The influence of cytomegalovirus infection on the immune response to the measles vaccine

In the developed world, infection with a virus called Cytomegalovirus (CMV) which sets up a lifelong infection in humans is linked with ageing of the immune system which may prevent people from responding properly to vaccines given to the elderly (such as influenza vaccine). Much less is known about the long-term effects of CMV infection in the developing world, where it most commonly occurs in babies and young children. This study will investigate if children infected with CMV respond less well to measles virus vaccination than children without the virus.

Studies in industrialised countries have indicated that cytomegalovirus (CMV) drives the immune system into a senescent state, as subclinical CMV infection is associated with large numbers of T cells that are unable to respond to other infections. Our previous studies in The Gambia have shown that CMV infection occurs much earlier than in industrialised countries, usually within the first six months of life, and is associated with an abundance of highly differentiated T cells similar to those reported in senior citizens in North America and Europe. The studies on senior citizens have associated the presence of these clones with vaccine failure and imminent mortality, but their significance when present in infants has not been studied.We postulate that subclinical infection with CMV in early life may affect the ability of the immune system to respond to subsequent infections or vaccinations. In order to test the hypothesis, we intend to assess whether infection with cytomegalovirus affects the immune response to the measles vaccine in 150 children who are enrolled in the Sukuta birth cohort. We will compare the immune response to measles vaccine among those with and without CMV infection at the time of vaccination.