Functional Cure for HIV: Lymphoid T cell Dynamics and PD-1 Immunotherapy 公开

Mylvaganam, Geetha Hanna (2016)

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Human immunodeficiency virus (HIV) has emerged as one of the most devastating global health burdens in history with approximately 36 million individuals infected worldwide. The introduction of anti-retroviral therapy (ART) has greatly enhanced viral control and the quality of life for individuals living with HIV, but ART remains a life long therapy due to latently infected CD4 T cells that are seeded early during primary infection. The latent HIV reservoir is directly responsible for viral resurgence post treatment interruption. Due to the limited success in generating a highly effective prophylactic vaccine for HIV and with 15 million and a growing number of HIV infected individuals on ART, researchers have re-directed their focus towards generating a more feasible approach to treating HIV, termed a "functional cure". The key to achieving a functional cure for HIV requires reduction/elimination of viral reservoirs and restoration of functional anti-viral CD8 T cells. The viral reservoirs are concentrated at lymphoid sites and thus there is a need for understanding the dynamics of virus-infected CD4 T cells and anti-viral CD8 T cells in the lymphoid tissue during chronic infection. Using a macaque model system of SIVmac251 pathogenesis, our studies revealed critical findings. Firstly, we observed that PD-1hi Tfh cells are aberrantly enriched in the lymph nodes (LN) and rectal mucosa of chronically SIV infected macaques and contribute to ongoing viral replication and production. Secondly, we identified a novel subset of germinal center infiltrating CXCR5+ SIV specific CD8 T cells that rapidly expand in vaccinated SIV controllers, can limit the expansion of virally infected Tfh, and are associated with enhanced viral control. Lastly, immunomodulation of the PD-1 pathway prior to and during the initiation phase of ART in a therapeutic SIV/ART macaque trial demonstrated significantly enhanced proliferation, cytotoxic potential, and polyfunctionality of anti-viral CD8 T cells resulting in markedly faster suppression of virus replication following the initiation of ART. Together, these findings further our understanding of some of the fundamental aspects of basic HIV/SIV biology and provide insight into novel therapeutic interventions that can be administered in combination with ART.

Table of Contents

Table of Contents Abstract Dedication Acknowledgements Chapter 1: Introduction -------------------------------------------------------------- 1

History and Global Burden of HIV/AIDS ----------------------------------------- 1

Transmission and Pathogenesis ----------------------------------------------------- 1

ART and Viral Reservoirs ----------------------------------------------------------- 6

Immune Drivers of Viral Persistence ----------------------------------------------- 9

Immune Response to HIV ----------------------------------------------------------- 12

Innate immune response --------------------------------------------------- 12

Adaptive immune response ------------------------------------------------ 12

Humoral Immunity ------------------------------------------------ 13

Cell mediated immunity ------------------------------------------- 14

T Follicular helper cells and HIV ------------------------ 17

CD8 T cells and HIV ------------------------------------- 20

Immune Exhaustion and Check-point Inhibition --------------------------------- 22

Summary -------------------------------------------------------------- 27 Chapter 2: Diminished Viral Control during ----------------------------------------------- 30

SIV Infection is Associated with Aberrant

PD-1hi CD4 T cell Enrichment in the

Lymphoid Follicles of the Rectal Mucosa

Figure 2.1. Phenotypic characterization ofPD-1+-------------------------------- 51

subsets in the blood, lymph node (LN), and rectum

of healthy rhesus macaques (RM) Figure 2.2. Characterization of PD-1hi CD4 T cells in the ------------------------ 52

LN and rectum of chronically SIV infected vaccine-controller

and non-controller RM

Figure 2.3. CXCR5 expression and localization of ------------------------------- 53

PD-1hi CD4 T cells of chronically SIV infected

vaccine-controller and non-controller RM

Figure 2.4. Phenotypic characterization of PD-1hi -------------------------------- 54

CD4 T cells in the LN and rectum of chronically

SIV infected vaccine-controller and non-controller RM

Figure 2.5. Phenotypic characterization of CCR5 -------------------------------- 56

expression and infection status of PD-1hi CD4 T cells

in the LN and rectum of chronically SIV infected

vaccine-controller and non-controller RM

Figure 2.6. Association between anti-viral CD8 T cells --------------------------- 58

and PD-1hi CD4 T cells in the LN following SIV infection

Figure 2.7. Accumulation of PD-1hi CD4 T cells --------------------------------- 59

in the LN of SIV infected non-controlling RM

Figure 2.8. BCL-2 expression on Naïve and --------------------------------------- 60

