HIV Induced Aging of the Immune System Dr. Tammy Rickabaugh February 1, 2012

HIV Induced Aging of the HIV Induced Aging of the Immune SystemImmune System

Dr. Tammy Rickabaugh

February 1, 2012

OverviewOverview

I.I. Immunological Aging in Seronegative Immunological Aging in Seronegative IndividualsIndividuals

II.II. Premature Aging of the Immune System in Premature Aging of the Immune System in HIV-1HIV-1++ Individuals: Is this the cause of AIDS? Individuals: Is this the cause of AIDS?

III.III. Implications of Premature Immunological Implications of Premature Immunological Aging of HIV-1Aging of HIV-1++ Individuals Individuals

Immunological Aging in Immunological Aging in Seronegative IndividualsSeronegative Individuals

Kovaiou, Grubeck-Loebenstien, 2006

General Concepts of AgingGeneral Concepts of Aging

Age-Associated Changes in the Age-Associated Changes in the Immune SystemImmune System

• Elderly people are more susceptible to infectionsElderly people are more susceptible to infections

• Less protected by vaccinesLess protected by vaccines

• Infections in the elderly are characterized by Infections in the elderly are characterized by more severe symptoms, longer duration, and more severe symptoms, longer duration, and poorer prognosispoorer prognosis

• Reactivation of Varicella-Zoster, risks for Reactivation of Varicella-Zoster, risks for pneumonia, urinary tract infections, meningitis, pneumonia, urinary tract infections, meningitis, TB and viral gastroenteritisTB and viral gastroenteritis

• Related to age-related changes in the immune Related to age-related changes in the immune systemsystem

Jamieson, BD, et al, Jamieson, BD, et al, ImmunityImmunity, 1999, 1999

Adult ThymusAdult ThymusFetal ThymusFetal Thymus

The Human Thymus Involutes With AgeThe Human Thymus Involutes With Age

• Significant decrease in naïve T cell number and Significant decrease in naïve T cell number and increase in memory T cellsincrease in memory T cells

-hinders ability to respond to new infections-hinders ability to respond to new infections

• Diversity of the naïve CD4Diversity of the naïve CD4++ T cell compartment is T cell compartment is maintained until about 70 years of agemaintained until about 70 years of age

-a dramatic and sudden collapse of diversity occurs-a dramatic and sudden collapse of diversity occurs

-less diversity in T cell receptor, hinders ability to -less diversity in T cell receptor, hinders ability to respond to new antigensrespond to new antigens

Age-Associated Changes in Age-Associated Changes in CD4CD4++ T Cells T Cells

• Using cell surface markers normally used to identify Using cell surface markers normally used to identify naïve T cells is difficultnaïve T cells is difficult

- “naïve” cells in the elderly express receptors and - “naïve” cells in the elderly express receptors and functional abilities more like memory cellsfunctional abilities more like memory cells

• Signaling and cytokine secretion in naïve CD4Signaling and cytokine secretion in naïve CD4++ T cells T cells is altered and the activation potential of memory cells is is altered and the activation potential of memory cells is also decreasedalso decreased

-hinders ability to mount effective immune responses to -hinders ability to mount effective immune responses to antigensantigens

Age-Associated Changes in Age-Associated Changes in CD4CD4++ T Cells T Cells


Model for CD4Model for CD4++ T Cell Differentiation T Cell Differentiation During Healthy AgingDuring Healthy Aging


Summary of Age-Related Changes Summary of Age-Related Changes Within the CD4Within the CD4++ T Cells T Cells

Summary of Age-related Changes Summary of Age-related Changes Within the CD8Within the CD8++ T Cells T Cells

• Increase in terminally differentiated cellsIncrease in terminally differentiated cells

• Decrease in naïve CD8Decrease in naïve CD8++ T cells T cells

• See an increase in Type 1 (IL-2, IFN-g,TNF-a) and See an increase in Type 1 (IL-2, IFN-g,TNF-a) and Type 2 (IL-4, IL-6, IL-10) cells- associated with Type 2 (IL-4, IL-6, IL-10) cells- associated with chronic pro-inflammatory statuschronic pro-inflammatory status

• Increase in clonal expansionsIncrease in clonal expansions

• Decrease in T cell receptor diversityDecrease in T cell receptor diversity

• Shortening of telomere lengthShortening of telomere length

What are the implications of What are the implications of increased numbers of increased numbers of senescent T-cells???senescent T-cells???

