IMMUNE CONTROL OF HIV

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1 IMMUNE CONTROL OF HIV Giuseppe Pantaleo, M.D. Professor of Medicine Head, Division of Immunology and Allergy Executive Director, Swiss Vaccine Research Institute Lausanne University Hospital, Lausanne, Switzerland

2 Immune Response to HIV General Background Factors Driving the phenotypic and functional profile of HIVspecific Tcell responses Immune response profile associated with spontaneous longterm control of HIV replication Major immunological obstacles to HIV Functional Cure

3 Immune Response to HIV General Background Factors Driving the phenotypic and functional profile of HIVspecific Tcell responses Immune response profile associated with spontaneous longterm control of HIV replication Major immunological obstacles to HIV Functional Cure

4 Natural course of HIV infection1 Progressive disease (99% of cases) in the absence of ART Partial immune control of virus replication Total loss of viral control Magnitude Exhausted T cell CD8 T cell response Viral Load HIV specific CD8 T cell response CD4 T cell counts HIV specific CD4 T cell response Time after HIV infection (Years) 81 AIDS

5 LongTerm NonProgressors/Elite Controllers Long Term NonProgressors (LTNP) and Elite Controllers, (1% of cases) Immune control of virus replication Magnitude HIV specific CD8 T cell response CD4 T cell counts Time after HIV infection HIV specific CD4 T cell response Viral Load A minority of HIV1 infected patients do not progress to AIDS, maintain normal CD4 counts in the absence of treatment for several years, have low (LTNP or viremic controllers) or even non detectable (elite controllers) viral replication in the blood

6 Antibody Response in HIV infection Binding antibodies 68% of subjects <2% of subjects Mascola and Montefiori, Annu. Rev. Immunol :41344 No role of antibodies in the control of chronic HIV infection

7 Immunological Measures Associated with Control of HIV Replication I Epitopes targeted More Gag and fewer Envepitopes (Kiepiela, Nature, 26) Conserved among strains (Turnbull, J Immunol, 26) Mutations having a fitness cost (MartinezPicardo, J Virol, 26) Immune Activation (lack of immune activation) (Many, Many Investigators) Genetic Factors Longterm nonprogressors (LTNP) and Elite controllers (EC): spontaneous control of HIV1 replication and preservation of high CD4 Tcell counts in the absence of ART HLAB*57, HLAB*27 and HLAB*581 genotypes are associated with viral control (Carrington M, Annu Rev Immunol 23) Genomewide association studies indicate that: The HLAviral peptide interaction is the main determinant of HIV1 control (Pereyra F, Science 21) Specific amino acids in the HLAB peptidebinding groove are important in HIV1 control (The international HIV controllers study, Science 21)

8 CD8 TCell Responses to Different HIV Proteins Have Discordant Associations with Viral Load Kiepiela, et al, Nat Med, 26

9 Dominant influence of HLAB in mediating the potential coevolution of HIV and HLA Kiepiela, et al, Nature, 24

10 Immunological Measures Associated with Control of HIV Replication II Functional profile Proliferation capacity (Migueles et al. Nat Immunol 22, Zimmerli, PNAS, 25; Day, J Virol, 27) Polyfunctional cytokines profile (Pantaleo and Koup, Nat Med 24, Harari et al., Blood 24; Harari et al., J Immunol 24, Betts et al., Blood, 26) Cytotoxic profile Perforin/GrmB expression (Hersperger, PLoS Path, 21; Migueles et al., Immunity 28) Inhibition of virus replication (Freel et al., J Virol, 21; Yang, JID, 212) TCR clonotypes and protective role of HLA class I molecules (Chen et al. Nat Immunol, 212) Lack of exhaustion markers (Day, Nature, 26; Trautmann, Nat Med, 26) TCR avidity (Almeida et al., J Exp Med, 27)

