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The rabbit haemorrhagic disease (RHD) virus was first described in 1984 in China, where it caused a rabbit plague characterized by an acute course. At present, the disease has spread to rabbits on all continents, and is characterized by morality reaching 100%. Research on the immune response in rabbits after infection by RHD virus strains has so far only been performed by the Deptuła team. In turn, it must be stated that similar research worldwide has been performed in the Chinese centre, yet referring exclusively to rabbits after immunization with inactivated RHD virus. Such research indicates that shortly after immunization, the immunity is coordinated by macrophages and lymphocytes T and B, while farther on the protection against the infection is conditioned by humoral immunity. Deptula's team has investigated 22 strains of RHDV in the aspect of non-specific cellular and humoral immunity, as well as specific cellular and humoral immunity including 3 French strains (FR-1, Fr-2, 9905RHDVa), 10 Polish strains (K-l, Kr-1, KGM, SGM, MAŁ, BLA, PD, GSK, Ż, ŻD), 4 German strains (Hagenow, Frankfurt, Triptis, Hartmannsdorf), 3 Italian strains (BS89-reference strain, Vt97, PV97), 1 English strain (Rainham), and 1 Spanish strain (Asturias). The strains were analyzed in the aspect of such parameters as capacity of adherence and absorption of PMN cells, PMN cell cidal property measured with spontaneous, stimulated, and spectrophotometric NBT test, stimulation index and PMN metabolic activity coefficient; and MPO activity, as well as concentration and activity of LZM. Also, the number was marked of lymphocytes T CD5+, Th with receptor CD4+, Tc/Ts with receptor CD8+, and the number of lymphocytes with receptor CD25+, as well as the percentage of lymphocytes B (IgM). The research indicates the presence of immunogroups within the RHD virus. Assessment of pathogenicity of the RHD virus is actually performed based on the mortality rate in rabbits infected with the virus, which is dictated by the fact that the virus has so far not been obtained in vitro. Niedźwiedzka et al. divided the 10 analyzed strains into strains with high pathogenicity with mortality of 90-100%, up to 36/48 hour of the study (BS89, Hagenow, Rainham, Frankfart, Asturias, Triptis, Hartmannsdorf, Pv97, 9905RHDVa), and strains with lower pathogenicity with mortality of 30% up to 36/48h (Vt97). In turn, Tokarz-Deptuła divided the 10 analyzed strains of the RHDV (including 8 Polish and 2 French) into strains with mortality of 80-100% (Fr-2, ŻD, GSK, SGM, Fr-1, Kr-1, MAL), strains with mortality of 60-65% (KGM, BLA), and strains with mortality below 60% (PD). The aim of our study was to record changes to parameters of non-specific cellular immunity (capacity of adherence and absorption of PMN cells, cidal capacity of PMN cells measured with spontaneous NBT test, stimulated and spectrophotometric, and stimulation index and metabolic activity ratio of PMN cells) in rabbits experimentally infected with 4 haemagglutinogenic Czech strains of the RHD virus: CAMPV-351 (reference strain), CAMP-561, CAMPV-562, and CAMPV-558, with different pathogenicity; which strains have not yet been analyzed in this respect. The assessment of pathogenicity of the analyzed strains of the RHDV was performed on the basis of mortality rate among rabbits infected with these strains. On the basis of the number and duration of changes to analyzed parameters of non-specific cellular immunity, the 4 analyzed Czech strains are determined to differentiate in the aspect of immunogenicity into three groups. The first group is formed by the most immunogenic reference strain CAMPV-351, the second - by two medium-immunogenic strains - CAMPV-561 and CAMPV-558, whereas the third one - by the least immunogenic strain CAMPV- 562. The results obtained in the area of pathogenicity are not reflected in the division of the analyzed Czech strains according to their immunogenicity.
RHD (rabbit haemorrhagic disease) virus (RHDV) is the aetiological factor of the haemorrhagic disease of rabbits and is currently present on all continents. RHDV is a small, envelope-free virus containing genetic material in the form of a 7437-nucleotide long RNA strand. Studies indicate that genetic variability of RDHV strains originating from various parts of the world is approximately 14%, regardless the time and place of isolation. The aim of this study was to evaluate the genetic variability of 6 RHD virus strains from the Czech Republic (CAMPV-561, CAMPV-562, CAMPV-558) and Germany (Frankfurt, Wika, Rossi) based on analysis of fragment of a gene coding a nonstructural p30 protein. The largest variability of nucleotide sequences within the studied fragment was found for the Rossi strain and CAMPV-562 (13.5%) and CAMPV-558 (13.5%), Wika and Frankfurt (12.1%), and CAMPV-561 and Wika (11.2%). Among the Czech strains the largest genetic distance was noted for strains CAMPV-558 and Iowa (0.130/0.140), and in the case of the German strains, for Frankfurt and Iowa (0.123/0.132). A homology tree constructed based on a fragment of ap30 protein-coding gene divided the 14 analysed strains into IV groups of 88% homology. Phylogenetic relationships also divided the tested strains into 4 genetic groups (G1-G4). The larger genetic distance exists between the Czech and German strains and the American ones, and the smallest between them and the European strains.