Why Do Senescent Cells Accumulate Why Do Senescent Cells Accumulate With Age?With Age?

• One main reason is an age-related One main reason is an age-related decrease in apoptosisdecrease in apoptosis

• Apoptosis is necessary to create Apoptosis is necessary to create “immunological space” for naïve cells to “immunological space” for naïve cells to inhabitinhabit

• This is more prominent in CD8This is more prominent in CD8++ T-cells T-cells

• Senescent cells are not susceptible to Senescent cells are not susceptible to normal death signalsnormal death signals

Mountz, JD, et al. Immunological Reviews, 2005

T-cells Become Resistant to T-cells Become Resistant to Activation-Induced Cell Death (AICD) Activation-Induced Cell Death (AICD)

-Happens at a stage prior to complete senescence-AICD is a mechanism to prevent the expansion of unwanted T-cells

Increase in Senescent Cells Occupying Increase in Senescent Cells Occupying “Immunological Space” Results in a Decrease “Immunological Space” Results in a Decrease

in the Virus-Specific CTL Responsein the Virus-Specific CTL Response

Mountz, JD, et al. Immunological Reviews, 2005

-This can also contribute to “inflammaging”

Consequences of “Inflammaging”Consequences of “Inflammaging”

• In aging there is a profound modification in the cytokine network

• General increase in the levels of pro-inflammatory cytokines

• Chronic low grade pro-inflammatory condition is called “inflammaging”

Inflammaging can trigger the Inflammaging can trigger the following conditions:following conditions:

Franceschi, C., et al., Neuroimmunomodulation, 2008

Some of our data…….Some of our data…….

The Proportion of Naïve T-cells Decreases The Proportion of Naïve T-cells Decreases Only Moderately Throughout AdulthoodOnly Moderately Throughout Adulthood

PERCENT OF CELLS EXPRESSING CD45RA DECREASES SLIGHTLY WITH AGE

PARTICIPANT AGE

25 35 45 5520 30 40 50 60

% O

F C

D4

+ T

-CE

LL

S E

XP

RE

SS

ING

CD

45

RA

10

30

50

70

90

0

20

40

60

80

100

% o

f C

D4+

T-c

ells

Exp

ress

ing

CD

45R

A%

of

CD

4+ T

-cel

ls E

xpre

ssin

g C

D45

RA

Participant AgeParticipant Age

100100

9090

8080

7070

6060

5050

4040

3030

2020

1010

002020 2525 3030 3535 4040 4545 5050 5555 6060

CD4CD4++ CD45RA CD45RA+ +

8% 48%

14%CD

31C

D31

CD45RACD45RA

Four CD4Four CD4++ T-cell Subsets Defined by CD45RA T-cell Subsets Defined by CD45RA and CD31and CD31

NaiveNaive

RA+31RA+31+

RA+31RA+31--

TREC HighTREC High

TREC LowTREC Low

Least DifferentiatedLeast Differentiated

DifferentiatedDifferentiated

Maintenance of Naïve CD4Maintenance of Naïve CD4++ T-cells During Aging Is T-cells During Aging Is Due To Stability of CD45RADue To Stability of CD45RA++CD31CD31-- Subset Subset

p=0.38

Participant Age (Years)

20 30 40 50 60

60

40

50

30

20

10

0

60

50

40

30

20

10

0

20 30 40 50 60

Cross Sectional Study

3131++

3131- -

Kilpatrick, R, Rickabaugh, T, et. al, J. Immunology, 2008

Participant Age (Years)

% C

D45

RA

+C

D31

- ce

lls

% C

D45

RA

+C

D31

+ c

ells

TelomeresTelomeres• Hallmark of cellular agingHallmark of cellular aging• Region of repetitive DNA at the ends of Region of repetitive DNA at the ends of

chromosomeschromosomes• Protects the end of chromosome from damageProtects the end of chromosome from damage

-similar to tips on shoelaces that keep it from -similar to tips on shoelaces that keep it from unravelingunraveling-shortens with each replication of the cell-shortens with each replication of the cell

• Telomere shortening in humans can result in Telomere shortening in humans can result in senescence (cells lose the ability to divide) and senescence (cells lose the ability to divide) and block cell divisionblock cell division

• Cells have a limited capacity to replicate and this Cells have a limited capacity to replicate and this appears to be partly determined by telomere lengthappears to be partly determined by telomere length