Memory CD4 T cells in the LN and Rectum

of SIV infected macaques

Figure 2.9. Accumulation of SIV infected Tfh ----------------------------------- 61

within the LN and Rectal mucosa of SIV infected

Non-controlling RM Chapter 3: Follicular Anti-viral CD8 T cells Contribute ----------------------------------- 62

to Enhanced Control of Pathogenic SIV

Figure 3.1. Rapid expansion of CXCR5+ SIV specific --------------------------- 79

CD8 T cells is associated with enhanced

control of chronic SIV infection

Figure 3.2. CXCR5+ SIV specific CD8 T cells are -------------------------------- 80

more polyfunctional than CXCR5- SIV specific CD8 T cells

in the blood

Figure 3.3. CXCR5+ SIV-specific CD8 T cells are localized -------------------- 81

in the germinal centers (GC) of vaccinated controllers

and limit Tfh expansion in vitro

Figure 3.4. Global gene expression analysis revealed distinct ------------------- 82

gene expression profile for CXCR5+ SIV specific CD8 T cells

Figure 3.5. Correlations between the percentage of ------------------------------ 83

CXCR5+ GagCM9+ CD8 T cells at week 2-3 and

week 12-24 post SIV infection and set-point VL

Figure 3.6. Percentage of CXCR5+ GagCM9 CD8 T cells ----------------------- 84

in unvaccinated animals at week 12-24 post SIV infection

inversely correlates with set-point viral load

Figure 3.7. Representative FACS plots from a controller ------------------------ 85

and non-controller RM at week 24 post SIV infection

Figure 3.8. Representative immunofluorescence staining ------------------------ 86

of CD8 T cells in LN sections from SIV+ non-controller

and SIV+ vaccine controller RM at week 24 and

week 2-3 post SIV infection Figure 3.9. Representative in situ tetramer staining images ---------------------- 87

of MLN, spleen and rectal tissue of SIV infected controller RM

Figure 3.10. Induction of perforin and -------------------------------------------- 88

granzyme co-expression on CXCR5+ and - CD8 T cells

co-cultured with P11c antigen pulsed Tfh

Figure 3.11. Representative histogram plots showing ---------------------------- 89

the expression of phenotypic markers on

naïve and memory CXCR5+ and CXCR5-

GagCM9 CD8 T cells, and Tfh cells

Table 2. Cohort of SIV infected rhesus macaques used for sample collection - 90

Figure 3.12. Greater Frequency and Function ------------------------------------ 91

of Germinal Center (GC) Infiltrating CXCR5+ CD8 T Cells

During Controlled SIV Infection Chapter 4: In vivo PD-1 blockade as a Therapeutic --------------------------------------- 92 Adjuvant to Antiretroviral Treatment Figure 4.1. In vivo PD-1 ART trial design ----------------------------------------- 114

Figure 4.2. Rapid and discernable PD-1 blockade in vivo ----------------------- 115

Figure 4.3. PD-1 blockade results in enhanced ----------------------------------- 116

in vivo proliferationof CD4 and CD8 T cells

Figure 4.4. PD-1 blockade results in enhanced ----------------------------------- 117

polyfunctionality of SIV specific CD8 T cells

Figure 4.5. PD-1 blockade results in enhanced ----------------------------------- 118

functional quality of CD8 T cells

Figure 4.6. In vivo PD-1 blockade synergizes ------------------------------------ 119

with ART resulting in increased viral suppression

Figure 4.7. In vivo PD-1 blockade enhances -------------------------------------- 120

Th17 reconstitution in the rectal mucosa under

suppressive ART

Figure 4.8. Partial reconstitution of CD4 T cells ---------------------------------- 121

in the blood and rectal mucosa of ART treated macaques

Figure 4.9. Levels of cell associated Gag DNA ----------------------------------- 122

within memory CD4 T cell subsets in PD-1 treated and

control groups during suppressive ART

Chapter 5: Discussion -------------------------------------------------------------- 123

Early ART Initiation -------------------------------------------------------------- 125

Targeting the Tfh Viral Reservoir -------------------------------------------------- 127

HIV Sanctuary - Exposing the Germinal Center Reservoir ---------------------- 131

Modulating Anti-viral Immunity under ART ------------------------------------- 134

Biologicals -------------------------------------------------------------- 134

Therapeutic Vaccines ------------------------------------------------------ 135

Cytokine based therapies and Latency Reversing Drugs (LRA's) ------ 138

Conclusions -------------------------------------------------------------- 141

Figure 5.1 Potential mechanisms of viral control ------------------------ 142

by therapeutic vaccines

References ------------------------------------------------------------------------------------- 143

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