Heterogeneity in virus populations and immunosuppression of the host could cause tick-borne encephalitis virus vaccine failures. These are the results of a study recently published in Microorganism by the Karganova group, the TBFVnet partner from Moscow.
The only vaccine currently available to prevent tick-borne diseases is for tick-borne encephalitis virus (TBEV). However, some cases have been reported in which this vaccine failed to induce effective immunity against the disease. The research group led by prof. Karganova, the TBFVnet partner from the Chumakov FSC R&D IBP RAS in Moscow, recently investigated the reasons for this problem. According to their results, TBEV vaccine failures are explained by two factors: virus heterogeneity and immunosuppression of the host.
Vaccine failures occur when people who are completely vaccinated become infected and develop diseases symptoms. Few cases have been reported for TBE vaccinated people. Usually, these are characterized by a mild clinical course, but in some cases, the effects are severe or even lethal. Investigating the causes of these failures is pivotal to enhance vaccine effectiveness and moreover, can give insight into the mechanisms of virus and host interactions.
The study has revealed two main reasons on the basis of vaccine failures: heterogeneity of virus population and host immunosuppression. TBE virus populations are not uniform within a given geographic region and show some structural differences. The more different the virus particles are within a population, the more difficult it will be for the immune system to react to new infections. These differences, in fact, could mislead the immune system and cause failure in protecting the organism. Moreover, if the host immune system is even slightly depressed before vaccination this could impair proper immunity against the virus.
The results of the study could lead to the development of more effective vaccines against TBEV. Moreover, this evidence could help in the future production of effective vaccines for other tick-borne flaviviruses. The research article has been published in Microorganisms in May 2021.
