Is a small artificial virus fragment the key to a Chikungunya vaccine?

Chikungunya virus Chikungunya virus (CHIKV) is transmitted by Aedes mosquitoes and causes Chikungunya fever. CHIKV occurs in the tropical and subtropical parts of the world. Regions where it has already caused epidemics include Africa, territories around the Indian Ocean, Southeast Asia, and meanwhile also the Caribbean, Central America, and South America. Around 1.2 million people are estimated to be infected so far during an epidemic in America. Since the Aedes albopictus mosquito, also known as Asian tiger mosquito, has now reached southern Europe and the USA, we are faced with further spreading of the virus.

Chikungunya fever is characterized by fever and severe joint pain, hence its name, which means “that which bends up”. In 30 to 40 percent of the cases, these joint pains can last several months or even up to several years. Attempts at developing suitable vaccines have up to now been unsuccessful. To develop an effective vaccine, it is nessecary to identify a suitable antigen structure of the virus which will create an effective immune response in humans. Previous approaches have used the entire E2 surface protein as a basis for the vaccine, partly in combination with other virus proteins. These proteins, however, have a relatively large structure, which would make commercial vaccine production difficult.

A new paper investigates whether smaller more specific and less complex parts of E2 would suffice for generating a protective immune response. Based on the three-dimensional structure of the protein, researchers selected different areas exposed on the surface to joined them together, creating several artificial protein fragments. After production in E. coli and purification, mice were immunized with these protein fragments, and their blood was examined for neutralizing antibodies later on. In this experiment, one fragment, described as sAB+, proved to be the most effective one to induce neutralizing antibodies. It was used to immunize mice which were then infected by the wild-type Chikungunya virus. Compared with non-vaccinated animals, the mice treated showed significantly less virus RNA in the blood – a sign of partial immune protection.

A Small Antigenic Determinant of the Chikungunya Virus E2 Protein Is Sufficient to Induce Neutralizing Antibodies which Are Partially Protective in Mice. (2015) PLoS Negl Trop Dis 9(4): e0003684. doi:10.1371/journal.pntd.0003684

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