It beat smallpox. So now what else can it do?

Genetically altered, the anti-smallpox virus vaccinia can fight many other diseases, writes Bernard Dixon

Is smallpox vaccine due for a comeback? It may seem perverse to ask such a question in 1996. This is the 200th anniversary of Edward Jenner's successful vaccination of young James Phipps, which led to the widespread adoption of Jenner's method of preventing smallpox by infecting people with the related cowpox virus (vaccinia). Two centuries later, having eradicated smallpox using Jenner's technique, the World Health Organisation has announced that the two remaining laboratory stocks of the virus are to be destroyed.

With smallpox gone, there might seem to be little further use for vaccinia. But many other viruses continue to cause disease and death on a vast scale throughout the world. And one means of combating them may be to use genetically altered forms of vaccinia.

One expert who believes so is Enzo Paoletti. More than 10 years ago he discovered how to insert genes from other microbes into the DNA of vaccinia. In principle, if such an inserted gene normally produces a particular protein in the donor microbe, then it could do so in the cells of its new host too. And if that protein, in its original place, induced an infected animal to produce antibodies, the augmented vaccinia virus might do the same thing.

It worked. Scientists have since engineered several such "recombinant vaccines". One is a version of vaccinia designed to provoke immunity against rabies when taken by mouth. It has been distributed in several parts of Western Europe, injected into chicken heads left to be eaten by wild foxes, which can carry rabies. Many foxes took the bait and the disease is virtually extinct in Belgium.

Although such vaccines appear to be safe, scientists remain cautious about the prospects of using similar ones in humans, or in animals in contact with humans. First, the procedure is not trouble-free. At the injection site, vaccinia can cause unpleasant reactions, which are likely to be severe in individuals whose immune systems are impaired - by Aids, for example, or by drugs given to prevent the rejection of transplanted organs. Second, it is theoretically possible that a genetically altered vaccinia virus could pass from humans to wildlife, or interact with related viruses, with uncertain consequences.

Paoletti believes that an alternative approach may prove more acceptable and equally effective: to use viruses that have the advantages of the first generation of recombinant vaccines, but none of their disadvantages. Several are being developed which have virtually no side-effects, provoke immunity and, like conventional vaccinia, are "live"; they do not reproduce (or do so poorly) in recipients' cells and so cannot spread to other animals.

As a basis for one range of vaccines, Paoletti and colleagues have removed several regions of DNA from vaccinia that it require to multiply harmfully. Known as NYVAC, the resulting virus retains the capacity to grow normally in chick embryo cells, yet can scarcely grow at all in human and other animal cells. NYVAC does not produce inflammation at the injection site, and has negligible ill-effects, even in mice whose immune systems have been compromised. When researchers incorporated into NYVAC relevant genes taken from Japanese encephalitis virus and equine influenza virus, the resulting vaccines protected pigs and horses respectively against these infections.

Another strategy, pioneered by the Virogenetics Corporation, focuses on vaccinia-related viruses that normally infect birds. These too can be genetically altered so that they immunise various mammals against other microbes, even though the viruses do not multiply in mammalian cells. A modified canarypox virus, for example, has protected dogs and cats experimentally against rabies.

A recently recognised use for recombinant poxviruses is in cancer treatment. Many types of tumour cell have on their surface antigens - proteins characteristic of those tumours - which can induce the body to make antibodies. Unfortunately, the response of the immune system to such antigens is normally weak or non-existent. However, a poxvirus carrying not only a tumour antigen but also a cytokine (a natural substance that heightens the immune response) might provoke the production of sufficient antibody to attack a patient's tumour.

Start your day with The Independent, sign up for daily news emails
PROMOTED VIDEO
ebooks
ebooksA special investigation by Andy McSmith
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Tradewind Recruitment: English Teacher

Negotiable: Tradewind Recruitment: My client is an excellent, large partially ...

Tradewind Recruitment: Science Teacher

£90 - £140 per day: Tradewind Recruitment: I am currently working in partnersh...

Tradewind Recruitment: Year 3 Primary Teacher

£100 - £150 per day: Tradewind Recruitment: Year 3 Teacher Birmingham Jan 2015...

Ashdown Group: Lead Web Developer (ASP.NET, C#) - City of London

£45000 - £50000 per annum + Excellent benefits: Ashdown Group: Lead Web Develo...

Day In a Page

Isis hostage crisis: The prisoner swap has only one purpose for the militants - recognition its Islamic State exists and that foreign nations acknowledge its power

Isis hostage crisis

The prisoner swap has only one purpose for the militants - recognition its Islamic State exists and that foreign nations acknowledge its power, says Robert Fisk
Missing salvage expert who found $50m of sunken treasure before disappearing, tracked down at last

The runaway buccaneers and the ship full of gold

Salvage expert Tommy Thompson found sunken treasure worth millions. Then he vanished... until now
Homeless Veterans appeal: ‘If you’re hard on the world you are hard on yourself’

Homeless Veterans appeal: ‘If you’re hard on the world you are hard on yourself’

Maverick artist Grayson Perry backs our campaign
Assisted Dying Bill: I want to be able to decide about my own death - I want to have control of my life

Assisted Dying Bill: 'I want control of my life'

This week the Assisted Dying Bill is debated in the Lords. Virginia Ironside, who has already made plans for her own self-deliverance, argues that it's time we allowed people a humane, compassionate death
Move over, kale - cabbage is the new rising star

Cabbage is king again

Sophie Morris banishes thoughts of soggy school dinners and turns over a new leaf
11 best winter skin treats

Give your moisturiser a helping hand: 11 best winter skin treats

Get an extra boost of nourishment from one of these hard-working products
Paul Scholes column: The more Jose Mourinho attempts to influence match officials, the more they are likely to ignore him

Paul Scholes column

The more Jose Mourinho attempts to influence match officials, the more they are likely to ignore him
Frank Warren column: No cigar, but pots of money: here come the Cubans

Frank Warren's Ringside

No cigar, but pots of money: here come the Cubans
Isis hostage crisis: Militant group stands strong as its numerous enemies fail to find a common plan to defeat it

Isis stands strong as its numerous enemies fail to find a common plan to defeat it

The jihadis are being squeezed militarily and economically, but there is no sign of an implosion, says Patrick Cockburn
Virtual reality thrusts viewers into the frontline of global events - and puts film-goers at the heart of the action

Virtual reality: Seeing is believing

Virtual reality thrusts viewers into the frontline of global events - and puts film-goers at the heart of the action
Homeless Veterans appeal: MP says Coalition ‘not doing enough’

Homeless Veterans appeal

MP says Coalition ‘not doing enough’ to help
Larry David, Steve Coogan and other comedians share stories of depression in new documentary

Comedians share stories of depression

The director of the new documentary, Kevin Pollak, tells Jessica Barrett how he got them to talk
Has The Archers lost the plot with it's spicy storylines?

Has The Archers lost the plot?

A growing number of listeners are voicing their discontent over the rural soap's spicy storylines; so loudly that even the BBC's director-general seems worried, says Simon Kelner
English Heritage adds 14 post-war office buildings to its protected lists

14 office buildings added to protected lists

Christopher Beanland explores the underrated appeal of these palaces of pen-pushing
Human skull discovery in Israel proves humans lived side-by-side with Neanderthals

Human skull discovery in Israel proves humans lived side-by-side with Neanderthals

Scientists unearthed the cranial fragments from Manot Cave in West Galilee