Intradermal (ID) immunization is an attractive route of vaccination because it targets tissue rich in dendritic cells, has dose-sparing potential, and allows needle-free delivery. However, few adjuvants are effective, nonreactogenic, and compatible with needle-free delivery devices. In this study, we demonstrate that a combination adjuvant composed of cyclic-di-AMP (cdAMP) and the plant-derived nanoparticle adjuvant Nano-11 significantly enhanced the immune response to ID-injected vaccines in mice and pigs with minimal local reaction at the injection site. The cdAMP/Nano-11 combination adjuvant increased Ag uptake by lymph node–resident and migratory skin dendritic cell subpopulations, including Langerhans cells. ID immunization with cdAMP/Nano-11 expanded the population of germinal center B cells and follicular helper T cells in the draining lymph node and Ag-specific Th1 and Th17 cells in the spleen. It elicited an enhanced immune response with a significant increase of IgG1 and IgG2a responses in mice at a reduced dose compared with i.m. immunization. An increased IgG response was observed following needle-free ID immunization of pigs. Nano-11 and cdAMP demonstrated a strong synergistic interaction, as shown in the activation of mouse, human, and porcine APC, with increased expression of costimulatory molecules and secretion of TNF and IL-1β. The combination adjuvant induced robust activation of both NF-κB and IFN regulatory factor signaling pathways and the NLRP3 inflammasome. We conclude that the combination of Nano-11 and cdAMP is a promising adjuvant for ID delivery of vaccines that supports a balanced immune response.

The development of cross-protective vaccines against the zoonotic swine influenza A virus (swIAV), a potential pandemic-causing agent, continues to be an urgent global health concern. Commercially available vaccines provide suboptimal cross-protection against circulating subtypes of swIAV, which can lead to worldwide economic losses and poor zoonosis deterrence. The limited efficacy of current swIAV vaccines demands innovative strategies for the development of next-generation vaccines. Considering that intramuscular injection is the standard route of vaccine administration in both human and veterinary medicine, the exploration of alternative strategies, such as intradermal vaccination, presents a promising avenue for vaccinology. This investigation demonstrates the first evaluation of a direct comparison between a commercially available multivalent swIAV vaccine and monovalent whole inactivated H1N2 swine influenza vaccine, delivered by intradermal, intranasal, and intramuscular routes. The monovalent vaccines were adjuvanted with NanoST, a cationic phytoglycogen-based nanoparticle that is combined with the STING agonist ADU-S100. Upon heterologous challenge, intradermal vaccination generated a stronger cross-reactive nasal and serum antibody response in pigs compared with intranasal and intramuscular vaccination. Antibodies induced by intradermal immunization also had higher avidity compared with the other routes of vaccination. Bone marrow from intradermally and intramuscularly immunized pigs had both IgG and IgA virus-specific antibody-secreting cells. These studies reveal that NanoST is a promising adjuvant system for the intradermal administration of STING-targeted influenza vaccines.

It is necessary for the dairy industry to reduce calf morbidity and mortality, and the reliance on antibiotics to treat sick calves, to address the growing concern regarding antibiotic resistant bacteria. The primary objective of this study was to evaluate the effect that feeding dairy calves medium-chain fatty acids (MCFA) has on growth performance and health, and the secondary objective was to evaluate the effect of MCFA on energy status around weaning and the adaptive immune response following a vaccine challenge. Thirty-three Holstein bull calves (5 ± 1.6 d of age) were randomly assigned to 1 of 2 treatments. Control (CON) calves were fed milk replacer with no C8:0 or C10:0 oil added and MCFA calves were fed milk replacer with 0.5% of a combination of C8:0 or C10:0 oil added. Body weight and average daily gain were measured weekly. Feed efficiency (gain/feed) and the change in body condition score, hip width, hip height, heart girth, and paunch girth were calculated for the duration of the study. Fecal scores were recorded daily and all medical treatments were documented for the duration of the trial. On d 42, 49, and 56 of the study, a serum sample was collected from each calf and used to measure nonesterified fatty acids, β-hydroxybutyric acid, insulin, and glucose concentrations to evaluate energy status around weaning. A subset of 11 calves per treatment were enrolled in a vaccine challenge. At 21 ± 1.9 d of age (mean ± standard deviation) calves were vaccinated intramuscularly with 1 mL of endotoxin-free ovalbumin (OVA) mixed with aluminum hydroxide adjuvant. At 42 d of age (±1.9 d), blood samples were collected and used to analyze OVA-specific IgG₁ and IgG₂, and calves were vaccinated a second time. At 56 d of age (±1.9 d), blood samples were collected to analyze IgG₁ and IgG₂ as well as IFN-γ and IL-4 secreted from peripheral blood mononuclear cells (PBMC) treated with OVA or phytohemagglutinin. Data were analyzed as a completely randomized design with repeated measures when applicable. A tendency for greater daily fecal score was observed for MCFA calves compared with CON. At d 42 of the study, nonesterified fatty acid concentrations were greater in CON calves compared with MCFA. At 42 and 56 d of age, anti-OVA IgG₁ concentrations for CON and MCFA calves were greater than prevaccination samples. This study suggests that feeding MCFA to calves affects the energy status of calves around weaning and vaccinating dairy calves with ovalbumin combined with an aluminum hydroxide adjuvant is an effective way to evaluate the adaptive immune responses.

