latency
HSV will infect _______ cells and undergo ______ cycle, spreading to ________ where it persists in latent state. Neurons express low levels of ____ so virus is poorly presented to T cells
epithelial;
lytic;
trigeminal ganglion (sensory neuron)
MHC I
HSV can be reactivated by ______ or ______ like with organ transplantation, which will produce infectious virions and reinfect ____________-
stress or immunosuppressive drugs;
skin innervated by infected neuron
How does Streptococcus pnemoniae avoid immune system?
Antigenic hypervariability - 84 serotypes of Strep that are antigenically distinct capsular polysaccharides so the antibodies from previous infection of strep do not recognize the new strep.
A new adaptive immune response is needed for each infection of S. pneumoniae
What are trypanosomes?
insect borne protozoa that cause sleeping sickness
The surface antigens on trypanosomes are called _____. Although they have _______ different genes in the genome, only ____ is expressed at once,
Variant specific glycoproteins (VSG);
1000;
one
How can trypanosome hijack your immune system?
Antigenic hypervariability - Your immune system prepares antibodies for VSG. The VSG gene can be changed by putting a new gene into the active expression site by genetic recombination, so new parasites have an advantage
How is antigenic hypervariability different in Strep pneumoniae and trypanasome?
Strep is 84 different strains and is useful for subsequent infection of a different strain
Trypanasomes are in the same infection and is 1 version of the same glycoprotein
Antigenic mutation in influenza includes _____ and _____
antigenic shift and drift
Antigenic drift is caused by _______ in _______ and ______ and is responsible for ________.
point mutations in hemagglutinin and neuraminidase;
seasonal flu (mild epidemics)
Antigenic shift is caused by ________of _________ between ________ and _________. It is responsible for _________ and is due to _______.
Antigenic shift is caused by reassortment of segmented RNA encoding viral genes between human and avian species. It is responsible for global pandemics and is due to packaging of genes in mixing vessel (swine).
What mechanism does HIV use to evade host responses?
Antigenic mutation - point mutations in peptides of CTL epitopes at key residue (aa 2 and 9) so it cannot bind to MHC I but it can still be a viable virus.
Then there is no CTL response. (CTL escape)
What mechanism does dengue use to evade host defense?
antibody dependent enhancement -
antibodies can bind to all serotypes of Dengue (1-4), but cannot neutralize other serotypes (new strain) only the old strain. It leads to opsonization through binding of Fc on macrophages leading to enhanced infection of macrophages
Antibody dependent enhancement is an example of _________ - the immune response making things worse
immunopathogenesis
How does HSV1 block peptide entry to endoplasmic reticulum?
ICP47 blocks peptide binding to TAP
