Hexon-chimaeric adenovirus serotype 5 vectors circumvent pre-existing anti-vector immunity

Adenovirus 5 (Ad5) causes mild respiratory tract infections in humans but its main claim to fame is as a potential vaccine vector for key diseases such as HIV/AIDS and malaria. Its potential clinical utility is, however, hampered by the fact that about half of the population in developed countries and 90% in Africa have been exposed to Ad5 before and have built up immunity. A team based at Harvard Medical School and the Dutch biotechnology company Crucell has devised a way of circumventing this problem by replacing parts of an Ad5 viral capsid protein with those from a related virus, the much rarer Ad48 adenovirus. The strategy was effective in tests in mice and monkeys; if the work can be repeated in humans then modified Ad5 will be a strong candidate as a vector for vaccines and also for delivering gene therapy.