Identification of an epitope of SARS-coronavirus nucleocapsid protein

The nueleocapsid (N) protein of severe acute respiratory syndrome-coronavirus (SARS-CoV) is a major virion structural protein. In this study, two epitopes (Nl and N2) of the N protein of SARS-CoV were predicted by bioinformatics analysis. After immunization with two peptides, the peptides-specific antibodies were isolated from the immunized rabbits. The further experiments demonstrated that N1 peptide-induced polyclonal antibodies had a high affinity to bind to E. coli expressed N protein of SAR,S-CoV. Furthermore, it was confirmed that Nl peptide-specific IgG antibodies were detectable in the sera of severe acute respiratory syndrome (SARS) patients. The results indicated that an epitope of the N protein has been identified and N protein specific Abs were produced by peptide immunization, which will be useful for the study of SARS-CoV.

Effects of recombinant human growth hormone on rat septic shock with intraabdominal infection by E.coli

AIM: To investigate the therapeutic effects of recombinant human growth hormone (rhGH) on rat septic shock with intraabdominal infection by E. coli and its possible mechanism. METHODS: 76 SD rats were divided into 3 groups randomly:control group (group C, n=16) without any special treatnent,of E. coli(1×1010 cfu@ L-1,15 ml@kg-1, ip), treated group (group by rhGH injection (2.25 U@kg-1@d-1, im). Group S and group T were further divided into 1d and 3d subgroups, respectively (n=15 each). Mean arterial pressure (MAP), levels of plasma TNFα and endotoxin and leukocyte count were determined on 1st day and 3rd day after E. coli injection. Another 39 SD rats were divided into groups C, S and T (n=13 each) just for observing survival rate within 1 week.RESULTS: (1) On 1st and 3rd day, MAP in group S decreased markedly, and MAP on 1st day lowered more than that of 3rd day (P＜0.01), while MAP in group T just decreased slightly. The survival rate within 1 week was much higher in group T (84.6 %) than in group S (46.2 %) (P＜0.01). (2)On 1st day, plasma TNFα and endotoxin elevated significantly in group S and group T (P＜0.05), and endotoxin in group S had more increase (P＜0.01). On 3rd day, TNFα in group S returned to the level of group C (P＞0.05),while TNFα in group T went down below the level of group C(P＜0.01). On 3rd day, endotoxin in group S declined, but was still higher than that of group C (P＜0.01), endotoxin in group T returned to the level of group C (P＞0.05). (3) On 1st day, neutrophil ratio in total leukocyte count in both group S and group T increased significantly (P＜0.05 vs group C).CONCLUSION: rhGH showed beneficial effects on rat septic shock. The possible mechanisms may involve the attenuation of bacteria/endotoxin translocation and decreased systemic endotoxin level; inhibition of the production and release of TNFα; improved circulatory function; improved systemic host defenses and maintenance of intestinal mucosa barrier.

31nstitute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Taiyuan Road,Shanghai 200031, China.

Spike protein is one of the major structural proteins of severe acute respiratory syndrome-coronavirus. It is essential for the interaction of the virons with host cell receptors and subsequent fusion of the viral envelop with host cell membrane to allow infection. Some spike proteins of coronavirus, such as MHV, HCoV-OC43, AIBV and BcoV, are proteolytically cleaved into two subunits, S 1 and S2. In contrast, TGV, FIPV and HCoV-229E are not. Many studies have shown that the cleavage of spike protein seriously affects its function. In order to investigate the maturation and proteolytic processing of the S protein of SARS CoV, we generated S 1 and S2 subunit specific antibodies (Abs) as well as N, E and 3CL protein-specific Abs. Our results showed that the antibodies could efficiently and specifically bind to their corresponding proteins from E.coli expressed or lysate of SARS-CoV infected Vero-E6 cells by Western blot analysis. Furthermore, the anti-S 1 and S2 Abs were proved to be capable of binding to SARS CoV under electron microscope observation. When S2 Ab was used to perform immune precipitation with lysate of SARS-CoV infected cells, a cleaved S2 fragment was detected with S2-specific mAb by Western blot analysis. The data demonstrated that the cleavage of S protein was observed in the lysate, indicating that proteolytic processing of S protein is present in host cells.