The role of neighborhood relations in maintenance of the spatial-ethological structure of local settlements as exemplified by the water vole (Arvicola amphibius).

Adult males of the water vole have been found experimentally to recognize their neighbors and react to them differently depending on the degree of spatial proximity in nature. Most tensions (estimated by the number of aggressive acts in the encounters) were observed between distant neighbors (from neighboring settlements), which did not belong to the same groups with established hierarchy and a relatively reduced aggression. These are probably perceived as the most likely competitors (because of their spatial proximity). At the same time, male voles kept away from the obviously unfamiliar ones, though they do not express any apparent aggression.

Dynamics of testosterone concentration in male steppe lemmings (Lagurus lagurus) in the reproductive cycle reflects the species-specific mating system.

In the blood of male steppe lemmings, relatively low background levels of testosterone were detected, this is characteristic of a monogamous species. A significant increase in testosterone level, more expressed in sexually active males, was observed at the initial stage of formation of reproductive couples. Apparently, in the future, the couple will exist in a stable relationship, and, hence, the maintenance of a high testosterone level becomes excessive. The decrease in, and the relative "normalization" of, the hormone level during the existence of the pair, including raising of the young, promotes higher expression of the male paternal care of the offspring at the species level.

Evaluation of immune response and protective effect of four vaccines against the tick-borne encephalitis virus.

Among three main subtypes of the tick-borne encephalitis virus (TBEV), the Siberian subtype is currently dominant in a majority of the endemic regions of Russia. However, inactivated vaccines are based on TBEV strains of the heterologous Far Eastern or the European subtypes isolated 40-77 years ago. To analyze the efficacy of the available vaccines against currently prevailing TBEV isolates of the Siberian subtype, mice were immunized subcutaneously three times (one group per each vaccine). The expression of seven cytokine genes was determined using RT-PCR. Sera were studied using homologous and heterologous ELISA, hemagglutination inhibition (HI) and neutralization tests with TBEV strains of the Far Eastern, Siberian and European subtypes. Cross-protective efficacy of the vaccines was evaluated with the TBEV strain 2689 of Siberian subtype isolated from an ixodid tick from the Novosibirsk, South-Western Siberia, Russia in 2010. The cytokine gene expression profile indicates a predominantly Th2 response due to exogenous antigen presentation. Titers for homologous combinations of vaccine strain and strain in ELISA, HI and neutralization tests exceeded those for heterologous antigen-antibody pairs. Despite antibody detection by means of ELISA, HI and neutralization tests, the mouse protection afforded by the vaccines differed significantly. Complete protection of mice challenged with 100 LD50 virus of the Siberian subtype was induced by the vaccine "Encevir" ("Microgen", Tomsk, Russia). The minimal immunization doze (MID50) of "Encevir" protecting 50% of the mice was less than 0.0016 ml. Partial protective effect of vaccines produced in Moscow, Russia and Austria revealed MID50 within recommended intervals (0.001-0.017 ml). However, the MID50 for the vaccine "Encepur" (Novartis, Germany) 0.04 ml exceeded acceptable limits with total loss of mice immunized with vaccine diluted 32, 100 and 320 fold. These results suggest regular evaluation of TBEV vaccines in regions where heterologous virus subtypes prevail.

Vertical transmission of tick-borne encephalitis virus between generations of adapted reservoir small rodents.

Vertical transmission of tick-borne encephalitis virus (TBEV) between generations of the small rodents-red voles Myodes rutilus Pallas (previously known as Clethrionomys rutilus Pallas) was shown for naturally infected reservoir hosts and after experimental infection with different sublethal doses of the viral strains. For wild red voles and for their progeny born in 240-280 days after experimental infection of their parents the TBEV was detected in up to 90% of samples by RT-PCR, ELISA and bioassays. Small amounts of the TBEV RNA found in embryos, placenta and blood cells could serve as evidence of prenatal transmission. Postnatal transfer of the virus might occur through the rodent milk. Analysis of the TBEV E gene nucleotide sequences of RT-PCR products revealed missense mutations resulting in amino acid substitution K280Q in newborn red vole in comparison with its parent female. Taken together, the data confirmed the TBEV vertical transmission among generations of its adapted mammal reservoir hosts. The virus transfer might occur before, during and/or after birth of the small rodents with high frequencies. In the wild it could provide the TBEV long-term persistence in mammal hosts without an (any) involvement of arthropod vectors thus selecting dangerous mammal-adapted variants.