1. Mirko Paiardini, PhD Emory University, YNPRC
Low levels of SIV infection in SM CD4+ TCM cells are associated with limited CCR5 expression
Mirko Paiardini, PhD
Emory University, YNPRC
IAS 2011, Rome, July 20th, 2011
Good morning, I would like to thank the organizers for giving us the opportunity to share with you some data on susceptibility of CD4 central memory cells to SIV infection in natural vs nonnatural hosts for SIV

2. Comparative AIDS Research
HIV-1 infection of humans and SIV infection of Asian macaques leads, if left untreated, to AIDS
SIV infections of African monkey species that are infected in the wild are typically non pathogenic
Sooty mangabey
Vervet monkey
Mandrill
Understanding why natural SIV infections are nonprogressive
is a key priority in contemporary AIDS research, with important
implications in terms of HIV pathogenesis, therapy and vaccines

3. CD4+ T cell depletion is not sufficient to induce AIDS in SM
Mir K et al, Microbes Infect 2011
AGM SM
Humans RM
Example of mucosal CD4 depletion without AIDS,
And there is a even more extreme example
Brenchley & Paiardini, Blood 2011

4. CD4+ T cells are very heterogeneous
differentiation status
R. Ahmed et al, Nature Rev Immunol 2002
effector functions
Th1
Th2
Th17
Not all CD4 are created equal
Novel working model of HIV pathogenesis: The quality of preserved CD4+ T cells is more important than the quantity

5. Infection and depletion of TCM cells is crucial for progression to AIDS
Picker et al. Progressive CD4 TCM decline results in CD4 TEM insufficiency and overt disease in
chronic SIV infection. J Exp Med 2007;
“the tempo of disease onset is largely determined by destruction and gradual decline of CD4 TCM”
Letvin et al. Preserved CD4 TCM cells and survival in vaccinated SIV-challenged monkeys. Science 2006;
Mattapallil et al. Vaccination preserves CD4 TCM cells during acute SIV challenge. J Exp Med 2006
RMs
TCM cells are a self-renewing source of TEM cells and activated T cells (that produce most virus)

6. SM CD4+ TCM are relatively resistant to SIV infection
CD4+ TCM and TEM cells purified from 18 SIV-infected SM and 7 SIV-infected RM
in vivo frequency of infection determined by quantification of copy numbers
of cell-associated SIVgag-DNA by q-PCR
Paiardini et al, Nat Med 2011

7. SM CD4+ TCM are relatively resistant to SIV infection
in vitro frequency of infection determined by using a molecular clone of SIVsmm expressing GFP.
PBMCs activated with ConA + IL-2, infected at day 3, GFP staining is measured at day 7.
in vitro frequency of infection determined by using a molecular clone of SIVsmm expressing GFP in the Nef ORF.
PBMCs are activated with ConA + IL-2, infected via spinoculation at day 3, and GFP staining is measured at day 7.
Paiardini et al, Nat Med 2011

8. SM CD4+ TCM are relatively resistant to SIV infection
by using SIVmac and an isolate of SIVsmm that replicates well in both species.
level of in vitro infection determined in SORTED CD4+ TCM and TEM
CD4+ TCM and TEM activated (ConA + IL-2), infected at day 3, and p27 levels in the supernatants were measured at day 3, 6, 9, 12, and 15 post-infection.
Paiardini et al, Nat Med 2011

9. Low fraction of CCR5+ cells after in vitro activation of SM CD4+ TCM
CD4+ TCM of SM and RM are similarly recruited to cell cycle
Paiardini et al, Nat Med 2011

10. Multiple ways to protect CD4+ TCM in SIV-infected natural host
~5-7% of animals protected
CCR5 gene on ALL cells
by knocking down
Rare animals with X4-tropic
viruses are protected by expanding CD4-negative
TCM helper cells
Protected by down-modulating
CD4 expression during naïve to
memory CD4+ T cell transition
>90% of animals protected
by down-modulating
CCR5 on CD4+ TCM
Additional, CCR5-independent entry and/or post-entry mechanisms of SIV restriction may play a role in protecting TCM
Paiardini et al.
Nat Med 2011
Reddick et al.
PLoS Pathogens 2010
Milush, Mir et al.
J Clin Invest 2011
Beaumier et al.
Nat Med 2009
AGMs
Sooty mangabeys

11. Low virus replication in
Protection of CD4+ TCM is a key determinant of the benign nature of SIV infection in SM
Maintenance of CD4 T cell
homeostasis
Resolution of immune activation & residual inflammation
Maintenance of LN architecture &
lymphoid niche
Low virus replication in
CD4+ TCM cells
Non-Progressive Infection
Infection of CD4+ TCM may result in global CD4+ T cell depletion and thus trigger homeostatic responses that in turn may help establish a more “immune activated” environment
Infection of CD4+ TCM may promote immune activation by increasing virus replication in tissues where innate & adaptive immune responses are primed (LNs, spleen, Peyer patches)
Chronic immune activation may promote CD4+ TCM depletion by (i) favoring direct virus infection; (ii) disrupting the niche /inducing tissue fibrosis; (iii) inducing bystander cell death.

12. Acknowledgments Paiardini Lab University of Pennsylvania Ron Collman
Barbara Cervasi
Luca Micci
Zachary Ende
Michelle Bonkosky
University of Pennsylvania
Ron Collman
Nadeene Riddick
Nicholas Francella
Paul Hallberg
Hank Pletcher
National Institutes of Health
Jason Brenchley
Carol Vinton
Daniel Douek
Jeff Lifson
Jake Estes
Case Western
Michael Lederman
and the CLIC/BBC
University of Pittsburgh
Ivona Pandrea
Cristian Apetrei
Emory University
Bob Mittler
Francois Villinger
Tab Ansari
Yerkes Primate Center
Elizabeth Strobert
Stephanie Ehnert
Tracy Meeker
James Else
Silvestri Lab
Ann Chahroudi
Paul Carnathan
Diane Carnathan
Alex Ortiz
Vandy Vanderford
Steven Bosinger
Kiran Mir
Tim Hayes
Katherine Sheehan
Kathryn Folkner
Univ. of Ulm
Frank Kirchhoff
Jan Munch
Supported by NIH (R01, R56)

13. Implications for HIV infection in humans
Is the infection of CD4+ TCM a prognostic marker of both HIV-associated immune activation and disease progression?
Is residual infection of CD4+ TCM in ART-treated individuals a predictor of persistent immune activation and poor immune reconstitution?
Could therapy aimed at preventing or reducing virus infection of CD4+ TCM have a beneficial impact on the course of HIV disease?