Mechanisms of protective immunity to Staphylococcus aureus infection in humans remain elusive. While the importance of cellular immunity has been shown in mice, T cell responses in humans have not been characterised. Using a murine model of recurrent S. aureus peritonitis, we demonstrated that prior exposure to S. aureus enhanced IFNγ responses upon subsequent infection, while adoptive transfer of S. aureus antigen-specific Th1 cells was protective in naïve mice. Translating these findings, we found that S. aureus antigen-specific Th1 cells were also significantly expanded during human S. aureus bloodstream infection (BSI). These Th1 cells were CD45RO+, indicative of a memory phenotype. Thus, exposure to S. aureus induces memory Th1 cells in mice and humans, identifying Th1 cells as potential S. aureus vaccine targets. Consequently, we developed a model vaccine comprising staphylococcal clumping factor A, which we demonstrate to be an effective human T cell antigen, combined with the Th1-driving adjuvant CpG. This novel Th1-inducing vaccine conferred significant protection during S. aureus infection in mice. This study notably advances our understanding of S. aureus cellular immunity, and demonstrates for the first time that a correlate of S. aureus protective immunity identified in mice may be relevant in humans.

The inflammatory effects of carbon nanoparticles (NPs) are highly disputed. Here it is demonstrated that endotoxin-free preparations of raw carbon nanotubes (CNTs) are very limited in their capacity to promote inflammatory responses in vitro, as well as in vivo. Upon purification and selective oxidation of raw CNTs, a higher dispersibility is achieved in physiological solutions, but this process also enhances their inflammatory activity. In synergy with toll-like receptor (TLR) ligands, CNTs promote NLRP3 inflammasome activation and it is shown for the first time that this property extends to spherical carbon nano-onions (CNOs) of 6 nm in size. In contrast, the benzoic acid functionalization of purified CNTs and CNOs leads to significantly attenuated inflammatory properties. This is evidenced by a reduced secretion of the inflammatory cytokine IL-1β, and a pronounced decrease in the recruitment of neutrophils and monocytes following injection into mice. Collectively, these results reveal that the inflammatory properties of carbon NPs are highly dependent on their physicochemical characteristics and crucially, that chemical surface functionalization allows significant moderation of these properties.

Despite its long record of successful use in human vaccines, the mechanisms underlying the immunomodulatory effects of alum are not fully understood. Alum is a potent inducer of interleukin-1 (IL-1) secretion in vitro in dendritic cells and macrophages via Nucleotide-binding domain and leucinerich repeat-containing (NLR) family, pyrin domain-containing 3 (NLRP3) inflammasome activation. However, the contribution of IL-1 to aluminduced innate and adaptive immune responses is controversial and the role of IL-1a following alum injection has not been addressed. This study shows that IL-1 is dispensable for alum-induced antibody and CD8 T cell responses to ovalbumin. However, IL-1 is essential for neutrophil infiltration into the injection site, while recruitment of inflammatory monocytes and eosinophils is IL-1 independent. Both IL-1a and IL-1b are released at the site of injection and contribute to the neutrophil response. Surprisingly, these effects are NLRP3-inflammasome independent as is the infiltration of other cell populations. However, while NLRP3 and caspase 1 were dispensable, alum-induced IL-1b at the injection site was dependent on the cysteine protease cathepsin S. Overall, these data demonstrate a previously unreported role for cathepsin S in IL-1b secretion, show that inflammasome formation is dispensable for alum-induced innate immunity and reveal that IL1a and IL-1b are both necessary for alum-induced neutrophil influx in vivo.

Many biomaterials that are in both preclinical and clinical use are particulate in nature and there is a growing appreciation that the physicochemical properties of materials have a significant impact on their efficacy. The ability of particulates to modulate adaptive immune responses has been recognized for the past century but it is only in recent decades that a mechanistic understanding of how particulates can regulate these responses has emerged. It is now clear that particulate characteristics including size, charge, shape and porosity can influence the scale and nature of both the innate and adaptive immune responses. The potential to tailor biomaterials in order to regulate the type of innate immune response induced, offers significant opportunities in terms of designing systems with increased immune-mediated efficacy.

Obesity is characterized by chronic inflammation associated with neutrophil and M1 macrophage infiltration into white adipose tissue. However, the mechanisms underlying this process remain largely unknown. Based on the ability of oil-based adjuvants to induce immune responses, we hypothesized that endogenous oils derived from necrotic adipocytes may function as an immunological "danger signal." Here we show that endogenous oils of human origin are potent adjuvants, enhancing antibody responses to a level comparable to Freund's incomplete adjuvant. The endogenous oils were capable of promoting interleukin (IL)-1a-dependent recruitment of neutrophils and M1-like macrophages, while simultaneously diminishing M2-like macrophages. We found that endogenous oils from subcutaneous and omental adipocytes, and from healthy and unhealthy obese individuals, promoted comparable inflammatory responses. Furthermore, we also confirmed that white adipocytes in visceral fat of metabolically unhealthy obese (MUO) individuals are significantly larger than those in metabolically healthy obese individuals. Since adipocyte size is positively correlated with adipocyte death, we propose that endogenous oils have a higher propensity to be released from hypertrophied visceral fat in MUO individuals and that this is the key factor in driving inflammation. In summary, this study shows that adipocytes contain a potent oil adjuvant which drives IL1a-dependent proinflammatory responses in vivo.Obesity is characterized by chronic, low-grade inflammation resulting in insulin resistance. Understanding the mechanisms underlying this inflammation would provide valuable insights into the disease and potentially offer new therapeutic targets. Early studies showing that sodium salicylate can reverse the symptoms of type 2 diabetes (1) highlighted roles for inhibitor of kB kinase b (IKKb) and Jun N-terminal kinase (JNK) in this process. JNK can directly phosphorylate Serine307 on insulin receptor substrate 1, thus impairing insulin signaling and mediating obesity-induced insulin resistance (2). IKKb can also phosphorylate insulin receptor substrate 1 (3), and myeloid-specific deletion of IKKb in obese mice protects against insulin resistance (4). In addition, IKKbmediated translocation of nuclear factor-kB into the nucleus