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

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

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

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

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)

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

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

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

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

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

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.

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)

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?