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Thumbi Ndung’u, BVM, PhD KwaZulu-‐Natal Research Ins@tute for Tuberculosis and HIV (K-‐RITH)
and HIV Pathogenesis Programme Nelson R. Mandela School of Medicine
University of KwaZulu-‐Natal
Biomedical HIV Preven2on Forum, Harare, Zimbabwe, 29 November 2015
HIV vaccine research and implica@ons for HIV control in Africa
• The need for an HIV vaccine
• Past vaccines: successes and challenges • Challenges and barriers to an HIV vaccine • Overcoming the challenges-‐ reasons for op>mism
-‐ Recent work on the CD8+ T cell immune responses -‐ Neutralizing and other an>body func>ons
• The need for involvement of African scien>sts and its young people
Presenta@on outline
Clinical trial evidence for preven@ng sexual HIV transmission
Efficacy
Study Effect size (CI)
Medical male circumcision (Orange Farm, Rakai, Kisumu) 54% (38; 66)
HIV Vaccine (Thai RV144)
31% (1; 51) 0% 10 20 30 40 50 60 70 80 90 100%
STD treatment (Mwanza, Tanzania)
42% (21; 58)
39% (6; 60) Microbicide (South Africa)
PrEP for MSMs (Americas, Thailand, South Africa) 44% (15; 63)
Treatment for preven>on (Africa, Asia, Americas) 96% (73; 99)
PrEP for heterosexuals (Botswana TDF2) 63% (21; 48)
PrEP for discordant couples (Partners PrEP) 73% (49; 85)
Modified from Abdool Karim, 2013 Lancet
Poten@al Impact of an HIV Vaccine
John Stover et al. Health Aff 2007;26:1147-‐1158
30% efficacy, 20% coverage
50% efficacy, 30% coverage
70% efficacy, 40% coverage
6 million
17 million
28 million
Total new infec@ons averted by an HIV vaccine
between 2015 -‐ 2030
“….but what renders the Cow Pox so extremely singular is that the person who has been thus affected is for ever acer secure from the infec@on of the Small Pox…” Edward Jenner, 1798.
A sterilizing, durable vaccine is a powerful public health tool
Vaccines take @me to develop…
Vaccine Discovery of causa@ve agent
Vaccine Developed for Human Use
Years to Vaccine
H. Influenzae-‐B 1892 1985 93
Herpes (HSV-‐1) 1919 Not available >90
Pertussis 1906 1926 20
Polio* 1909 1954 47
Yellow Fever 1900 1935 35
Influenza 1933 1945 12
Measles 1911 1957 46
Modified from H. Markel, NEJM, August 25, 2005
*In the 1930s, two experimental polio vaccines failed because they were determined to be unsafe, and polio vaccines were almost abandoned.
What is a vaccine ?
A vaccine is a substance that teaches the body’s immune system to recognize and protect against a disease caused by an infec>ous agent (e.g. virus or bacterium).
B cell
Th
Viral protein
Th
CTL
New virus assembly
HLA-‐1
HIV
Infected cell
Neutralizing an@bodies
Modified from Walker and Burton (2008), Science.
How might HIV vaccines work?
Viral load copies/ml
Time HIV
Viral load copies/ml
HIV
Viral load copies/ml
HIV
Goals of a prophylac@c HIV vaccine
Induces immunity that allows transient HIV replica>on
Induces sterilizing immunity-‐ no infec>on upon exposure
Induces immunity that greatly weakens the virus: no disease and no transmission
Disease/transmission threshold
Time
Time
How is a vaccine developed?
Discovery Vaccine design
Preclinical research Clinical trials
Stages of Clinical Trials
12 to 18 months Small group of healthy, HIV nega>ve par>cipants to test safety
Up to 2 years Hundreds of HIV nega>ve par>cipants to test safety and immune responses
3 to 4 years Thousands of par>cipants at risk to test safety and efficacy
PHASE I PHASE II PHASE III
HIV vaccine efficacy trials
No
NOTE: Phambili (HVTN 503) began to explore a regimen similar to STEP in South Africa (not included).
Why haven’t these vaccines worked? Scien@fic Obstacles
• The natural immune response to HIV infec>on does not eliminate the virus (we don’t understand what cons>tutes protec>ve immunity)
• Enormous sequence variability. We do not know how to construct an immunogen to cover this sequence variability
• Immune responses induced by vaccina>on are generally weak (low magnitude and breadth), no neutraliza>on
Viral diversity-‐ arguably the most significant challenge in HIV-‐1 vaccine development
Ndung’u and Weiss, 2012, AIDS Adapted with permission from Korber et al, 2001, Br. Med. Bull
Case studies of: • Overcoming diversity through mosaic immunogen designs
• Improving immunogenicity through novel vectors
• Novel designs for neutralizing an>bodies
How do we overcome scien@fic challenges in HIV vaccine development?
