| Porcine Reproductive and Respiratory Syndrome (PRRS), caused by porcine reproductive and respiratory syndrome virus (PRRSV), is an acute and highly infectious disease. Since2006to2007, the highly pathogenic PRRSV (HP-PRRSV) which was characterized by high mortality and fast spreading, had brought great economically impaction to the farmers in southern China.In order to better understand the epidemiology and genetic diversity characteristics of highly pathogenic PRRSV under different immune background in China, we collected clinical samples at different time and locations to investigate the epidemicity of PRRSV, sequenced and analysed partial NSP2sequence and ORF5sequence of46positive samples, the information of immune background and incidence of the samples are clear.At present, vaccine immunizations have become to the important measures to prevent and control HP-PRRS, although commercial attenuated vaccines can stimulate the boby to produce specific immune reaction, but the immune effect evaluation of commercial vaccines are still short of a perfect evaluation system, and its immune time, immune dose etc. appear to using chaotic. Then we evaluated the immunity effects of two commonly used commercial PRRS modified live vaccines, JXAl-R and CH-1R.The main contenes were as follows:1. The isolation and seguence analysis of PRRSVWe collected720clinical samples in Hubei, Hunan, Guangdong, Henan and etc. provinces from2012to2014, the total positive rate of PRRSV infection is49.3%. We sequenced and analysed partial NSP2sequence and ORF5sequence of46positive samples, the sequence analyses reveals that the amino acid homology between the46strains of PRRSV NSP2is83.8%~100%, and most of the NSP2detected have a discontinuous30amino acid deletion, same with the highly pathogenic strains JXA1. The amino acid homology of ORF5is91%~100%, the amino acid sequence analysies of ORF5showed a larger variation, especially in the antigen epitope which compared with the classical PRRSV. In addition, the locations and numbers of N glycosylation site are changed, the prediction of GP5TM areas of46positive samples showed that33strains have the highly amino acid variation area of TM1.2. The sequence analysis of HZ-31There was a novel PRRSV strain named HZ-31, sequence analysies reveals that HZ-31contains a discontinuous59aa deletion in aa471to500and aa533to561, and there is one nucleotide deletion in both ends of its genome non-coding regions.3. Immune evaluation of JXA1-R and CH-1R.The PRRS vaccine can stimulate the body to produce humoral immune rapidly. Compared with CH-1R live vaccines, the ELISA antibody thransforming postive phase of JXAl-R live vaccines was shorter and the level was higher, and the same in neutralizing antibodies, when against with the virulent PRRSV, JXAl-R induced neutralizing antibodies can neutralize the PRRSV in the serum, and was positive associated with viremia; During the period of immunization and challenged, two live vaccines can not induce IFN-γ; viremia could be produced by the two live vaccines during the period of immunization, after challenged the viremia was disappeared quickly in JXAl-R group, but in CH-1R group the viremia was continually exist; both JXAl-R and CH-1R had no nasal detoxification after challenged, while slightly detoxification was appeared in the control group. JXA1-R group had no rectal detoxification all the time, but the CH-1R group and control group appeared detoxification on10days after challenged. Slight lesion was appeared in JXA1-R group, lung hemorrhage and lymph nodes congestion were showed in individual pigs of CH-1R group, pulmonary sarcoidosis consolidation, lymph node congestion, kidney hemorrhage were showed in control group. Viral loading of lung, spleen, kidney, brain in JXAl-R group and CH-1R group were lower than the control group, and the difference was significant. |
