No abstract

Dysfunctional endothelium contributes to more disease than any other tissue in the body. Small interfering RNAs (siRNAs) have the potential to help study and treat endothelial cells in vivo by durably silencing multiple genes simultaneously, but efficient siRNA delivery has so far remained challenging. Here we show that polymeric nanoparticles made of low molecular weight polyamines and lipids can deliver siRNA to endothelial cells with high efficiency, thereby facilitating the simultaneous silencing of multiple endothelial genes in vivo. Unlike lipid or lipid-like nanoparticles, this formulation does not significantly reduce gene expression in hepatocytes or immune cells even at the dosage necessary for endothelial gene silencing. It mediates the most durable non-liver silencing reported to date, and facilitates the delivery of siRNAs that modify endothelial function in mouse models of vascular permeability, emphysema, primary tumour growth, and metastasis. We believe these nanoparticles improve the ability to study endothelial gene function in vivo, and may be used to treat diseases caused by vascular dysfunction.

Natural infections expose the immune system to escalating antigen and inflammation over days to weeks, whereas nonlive vaccines are single bolus events. We explored whether the immune system responds optimally to antigen kinetics most similar to replicating infections, rather than a bolus dose. Using HIV antigens, we found that administering a given total dose of antigen and adjuvant over 1-2 wk through repeated injections or osmotic pumps enhanced humoral responses, with exponentially increasing (exp-inc) dosing profiles eliciting >10-fold increases in antibody production relative to bolus vaccination post prime. Computational modeling of the germinal center response suggested that antigen availability as higheraffinity antibodies evolve enhances antigen capture in lymph nodes. Consistent with these predictions, we found that exp-inc dosing led to prolonged antigen retention in lymph nodes and increased Tfh cell and germinal center B-cell numbers. Thus, regulating the antigen and adjuvant kinetics may enable increased vaccine potency.vaccination kinetics | antigen retention | humoral response | computational immunology | germinal center formation S ubunit vaccines based on recombinant protein antigens combined with adjuvants can safely elicit protective humoral immune responses in humans, and they have become a cornerstone of modern public health (1, 2). Recent advances in structure-based vaccine design (3, 4) and progress in the development of adjuvants that are safe and effective for prophylactic vaccines (5) have helped drive the field. However, several challenges remain: A number of protein vaccines, such as candidate vaccines against HIV and malaria, have tended to elicit short-lived immunity (6, 7). In HIV, broadly neutralizing antibodies (BNAbs) isolated from infected patients are generally characterized by high degrees of somatic hypermutation (SHM) (8), but methods to generate such highly mutated antibodies by vaccination remain unknown. SHM occurs in germinal centers (GCs) within lymphoid organs, and data from animal models demonstrate a critical role for follicular helper T cells in the induction of GCs and promotion of affinity maturation (9, 10). To date, methods to promote Tfh generation and long-lived germinal centers during vaccination remain unclear (11-15). Much attention has focused on the use of adjuvants to promote affinity maturation, but it remains unclear if adjuvants alone can provide the necessary immunological driving forces for promoting extensive affinity maturation (16).During acute infections, which often provoke robust germinal center responses and durable humoral immunity, microorganism replication typically occurs over the course of one to several weeks (17-19). During this time, recognition of molecular danger signals contained within the pathogen sustains stimulation of the innate immune system, and a continuous supply of antigen is provided to the adaptive immune system. In contrast to these patterns of antigen and inflammatory cues during infection, typical subunit vaccines...