This paper was to observe the revaccination effect of domestic yeast-derived recombinant hepatitis B vaccine (YRHBV) to children who were born to HBsAg and HBeAg negative mothers and had been immunized with full course of blood-derived hepatitis B vaccine 4 years ago at their birth. The treated group was revaccinated with 5μg YRHBV while the control group with 10μg blood-derived HB vaccine, their anti-HBs response was determined 1,12,24 months after revaccination. The results showed that a nice anti-HBs response was discovered in group A childeren, no matter how about the anti-HBs level before revaccination was. The kinetics of anti-HBs after YDHBV revaccination was similar to that of the blood-derived HB vaccine, no statistical difference was found. So, 5μg of domestic yeast-derived recombinant HB vaccine gave same immune effect as well as 10μg blood-derived HB vaccine.

We have evaluated the plague epidemic situation in the Three Rivers Source Region,Qinghai Province in recent 20 years to provide the basis for revising the plague prevention countermeasures.We have analyzed the time distribution and the plague epidemic situation between animals and human beings during twenty years in the Three Rivers Source Region,Qinghai Province by describing epidemiology.The animal plague in the natural source of Marmot plague was extremely serious in the Three Rivers Source Region during the past 20 years.It mainly distributes in Yushu State and Tanggula County,Germu City and the serious season ran through the whole period of marmot camp ground activities and the peak was between June and August.Human plague epidemic took place between May and October each year and reached its peak between July and September.The peak covered about 41.67％ at most.It mainly endemic distributes in Nangqian and Xinghai Country.During the past 20 years,we have totally found 14 human plague epidemics in the Three Rivers Source Region,among which 48 cases took place and there were deaths of 17 cases.The fatality rate was 35.42％.The lung type was the majority among 48 cases,which startde with the glandular type.During the past 20 years the plague epidemic has been active and the animal plague epidemic broke out continuously in the Three Rivers Source Region,Qinghai Province.The variety of animals and insects infected the plague epidemic was increasing.The human plague epidemics is most serious with high fatality rate,but it is on the decline as a whole.

Objective To purify native F1 antigen from E pestis EV76 strain and determine its ef-ficacy against Y. pestis. Methods A new purification method was developed by the substitution of physical disruption ( glass beads) for organic solvent ( acetone and toluene) one, followed by a combination of ammo-nium sulfate fractionation and SephacrylS-200HR column filtration chromatography. Groups of mice were im-munized with F1 antigen adsorbed to 25% aluminum hydroxide in PBS by intramuscular route. The immu-nized animals were challenged subeutaneously(s, c. ) with 104 CFU of Y. pestis strain 141 at 18 weeks after the primary immunization. Results There was no IgG titre difference between two groups of mice with one-dose immunization, whereas in the two-dose immunization groups, the group F1-40 μg induced a statistically higher antibody titre than the group F1-20 μg. Complete protection was observed for animals immunized with purified F1 antigen by s.c. route. In contrast, the control mice immunized with aluminum hydroxide suc-cumbed to a same dose of Y. pestis 141 challenge. Conclusion This purification strategy is a simple and ef-fective, and can be operated in a large scale. Native F1 antigen extracted from Y. pestis EV76 is highly im-munagenic, and can be used as a key antigen component to develop sub-unit vaccine of plague.