11 AntigenSpecific Proliferation of CD8 T cells in Different Models of Immune Response Subject 248 Subject 248 Subject 181 LTNP 273 Patient 292 Gated on CD8 T Cells Gated on CD8 T Cells Gated on CD8 T Cells Gated on CD8 T Cells Gated on CD8 T Cells Flu EBV CMV HIV1 HIV % 1.76 % 1.41 % 12.8 %.68 % CD8 CFSE Zimmerli et al. 25, PNAS

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15 Immune Response to HIV General Background Factors Driving the phenotypic and functional profile of HIVspecific Tcell responses Immune response profile associated with spontaneous longterm control of HIV replication Major immunological obstacles to HIV Functional Cure

16 TCR avidity in HIV Functional avidity or antigen sensitivity has been shown to be a critical factor of antiviral immunity Higher functional avidity CD8 Tcells are associated with superior antitumor activity and higher efficiency in eliminating «acute virus» (Zeh HJ, et al. Journal of immunology, 1999; Messaoudi I, et al. Science, 22) Higher functional avidity were associated with superior control of HIV (Almeida JR, et al. Blood, 29; Almeida JR, et al. JEM, 27; Berger CT, et al. J. virol, 211) Lower functional avidity was associated with a more polyfunctional profile in CMV and EBV and also in HIV infection (Harari A, et al. PNAS, 27) CD8 Tcells with higher functional avidity are associated with escape mutations in both SIV and HIV infections and are more susceptible to activationinduced cell death and exhaustion (Iglesias MC, et al. Blood, 211; Leslie, et al. J Immunol, 26) Selective depletion of high avidity HIVspecific CD8 T cells after early HIV infection (Lichterfeld, et al. JVI, 27)

17 CD8 T cell functional avidity and control of viral replication Almeida et al. Journal of Experimental Medicine 28:24: Inverse correlation between functional avidity of immunodominant HIVspecific CD8 T cell responses and HIV cell associated viral load

18 Avidity During Primary and Chronic HIV infection Crosssectional study to assess the avidity of CD8 T cell responses at different stages of HIV infection 85 HIV infected patients 37 patients at very early stage of acute infection (PHI) 39 patients with progressive chronic infection (CP) 9 patients with non progressive chronic infection (LTNP) 194 optimal HIV1 derived CD8 TCell epitopes were used to assess HIVspecific CD8 Tcell responses 9 to 11 mers, covering 6 different HLA Class I Alleles

19 Magnitude of HIVspecific CD8 Tcells No significant differences in the magnitude of HIVspecific CD8 Tcell responses Vigano et al. PLOS Pathogens, 213

20 Functional Avidity of HIVSpecific CD8 TCells Overall, lower functional CD8 Tcell avidity observed in PHI patients than in chronic or LTNP patients

21 PeptideSpecific Functional Avidity Comparison of common epitopes recognized in the different cohorts

22 Association Between Magnitude and Functional Avidity of HIVSpecific CD8 TCell Responses PHIB (P=n.s.; r=.6; n=45) CPB (P=n.s.; r=.22; n=4) LTNP (P=n.s.; r=.8; n=27) EC 5 Frequency of total HIVspecific CD8 T cells No significant association between functional avidity and magnitude of the immune response

23 Functional Profile of CD8 TCell Responses Gated on CD8 T cells IL TNFα Perforin PHIB7 B*442AENLWVTVYY e CPB121 A*261EVIPMFSAL e LTNP13 A*21 FLGKIWPSYK IFNγ IFNγ IFNγ

24 Functional Profile of CD8 TCell Responses Perforin expression higher in PHI patients IL2 production higher in cell isolated from LTNP IFNγ producing cells mainly found in larger numbers in chronic progressor

25 Cytotoxic Granules in Acute HIV1 Infection and Changes After ART HIVspecific CD8 Tcell response during acute HIV1 infection Patient 116 Gated on A*2SLYNTVATL CD8 T cells BSL W BSL, n=5 GrmB GrmK Perforin GrmA % of HIVspecific CD8 Tcells (meanse) Perforin Granzyme B Granzyme A Granzyme K (Pies) * * BSL Year 3 * P<.1 * * Year 3, n=5 * * CD CD45RA