TelomeresTelomeres

Human chromosome is gray and telomeres are the white dots

Kilpatrick, R, Rickabaugh, T, et. al, J. Immunology, 2008

Evidence of Telomere Shortening in Evidence of Telomere Shortening in Naïve CD4Naïve CD4++ T cells with Age T cells with Age

CD45RACD45RA++CD31CD31++ CD45RACD45RA++CD31CD31--

Premature Aging of the Immune Premature Aging of the Immune System in HIV-1System in HIV-1++ Individuals: Individuals:Is This the Cause of AIDS?Is This the Cause of AIDS?

Some Causes of Clinical Some Causes of Clinical ImmunodeficiencyImmunodeficiency

• Not completely clear why the immune system initially Not completely clear why the immune system initially controls HIV-1 infection and then ultimately fails to controls HIV-1 infection and then ultimately fails to control viral replicationcontrol viral replication

– Viral escape with mutations in epitopes recognized by Viral escape with mutations in epitopes recognized by cytotoxic T lymphocytes (CTLs)cytotoxic T lymphocytes (CTLs)

– Functional impairment of HIV-specific CTLsFunctional impairment of HIV-specific CTLs

– High levels of immune activationHigh levels of immune activation

HIV-specific CD8HIV-specific CD8++ T cell response: T cell response: Impaired or Fully Functional?Impaired or Fully Functional?

• In primary HIV-1 infection there is a rapid expansion of HIV-In primary HIV-1 infection there is a rapid expansion of HIV-specific effector CD8specific effector CD8++ T cells T cells-phenotypically the cells appear to be at an intermediate stage -phenotypically the cells appear to be at an intermediate stage of differentiationof differentiation-but they are fully functional-but they are fully functional

• Why is the virus not cleared??Why is the virus not cleared??-the combination of CD4-the combination of CD4++ T cell depletion and immune escape T cell depletion and immune escape may lead to an inability of the CD8may lead to an inability of the CD8++ T cells to respond to low T cells to respond to low levels of viral replication (around the set point)levels of viral replication (around the set point)

- fully functional but unable to mount an effective response- fully functional but unable to mount an effective response

HIV-1 Strategies to Evade Host HIV-1 Strategies to Evade Host ImmunityImmunity

Appay, V and Rowland-Jones, SL, Trends in Immunology, 2002

HIV-1 Strategies to Evade Host HIV-1 Strategies to Evade Host ImmunityImmunity



The Adaptive Immune System in Aging The Adaptive Immune System in Aging and HIV-1 Infectionand HIV-1 Infection

Parallels Between HIV-1 Pathogenesis Parallels Between HIV-1 Pathogenesis and Human Agingand Human Aging

• Lifespan of both CD4Lifespan of both CD4++ and CD8 and CD8++ T cells is shortened to about a third T cells is shortened to about a third of normalof normal

-increase of CD8-increase of CD8++ T cells but CD4 T cells but CD4++ cannot keep up with the pace of cannot keep up with the pace of destructiondestruction

• Increase in the amount of terminally differentiated T cells- Increase in the amount of terminally differentiated T cells- consequence of immune activationconsequence of immune activation

-leads to immunosenescence, also occurs with CMV-leads to immunosenescence, also occurs with CMV

-get an accumulation of immune cells that cannot function or -get an accumulation of immune cells that cannot function or replicate normally, but are more resistant to apoptosisreplicate normally, but are more resistant to apoptosis

• AIDS is much more severe immune senescence than what is seen AIDS is much more severe immune senescence than what is seen in normal agingin normal aging


Post-Thymic Development of CD8Post-Thymic Development of CD8++ and CD4and CD4++ T cells T cells

Appay, V, et al. Experimental Gerontology, 2007

Accumulation of Terminally Accumulation of Terminally Differentiated T cells in HIV infectionDifferentiated T cells in HIV infection

Exhaustion of Immune Resources by Exhaustion of Immune Resources by HIV-1 Leads to AIDSHIV-1 Leads to AIDS

• Chronic Immune Activation:Chronic Immune Activation:-In primary infection there is massive immune -In primary infection there is massive immune activationactivation-In chronic infection still have chronic immune -In chronic infection still have chronic immune activation due to viral reboundsactivation due to viral rebounds-Indirect immune activation as depletion of CD4-Indirect immune activation as depletion of CD4++ T T cells results in more common infections and cells results in more common infections and opportunistic infectionsopportunistic infections

• This can result in premature aging of the immune This can result in premature aging of the immune system and exhaustion of immune resourcessystem and exhaustion of immune resources


Exhaustion of HIV-specific CD8Exhaustion of HIV-specific CD8++ T cell T cell Clonal PopulationsClonal Populations





Some of our own data regarding Some of our own data regarding naïve CD4naïve CD4++ T cells……. T cells…….