Input: Single clade or M group
Mosaic antigens can be designed to increase coverage of HIV diversity
Fischer et al. Nat. Med. 2007; 13:100-‐106
The Ad26 mosaic vaccine yielded many more Gag, Pol, and Env (A) epitope-‐specific T lymphocyte responses as well as (B) numbers of epitope response regions to PTE pep>des than did the Ad26 M consensus, clade B + clade C, or op>mal natural clade C vaccines
Expanded breadth by mosaic compared with
consensus or natural Gag/Pol/Env an@gens in Rhesus Monkeys
Barouch et al. Nat. Med. 2010; 16:319-‐323
Novel vectors –such as replica@ng CMV may overcome the kine@c mismatch problem!
52% (25/48) of CMV vector-‐vaccinated RM, upon infec@on, manifested immediate virologic control and eventual viral clearance in some for >52 weeks.
Barouch and Picker, 2014, Nat Rev Micro
Hansen et al, Science 2013
Plausibility of approach-‐ even berer with recent discovery of vectors that violate the CD8+ epitope recogni@on paradigm
Immunogens to prevent escape or arenuate the virus tat
3’LTR
5’ LTR gag
pol env
vif
vpr
vpu
nef
3’ LTR
rev
Time post HIV infection
Vira
l fitn
ess
Mann and Ndung’u, 2015, Virol Journ
Prototype broadly nAbs: binding regions
A. Ward & C. Corbaci
Gray -‐ Gp120 Red-‐ the CD4 binding site on gp120
Image credit: NIAID/NIH Vaccine Research Center
Green & Purple – the VRC01 an>body alached to the CD4 binding site
VRC01: a bnAb to the CD4bs on gp120
• Discovered in an individual HIV-‐1 infected for >15 yrs, who maintained virologic control on no ART
• Developed by John Mascola & colleagues at the Vaccine Research Center of the Na>onal ins>tutes of Health
VRC01 is broadly neutralizing
Panel of 190 Diverse Viral Isolates
Rational design of envelope identifies broadly neutralizing human monoclonal Antibodies to HIV. Science. 2010
Vector Mediated Gene Delivery of Broadly Neutralizing An@bodies: AAV1-‐PG9 Prototype
Slide modified courtesy of P Johnson and F Priddy
• Mosaic Antigens: Ad26, MVA, gp140 (J&J) (~ PhIIb 2018) • Conserved-Mosaic Antigens: chAd, MVA (PhIIb 2019 – 2020)
• HIV ENV trimers • ENV epitopes • Env DNA
• Attenuated VSV • Vaccinia virus Tiantan • Sendai • Adeno 4
• CMV • CDV • VSV • Pox: NYVAC • RepliVax (Flavi)
Improving RV-144: CMI + non-neutralizing Ab
Improve the breadth of vaccine
Candidates to Elicit bnAbs
Replicating Vectors- Improve durability
ALVAC + gp120/MF59 Licensure RSA
DNA + NYVAC + gp120 Test of Concept Trial NYVAC + gp120
Basic research
Applied research
Preclinical development Phase I / II Large-scale Efficacy trials
HIV Vaccine Pipeline – October 2015
• epDNA + IL12+ VSV + Single Chain • DNA + MVA • DNA + Tiantan-VV
• Passive Abs • AAV –bnAb delivery
IAVI-partnered product VxPDC partners
Immunoprophylaxis
• Adeno 26
Africa has very limited research capacity in all fields of science-‐ par@cularly discovery science
Programmmes such as WT DELTAS, IAVI VISTA, NIH Fogarty & MEPI-‐ but more needed
New Minds: Making Breakthrough Discoveries Nobel Laureates 1901-‐2003 in Three Disciplines Stra@fied by Age at Time of Award-‐
Winning Discovery
Dietrich, Arne, and Narayanan Srinivasan. 2007. The op>mum age to start a revolu>on. Journal of Crea3ve Behavior. 41: 54-‐74.
• A vaccine will most likely be needed to end the HIV/AIDS epidemic
• The RV144 vaccine trial that was par>ally effec>ve provides proof of concept that an HIV vaccine is possible
• Recent advances in immunogen design, delivery systems and basic understanding of HIV biology offer hope and a pathway to vaccine development
• Africa must invest in science and especially in young people for its future
Summary
Acknowledgements Useful discussions and slides • Frances Priddy (IAVI) • Simba Takuva (HVTN) • Dennis Burton (Scripps) • Dan H Barouch (Harvard) • Lynn Morris (NICD) • Bruce Walker (Harvard) UKZN • Ndung’u lab (K-‐RITH) • HPP lab (UKZN)
Funding • Na>onal Research Founda>on • CANNSA network funded by
the Canadian CIHR • IAVI • HHMI • Victor Daitz Founda>on • Bill and Melinda Gates
Founda>on • Wellcome Trust
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