Systemic immune response to a CD40 agonist antibody in nonhuman primates.

The cell surface molecule CD40 is a member of the tumor necrosis factor receptor superfamily and is broadly expressed by immune cells including B cells, dendritic cells, and monocytes, as well as other normal cells and some malignant cells. CD40 is constitutively expressed on antigen-presenting cells, and ligation promotes functional maturation, leading to an increase in antigen presentation and cytokine production, and a subsequent increase in the activation of antigen-specific T cells. It is postulated that CD40 agonists can mediate both T cell-dependent and T cell-independent immune mechanisms of tumor regression in mice and patients. In addition, it is believed that CD40 activation also promotes apoptotic death of tumor cells and that the presence of the molecule on the surface of cancer cells is an important factor in the generation of tumor-specific T cell responses that contribute to tumor cell elimination. Notably, CD40 agonistic therapies were evaluated in patients with solid tumors and hematologic malignancies with reported success as a single agent. Preclinical studies have shown that subcutaneous administration of CD40 agonistic antibodies reduces systemic toxicity and elicits a stronger and localized pharmacodynamic response. Two independent studies in cynomolgus macaque (Macaca fascicularis) were performed to further evaluate potentially immunotoxicological effects associated with drug-induced adverse events seen in human subjects. Studies conducted in monkeys showed that when selicrelumab is administered at doses currently used in clinical trial patients, via subcutaneous injection, it is safe and effective at stimulating a systemic immune response.

Marked enhancement of the antigen-specific immune response by combining plasmid DNA-based immunization with a Schiff base-forming drug.

Although plasmid DNA (pDNA)-based immunization has proven efficacy, the level of immune responses that is achieved by this route of vaccination is often lower than that induced by traditional vaccines, especially for primates and humans. We report here a simple and potent method to enhance pDNA-based vaccination by using two different plasmids encoding viral or bacterial antigens. This method is based on coadministration of low concentrations of a recently described immunopotentiating, Schiff base-forming drug called tucaresol which has led to significant augmentation of antigen-specific humoral and cellular immune responses. Our data suggest that enhancement of the immune response with tucaresol might provide a powerful tool for the further development of pDNA-based immunization for humans.

Angiogenic effects of prostaglandin E2 are mediated by up-regulation of CXCR4 on human microvascular endothelial cells.

Stimulation of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) increases the expression of CXCR4 on endothelial cells, rendering these cells more responsive to stromal-derived factor 1 (SDF-1), an angiogenic CXC chemokine and unique ligand for CXCR4. Here, we show that prostaglandin E2 (PGE2) mediates the effects of bFGF and VEGF in up-regulating CXCR4 expression on human microvascular endothelial cells (HMECs). Forskolin or 3-isobutyl-1-methyl xanthine (IBMX), 2 inducers of adenylate cyclase, markedly enhanced, whereas cyclooxygenase (COX) inhibitors including aspirin, piroxicam, and NS398 markedly inhibited CXCR4 expression on HMECs. Furthermore, the ability of PGE2 to augment in vitro tubular formation in SDF-1alpha containing matrigel was inhibited completely by blocking CXCR4. Treatment of bFGF- or VEGF-stimulated HMECs with COX inhibitors blocked tubular formation by about 50% to 70%. Prostaglandin-induced human endothelial cell organization and subsequent vascularization can be inhibited to a greater extent by a neutralizing antibody to human CXCR4 in severe combined immunodeficient mice. Additionally, VEGF- and bFGF-induced angiogenesis in vivo was also inhibited by about 50% by NS-398 or piroxicam, and this inhibitory effect was accompanied by decreased expression of CXCR4 on murine endothelial cells. Consequently, by inducing CXCR4 expression, prostaglandin accounts for about 50% of the tubular formation in vitro and in vivo angiogenic effects of VEGF and bFGF. Moreover, augmentation of CXCR4 expression by VEGF, bFGF, and PGE2 involves stimulation of transcription factors binding to the Sp1-binding sites within the promoter region of the CXCR4 gene. These findings indicate that PGE2 is a mediator of VEGF- and bFGF-induced CXCR4-dependent neovessel assembly in vivo and show that angiogenic effects of PGE2 require CXCR4 expression.