Evaluation of Immunological Efficiency Among Patients Vaccinated Against Tick-Borne Encephalitis

Abstract

Tick-borne encephalitis virus (TBEV) widespread in the Eurasian continent is a member of the genus Flavivirus, family Flaviviridae. Human TBE cases are registered in more than 30 countries of the world [Charrel RN et al., 2004]. TBEV is subdivided into three main subtypes according to its genetic structure and antigen specificity: European, Siberian, and Far Eastern ones [Holzmann H, et al.1992; Ecker M. et al. 1999]. Differences in nucleotide sequences of TBEV genome of these subtypes may reach about 20% [Loktev VB et al. 2007]. Probably, a high TBEV genetic diversity provides its differences in human pathogenicity. Human pathogenicity of European subtype TBEV is less marked; however, towards the east, a severity of infection increases as well as lethality [Loktev VB et al. 2007; Pogodina VV et al. 2007]. In the Russian Far East, the lethality caused by this infection remains at the highest levels [Pavlenko et al. 2010]; for the last 40 years it has reached, on average, 17,5% [Leonova et al., 2006; Leonova, 2009]. A vaccination is known to provide the most reliable and effective protection from many virus infections. Tick-borne encephalitis (TBE) as a very danger infection for humans is not the exception as well. Practical application of different vaccines against tick-borne diseases shows that vaccination of the population is a key link in terms of mass TBE prevention in highly endemic territories [Kunz C., 2003; Onishchenko G.G., et al. 2007]. Tick-borne encephalitis is considered to be the international health issue, because the number of risk areas and reported cases across Europe, Russia, and parts of Asia is increasing. The incidence of TBE has fluctuated considerably from year to year in many countries, but in the past decade the number of TBE cases has significantly increased in the Baltic states, the Czech Republic, and Germany, in addition to the countries previously considered to be free from TBE, such as Denmark (specifically the main island of Zealand), France, and Italy. A number of factors have been suggested to explain the growth of incidence including climate changes, extended travelling, and outdoor pursuits increasingly placing people in contact with infected ticks [Eckhardt Petri et al., 2010]. Development of vaccine against TBE has started since the discovery of causative agent in 1937. A group of discoverers, headed by already well known virologist prof. L.A. Zilber, understood that only vaccine can become a reliable protection from this dangerous disease.