Diarrhea is the second leading cause of death in children younger than 5 years. Enterotoxigenic Escherichia coli (ETEC) strains are the most common bacterial cause of diarrhea in young children living in endemic countries and children and adults traveling to these areas. Pathogenesis of ETEC diarrhea has been well studied, and the key virulence factors are bacterial colonization factor antigens and enterotoxins produced by ETEC strains. Colonization factor antigens mediate bacteria attachment to host small intestinal epithelial cells and subsequent colonization, whereas enterotoxins including heat-labile and heat-stable toxins disrupt fluid homeostasis in host epithelial cells, which leads to fluid and electrolyte hypersecretion and diarrhea. Vaccines stimulating host anti-adhesin immunity to block ETEC attachment and colonization and also antitoxin immunity to neutralize enterotoxicity are considered optimal for prevention of ETEC diarrhea. Vaccines under development have been designed to stimulate local intestinal immunity and are either oral vaccines or transcutaneous vaccines. A cholera vaccine (Dukoral®) does stimulate anti-heat-labile toxin immunity and is licensed for short-term protection of ETEC diarrhea in travelers in some countries. Newer experimental ETEC vaccine candidates are being developed with hope to provide long-lasting and more broad-based protection against ETEC. Some have shown promising results in safety and immunogenicity studies and are approaching field trials for efficacy. A key problem is the development of a vaccine that is both practical and inexpensive so that it can be affordable for use in poor countries where it is needed.

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Recombinant adenovirus (Adv)-mediated gene transduction is a powerful technology for cancer gene therapy. In this article, we report the generation of a fiber-mutant Adv vector, using the Adv genomic DNA-terminal protein complex (DNA-TPC) cotransfection method. First, a fiber-mutant construct in a plasmid carrying the right-side two-thirds of the human adenovirus type 5 (Ad5) genome (pTR) was cotransfected with Ad5 DNA-TPC, yielding the recombinant Adv with the desired fiber mutation. The DNA-TPC from the mutant Adv was then utilized to produce a second-step recombinant Adv with an expression cassette in the place of E1. By this procedure, we generated a fiber mutant, F/K20, that has a linker and a stretch of 20 lysine residues added at the C terminus of the fiber. By using Adv carrying a reporter lacZ gene (AxCAZ2) with either F/K20 or wild-type fiber (F/wt), we examined the transduction efficiency of F/K20-Adv. No significant difference in the transduction efficiency between F/K20 and F/wt-Adv was observed for a human fibroblast line, WI-38, or various tumor cell lines, including melanoma, prostate, esophageal, and pancreatic cancer lines. In clear contrast, F/K20-Adv showed a remarkably enhanced efficiency in genetic transduction of human glioma cells. In all four human glioma lines tested, the multiplicities of infection (MOIs) for transduction of 50% of the population (ED50) were decreased with F/K20-Adv compared with F/wt-Adv: 7-fold for T98G, 14-fold for U251, 9-fold for U373, and 42-fold for U87 cells. Therefore, we attempted to apply F/K20-Adv for gene therapy of malignant glioma. Glioma cells infected with F/K20-Adv carrying genes for interleukin 2 or interleukin 12 produced a high level of each cytokine at a much lower MOI than did cells infected with F/wt-Adv. Infection with F/K20-Adv carrying the wild-type p53 tumor suppressor gene resulted in an enhanced level of p53 protein expression and an increased incidence of F/K20-Adv in transduction efficiency for malignant glioma, providing promising tools for gene therapy.

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Pulsing dendritic cells (DCs) with tumor cell-derived mRNA is regarded as an attractive alternative in the development of DC-based tumor vaccines. Our aim is to improve the therapeutic efficacy of DC-based tumor RNA vaccines by augmenting the preferential chemotaxis of DCs to T cells. Mouse bone marrow-derived DCs were genetically modified with lymphotactin (Lptn) by adenovirus vector, which conferred on DCs preferential chemotaxis to CD4+ and CD8+ T cells (Cao et al., 1998). Lptn gene-modified DCs (Lptn-DCs) were pulsed with tumor mRNA and used for vaccination in the tumor models of 3LL lung carcinoma and B16 melanoma. In both tumor models, immunization with 4 X 10(4) tumor RNA-pulsed Lptn-DCs induced more potent CTL activity, compared with their counterparts, specifically against tumor cells and Mut1 or tyrosinase-related protein 2 (TRP-2) peptide-pulsed RMA-S cells, and rendered the immunized mice resistant to tumor challenge much more effectively. CD8+ T cells were necessary and sufficient to generate the protection of Lptn-DC-based RNA tumor vaccines, and CD4+ T cells were required for the induction of tumor rejection. In the preestablished 3LL and B16 tumor models, vaccination with DC-based or LacZ-DC-based tumor RNA vaccines (2 X 10(5) cells) could reduce pulmonary metastasis and extend survival of tumor-bearing mice, but was less effective than the Lptn-DC counterpart (with 60-80% mice surviving). When the immunizing dose was decreased to 4 X 10(4) cells, Lptn-DC-based tumor vaccines rather than their counterparts were still significantly effective. Our studies provide a potential strategy to improve the efficacy of DC-based vaccines, and a new approach to immunological intervention by chemokines.

The cysteinyl leukotrienes (CysLTs) are inflammatory mediators closely associated with neuronal injury after brain ischemia through the activation of their receptors, CysLT1R and CysLT2R. Here we investigated the involvement of both receptors in oxygen-glucose deprivation/recovery (OGD/R)-induced ischemic neuronal injury and the effect of the novel CysLT2R antagonistin comparison with the CysLT1R antagonist montelukast. In primary neurons, neither the nonselective agonist leukotriene D4 (LTD4) nor the CysLT2R agonist N-methyl-leukotriene C4 (NMLTC4) induced neuronal injury, and HAMI 3379 did not affect OGD/R-induced neuronal injury. However, in addition to OGD/R, LTD4 and NMLTC4 induced cell injury and neuronal loss in mixed cultures of cortical cells, and neuronal loss and necrosis in neuron-microglial cocultures. Moreover, they induced phagocytosis and cytokine release (interleukin-1b and tumor necrosis factor-a) from primary microglia, and conditioned medium from the treated microglia induced neuronal necrosis. HAMI 3379 inhibited all of these responses, and its effects were the same as those of CysLT2R interference by CysLT2R short hairpin RNA, indicating CysLT2R dependence. In comparison, montelukast moderately inhibited OGD/R-induced primary neuronal injury and most OGD/R-and LTD4-induced (but not NMLTC4-induced) responses in mixed cultures, cocultures, and microglia. The effects of montelukast were both dependent and independent of CysLT1Rs because interference by CysLT1R small interfering RNA had limited effects on neuronal injury in neuron-microglial cocultures and on cytokine release from microglia. Our findings indicated that HAMI 3379 effectively blocked CysLT2R-mediated microglial activation, thereby indirectly attenuating ischemic neuronal injury. Therefore, CysLT2R antagonists may represent a new type of therapeutic agent in the treatment of ischemic stroke.

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