Individuals Early in HIV Infection Have Individuals Early in HIV Infection Have Significantly Fewer Naïve CD4Significantly Fewer Naïve CD4++ T-cells T-cells

Rickabaugh, TM, et al., PLoS ONE in press

HIV Infection Results in a Greater Loss of HIV Infection Results in a Greater Loss of

CD31CD31-- T-cells T-cells


NaïveNaïve CD4 CD4+ + T-cells of HIV Infected Men Have Shorter T-cells of HIV Infected Men Have Shorter Telomere LengthsTelomere Lengths


CD

31 M

FI

CD

31 M

FI

00

10001000

20002000

30003000

40004000

50005000

Progressed to Progressed to AIDS within 1 yearAIDS within 1 year

Progressed to AIDS Progressed to AIDS within within >> 5 year 5 yearss

* p=0.038* p=0.038

CD31 Expression on CD4CD31 Expression on CD4++ T-cells is T-cells is Associated with Progression to AIDSAssociated with Progression to AIDS

Cao, WW et al., J Acquir Immune Defic Syndr 2008

What is the Effect of HAART What is the Effect of HAART on Naïve CD4on Naïve CD4++ T-cells? T-cells?

Reconstitution by HAART Does Not Reconstitution by HAART Does Not Completely Restore the CD31Completely Restore the CD31-- Naïve T- Naïve T-

Cell Compartment Cell Compartment

Rickabaugh, TM, et al., PLoS ONE, in press

CD31CD31+/Hi+/Hi T-cells Increase Significantly T-cells Increase Significantly Post-HAARTPost-HAART

Rickabaugh, TM, et al., PLoS ONE, in press

CD45RA+CD31+ CD45RACD45RA++CD31CD31--


HIV-1 Infection Compared to Human HIV-1 Infection Compared to Human AgingAging

Implications of Premature Implications of Premature Immunological Aging of HIV-1Immunological Aging of HIV-1++

IndividualsIndividuals

Deeks, SG, and Phillips, AN, BMJ, 2009

Evidence of Premature Aging Despite Evidence of Premature Aging Despite

Anti-Retroviral TreatmentAnti-Retroviral Treatment

Age-Related Diseases Diagnosed in Age-Related Diseases Diagnosed in HIVHIV++ Individuals Individuals

• Cardiovascular DiseaseCardiovascular Disease

-higher in untreated versus treated-higher in untreated versus treated

-link between lower CD4-link between lower CD4++ T cells and CD T cells and CD

-some anti-retroviral drugs are associated -some anti-retroviral drugs are associated with CDwith CD

• CancerCancer- Untreated HIV is associated with Kaposi’s - Untreated HIV is associated with Kaposi’s Sarcoma and non-Hodgkin’s lymphomaSarcoma and non-Hodgkin’s lymphoma- Even treated HIV individuals at increased risk - Even treated HIV individuals at increased risk

for lung cancer, skin cancer, for lung cancer, skin cancer, colorectal colorectal cancer, prostate cancer, anal cancercancer, prostate cancer, anal cancer- Higher risk is associated with less CD4- Higher risk is associated with less CD4++ T T cells, similar to immune compromised cells, similar to immune compromised transplant patientstransplant patients

Age-Related Diseases Diagnosed in Age-Related Diseases Diagnosed in HIVHIV++ Individuals Individuals

Age-Related Diseases Diagnosed in HIVAge-Related Diseases Diagnosed in HIV++ IndividualsIndividuals

Older HIV+ individuals are at even greater risk due to normal immunological aging coupled with aging caused by HIV-1 infection

Another problem….HIV infected Another problem….HIV infected people are getting olderpeople are getting older

CDC estimates that by 2015 over 50% of all HIV CDC estimates that by 2015 over 50% of all HIV infected people will be over the age of 50 in the USinfected people will be over the age of 50 in the US

