Ludmila Zakharova

Immunogenicity of recombinant vaccinia viruses expressing hepatitis B virus surface antigen in mice

The ability of different recombinant vaccinia viruses (RVV) expressing hepatitis B virus surface antigen (HBsAg) to induce anti-HBs and anti-vaccinia virus responses has been analyzed in mice. The RVVs tested differed with regard to the original vaccinia virus strain used as vector and the site of insertion of a foreign gene. It was found that the immunological responses to RVVs based on the WR strain were higher than those to RVVs based on the Lister strain. The immunological response was also quantitatively affected by the viral TK phenotype. The presence of the preS2 region in HBsAg gene, inserted into the RVV genome, led to the induction of anti-preS2 antibodies but decreased the antibody response to the S-portion of HBsAg.

Genetic instability of vaccinia virus containing artificially duplicated genome regions

A double recombinant of vaccinia virus (W-lacZ/J-tk/F) was obtained, which contains two inverted copies of the virus tk gene, separated by 45 kb: (i) the native copy located in the HindIII J fragment of the virus genome was inactivated due to insertion of E. coli lacZ gene; (ii) the second active copy was artificially inserted into the HindIII F fragment. The virus expressing both thymidine kinase and beta-galactosidase (tk+lac+ phenotype) was cloned. Due to the presence of duplicated inverted sequences of the tk gene in the virus genome extensive recombination was observed leading to genetic heterogeneity of the virus population. The population consisted mainly of the virions with the tk+lac- (77%) and tk+lac+ (23%) phenotypes. Passages in the presence of BUdR revealed minor fractions of the tk-lac+ and tk-lac- phenotypes. Structural analysis of DNA isolated from virions confirmed the genetic heterogeneity of the virus population. Nine different HindIII fragments were detected containing HindIII F, J and (or) lacZ sequences. The structure of these fragments indicates that predominantly two types of recombination events occur in the population: (i) translocation of the lacZ gene between duplicated sequences of the tk gene or displacement of lacZ by tk via intergenome and intragenome double crossing over; (ii) inversion of a 45 kb sequence in the conserved region of the genome between duplicated sequences of the tk gene due to a intragenome single crossing over.

Viable double vaccinia virus recombinants with the non-inducible phage T7 expression system.

Double vaccinia virus recombinants expressing both the T7 RNA polymerase gene, controlled by a weak early poxvirus PF promoter, and the Escherichia coli beta-galactosidase gene, controlled by the phage T7 promoter, have been obtained. The viability of the double recombinants depended on the T7 RNA polymerase expression level. If the T7 RNA polymerase gene was inserted into a recombinant already containing the beta-galactosidase gene, the efficiency of formation of the double recombinants was significantly higher compared to that for the reverse insertion order. The negative effect of the phage T7 terminator on beta-galactosidase expression in cells infected with the recombinant viruses has been shown. The dynamics and levels of beta-galactosidase formation by different vaccinia virus recombinants have been studied.

X-band SAR interferometry for forest dynamics detection

The study aims at the interferometric phase measurements in order to estimate the effective phase center shift for the forested area during short time intervals (11-22 days) in X-band. Regular repeated-pass TerraSAR-X/TanDEM-X observations in winter, spring and summer allow interferometric measurements under different weather conditions. Low values of phase difference variations are typical for dry weather. Larger values were observed under the wet conditions and probably during the active vegetation period.

Oil platforms in Caspian Sea as stable distributed radar scatterers for palsar calibration

An analysis of oil platforms long-term stability in Caspian Sea seen on the Japanese synthetic aperture radar PALSAR and PALSAR-2 images is made. It is shown that typical radar cross section stability of oil platforms is about 0.5 dB, what is close to the parameters of specially designed calibration targets. Possibility of PALSAR and PALSAR-2 intercalibration using the oil platforms under study is demonstrated.

Some peculiarities of polarimetric classification for winter data takes

The paper demonstrates a difference in polarimetric classification results for winter and summer data takes. 30 PALSAR scenes over 2 Siberian test sites were processed, and the results were compared with meteoarchive data. Scattering matrix elements decrease in different way under freezing conditions, so the dominant scattering mechanism changes. Thus in winter the surface type of scattering becomes the prevailing mechanism even for forests, whereas in summer they demonstrate volume scattering.

Monitoring of the forests state in the Chernobyl area using remote sensing data

The study of the area of Chernobyl nuclear power plant (NPP) using spaceborne SAR and optical data is devoted to the monitoring of the forests state in the surrounding area. The use of a SIR-C/X datatake from SRL-2 flight and series of ERS SAR data for the year interval 1992-1997, obtained at different meteorological conditions and in different seasons of the year, JERS-1 along with optical data were discovered to be very helpful for the classification of vegetation types, study of the forests state after the nuclear accident in the area. Various products derived from remote sensing data allowed to detect forest fire areas and to make conclusion about domination of damage from fires occurred significantly later the accident.