Vaccine for rare but deadly mosquito-borne viruses in clinical trial

Positive results for a vaccine for eastern equine encephalitis virus (EEEV), western equine encephalitis virus (WEEV), and Venezuelan equine encephalitis virus (VEEV) have been published in The Lancet Infectious Diseases. The vaccine was shown to be safe, and well-tolerated in a Phase I clinical trial, and to induce a neutralising antibody response in adult volunteers.

The vaccine candidate was developed by scientists at the National Institute of Allergy and Infectious Diseases (NIAID) Vaccine Research Centre (VRC), part of the National Institutes of Health (NIH).

For the Phase I clinical trial, 30 healthy adult volunteers, aged between 18 to 50 years, received varying doses of the vaccine via intramuscular injection. Participants then returned to receive the same dose as a boost eight weeks later. NIAID sponsored and funded the clinical trial, which was conducted at the Emory Vaccine Centre’s Hope Clinic, part of the Emory University in Atlanta.

EEEV, WEEV and VEEV are spread to humans through the bites of infected mosquitos. Infections are rare, but can lead to flu-like symptoms, and in some cases severe neurological damage, or death.

The viruses have caused recurrent, small outbreaks in North, Central, and South America. In 2019, an EEEV outbreak occurred in the north-eastern US, which led to 38 confirmed cases, and 15 deaths.

In the past, NIAID Director Anthony S Fauci, MD, and others, have emphasised the possible utility of an EEEV vaccine for those at high occupational risk of contracting the disease. Building on the successful development of a vaccine for chikungunya virus, VRC researchers designed a virus-like particle (VLP) vaccine candidate that uses proteins from the outer shells of the EEE, WEE and VEE viruses to prompt an immune response.

VLPs do not contain the genetic material that the viruses need to replicate inside cells, so VLPs cannot cause infection.

Ana Ovey