London vaccine trial seeks volunteers

This article is more than 23 years old.

120 HIV negative "low risk" volunteers are now being sought for preventive vaccine trials at two centres in London and Oxford.

The Clinical Trials Centre at St Mary's Hospital, Paddington, London, has joined with the MRC Human Immunology Unit in Oxford to launch a new trial (ICOX-PB001) which begins this month. This extends trials that have already begun in Oxford and Nairobi on a promising approach to AIDS vaccines, designed for final testing and possible use in Africa. The aim is to help evaluate candidate vaccines developed through an international partnership between the University of Nairobi, the UK's Medical Research Council and the International AIDS Vaccine Initiative (IAVI), which has previously been reported by aidsmap.

The latest trials are needed to gain more safety information and to "fine-tune" dosages and schedules, to get the best immune response possible with a prime-boost DNA and MVA vaccine strategy. Some volunteers, chosen at random, will receive placebos (inactive vaccines).

Glossary

deoxyribonucleic acid (DNA)

The material in the nucleus of a cell where genetic information is stored.

phase I

The first stage of human testing of a new drug or intervention, typically involving a small number (10-100) of participants who do not have the condition the drug is intended to treat. Phase I clinical trials evaluate safety, side-effects, dosage and how a drug is metabolised and excreted in the body.

unprotected anal intercourse (UAI)

In relation to sex, a term previously used to describe sex without condoms. However, we now know that protection from HIV can be achieved by taking PrEP or the HIV-positive partner having an undetectable viral load, without condoms being required. The term has fallen out of favour due to its ambiguity.

strain

A variant characterised by a specific genotype.

 

T killer cell

A type of immune cell that can kill certain cells, including foreign cells, cancer cells, and cells infected with a virus. A T killer cell is a type of white blood cell and a type of lymphocyte. Also called cytotoxic T cell, cytotoxic T lymphocyte or CD8 T cells. 

Volunteers will need to be able to attend the clinic on 12 occasions over 52 weeks. The first screening visit will take an hour. Four of these visits, when injections are given, will each last between two and three hours (at the most), but the remaining seven visits should take only half an hour. A number of blood samples will be taken through the trial, and tests including HIV antibody tests and (for women volunteers) pregnancy tests will be done. The timing of visits is important, so people will need to check that they are available for each planned visit before starting the trial. The costs of travel and time will be reimbursed, up to a total of £300 for the whole study (less if people do not complete all the visits).

Inclusion criteria for this trial differ slightly from those previously used in Oxford, although this is still a Phase I trial. It is important for individuals and for the project that people who are at any significant HIV risk do not volunteer for this trial. Nonetheless, the criteria used to define "low risk" are commonsense ones, rather than the precautionary criteria used, for example, by the National Blood Service for England and Wales.

Thus, volunteers who were born and have lived in Africa would be welcome; so would low risk lesbian and gay volunteers. The main criteria for low risk are:

  • No current high risk partner, e.g. one known to be HIV positive
  • No unprotected anal intercourse within the last 6 months
  • No unprotected vaginal intercourse outside of a monogamous relationship with a known/presumed HIV negative partner within the last 6 months.
  • No injecting drug use within the last ten years.

Pregnant women will be excluded from this trial because the effect of the vaccines on an unborn child is unknown. However, it is really important that the vaccine is tested on women as well as men.

It is stressed that volunteers should not assume any level of protection against HIV from these trial vaccines. As previously mentioned, some volunteers will receive placebos (inactive vaccines) in a randomised, double-blind design (so neither the trial staff nor the volunteers know who receives what until after the trial).

The vaccine designer, Dr Tomas Hanke, expects this to be only one component of a future vaccine going into full-scale trials, that delivers a greater range of HIV-related genes. The vaccine design is based on Subtype A strains of HIV circulating in Africa, not those which are commonest in the UK. The only way to find out if these vaccines are protective will be through large-scale (Phase III) trials in populations at high risk, ideally where matching viruses are circulating.

Nonetheless, the vaccine system - using carefully designed DNA grown in and extracted from bacteria to prime a response from a modified smallpox vaccine (MVA) which contains the same HIV-related DNA vaccine sequences - is seen as one of the most promising ways to get immunity against HIV based on killer T-cells. Animal studies with HIV-related viruses suggest that such responses can change the course of disease in those animals exposed to HIV-related viruses after vaccination.

It is not expected that anyone will test positive for HIV antibodies on standard tests as a result of receiving these vaccines. There are good theoretical reasons why this shouldn’t happen. However, in the unlikely event that it does happen, other tests can easily distinguish the effects of the vaccine from antibodies in response to HIV infection, and the trial staff will provide documents to explain the situation to anyone who needs to know.

Contacts: for more information on the London trial, call free (UK only) on 0800 587 4406 and talk to Ken Legg (study coordinator), Miranda Cowen (study nurse) or Dr Nicky Mackie (study doctor). For independent information, volunteers are invited to call the National AIDS Trust on 020 7814 6767.

Related aidsmap coverage:

First results from Oxford-Nairobi vaccine trials

Recombinant vectored vaccines

DNA vaccines and replicons