An experimental vaccine for chikungunya virus has been developed by scientists who have successfully tested it in monkeys.
The vaccine, developed by at the National Institute of Allergy and Infectious Diseases, the University of Texas Medical Branch at Galveston, Purdue University and Bioqual Inc, is composed of non-infectious "virus-like particles."
Although coated with the same proteins that enable chikungunya to pass through cell membranes, the vaccine particles lack the proteins that chikungunya uses to replicate inside cells.
They look like chikungunya to the immune systems of rhesus macaques, however, which respond to exposure by generating antibodies that defend the monkeys from infection by the real virus.
"This vaccine did an excellent job of protecting the macaques from chikungunya," said UTMB professor Stephen Higgs, one of the paper's authors.
"That it worked so well in a primate model is good news - these macaques are quite similar to humans in their response to chikungunya, and we badly need to develop an effective human vaccine for this virus," he added.
To create the virus-like particles used in the experimental vaccine, the researchers used genetic engineering techniques to produce the structural proteins that produce the spiky, roughly spherical exterior possessed by chikungunya viruses before they have entered a cell.
The proteins then assembled themselves into harmless balls that resembled particles of Sindbis virus - a relative of chikungunya and a fellow member of the alphavirus genus, which also includes a number of insect-borne viruses capable of causing dangerous encephalitis in humans.
Serum drawn from rhesus macaques injected with the virus-like particles contained substantial levels of antibodies that inactivated chikungunya virus. Two groups of macaques were then inoculated, either with virus-like particles or with a sham solution containing no vaccine.
When the researchers challenged the monkeys by injection with chikungunya 15 weeks later, they found that the vaccine had completely protected the animals from the virus.
The research has been described in the March issue of Nature Medicine.