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THE BASICS OF HIV CURE RESEARCH HIV Cure Research Training Curriculum HIV and Cure Basics Module by: Jessica Handibode, AVAC March The HIV CURE research training curriculum is a collaborative project aimed at making HIV cure research science accessible to the community and the HIV research field.
Objectives 1. Definition of “cure” 2. Elements of the reservoir 3. Strategies toward a cure 4. Overall challenges
The HIV infection pathway
Why aren’t ARV’s enough? - HIV latency Cell Death Resting State
History of HIV “cures” • Alternative (herbal therapies, dietary supplements, visualization, etc. ) • Cultural (rituals, practices, prayer, etc. ) Cure is NOT a new idea
History of HIV “cures” • Time magazine wrote that David Ho’s work “might, just might, lead to a cure”
What does cure mean-community perspective • Living without treatment • Not transmitting virus to others • Complete viral eradication
What does cure mean-scientific perspective • Scientists are still unclear what it means to be “cured” of HIV • There is still debate over what biological signs indicate a potential cure • There is still debate over whether virus must be completely gone from the body or not
Is “cure” the new “cancer”? Concept Eradication Advantages Powerful, galvanizing concept for advocacy Disadvantages Ambiguity between population and clinical senses Too high a bar? Sterilizing cure Seductive idea of definitive absence of HIV No reliable test to confirm viral absence Functional cure Less demanding than sterilizing cure Lifelong control? Unfamiliar concept of cure Remission Appeals to concerns about transmission Not a ‘real’ cure if HIV present More familiar to laypersons When does remission start? Less demanding, because no guarantee of ‘lifelong’ control Association with stigmatized cancer Denotes improvement but implies need for vigilance, monitoring Psychological uncertainty Transmission? S. Rennie
(2014) What is a reservoir? The collection of HIV infected resting cells Potential reservoirs include T-cells, macrophages and tissue compartments like gut and brain that contain these cells. Nature Reviews Immunology 14, 24 -35
How is a reservoir maintained? • Most HIV reservoir maintenance pathways are unknown. • This is a topic of intense research in the scientific community. • Active reservoirs are cells that produce virus in the presence of Antiretroviral Therapy. Generally these reservoirs are found in the tissue.
Does size matter? • Different assays can measure the size of the reservoir. There are several ways to do this including measuring HIV RNA or DNA • The size of an individual’s reservoir can vary greatly. Individuals diagnosed later in infection tend to have larger reservoirs • A larger reservoir means greater and more persistent immune activation • Sustained immune activation can lead to chronic inflammation, among other side effects which can lead to dangerous conditions like heart attacks and strokes
Early treatment and cure • Treating HIV early may reduces the size of the reservoir & it may also prevent reservoirs from forming in certain parts of the body • The definition of “early” is currently being debated in the scientific community • Early treatment is not in itself a cure
Natural immunity to HIV-1 Very rare No CCR 5 Receptor Homozygous • There is a very small percentage of the population who are naturally resistant to HIV. These individuals are of Northern European origin. • In order to have a T-cell without a CCR 5 receptor you must have two genes (one from each parent) with the CCR 5 deleted segments. • A person with two deleted CCR 5 gene segments is homozygous for the CCR 5Δ 32 mutation.
Living with HIV without treatment • Elite Controller: someone who can keep nearly undetectable levels of virus without antiretroviral therapy • Long Term Non-Progressor: someone who maintains a normal count of CD 4 and CD 8 Tcells for a minimum of 10 years without the aid of antiretroviral therapy
Scientific challenges to finding a cure • Understanding the latency pathway of HIV • Why do cells remain latent? • How does the reservoir persist over a lifetime • What, if any, effect does sex have on latency? • Factors still unknown/under debate • Determining the location of latently infected cells e. g. gut, T-cells • Measuring the size of infected reservoirs
Current cure research strategies 1. Kick and Kill 2. Gene therapy/alteration 3. Stem cell transplantation 4. Therapeutic vaccines
Kick and Kill This strategy aims at forcing cells out of a resting state so virus can be released and killed • Once cells begin to replicate, again they can be identified and killed • The virus that is released into the blood stream can infect cells, however effective ART blocks replication • However a kill component, like a therapeutic vaccine will be needed to eliminate virus.
Kick and kill in action “activate” HIV DNA HIV US RNA HIV proteins HIV DNA HIV virions Cell death
Kick and kill challenges 1. Not every infected latent cell will become active with latency reversing agents 2. It has been shown that a latent cell may need several rounds of stimulation to start purging virus 3. Finding effective latency reversing agents that actually stimulate the cells inside the body
Gene therapy/alteration The aim is to remove a key element the virus needs to invade the cell • The CCR 5 receptor is one of the necessary binding sites for HIV to enter a cell • Knocking out the genes that cause the CCR 5 receptor will make cells resistant to HIV
Gene therapy/alteration Scientists are working on ways to modify, culture and reintroduce these cells into the body of patients to increase resistance to HIV Cell collection Gene editing Patient Cell proliferation
Gene therapy/alteration challenges 1. Gene therapy does not kill existing virus. It just alters cells, making them HIV resistant or possibly improving immune fighting capabilities 2. Editing genes can lead to “off targets” or alterations in genetic sequences that was unintended. This could lead to side effects that include cancer.
Stem cell transplantation The goal is to use stem cells to produce new HIV -resistant cells in the body • When undergoing a stem cell transplant a person must undergo a dangerous conditioning process to wipe out their entire immune system • The conditioning process can involve several different types of drugs as well as radiation to completely kill the immune system
Stem cell transplantation • Conditioning creates space for the donor stem cells to replace the immune system. • If the donor stem cells lack the CCR 5 receptor, HIV can almost never enter the cell Basophil CFU-B Dendritic cell CFU-DC Macrophage CMP CFU-GM CFU-M Granulocyte CFU-G HSC Platelets HSC CFU-MK MPP Erythrocyte HSC CFU-E CLP Early NK NK cell Pro-T Pre-T T-cell Pro-B Pre-B B-cell
Stem cell transplantation challenges 1. Currently this procedure is dangerous and carries risks such as graft vs. host disease 2. An extremely small percentage of the population is naturally immune to HIV. 3. Expensive and not scalable
Therapeutic vaccines Strengthen the immune responses, to enable the destruction of newly infected cells in order to achieve a functional cure • Broadly neutralizing antibodies, antibodies that can bind and kill a variety of HIV mutations, are being pursued in both preventative and curative strategies.
Therapeutic vaccine challenges • HIV mutates very rapidly. It can be difficult to find a broadly neutralizing antibody that can effectively work long enough to knock out HIV • Over stimulation of the immune system can lead to an increase of target cells for the virus
General challenges to finding a cure Participant Risk Benefit Global capacity Knowledge • unlike treatment, most people living with HIV have effective regimens that work with their daily routine. Not all cure strategies will be worth the risk to study participants • there are very few labs in the world that have the technical equipment and personnel capabilities to conduct cure research • need for greater understanding of HIV latency in both infants and adult populations
Hope for the future Treatment Cure Prevention Diagnosis Treatment Diagnosis