Two reasons for this:Two reasons for this:

• Higher percentage of new infections in Higher percentage of new infections in people over 50people over 50

• Individuals with HIV infection are living Individuals with HIV infection are living longer on drug treatmentlonger on drug treatment

CDC

~46%

We also see an increase in new We also see an increase in new AIDS cases in >50 year oldsAIDS cases in >50 year olds

The Search for the Immunological The Search for the Immunological Fountain of YouthFountain of Youth

Possible Therapies to Improve Naïve Possible Therapies to Improve Naïve T-cell Numbers and FunctionT-cell Numbers and Function

• The first treatment in HIV patients was IL-2The first treatment in HIV patients was IL-2

-some evidence of efficacy-some evidence of efficacy

-results of the trials were not consistent and there -results of the trials were not consistent and there are concerns with toxicityare concerns with toxicity

• Human growth hormone (HGH) and Insulin Human growth hormone (HGH) and Insulin Growth Factor-1 (IGF1)Growth Factor-1 (IGF1)

- increased thymic volume in children with AIDS - increased thymic volume in children with AIDS but did not affect T-cell function significantly but did not affect T-cell function significantly

• IL-7 is a very promising treatmentIL-7 is a very promising treatment-cytokine that plays a key role in the thymus in -cytokine that plays a key role in the thymus in lymphocyte development and survivallymphocyte development and survival-in the periphery it is important for T-cell -in the periphery it is important for T-cell homeostasis and is required for homeostatic homeostasis and is required for homeostatic proliferation of CD4proliferation of CD4++ and CD8 and CD8++ T-cells T-cells

• When used in cancer patients it preferentially When used in cancer patients it preferentially expanded naïve T-cellsexpanded naïve T-cells

• In a phase I/IIa clinical trial in HIVIn a phase I/IIa clinical trial in HIV++ patients it was patients it was shown to increase naïve and central memory CD4shown to increase naïve and central memory CD4++ and CD8and CD8++ T-cells T-cells

• The T-cells are functional and the patients had The T-cells are functional and the patients had improved cell mediated immunityimproved cell mediated immunity

• There also seem to be very little side effectsThere also seem to be very little side effects

Possible Therapies to Improve Naïve T-cell Possible Therapies to Improve Naïve T-cell Numbers and FunctionNumbers and Function

What About Telomere Length??What About Telomere Length??

• A screen of Chinese medicine plant extracts for A screen of Chinese medicine plant extracts for telomerase inducing agents resulted in the discovery telomerase inducing agents resulted in the discovery of TAT2of TAT2

• TAT2 has been shown to transiently increase TAT2 has been shown to transiently increase telomerase levels in vitro in cells from HIV-, HIV+, and telomerase levels in vitro in cells from HIV-, HIV+, and individuals with AIDS (highest amounts)individuals with AIDS (highest amounts)

• This increase was associated with longer telomere This increase was associated with longer telomere lengths, improved immune effector function, and lengths, improved immune effector function, and increased ability for cellular proliferationincreased ability for cellular proliferation

• In vitro it has also been shown to reduce viral load and In vitro it has also been shown to reduce viral load and this is correlated to telomerase inductionthis is correlated to telomerase induction

TAT2 Can Improve Cellular TAT2 Can Improve Cellular Proliferation and Telomere LengthProliferation and Telomere Length

Fauce, SR, et al., J Immunol, 2008

SummarySummary• Immune resources decline with age leading to a reduced ability to Immune resources decline with age leading to a reduced ability to

respond to new and old antigensrespond to new and old antigens• HIV-1 infection appears to prematurely age both CD8HIV-1 infection appears to prematurely age both CD8++ and CD4 and CD4++

T cells T cells - this leads to immune exhaustion and senescence- this leads to immune exhaustion and senescence- may be a significant factor in the development of AIDS- may be a significant factor in the development of AIDS

• HIV-1HIV-1++individuals, treated or untreated, are at a higher risk for individuals, treated or untreated, are at a higher risk for non-AIDS related diseases seen in much older individualsnon-AIDS related diseases seen in much older individuals

• There are some promising therapeutics but more work must be There are some promising therapeutics but more work must be done to develop safe, effective, therapies to improve immune done to develop safe, effective, therapies to improve immune functionfunction

Documents

HIV Induced Aging of the Immune System Dr. Tammy Rickabaugh February 1, 2012