With pathogen-carrying ticks expanding their territories in many parts of the world, researchers have likewise expanded vaccine research to two typically rare pathogens with potential for public health importance.
Kyasanur Forest disease virus (KFDV) is an endemic arbovirus in western India. KFDV causes Kyasanur Forest disease (KFD), a syndrome including fever, gastrointestinal symptoms, and hemorrhages. There are no approved treatments, and the only vaccine licensed in India requires multiple doses, elicits a short duration of protection, and has questionable efficacy.
In a new study, researchers describe how they used genetically engineered vesicular stomatitis virus (VSV) as the platform to develop a single-dose KFD vaccine that was safe and protective in mice and non-human primates, and is ready for clinical trials.
The scientists also showed that the same vaccine, known as VSV-KFDV, generated cross-neutralizing immune responses against Alkhurma hemorrhagic fever (AHF), another rare flavivirus endemic to Saudi Arabia.
Both viruses are hemorrhagic fever viruses mainly spread by ticks, and can cause internal and external bleeding, organ failure, brain inflammation and death.
VSV, an animal virus that primarily affects cattle, was used to create the world’s first approved vaccine against Ebola virus. VSV now has been successfully tested as an experimental vaccine platform that has generated protective immunity against more than a dozen different viral infectious diseases. Scientists use VSV to deliver targeted proteins from a viral pathogen of interest – such as KFD virus – to a host. The host then generates an immune response that provides protection should the host be infected with that viral pathogen.
KFD virus was first identified in 1957 from a sick monkey in the Kyasanur Forest in India, according to the CDC. Since then, about 500 human cases have been reported each year, with fatality rates ranging from 3% to 5%. KFD has historically been limited to a specific part of India, but KFD virus has now expanded to new parts of India.
Alkhurma hemorrhagic fever virus was discovered in 1995 in a patient with bleeding and fever after slaughtering a sheep in Saudi Arabia, according to the World Health Organization. Little is known about the virus; a study published in 2022 states that 604 cases were reported in Saudi Arabia from 1995 to 2020.
Source: National Institute of Allergy and Infectious Diseases
Single-dose VSV-based vaccine protects against Kyasanur Forest disease in nonhuman primates. Science Advances, 6 Sep 2023.