Project Description

Trial Title: A Phase 1 Trial of ChAdOx1- and MVA-vectored Conserved Mosaic HIV-1 Vaccines in Healthy, Adult HIV-1-negative Volunteers in Eastern and Southern Africa.

Chief Investigator: Dr Paola Cicconi, MD, PhD,  The Jenner Institute University of Oxford

Chief Non-Clinical Investigator: Professor Tomáš Hanke, BSc, MSc, PhD, The Jenner Institute University of Oxford

Sponsor: University of Oxford, United Kingdom

Funder: European and Developing Countries Clinical Trials Partnership

Control of the HIV epidemic remains one of the global health priorities. Despite remarkable progress achieved in decreasing HIV transmission and AIDS-related deaths in the last decade due to development of over 30 antiretroviral drugs, HIV continues to spread, infecting approximately 1.8 million people in 2016(1). Around a third of people who are HIV positive do not know their status and hence do not receive treatment(1). For those who know their status: antiretroviral drugs may not be available on a regular reliable basis in many resource-poor settings(2). In addition to that, they have long-term side effects, their effective use requires rigorous daily compliance(3) and the circulating and/or transmitted viruses have been shown to develop resistance to several antiretroviral drugs. Also, there is unwillingness to take drugs in a surprisingly large proportion of infected individuals, even in the USA(4). Thus, a safe, effective, prophylactic HIV vaccine remains one of the priorities of HIV/AIDS research, and will be key to any strategy for halting the AIDS epidemic.

Phase 1 clinical trial HIV-CORE (COnserved REgions) 006 is a trial of a new combined vaccine regimen to determine safety and immunogenicity in healthy adults in Kenya, Uganda and Zambia. Immune responses may vary between populations and so it is important to confirm that the vaccines are suitable for the people and environment where they will be deployed for protection against HIV/AIDS. There are many different strains of HIV-1, and the virus can change to escape immune responses. This vaccine regimen is designed to work in all parts of the world.
Our aim is to induce effective cytotoxic T lymphocytes (CTL) against HIV-1. These could complement broadly neutralizing antibodies in prophylaxis and play a central role in cure. CTL exert their effector functions by killing HIV-1-infected cells and producing soluble factors, which directly or indirectly counteract the HIV-1 replicative cycle. In future, this approach could be combined, in human efficacy testing, with other immunogens that stimulate humoral responses, with the goal of effectively preventing HIV-1 infections.

The central principle of our strategy is to focus T-cell immune responses on the most conserved regions of the HIV-1 proteome. These regions are common to most variants and, if mutated, reduce the ability of the virus to grow(5); these regions are the “Achilles heel” of HIV-1. Targeting of conserved regions is further enhanced by using ‘mosaic’ proteins, which are designed by computer to maximize the match of the vaccine with global HIV-1 variants and to block common ways the HIV-1 changes to escape the immune response. Vaccines should match circulating HIV-1 variants as much as possible to stop them efficiently. When T cells attack conserved parts of HIV-1 proteins (parts that seldom or never change), the disease is better controlled—this vaccine includes those parts. The HIV-1-derived mosaic genes are called tHIVconsvX and are delivered by two safe, non-replicating vaccine vectors derived from chimpanzee adenovirus and poxvirus modified vaccinia virus Ankara (MVA). Adenoviruses, if able to grow, normally cause respiratory and gastrointestinal ailments, while the unmodified chimpanzee adenovirus is not known to cause disease in humans; the engineered vaccine vector called ChAdOx1 is crippled so it cannot grow. ChAdOx1 and similar experimental vaccines have been shown to be safe in over 1,500 human volunteers(6–8). MVA is a poxvirus, which does not replicate in humans. It was used safely as the smallpox vaccine in over 120,000 people at the end of the smallpox-eradication campaign and as an experimental vaccine vector against a variety of diseases in many clinical trials(9).

Humans and microbiota, which consist of bacteria, fungi, viruses and eukaryotic species, have co-evolved over millions of years and their coexistence is beneficial to both parties. Human immune system is constitutively exposed to microbial stimulation and any vaccine design and responsiveness needs to be considered in the context of host-microbiota interactions. Manipulation of the microbiota functions and composition through diet, engraftment and/or any other means may thus become a viable strategy for improving vaccine responsiveness as well as treating malfunctions of the immune system (10). The first reports on the influence of gut microbiota diversity and composition on responses to vaccination have
HIV-CORE 006 version 2.0 2nd January 2020 CONFIDENTIAL been emerging for some time (11–15). As part of the exploratory endpoints for this trial, we shall characterize the gut microbiome of study volunteers for composition and richness before and after administration of the study vaccines.

The ChAdOx1-vectored HIV-1 vaccine in this trial will be tested for the first time in humans, and MVA.tHIVconsv3 and MVA.tHIVconsv4 are currently administered to HIV-positive individuals in the first-in-human clinical trial in the USA (NCT03844386). However, this is the first time these C1-M3M4 vaccines will be administered to humans sequentially. In parallel with HIV-CORE 006, these vaccines will be tested for safety in the United Kingdom, in a phase I trial HIV-CORE 0052. The tHIVconsvX vaccines have been designed for global use irrespective of the HIV-1 strain and are therefore very suitable for Africa, where multiple strains are responsible for the epidemic, mainly from the HIV-1 families A, D and C. The HIV-CORE 006 trial will take place at four sites in Africa and will enroll healthy adults between 18 and 50 years of age. We do not yet know whether the vaccine will have a beneficial effect, no effect, or whether it could cause harm. The health of trial volunteers will be monitored carefully, and volunteers will receive counselling and support to minimize HIV-1 infection. Prior to the trial, consultations with policy makers, healthcare service providers and community leaders will take place to understand and address the obstacles and unmet demand for HIV services and healthcare services and to determine the appropriate level of baseline HIV-1-preventive services.