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Sera sampled from 2,884 farming animals in the Astrakhan region in 2001 to 2004 were investigated by the hemagglutination inhibition test (HIT) in order to indicate specific antibodies to West Nile virus (WNV). HIT-positive samples were investigated by the neutralization test (NT). WNV antibodies were detected in all the examined species of animals: horses (the proportion of positive tests throughout the observation averaged 9.8%; the agreement with NT results was 94.1%), cattle (6,4 and 72.%), camels (5.2 and 41.7%), pigs (3.1 and 75%), and sheep (2.2 and 57.1). Relationships between the environmental features of WNV in different natural zones, the infection rate, and the conditions of keeping farming animals in the Astrakhan region are analyzed.

Infection of birds, residing in the Volga lower and middle delta, with West Nile Virus (WNV) genome was detected by the RT-PCR method. A total of 315 samples of bird organs, collected in the Astrakhan region in August 2001, were examined. Positive results, with various severity degrees, were found in coots (15.1%) and in cormorants (14.3%) in the lower delta. As for the middle delta, the infection rate among coots, herons, sea-gulls and terms was found to be identical and amounted to 8-13%, it was essentially higher in cormorants--42%. The infection rate of land-based birds did not exceed 5% in synanthropic biocenosis. According to a partial sequencing of the 5'-end region of WNV genome, all positive tests can be described as belonging to the 1st WNV genotype. The obtained results are indicative of a high activity of circulation of WNV among the birds of the water and near-water complexes in the mentioned region.

Four strains identified as West Nile fever virus by inhibited hemagglutination and neutralization tests, enzyme immunoassay, and reverse transcription polymerase chain reaction were isolated during a virological examination of birds and their collected ticks in the natural and synanthropic biocenoses of the Volga delta. The strains were isolated from the great cormorant (Phalacrocorax carbo), the crow (Corvus corone) and its collected Hyalomma marginatum nymphs. The types of interpopulational relations in the ecological system wild-birds-virus-mosquitoes-synanthroic birds-ticks are discussed.

NK lymphocytes destroyed target cells contaminated with Mycoplasma to a greater extent as compared with normal cells. The mechanism of that phenomenon is based on the production into the environment by effector lymphocytes cocultivated with contaminated cells of high quantity of mycoplasma that has a non-specific cytolytic effect.

Malignant LS cells obtained from benign L cells by selection retained their immunogenicity in syngeneic recipients. Nevertheless, such selection resulted in a partial change in their antigenic structure, which was manifested by the fact that only partial cross reactivity existed between L and LS cells on the level of both humoral and cellular immunity. The preliminary inoculation of L cells induced statistically significant lymphocytic reaction in the animals against LS cells, sufficient to protect 30% of mice inoculated with these cells.