The aim of this study was an attempt to apply PCR for diagnosis of Marek's disease. Eighteen field Marek's disease virus strains and 4 standard strains: virulent HPRS₁₆ strain and attenuated CVI 988 strain (serotype 1 - MDV-1), apathogenic SB 1strain (serotype 2 - MDV-2) and non - pathogenic turkeys HVT FC 126 strain (serotype 3 MDV-3) were used. Chicken anaemia virus (CAV) and infectious laryngotracheitis virus (ILTV) were used as control of PCR. The virus strains were cultured in CEF and total DNA was isolated by A@A Biotechnology kit. Three pairs of primers were used: for gene A of serotype 1, for 132 bp sequence of serotype 1 and for gene A of serotype 3. PCR was carried out under the following conditions: 94°C - 1 min (denaturation), 55°C - 30 s (annealing), 72°C -30 s (elongation). PCR products were analysed by electrophoresis in 2% agarose gel at 100 V/h. The PCR product of 314 bp was obtained from all field strains and HPRS₁₆ standard after the primers for gene A of serotype 1 were used. After the primers for 132 bp sequence of serotype 1 were used, 434 bp fragment for 19 DNA samples derivied from field strains and standard HPRS₁₆ strain and 1033 bp fragment from attenuated CVI 988 strain were obtained. Application of primers for gene A serotype 3 allowed the detection of 436 bp product only from non-pathogenic HVT FC 126 strain (serotype 3). These results indicated that the PCR technique can be used for the differentiation of MDV strains.
Feline Calicivirus (FCV) has been recognised as major oral and respiratory pathogen of cats. The high correlation among the field viruses and FCV-F9 serotype has represented the immunological bases for the employ of FCV-F9 serotype as a vaccine for calicivirosis in cats. The aim of this paper was to evaluate, by in vitro neutralization assays, the antigenic correlation among the vaccine F9 and FCV field strains isolated in Sicily (Italy) from cats showing clinical forms referable to calicivirus infection. The results confirm the low correlation between FCV-F9 strain and calicivirus strains spread in the feline population.
In order to determine the genetic variability of Polish RHD virus strains and to confirm the presence of genetic variant (RHDVa) subtype the partial nucleotide sequences of capsid protein gene, including two highly variable regions C and E, were examined. Phylogenetic analyses of 15 viral strains obtained over 18 years revealed the presence of three genetic groups. The oldest RHDV strains exhibit very close amino acid sequence similarity (98-99%) to the German FRG89 reference strain and most of European strains of the same period, as well as Chinese isolate from 1984. The HA-negative strains and isolates with variable reactivity in the HA test belong to the second subgroup and exhibit an intermediate level of variability (about 3%) in the analysed VP60 gene fragment. The most genetically variable strains (6-7%) clustered to RHDVa subtype. The analysis of nucleotides and amino acid sequences demonstrated three pairs of well conserved RHDV strains, isolated over 3, 6 and 10-year period.
A panel of four monoclonal antibodies (MAbs) was used to study the immunological profile of Rice yellow mottle virus (RYMV) genus Sobemovirus. Serological profiles of 35 representative isolates of RYMV from Borno, Gombe, Kaduna, Kano, Niger, Sokoto and Zamfara states in Northern Nigeria. All the RYMV isolates were classified into three major serogroups (SG1, SG2 and SG3) and further separated into six subgroups (Sg1a, Sg1b, Sg2a, Sg2b, Sg3a and Sg3b). The results demonstrate a significant serological variability among RYMV isolates in Northern Nigeria. The hierarchical analysis of the serological profiles data revealed high viral load in Kano, Kaduna and Gombe states, these show they are suitable locations for strategic RYMV diagnostic and field epidemiological studies.
The objective of this study was to evaluate the diversity and persistence of porcine reproductive and respiratory syndrome virus (PRRSV) in a swine herd where American type of modified live vaccine (MLV) was used. The study was carried out on the farrow-to-finish farm with 2 500 sows, which had a history of endemic PRRSV manifested as periodic mini-outbreaks of PRRS. The farm has been endemically infected with PRRSV-EU since 1998. The vaccination programme with the MLV was first applied in 2001 and consisted of vaccinating all sows every six months and all gilts 60 d before farrowing. All incoming gilts were also vaccinated twice with a two-week interval. During the monitoring period, PRRSV-EU type was detected in 28 of 63 samples collected from two to three-month-old piglets. PRRSV-US type was detected in 20 samples. Nineteen samples were positive for both EU and US types of PRRSV at the same time. The results of RT-PCR testing serum samples from 58 sows were negative. ORF5 RT-PCR products from samples containing both PRRSV-EU and PRRSV-US types were sequenced. Phylogenetic analyses, showed a close relationship to the American genotype of PRRSV strains from the monitored farm to the known vaccine strain V2332 present in the American type PRRS MLV. The presence of the PRRSV-US in the two-three-month-old piglets indicates that the American type of vaccine virus has spread from vaccinated sows to the non-vaccinated piglets. Simultaneous presence of both PRRSV-EU and US strains in 19 samples suggests very low cross protection between the American type PRRS MLV and very diverse Lithuanian EU type field strains. In this situation an increased chance for inter-genotypic recombination can be a threat.
In 2000-2001 35 isolates of Potato virus Y (PVY) were characterized by serologic al and biological methods. These isolates represented 5 distinct strains: PVYc, PVyo, PVYN, PVYN W, PVYNTN. Among isolates belonging to PVYN W and PVYNTN isolates which are able to overcome the resistance in three tobacco cultivars (VAM, Wiślica, PBD6) were found. They were obtained from tobacco plants grown in Poland or Hungary. Isolates obtained from potato plants were able to cause only mild symptoms on cvs. Wiślica and PBD6.
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