Washington: In a breakthrough, scientists have developed a new vaccine candidate to provide protection from the mosquito-borne viral illness chikungunya.
The experimental vaccine elicited neutralising antibodies in all 25 adult volunteers who participated in a recent early-stage clinical trial conducted by researchers at the National Institute of Allergy and Infectious Diseases (NIAID).
The most distinctive symptom of chikungunya infection is severe joint pain accompanied by headache and fever. There are currently no vaccines or specific drug treatments for chikungunya.
In 2010, Vaccine Research Centre (VRC) scientists and colleagues tested this candidate chikungunya vaccine in non-human primates.
All of the immunised animals were protected from infection when later exposed to chikungunya virus.
In the newly reported trial, 23 healthy volunteers received three injections (two other volunteers received two injections) of vaccine at one of three different dosages (10, 20 or 40 microgrammes) over a 20-week span.
Antibody production was measured at multiple time points following each injection.
Investigators detected chikungunya neutralizing antibodies in all volunteers following the second injection, with a significant boost of neutralising antibodies seen following the third injection.
Vaccine-induced antibodies persisted in all volunteers, even those who received the lowest dosage, for at least 11 months after the final vaccination, suggesting that the vaccine could provide durable protection against disease.
"The candidate vaccine prompted a robust immunological response in recipients and was very well tolerated," noted VRC scientist Julie E Ledgerwood, principal investigator of the trial.
"Notably, the levels of neutralising antibody produced in response to the experimental vaccine were comparable to those seen in two patients who had recovered from a chikungunya virus infection acquired elsewhere.
"This observation gives us additional confidence that this vaccine would provide as much protection as natural infection," Ledgerwood said.
Whereas traditional vaccines are typically made from either killed viruses or from weakened live viruses, the experimental vaccine used in the trial is a different type: a virus-like particle (VLP) vaccine.
VLP vaccines contain the outer shell proteins of a virus without any of the material the virus needs to replicate inside cells.
The finding was published in The Lancet journal.
