L4: Immunotherapy Against Chronic Viruses (D. Brooks)

Question 1

chronic vs acute infection

Answer 1

acute: positive/negative, APCs, IFNgamma, TNFalpha, IL-2 –> left with a stable population of memory cells
chronic: negative/positive, IL-10, PD1/PDL1, Tim3, CTLA4, IDO, decreased cytolytic activity, T cell exhaustion (change from pro-inflammatory to anti-inflammatory environment)

Question 2

what is the decision point

Answer 2

after acute infection, will it be recovery or chronic infection

Question 3

viral persistence/chronic infection mechanisms

Answer 3

B cell dysfunctions
Alterations in innate immunity (immunosuppression with IL-10 and PDL1)
CD8 T cell exhaustion and deletion
CD4 Th cell skewing (normally both Th1 and Tfh, Tfh helps B cells, still good, but less Th1 means not enhancing CD8 responses)
Infected cells/tumor cells (upregulate PDL1, IL-10, IDO)
all these interact with each other

Question 4

CD8 T cell exhaustion

Answer 4

progressive decline
when you try to fix, might not be addressing all
multiparameter dysfunction: function, signaling pathways, receptor expression, cytokine dependence, epigenetic

Question 5

Mechanisms of antiviral exhaustion 1: immune ignorance

Answer 5

downregulation of antigen presenting machinery
(ex. HIV downregulating MHC 1)

Question 6

Mechanisms of antiviral exhaustion 2: immune suppression mediated by suppressor cells

Answer 6

Tregs
MDSCs (myeloid derived suppressor cells)

Question 7

Mechanisms of antiviral exhaustion 3: inhibition by checkpoint molecules

Answer 7

CTLA4
PD-1
Tim-3
Lag-3

Question 8

Mechanisms of antiviral exhaustion 4: immunomodulatory cytokines/enzymes

Answer 8

TGFbeta
IL10
IDO
ARG1
iNOS
PGE2

Question 9

How immunotherapy would disrupt or enhance interactions on T cells

Answer 9

receptors on APCs and T cells
enhancing positive signaling (CD28-CD80) and preventing negative signaling (PD1-PDL1)
the synergy of these is crucial for boosting immune function

Question 10

T cell intrinsic barriers

Answer 10

expression of cells changes with chromatin accessibility
in addition to molecules like PD-1 and TIM3

Question 11

LCMV

Answer 11

RNA virus ambisense - reads both ways, codes for 4 proteins
used in lab: Clones

Question 12

LCMV Clone 13

Answer 12

chronic infection

Question 13

LCMV- Armstrong

Answer 13

acute infection in the lab

Question 14

LCMV system has led to many fundamental discoveries of immune system. What are its strengths?

Answer 14

1-LCMV infection of natural rodent host is non-cytolytic - clear separation of virus-induced effects, does not harm mice
2- different modes result in diverse outcomes - helps us explore multiple immune mechanisms
3- applicable across many species

Question 15

immune restorative therapeutic targets: negative regulatory factors for overcoming T cell exhaustion

Answer 15

IL-10, TGFbeta, IDO, IFNgamma, IFN-I, IL-2

Question 16

Early differentiation of exhausted CD8+ T cells

Answer 16

2 populations:
Tpex: ability to self-renew, TCF-1 HI, CD127 HI
Tex: exhausted CD8 T cell population, lose the ability to self-renew, PD-1 HI, TIM-3 HI, Tox HI

Question 17

what happens to CD8 Tpex cells during chronic infection

Answer 17

self-renew and maintain the terminally differentiated Tex cells
Tpex cells respond to anti-PD-1 blockade - rejuvinate themsehlves and help produce/turn Tex’s into effector cells that are not as exhausted

Question 18

CD4 T cell mediated help

Answer 18

CD8 T cells, DCs, B Cells, macrophages/ myeloid cells, CD4 CTLs

Question 19

what happens to Tfh and Th1 cells differentiated from CD4 during chronic infection

Answer 19

loss of Th1 –> decline in CD8 T cell effects

Question 20

how does skewing of CD4 Th affect immune-restorative therapies

Answer 20

general thought: not functionally restored in vivo by blocking PD1/PDL1
however, PD1/PDL1 associated with increased cd4 in some cancers - not clear
hypothesize that the mixed results with CD4 T cells are due to differential sensitivity of different Th subsets to PD1-PDL1 mediated suppression, despite similar PD1 expression

Question 21

effect of anti-PDL1 on Th1 and Tfh

Answer 21

Th1: increased proliferation, restoration of cytolytic activity
Tfh: not much effect

Question 22

viro-therapy

Answer 22

using viruses as therapies in order to kill tumor cells and draw the immune response in to fight virus and tumor

Question 23

does the immunosuppressive environment during established during a chronic infection prevent T cell responsiveness to vaccination

Answer 23

yes

Question 24

vaccines and IL-10 blocking impacts

Answer 24

IL-10 - exhausted T cells –> failure to control persistent infection
block IL-10 –> enhanced virus control
therapeutic vaccine –> minimal impact
vaccine + blocking PD1 or ıl-10 –> huge T cell restoration and virus infection elimination

Question 25

Adoptive T cell therapy

Answer 25

TIL or TCR/CAR
used for human chronic virus infections, human cancers, will likely be applicable to other infections

Question 26

immunocytotherapy: LCMV specific memory T cells

Answer 26

mouse with a lot of viral replication of LCMV –> inject LCMV-specific memory T cells –> infection controlled, virus eliminated
combination of CD4 and CD8 cells are needed for this! (naive does not work too)

Question 27

Describe the ways in which CD4 helper T cells influence immune responses to chronic infections.
Create an experiment where you would use a LCMV infection to determine contributions of
CD4/CD8 T cells to viral clearance and describe the expected results.

Answer 27

CD4 T cells increase:
- CTL response
- Dendritic cell activation
- Myeloid cell activation
- B cell activation

Experimental model:
- Harvest LCMV T cells from chronic mice, sort and expand CD4+ and CD8+ T cells and
reintroduce into the mice (adoptive cell transfer immunotherapy).

Controls + Results:
Mouse + LCMV -> chronic infection
Mouse + CD4 + LCMV -> small decrease in viral titers than chronic infection
Mouse + CD8 + LCMV -> large decrease in viral titers than chronic infection
Mouse + CD4/CD8 + LCMV -> clearance of viral titers