26 Expression of Inhibitory Receptors Gated on CD3 T cells Gated on CD8 T cells Tet PHIB137 B*142DRFYKTLRA 38.2 PHIB CPB11 A*21SLYNTVATL 45.3 CPB Gated on CD8 T cells LTNP281 A*21SLYNTVATL LTNP.994 CD8 Tet B B PHIB137 B*142DRFYKTLRA CPB11 A*21SLYNTVATL CD CD CD PD CD16 LTNP281 A*21 SLYNTVATL

27 Expression of Inhibitory Receptors Analysis performed on Tet cells Number of inhibitory molecules coexpressed Higher proportion of cells expressing 2 (2B4 CD16) or 3 coinhibitory receptors (2B4, CD16, PD1) in chronic and LTNP patients than PHI patients Most of the cells from PHI patients express no or 1 (2B4) inhibitory receptor

28 Impact of Early ART Treatment on CD8 TCell Functional Avidity Magnitude Functional avidity Following early ART treatment HIVspecific CD8 Tcell responses may be lost, maintained or newly generated No differences in the functional avidity between responses that are either maintained, lost or newly generated

29 Changes in the Functional and Phenotypic Profile Following ATI HIV1 RNA copies/ml ( ) HIV1 RNA copies/ml ( ) st point 2 nd point Pt#PHI Weeks 1 st point 2 nd point Pt#PHI Weeks CD4 T cells/ μ l ( ) CD4 T cells/ μ l ( ) % of HIV1specific CD8 Tcells PHIT1Y n=6 ( ) IFNγ IL2 Perforin * * PHIATI n=45 ( ) P <.1 PHIT5Y n=16 ( ) * Significantly different from all others (P<.1) % of max Pt#PHI117 B*72GPGHKARVL 1 st point 2 nd point PD1 % of max Pt#PHI123 B*72GPGHKARVL 1 st point 2 nd point PD1 PD1 expression (MFI) PHIT1Y n=21 P=.65 P=n.s. PHIATI n=1 P=n.s. PHIT5Y n=7 % of single IFNγproducing HIV1specific CD8 T cells P=.2 R=.66 3 n= PD1 expression (MFI)

30 Effect of Viral Rebound on Functional Avidity Before treatment interruption After treatment interruption Significant increase in CD8 Tcell avidity after treatment interruption in one patient

31 Effect of Viral Rebound on Functional Avidity Positive correlation was observed between the expression of inhibitory receptors and functional avidity Statistical model to assess the evolution of functional avidity as function of time and virus rebound. The model indicates that functional avidity does not change under steady state conditions. However an immediate increase of functional avidity of HIVspecific CD8 Tcells of about 1 log occurs after treatment interruption and this was not related to the duration of ART prior to treatment interruption

32 Conclusions HIVspecific CD8 T cells generated during acute infection are of lower functional avidity when compared to responses measured during chronic progressive and nonprogressive infection Early treatment of HIV infection prevent the selection of high functional avidity CD8 T cells No loss or preferential deletion of high functional avidity cells is observed In the absence of high antigen exposure the functional avidity does not increase significantly over a short period of time Acute antigen exposure of HIVspecific CD8 Tcells leads to a significant increase in functional avidity associated with a Tcell exhaustion phenotype and differentiation toward an effector phenotype

33 Immunological Markers Preservation of HIVspecific CD4 and CD8 Tcell proliferation Polyfunctional profile Lack of expression of inhibitory receptors The best immunological markers associated with virological control in HIV infected subjects with detectable viremia

34 Immune Response to HIV General Background Factors Driving the phenotypic and functional profile of HIVspecific Tcell responses Immune response profile associated with spontaneous longterm control of HIV replication Major immunological obstacles to HIV Functional Cure

