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 further on the protection against the infection is conditioned by humoral immunity. Deptuła’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-1, 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, Frankfurt, 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, MAŁ), 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.