BLACKHERBALS.COM
Measles Vaccine Proposed for
Global AIDS Protection
Julian Meldrum
September 02, 2004
In two separate presentations at the AIDS Vaccine 04 meeting in Lausanne,
Dr Frederic Tangy from the ANRS in Paris advocated the use of a licensed
live attenuated measles vaccine – the very same one used in the MMR
system given to millions of children – as a vehicle to deliver an HIV
vaccine for future generations.
The proposal marked a welcome shift in the direction of serious
consideration of how to make future HIV vaccines available to infants
and adolescents – especially girls - who are, in many countries, the
populations most desperately in need of protection against the epidemic.
A Swiss company, Berna Biotech, has already made prototypes based on a
live measles vaccine with HIV genes inserted, and a progress report on
this work was also presented.
The vision would be that a child would be vaccinated from before the age
of one and boosted at around the age of 10 to achieve a level of
immunity that could and should last until adulthood. Adults with
pre-existing immunity to measles – or at least those who have been
previously vaccinated – could either receive repeated doses of
measles-based vaccine or a prime-boost using measles with another
vector, both containing HIV-related sequences.
The arguments put forward in support of this strategy include the
excellent safety record of this live vaccine, its remarkable ability to
offer long-term and boostable protection against disease, and that
large-scale manufacturing facilities in several countries produce tens
of millions of doses at extremely low cost. By inserting HIV-related
sequences in one or more of three distinct locations in the vaccine
strain, immunity to HIV could be induced in addition to protection
against measles at no extra cost.
There are, however, one or two problems identified in the course of the
meeting.
The first difficulty is that no-one knows precisely what components of
HIV, and in what form, should be included in such a vaccine. The very
long-acting effect of the measles vaccine could itself generate serious
problems, if the wrong elements were added to it. At worst, children
vaccinated in infancy might have inappropriate immune responses and
would be unable to benefit as adolescents from a better vaccine that
might by then be available to them.
The second problem is that the idea of using an established vaccine in
this way would need to be discussed and agreed with stakeholders who are
not currently involved in the AIDS vaccine effort and were not
represented at the meeting in Lausanne. Given that millions of children
in developing countries are still dying each year from measles, nothing
should be done that could in any way undermine public confidence in the
vaccine programme.
Measles is far from being eradicated, and mass vaccination with the live
vaccine is therefore likely to continue for decades to come. However,
the same is hopefully not the case for polio.
Some researchers would like to include HIV antigens in a version of the
currently licensed live Sabin polio vaccine.They point to animal studies
in which polio-vectored SIV components have been one of the very few
systems shown to protect monkeys against some particularly virulent
forms of SIV. The only comparable protection has been achieved with live
attenuated forms of SIV itself, which is unacceptable as a prototype for
HIV in the light of evidence that such viruses do, eventually, cause SIV-related
disease.
This proposal flies in the face of moves in countries such as the UK to
abandon live polio vaccine in favour of less potent but non-replicating
vaccines given by injection. If the politics and other circumstances of
the last refuges of the virus in Africa and Asia allow polio to be
eradicated, will anyone really want to continue to use live polio
vaccines? Those vaccines can – at a rate of less than one in a million
– revert to forms that cause damage to the nervous system. It is
claimed that with “high fidelity” variants of a key enzyme, this
risk can be reduced. But since the only way to prove this would be
through giving the vaccine to millions of people, will anyone ever be
prepared to make the experiment, at the risk of re-introducing polio in
a world where immunity to the disease would be waning fast?
References
Andino R. Polio vector – another strategy with a pediatric vaccine.
AIDS Vaccine 04, Lausanne, Abstract 76b.
Lorin C et al. Measles vaccine as a potential vector for AIDS
vaccination. AIDS Vaccine 04, Lausanne, Abstract 13.
Tangy F. Viral vectors overview. AIDS Vaccine 04, Lausanne,
Abstract 74.
Zuniga A et al. Live attenuated measles virus: a candidate vector for
HIV vaccine. AIDS Vaccine 04, Lausanne, Abstract 12.