35 Case Study: Patient 11 Cyclosporine A 1 Stavudine Lamivudine Nelfinavir Saquinavir No treatment HIV1 RNA copies/ml < CD4 count (cells/µl) CD8 count (cells/µl) 1 HIV exposure Emergency room admission Start of HAART and CsA 2 days later Treatment interruption Hypersensitive amplicor Assay (LOD: 5 c/ml)

36 Genetic background of patient 11 HLA class I genotype Twodigit PCR Locus A CCR5 genotype PCRbased assay Locus B Locus B 189bp 157bp A3/AX/B7/B4 Fourdigit: A*31, B*72, B*42 Wildtype homozygous Data generated by Erika Castro

37 HIV replication in CD4 Tcells of Pt. #11 MA.A336 : CD4 T cell infection kinetic by HIVNL43BE 1 8 donor 21 cyclo 11 p24 [pg/ml] Time postinfection [days] Data generated by Miguel Munoz and Amalio Telenti, Institut de Microbiologie CHUV

38 HIV1Specific CD8 and CD4 T Cell Responses During Primary Infection in Patient # 11 Baseline (prior to ART) 2 years after primary infection and 3 months after spontaneous treatment interruption 3 years after primary infection and 15 months after spontaneous treatment interruption Unstimulated Pool GAG Unstimulated Pool GAG Unstimulated Pool GAG Gated on CD4 T cells IL Gated on CD8 T cells IFNγ

39 Functional Profile of HIV1Specific CD8 TCells Over Time in Patient #11 Week 3 (1999) Gated on CD8 Tcells Week 135 (21) Unstimulated CD8 Tcell responses B*72 GPSHKARVL gag IL B*72 IPRRIRQGL env A*31 HMYISKKAK vif IFNγ

40 HIV1specific CD4 and CD8 Tcell proliferation in Pt. # 11 Unstimulated Unstimulated e CD4 1 3 CD VDRFYKTLRAEQASQ (gag) B*72GPSHKARVL (gag) CFSE CFSE

41 HIV1Specific CD8 TCell Responses in Patient #11 in e e e Neg e e e e3 IL TNFα Perforin GPGHKARVL (B*72gag) e IPRRIRQGL (B*72env) e IFNγ

42 Distribution of Perforin and Granzymes (A, B and K) in HIVSpecific CD8 T Cells in Patients 11 as Compared to Different Groups of Patients Pt# 11 Acute Infection (baseline) Acute Infection (after 3 years of treatment) Chronic Infection % of HIVspecific CD8 T cells Perforin Granzyme B Granzyme A Granzyme K (Pies) Chronic infection Untreated acute infection Treated acute infection Pt# 11

43 Differentiation Stage of HIV1Specific CD8 TCell Responses in Patients #11, #117 and #123 Gated on Tet CD8 Tcells <FITCA>: CCR <PECy7 [532]A>: CD <APCA>: CD <ECDA>: CD <PECy5 [532]A>: CD45RA <PECy5 [532]A>: CD45RA <PECy5 [532]A>: CD45RA <PECy5 [532]A>: CD45RA CCR7 <FITCA>: CCR7 <FITCA>: CCR <PECy5 [532]A>: CD45RA CD127 <PECy7 [532]A>: CD127 <PECy7 [532]A>: CD <PECy5 [532]A>: CD45RA CD27 <APCA>: CD27 <APCA>: CD <PECy5 [532]A>: CD45RA CD28 <ECDA>: CD28 <ECDA>: CD <PECy5 [532]A>: CD45RA Pt# 11 B*72GPGHKARVL Pt# 117 B*72GPGHKARVL <PECy5 [532]A>: CD45RA <PECy5 [532]A>: CD45RA <PECy5 [532]A>: CD45RA <PECy5 [532]A>: CD45RA <FITCA>: CCR <PECy7 [532]A>: CD <APCA>: CD <ECDA>: CD Pt# 123 B*72GPGHKARVL <PECy5 [532]A>: CD45RA <PECy5 [532]A>: CD45RA CD45RA <PECy5 [532]A>: CD45RA <PECy5 [532]A>: CD45RA

