To prepare monoclonal antibody to the N protein of porcine reproductive and respiratory syndrome virus(PRRSV),BALB/c mice were immunized with the purified N protein of the PRRSV-2 strain expressed by prokaryotic expression system.Mouse splenocytes were fused with myeloma cells using hybridoma technique,hybridoma cells were identified by indirect ELISA method and indirect immunofluorescence assay(IFA),and positive hybridoma cells were screened for subclones using the limited dilution method.The results showed that a monoclonal antibody cell line 4A7 was successfully obtained,and the results of Western blot and IFA indicated that the monoclonal antibody could accurately recognize the N proteins of type 1 and type 2 PRRSV.Mean-while,the N protein gene was truncated and expressed by prokaryotic expression system,and the amino acid sequence of the B-cell antigenic epitope recognized by 4A7 was screened as 51EKPHF55 using Western blot.Comparison of epitope amino acids in the N protein gene sequences of different strains revealed that the antigenic epitope 51EKPHF55 recognized by the monoclonal antibody 4A7 has no amino acid difference in the sequences of three subtypes among the PRRSV-1 strains and nine lineages among the PRRSV-2 strains,indicating a high degree of conservation.The results of the study provide a foundation the development of PRRSV diagnostic kits and novel vaccines.

To prepare monoclonal antibody to the N protein of porcine reproductive and respiratory syndrome virus(PRRSV),BALB/c mice were immunized with the purified N protein of the PRRSV-2 strain expressed by prokaryotic expression system.Mouse splenocytes were fused with myeloma cells using hybridoma technique,hybridoma cells were identified by indirect ELISA method and indirect immunofluorescence assay(IFA),and positive hybridoma cells were screened for subclones using the limited dilution method.The results showed that a monoclonal antibody cell line 4A7 was successfully obtained,and the results of Western blot and IFA indicated that the monoclonal antibody could accurately recognize the N proteins of type 1 and type 2 PRRSV.Mean-while,the N protein gene was truncated and expressed by prokaryotic expression system,and the amino acid sequence of the B-cell antigenic epitope recognized by 4A7 was screened as 51EKPHF55 using Western blot.Comparison of epitope amino acids in the N protein gene sequences of different strains revealed that the antigenic epitope 51EKPHF55 recognized by the monoclonal antibody 4A7 has no amino acid difference in the sequences of three subtypes among the PRRSV-1 strains and nine lineages among the PRRSV-2 strains,indicating a high degree of conservation.The results of the study provide a foundation the development of PRRSV diagnostic kits and novel vaccines.

Objective To evaluate endoscopically insertion of feeding tube via nose(EIFTN). Method Jejunal feeding tube was placed endoscopically via the nose in all 136 coma patients. Results This procedure was successful in all patients. The procedure took an average time of 5 minutes. In patients with deep coma,the procedure had no influence on HR,MAP, ECG and SaO2; In semicoma patients, HR and R increased during the procedure (t=3.902, P

0. 05 ) , but the control group had(P