07 December 2009
ByAppeared in BioNews 537
In the future children could be given 'personalised' vaccine shots if they are found to be in the genetic minority of people who don't benefit fully from standard forms of a vaccine. Not everyone produces the same amount of disease specific antibodies in response to a vaccine, meaning that a vaccination will not protect some people when they later come into contact with that disease. However, scientists from the National Institute for Occupational Safety and Health (NIOSH), Morgantown, West Virginia, US, have recently discovered specific gene variants that appear to predict whether someone will produce enough antibodies to benefit from the standard vaccine. If an individual is found likely to have an abnormally weak vaccine response then they could be given an alternative immunisation, such as higher doses of the standard vaccine or a modified version that is tailored to their needs. The American scientists published their findings in the journal Vaccine.
When someone is vaccinated they are exposed to an inert, deactivated form of some disease agent, and the immune system responds by producing antibodies - special proteins that are used to help identify and neutralise foreign objects in the bloodstream such as bacteria and viruses. If the vaccinated person is later exposed to the same disease their immune system has a head-start in winning the battle as the antibodies already exist and can bind to the real disease causing agent, thereby acting as a 'marker' and stimulating other immune processes that either remove or destroy the pathogen.
The problem with the current system lies with the fact that everyone gets given the same doses of the same vaccines, and not everyone produces enough antibodies from this standardised immunisation for it to be beneficial. It is estimated that between five and 20 per cent of people vaccinated against hepatitis B, and between two and 10 per cent of those vaccinated against measles, would not be protected should they ever encounter those viruses. Although a number of factors may affect whether a vaccine is successful, it is clear that genetics plays some role and that is what prompted Berran Yucesoy, from the NIOSH, to investigate the problem.
Yucesoy, and her team, focused on genes that code for cell-signalling molecules, called cytokines, that are known to help produce antibodies and recruit other cells that fight infection. They analysed the DNA from 141 healthy babies between the ages of 11.5 and 14 months looking for variations in 11 particular cytokine genes. Next they administered routine vaccines for hepatitis B and pneumococcus, as well as a standard diphtheria-tetanus-whooping cough combination vaccine, then recorded the level of antibodies in the blood. After further analysis Yucesoy found that infants who produced low levels of antibodies were more likely to have certain single-letter variations in seven of the cytokine genes studied.
The next step will be to confirm the findings in a larger sample of infants. But if the findings are duplicated then it may lead to children being routinely screened for these genetic variants before vaccination. If an infant had some of the variants then they could be administered higher doses of the standard vaccine, a special vaccine with added immune stimulants, or even one that contained the missing cytokines.