44 Pt# 11 Pt# 117 Pt# CCR7 CD27 CD28 CD45RA CD127 (Pies) Pt# 11 Pt# 117 Pt# 123 Differentiation Stage of HIV1Specific CD8 TCell Responses in Patients 11, 117 and 123 % of HIVspecific CD8 T cells

45 Conclusions The prototypic immunological profile of an HIV1 infected patient (#11) with optimal virological control in the absence of ART, i.e. very low DNA load in blood and gut CD4 Tcells (about 1 HIV DNA copies per 1 6 cells, no isolation of infectious virus, viremia below 5 HIV RNA copies has the following characteristics: Central memory differentiation stage: >8% of CD8 Tcells CD127, CCR7, CD27 and CD28 Central memory functional cytokine profile: highly polyfunctional (>3/4 of CD4 and CD8 Tcells secreting IL2) Central memory proliferation profile: extensive CD4 and CD8 Tcells proliferation capacity Central memory cytotoxic profile: lack of expression of cytotoxic granules such as perforin and GrmB critical for the cytotoxic activity of CD8 Tcells

46 Loss of virus control Turning point HIV1 RNA copies/ml CD4 count (cells/µl) CD8 count (cells/µl) 1

47 Evolution Of The Magnitude Of HIVSpecific CD8 TCell Responses Virus rebound Frequency of peptide specific CD8 T cell producing IFNγ a RLRPGGKKK IEIKDTKEAL GPGHKARVL GPGSKARVL IPRRIRQGL QVPLRPMTYK GIPHPAGLK AIFQSSMTK IEELRQHLL QIYPGIKVR HMYISKKAK A*31 gag B*41 gag B*72 gag B*72 gag B*72 env A*31 nef A*31 RT pol A*31 RT pol B*41 RT pol A*31 RT pol A*31 vif Decrease of Gag B*72 (49 and 49a) and RT pol A*31 (127) responses Increase of Gag A*31 (8), B*41 (15), Env B*72 (82), Vif A*31 (152)

48 Cumulative HIVSpecific CD8 TCell Responses Overtime % of HIVspecific CD8 T cell responses of CD8 T cells a RLRPGGKKK IEIKDTKEAL GPGHKARVL GPGSKARVL IPRRIRQGL A*31 B*41 B*72 B*72 B*72 gag gag gag gag env QVPLRPMTYK A*31 nef GIPHPAGLK A*31 RT pol AIFQSSMTK A*31 RT pol IEELRQHLL B*41 RT pol QIYPGIKVR A*31 RT pol 152 HMYISKKAK A*31 vif

49 Evolution Of The Functional Profile Of All HIVSpecific CD8 TCell Responses RLRPGGKKK A*31 gag IEIKDTKEAL B*41 gag GPGHKARVL B*72 gag GPGSKARVL B*72 gag % of HIVspecific CD8 T cellresponses IFNγ IL2 TNFα IPRRIRQGL GIPHPAGLK AIFQSSMTK IEELRQHLL QIYPGIKVR HMYISKKAK B*72 env A*31 RT pol A*31 RT pol B*41 RT pol A*31 RT pol A*31 vif

50 Evolution Of The Functional Profile Of The Three Initial HIV Specific CD8 TCell Responses (Gated on IFNγproducing CD8 T cells) #49 GPGHKARVL B*72 gag % of HIVspecific CD8 T cellresponses IL2 Perforin TNFα The response to peptide 49 gag (B*752) decreases after virus rebound (from 6 to 2%) however the cytokine profile does not change dramatically. Slight increase in the proportion of IFNγ TNF secreting cells after viral rebound

