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Articles by Qiang Xu
Total Records ( 2 ) for Qiang Xu
  Xiaowen Liu , Laurel A. Lagenaur , Peter P. Lee and Qiang Xu
  Women are at significant risk of heterosexually transmitted human immunodeficiency virus (HIV) infection, with the mucosal epithelium of the cervix and vagina serving as a major portal of entry. The cervicovaginal mucosa naturally harbors dynamic microflora composed predominantly of lactobacilli, which may be genetically modified to serve as a more efficient protective barrier against the heterosexual transmission of HIV. We selected a vaginal strain of Lactobacillus, L. jensenii 1153, for genetic modification to display surface-anchored anti-HIV proteins. Genomic sequencing analyses revealed that L. jensenii 1153 encodes several unique high-molecular-weight cell wall-anchored proteins with a C-terminal cell wall sorting LPQTG motif. In this report, we employed these proteins to express a surface-anchored two-domain CD4 (2D CD4) molecule in L. jensenii 1153. Our studies indicated that the C-terminal cell wall sorting signal LPQTG motif alone is insufficient to drive the surface expression of heterologous proteins, and the display of surface-anchored 2D CD4 molecules required native sequences of a defined length upstream of the unique C-terminal LPQTG cell wall sorting signal and the positively charged C terminus in a Lactobacillus-based expression system. The modified L. jensenii strain displayed 2D CD4 molecules that were uniformly distributed on bacterial surfaces. The surface-anchored 2D CD4 molecule was recognized by a conformation-dependent anti-CD4 antibody, suggesting that the expressed proteins adopted a native conformation. The establishment of this Lactobacillus-based surface expression system, with potential broad applicability, represents a major step toward developing an inexpensive yet durable approach to topical microbicides for the mitigation of heterosexual transmission of HIV and other mucosally transmitted viral pathogens.
  Wei Liu , Yu Yue Du , Bao Qi Guo , Chun Yan and Qiang Xu
  Dynamic Description Logic (DDL) is an extension of description logic. In dynamic description logic, both services and the service composition can be expressed in formulae, but there is still much room to promote the efficiency. In this study, a fast and effective method for web service composition is proposed for the services which perform in sequence. This method takes advantage of the partial order relation among services, dividing the service composition into two phases:on the first stage, the partial order diagram is generated in the registration server; on the second stage, the fast algorithm is run based on the partial order diagram to return web service composition to meet requests of users. By analysis and verification, the fast algorithm for web service composition presented in this study can be implemented in a linear time complexity, greatly shortening response time of the system.
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