[Cloning and expression of recombinant truncated SElX protein and evaluation on the related emetic activities].

Objective: To analyze the amino acid polymorphism of truncated Staphylococcal enterotoxin-like toxin X (tSElX), and to evaluate its related emetic activities. Methods: Sequence of tselx was compared with both the genome sequence of 145 CC398 strains completed in our research group and the NCBI database. Primers were designed to amplify the target gene of tselx, and the fragment was recombined into pMD18-T vector and sequenced. PCR product was digested with BamHⅠ and EcoRⅠ, and constructed into plasmid pGEX-6P-1 and pET-28a (+). After recombinant plasmid was identified, the protein expression was induced by IPTG. Proteins expressed in the form of inclusion bodies were denatured and renatured, then purified by affinity chromatography and ultrafiltration. Purified tSElX protein was then fed to common marmosets with the dose of 250 µg/kg to observe the vomiting reaction. Results: tselx gene was present in 145 strains of CC398 strains from the different origins (patients, healthy people and animals) in China. Homology of the amino acid sequence of the protein from the Chinese strains appeared 100.0%, while the homology with the four American strains were 97.8%(1) and 98.9%(3), respectively. Through two sets of expression systems and different induction conditions, tSElX was expressed in the form of inclusion bodies. The high purity soluble recombinant tSElX was thus obtained by denaturated and renaturated processes. At the dose of 250 µg/kg, tSElX protein did not cause vomiting in common marmosets. Conclusions: Results of this study showed that the amino acid sequence of tSElX was highly conserved and was universally present in a particular clone group. We obtained soluble recombinant tSElX protein with high purity. We also noticed that tSElX did not have the animal emetic activity at a dose of 250 µg/kg.

Epidemiological studies on hemorrhagic fever with renal syndrome in China.

Hemorrhagic fever with renal syndrome (HFRS) has been reported from greater than 20 provinces in China. The number of reported cases has increased markedly in recent years and surpassed 80,000 human cases in 1983. All of the cases reported before 1981 were from rural areas and were attributed to Apodemus rats. In 1981, outbreaks of cases associated with house rats were first reported. Cases associated with Apodemus agrarius were more severe than those associated with the house rat Rattus norvegicus. The rate of inapparent infection in the rural population of areas endemic for Apodemus-associated disease was lower than that of Rattus-associated urban disease. After the onset of the disease, IgG antibody levels increase rapidly, peak after one week, and persist for as long as 25 years. Lung tissues from 16 species of rodent, from two species of sorex, and from cats and weasels in the epidemic areas have been found to carry antigen. A. agrarius, Apodemus peninsulae, and R. norvegicus serve as the main reservoirs of HFRS in rural areas, forest areas, and urban areas, respectively.