51 Evolution Of The Functional Profile Of The Three Initial HIV Specific CD8 TCell Responses (Gated on IFNγproducing CD8 T cells) #82 IPRRIRQGL B*72 env.2% 2.5% 3.5% 4.5% #152 HMYISKKAK A*31 vif.2%.3%.3%.5% % of HIVspecific CD8 T cellresponses IL2 Perforin TNFα % of HIVspecific CD8 T cellresponses IL2 Perforin TNFα These responses increase after virus rebound. In this case the cytokine profiles changes dramatically : for 82 env : increase in IFNγ TNF producing cells and decrease IL2 production, i.e. change towards an effector cell cytokine profile

52 Case Study: Patient 11 Cyclosporine A 1 Stavudine Lamivudine Nelfinavir Saquinavir No treatment HIV1 RNA copies/ml < CD4 count (cells/µl) CD8 count (cells/µl) 1 HIV exposure Treatment interruption Emergency room admission Start of HAART and CsA 2 days later Hypersensitive amplicor Assay (LOD: 5 c/ml)

53 Lesson Learned from Patient #11 Patient #11 has been treated within 15 days from HIV exposure. He therefore fits very well within the beneficial effect observed in other cohorts of patients treated early during primary infection HIV in Patient #11 has come back after almost 1 years It is slowly taking over the immune control Caution should be exerted in considering patients with long term virological control cured from HIV Nonetheless Patient #11 is a perfect example of what should be achieved with HIV functional cure, i.e. extended period of time with full virus control in the absence of ART

54 Immune Response to HIV General Background Factors Driving the phenotypic and functional profile of HIVspecific Tcell responses Immune response profile associated with spontaneous longterm control of HIV replication Major immunological obstacles to HIV Functional Cure

55 The First TCell Response to the Transmitted/Founder Virus Contributes to the Control of Acute Viremia in HIV1 Infection Days after infection Virus sequence changes emerge both early and rapidly at multiple sites across the HIV1 proteome Epitopes Numerous CD8 T cell responses induced following HIV infection Goonetilleke N et al. J Exp Med 29;26: Extremely rapid appearance of mutations driven by CD8 Tcell responses in the first few days of infection Responses to the transmitted form of the virus disappeared after selecting early virus escape mutants

56 Why Does HIV Persist In Infected Individuals? Two Main Hypotheses Latent HIV Reservoir Residual HIV Replication T CM /T TM CD4 T cells Size: cells Half life memory CD4 T cells: 43 months Estimated time for eradication: ~7 years under full virus suppression by ART Not susceptible to ART Not susceptible to the immune system CD4 T cells? Macrophages? DCs? Covert cellular reservoir Priveleged anatomic compartment Resistant to HIV cytopathic effect Poorly accessible to cytotoxic CD8 T cells Minimal virus spreading Replenishment of the latent cellular reservoir

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58 Tfh Cells and CXCR5 PD1 CD4 TCells Are Enriched in HIVSpecific CD4 TCells

59 Tfh Cells and CXCR5 PD1 CD4 TCells Are Enriched in CD4 TCells Containing HIV DNA DNA extraction Taqman RTPCR HIV1 gag gene

60 Tfh Cells and CXCR5 PD1 CD4 TCells Are the Most Efficient in Supporting Production of HIV Anti CD3/CD28 Collection of SNs p24 detection D D2 D5 High viremia (>15 HIV RNA copies/ml)

61 HIV Isolation from Patients with Low (<1 HIV RNA copies/ml of plasma) in Different CD4 TCell Populations CD8depleted PBMCs Coated CD3/28 Collection of SNs p24 detection D D3 D7 Low viremia (<1 HIV RNA copies/ml) Tfh and CXCR5 PD1 but not CXCR5 PD1 and CXCR5 PD1 CD4 Tcells efficiently support virus isolation and production in patients with low viremia levels

62 The Percentage of Tfh Cells Correlates with HIV Viremia Levels

63 Sequencing Results Sequencing of HIV in plasma and in different memory CD4 Tcell populations has indicated that the virus isolated from Tfh cells is identical to that found in plasma PD1CXCR5 CD4 Tcells contains HIV almost identical to that circulating in plasma These results demonstrate that Tfh cells are mostly responsible for the production of circulating HIV