Invasive Candida albicans (CA) infections often arise from the intestine and cause life-threatening infections in immunocompromised individuals. The role of gut commensal microbiota, metabolites, and host factors in the regulation of CA colonization in the intestine is poorly understood. Previous findings from our lab indicate that taurocholic acid (TCA), a major bile acid present in the intestine, promotes CA colonization and dissemination. Here, we report that oral administration of TCA to CA-infected mice significantly decreased the number of mononuclear phagocytes and CD4+ IL17A+ T helper 17 cells that play a critical role in controlling CA in the intestine. Collectively, our results indicate that TCA modulates mucosal innate and adaptive immune responses to promote CA colonization in the intestine.

A critical aspect of cancer vaccine development is the formulation with effective adjuvants. This study evaluated whether combining a cationic plant-derived nanoparticle adjuvant (Nano-11) with the clinically tested STING agonist ADU-S100 (MIW815) could stimulate anticancer immunity by intradermal vaccination. Nano-11 combined with ADU-S100 (NanoST) synergistically activated antigen-presenting cells, facilitating protein antigen cross-presentation in vitro and in vivo. Intradermal vaccination using ovalbumin (OVA) as a tumor antigen and combined with Nano-11 or NanoST prevented the development of murine B16-OVA melanoma and E.G7-OVA lymphoma tumors. The antitumor immunity was abolished by CD8⁺ T cell depletion but not by CD4⁺ T cell depletion. Therapeutic vaccination with NanoST increased mouse survival by inhibiting B16-OVA tumor growth, and this effect was further enhanced by PD-1 checkpoint blockade. Our study provides a strong rationale for developing NanoST as an adjuvant for intradermal vaccination and next-generation preventative and therapeutic cancer vaccines by STING-targeted activation.

Swine influenza A viruses (SwIAVs) are pathogens of both veterinary and medical significance. Intranasal (IN) vaccination has the potential to reduce flu infection. We investigated the efficacy of split SwIAV H1N2 antigens adsorbed with a plant origin nanoparticle adjuvant [Nano11–SwIAV] or in combination with a STING agonist ADU-S100 [NanoS100–SwIAV]. Conventional pigs were vaccinated via IN and challenged with a heterologous SwIAV H1N1-OH7 or 2009 H1N1 pandemic virus. Immunologically, in NanoS100–SwIAV vaccinates, we observed enhanced frequencies of activated monocytes in the blood of the pandemic virus challenged animals and in tracheobronchial lymph nodes (TBLN) of H1N1-OH7 challenged animals. In both groups of the virus challenged pigs, increased frequencies of IL-17A⁺ and CD49d⁺IL-17A⁺ cytotoxic lymphocytes were observed in Nano11–SwIAV vaccinates in the draining TBLN. Enhanced frequency of CD49d⁺IFNγ⁺ CTLs in the TBLN and blood of both the Nano11-based SwIAV vaccinates was observed. Animals vaccinated with both Nano11-based vaccines had upregulated cross-reactive secretory IgA in the lungs and serum IgG against heterologous and heterosubtypic viruses. However, in NanoS100–SwIAV vaccinates, a slight early reduction in the H1N1 pandemic virus and a late reduction in the SwIAV H1N1-OH7 load in the nasal passages were detected. Hence, despite vast genetic differences between the vaccine and both the challenge viruses, IN vaccination with NanoS100–SwIAV induced antigen-specific moderate levels of cross-protective immune responses.