Oxygen dependent pyruvate oxidase expression and production in Streptococcus sanguinis / 国际口腔科学杂志·英文版

The objective of this study was to characterize the oxygen dependent regulation of pyruvate oxidase (SpxB) gene expression and protein production in Streptococcus sanguinis (S. sanguinis). SpxB is responsible for the generation of growth-inhibiting amounts of hydrogen peroxide (H2O2) able to antagonize cariogenic Streptococcus mutans (S. mutans). Furthermore, the ecological consequence of H2O2 production was investigated in its self-inhibiting ability towards the producing strain. Expression of spxB was determined with quantitative Real-Time RT-PCR and a fluorescent expression reporter strain. Protein abundance was investigated with FLAG epitope engineered in frame on the C-terminal end of SpxB. Self inhibition was tested with an antagonism plate assay. The expression and protein abundance decreased in cells grown under anaerobic conditions. S. sanguinis was resistant against its own produced H2O2, while cariogenic S. mutans was inhibited in its growth. The results suggest that S. sanguinis produces H2O2 as antimicrobial substance to inhibit susceptible niche competing species like S. mutans during initial biofilm formation, when oxygen availability allows for spxB expression and Spx production.

Enhancing DNA vaccine potency against hantavirus by co-administration of interleukin-12 expression vector as a genetic adjuvant / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The heavy incidence and mortality of hemorrhagic fever with renal syndrome, as well as no specific drugs in curing the disease, clearly indicate the need for development of the more effective hantavirus vaccine. Refining the DNA vaccination strategy to elicit more clinically efficacious immune responses is now under intensive investigation. In the present study, we examined the effects of using an interleukin-12 expression plasmid as a genetic adjuvant to enhance the immune responses induced by a DNA vaccine based on the S gene encoding nucleocapsid protein against hantavirus.</p><p><b>METHODS</b>BALB/c mice were immunized three times by intramuscular inoculations of DNA vaccine encoding of hantanvirus nucleocapsid protein alone or in combination with a plasmid expressing murine interleukin-12 (pcIL-12). Booster immunizations were employed 2 times at 2-week interval. To evaluate the humoral and cellular immune responses, antigen-specific lymphocyte proliferation and antibody production were assayed by MTT method and ELISA respectively. The level of interleukin-4 and interferon-gamma in the splenic lymphocytic cultured supernatant were detected with ELISA kit at day 5, 10, 17, 35 and 42 after primary immunization.</p><p><b>RESULTS</b>Antigen-specific IgG antibodies was increased markedly at day 17 in the experiment groups and reached a plateau after day 35. As pcIL-12 co-injected, a significant inhibition of antigen-specific IgG levels was displayed over the period and the antibody mean titre was decreased to only about 1:50 at day 42 after primary immunization, significantly lower than the group immunized with pcDNA3.1 + S alone, in which the mean titre was about 1:70. Interferon-gamma was increased remarkably by the co-injection of pcIL-12 compared with the injection of pcDNA3.1 + S alone. However, the production of interleukin-4 was inhibited by pcIL-12 co-injection. Furthermore, pcIL-12 co-injection efficiently enhanced antigen-specific lymphocyte proliferation.</p><p><b>CONCLUSION</b>Humoral and cytokine responses elicited by pcDNA3.1 + S inoculation can be modulated by co-inoculation with pcIL-12 and efficiently induced Th1-dominant immune responses.</p>

The Application of PBL Teaching Mode in the Theory Teaching of Microbiology / 微生物学通报

PBL teaching method is a new mode of teaching which is originated from the West and implemented into China in recent years with an expectation that it would mainly develop the students’ self-learning ability,and enhance their skills of comprehensive thinking and solving actual problems.The author summarizes the practical experience of using PBL teaching methods in the theory teaching in Department of Medical Microbiology and Human Parasitology,China Medical University in the past three years,and then proved this method is very helpful to improving the students’integrated thinking by analysis of sample.At the same time the results also suggested that the students showed high enthusiasm in discussing the cases.By this way,the students showed great subjective intiative in their studies.

Model Case Design for Problem-based Learning in Medical Microbiology and Human Parasitology / 微生物学通报

Problem-based learning(PBL)is an important part of creative education in medical colleges.Choice and design of cases are of the vital importance to success or failure of PBL course.To enhance students' ability of independent,creative thinking,and their ability of analyzing and solving problems,the roles of primitive cases and model cases as well as interrelation between them were discussed respective- ly.Moreover,five basic principles to be followed in model case design for PBL in Medical Microbiology and Human Parasitology,i.e.objec- tivity,flexibility,consistency,illumination and relevance,were proposed in this study.