Incorporation of Phosphonate into Benzonaphthyridine Toll-like Receptor 7 Agonists for Adsorption to Aluminum Hydroxide.

Small molecule Toll-like receptor 7 (TLR7) agonists have been used as vaccine adjuvants by enhancing innate immune activation to afford better adaptive response. Localized TLR7 agonists without systemic exposure can afford good adjuvanticity, suggesting peripheral innate activation (non-antigen-specific) is not required for immune priming. To enhance colocalization of antigen and adjuvant, benzonaphthyridine (BZN) TLR7 agonists are chemically modified with phosphonates to allow adsorption onto aluminum hydroxide (alum), a formulation commonly used in vaccines for antigen stabilization and injection site deposition. The adsorption process is facilitated by enhancing aqueous solubility of BZN analogs to avoid physical mixture of two insoluble particulates. These BZN-phosphonates are highly adsorbed onto alum, which significantly reduced systemic exposure and increased local retention post injection. This report demonstrates a novel approach in vaccine adjuvant design using phosphonate modification to afford adsorption of small molecule immune potentiator (SMIP) onto alum, thereby enhancing co-delivery with antigen.

Protection against influenza A virus by memory CD8 T cells requires reactivation by bone marrow-derived dendritic cells.

Influenza A virus is the causative agent of an acute inflammatory disease of the airway. Although Abs can prevent infection, disease and death can be prevented by T cell-mediated immunity. Recently, we showed that protection against lethal influenza A (PR8/34) virus infection is mediated by central memory CD8 T cells (T(CM)). In this study, using relB(-/-) mice we began to investigate the role of bone marrow (BM)-derived dendritic cells (DCs) in the mechanism of protection. We found that in the absence of functional DCs, memory CD8 T cells specific for the nucleoprotein epitope (NP(366-374)) fail to protect even after adoptive transfer into naive recipients. Through an analysis of Ag uptake, activation of memory CD8 T cells, and display of peptide/MHC complex by DCs in draining LNs and spleen early after virus infection, we established that lack of protection is associated with defective Ag presentation by BM-derived DCs and defective homing of memory T cells in the lymph nodes draining the airway tract. Collectively, the data suggest that protection against the influenza A virus requires that memory CD8 T cells be reactivated by Ag presented by BM-derived DCs in the lymph nodes draining the site of infection. They also imply that protection depends both on the characteristics of systemic adaptive immunity and on the coordinated interplay between systemic and local immunity.

Increasing transplant mass results in long-term allograft survival and recovery from transplant vasculopathy.

Late allograft rejection due to transplant vasculopathy continues to be a major clinical problem. Increasing the ratio of donor transplant size to recipient weight has been shown to reduce the incidence of late allograft failure. Using a murine pancreas transplant model we have tested the hypothesis that increasing the donor transplant size in a recipient can promote long-term allograft survival by promoting recovery from transplant vasculopathy. Recipients of an allograft that showed extensive vasculopathy were transplanted with a second donor transplant. The effect of the second allograft on the vasculopathy present in the first graft was measured. Transplanting a second allograft reversed all signs of ongoing rejection, including transplant vasculopathy, resulting in long-term survival of the first graft. Vasculopathy was only reversed if the first and second grafts were from the same mouse strain, suggesting an antigen-specific mechanism. However, the recovery of the first graft was not associated with antigen-specific peripheral tolerance.

IL-4 expression delays eosinophil-independent vasculopathy and fibrosis during allograft rejection in the mouse.

Transplant vasculopathy in the mouse is thought to be dependent on IL-4 and mediated by IL-5 and eosinophils, whereas in the rat and human systems, IL-4 is associated with the absence of transplant vasculopathy and down-regulation of a Th1-type response. In this study we tested the possibility that the apparent difference in the role of IL-4 in transplant vasculopathy is related to protocol differences rather than to the species being studied. Using a protocol that closely resembles that used in rat and human studies, we developed a model of transplant vasculopathy in the mouse that is associated with Th1-type cytokines and independent of IL-5 and eosinophil infiltration. In this model IL-4 promotes a significant delay in vasculopathy in the graft (P = 0.04) and a decrease in the incidence of allograft rejection (P = 0.02). The data suggest that the role of IL-4 in transplant vasculopathy can be controlled by the protocol used to treat the transplant recipient.