64 Events Occurring in the Germinal Centers in Viremic HIVInfected Patients Germinal center reaction Centrocyte HIVspecific) GCcell Plasma cells (late response) Memory Bcells Defective Tfh help to Bcells and decreased Ig production High levels of HIV replication and production within T FH cells. Correlation with viremia levels

65 Events Occurring in the Germinal Centers in ART HIV Suppressed Patients NonHIV Ag Stimulation Bcell zone BCR Bcell SCS macrophage primary follicule FDC HIV germinal center Bcell Bcells proliferation Secondary follicule GC T FH cells Tcell zone antigen presentation NonHIV Ag stimulation pregc T FH cells centroblasts proliferation DC CD4 T cells proliferation T H cells pregc T FH cell plasma cells (early response)

66 Events Occurring in the Germinal Centers in ART HIV Suppressed Patients NonHIV Ag Stimulation Germinal center reaction centrocyte memorycells germinal center B cell No HIV spreading because of ART plasma cells (late response) Transient bursts of HIV replication and production within T FH cells. Responsible for virus blips? Transient Virus Blips

67 Primary Anatomic Sites of HIV Replication Lymphoid tissues represent the primary site for HIV infection and replication even during the asymptomatic clinical phase of infection (Pantaleo et al., 1991; Pantaleo et al., 1993; Embretson et al., 1993 and Brenchley et al., 24). Pantaleo et al., Nature 1993

68 Regulation of TCell Entry Within GCs Loss of CCR7 expression Expression of CXCR5 Production of CXCL13 (ligand for CXCR5) by FDCs Therefore, access of cells to GCs is highly selective CD8 Tcells have very limited accessed to GCs, e.g. small proportion exppress CXCR5

69 Low CXCR5 expression on HIVspecific CD8 Tcells Untreated HIVinfected donor #CNA 266 (HIV RNA 3225 copies/ml) Gated in memory CD8 T cells A*3 Gag RLRPGGKKK Total memory CD8 PD1 Tetramer PD1 5 CXCR5 * 11 Viability dye **** 1 CXCR5 *** p<.5 * p<.5 p<.1 *** **** Percentage of CXCR5 memory CD8 T cells Percentage of PD1 memory CD8 T cells Percentage of memory CD8 T cells 5 **** *** Total memory CD8 T cells HIVspecific CD8 T cells Total HIVspecific 7 Total HIVspecific PD1 CXCR5

70 Conclusions Tfh Cells Serve as the Major CD4 TCell Compartment for HIV Infection, Replication and Production (Perreau et al. JEM 213) Tfh Cells and CXCR5 PD1 Cells May Represent the Primary Obstacle for Achieving Functional HIV Cure/Eradication HIV infected Tfh cells reside in a privileged anatomic site, i.e. germinal centers, with limited accessed to HIVspecific cytotoxic CD8 Tcells

71 THE FUTURE

72 Therapeutic Vaccine i.m. Multivalent Biological Approach Potentiation HDACi Nef Nef Nef Nef Activation of HIV Replication PD1 Nef HIV Nef Reactivation/Boosting HIV Replication CD4 i.v. Potentiation ADC Bispecific Abs: PD1/HIV env CD4/HIV env PD1/CD4 Generation / Boosting of HIVspecific CD8 Tcells Killing of HIV infected CD4 Tcells

73 Final Considerations The solely potentiation of the HIVspecific immune response is not sufficient to achieve control of HIV replication Major reduction in the pool of CD4 Tcells containing replication competent HIV is necessary in order to promote immunebased virus control Therefore, therapeutic interventions targeting and causing massive depletion of memory CD4 Tcell populations containing HIV replication competent is required to achieve HIV functional cure

74 IMMUNE CONTROL OF HIV Giuseppe Pantaleo, M.D. Professor of Medicine Head, Division of Immunology and Allergy Executive Director, Swiss Vaccine Research Institute Lausanne University Hospital, Lausanne, Switzerland