Studies on plasmid stability and LTB production by recombinant Vibrio cholerae in batch and chemostat cultures: a lesson for optimizing conditions for chemical induction

HPV16L1-attenuated Shigella recombinant vaccine induced strong vaginal and systemic immune responses in guinea pig model

Though human papillomavirus (HPV) vaccines based on L1 virus-like particles (VLPs) have excellent protective effect against HPV-induced cervical cancer, they are too expensive to be afforded by the developing countries, where most cases of cervical cancer occur. A live bacterial-based vaccine could be an inexpensive alternative. The aim of this study was to evaluate the potential value of live attenuated Shigella. flexneri 2a sc602 strain-based HPV16L1 as a high-efficiency, low-cost HPV16L1 mucosal vaccine. Recombinant sc602/L1 vaccine induced high L1-specific systemic and mucosal immune responses as well as cell-mediated Th1 and Th2 immune responses in guinea pig model. Sc602/L1 vaccine induced higher L1-specific IgG and IgA antibodies as well as HPV16-neutralizing antibodies in genital region in sc602/L1 mucosal immunized animals than in L1 intramuscular immunized animals. Though both are via mucosal delivery, immunized sc602/L1 vaccine by rectum route induced higher L1-specific IgA and IgG titers in genital region than by conjunctiva route. In addition, sc602/L1 also strongly increased L1-specific IFN-γ and IL-4 expression, implying its effect on cell-mediated immune response. HPV16L1 was expressed in sc602 bacteria and their biologic characteristics were detected by immunoblot, electron microscope and HeLa cell invasion assay. Guinea pigs were immunized with sc602L1 through conjunctiva (i.c.) or rectum (i.r.). Mucosal and systemic immune responses were detected by ELISA, ELISPOT and Neutralization activity assays. Strong mucosal and systemic immune responses were induced by sc602/L1 vaccine. This study provides evidence that sc602/L1 vaccine may have protective effect on HPV infection.

On-line multi-analyzer monitoring of biomass, glucose and acetate for growth rate control of a Vibrio cholerae fed-batch cultivation

In situ near-infrared (NIR) spectroscopy and in-line electronic nose (EN) mapping were used to monitor and control a cholera-toxin producing Vibrio cholerae fed-batch cultivation carried out with a laboratory method as well as with a production method. Prediction models for biomass, glucose and acetate using NIR spectroscopy were developed based on spectral identification and partial-least squares (PLS) regression resulting in high correlation to reference data (standard errors of prediction for biomass, glucose and acetate were 0.20 gl(-1), 0.26 gl(-1) and 0.28 gl(-1)). A compensation algorithm for aerated bioreactor disturbances was integrated in the model computation, which in particular improved the prediction by the biomass model. First, the NIR data were applied together with EN in-line data selected by principal component analysis (PCA) for generating a trajectory representation of the fed-batch cultivation. A correlation between the culture progression and EN signals was demonstrated, which proved to be beneficial in monitoring the culture quality. It was shown that a deviation from a normal cultivation behavior could easily be recognized and that the trajectory was able to alarm a bacterial contamination. Second, the NIR data indicated the potential of predicting the concentration of formed cholera toxin with a model prediction error of 0.020 gl(-1). Third, the on-line biomass prediction based on the NIR model was used to control the overflow metabolism acetate formation of the V. cholerae culture. The controller compared actual specific growth rate as estimated from the prediction with the critical acetate formation growth rate, and from that difference adjusted the glucose feed rate.