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Adenoviral vectors are being developed as vaccines against infectious agents and tumour-associated antigens, because of their ability to induce cellular immunity. However, the protection afforded in animal models has not easily translated into primates and clinical trials, underlying the need for improving adenoviral vaccines-induced immunogenicity. A Toll-like receptor signalling molecule, TRAM, was assessed for its ability to modify the immune responses induced by an adenovirus-based vaccine. Different adenovirus vectors either expressing TRAM alone or co-expressing TRAM along with a model antigen were constructed. The modification of T-cell and antibody responses induced by TRAM was assessed in vivo in mice and in primates. Co-expression of TRAM and an antigen from adenoviruses increased the transgene-specific CD8+ T cell responses in mice. Similar effects were seen when a TRAM expressing virus was co-administered with the antigen-expressing adenovirus. However, in primate studies, co-administration of a TRAM expressing adenovirus with a vaccine expressing the ME-TRAP malaria antigen had no significant effect on the immune responses. While these results support the idea that modification of innate immune signalling by genetic vectors modifies immunogenicity, they also emphasise the difficulty in generalising results from rodents into primates, where the regulatory pathway may be different to that in mice.

The capsular group B meningococcal (MenB) four component vaccine (4CMenB) has been licensed for the prevention of invasive disease caused by MenB. The vaccine causes fever in infants, particularly when given in combination (concomitant) with other routinely-administered vaccines (routine), such as the standard diphtheria, tetanus, pertussis (DTP)-containing vaccine. To assess the suitability of a mouse immunisation model to study this phenomenon, we monitored temperature in mice after a second dose of routine vaccines, with or without 4CMenB, and compared the results with those in humans. Using this mouse model, we explored the reactogenicity of 4CMenB components by measuring changes in temperature, cytokines, and gene expression induced by 4CMenB, one of its components, wild-type or attenuated endotoxin outer membrane vesicles (OMVs), or lipopolysaccharide (LPS). A significant rise (p < 0.01) in temperature was observed in mice immunised with 4CMenB, wild-type OMVs, and LPS. RNA-sequencing of mouse whole blood revealed a gene signature shared by the 4CMenB, OMV, and LPS groups consisting of bacterial pattern recognition receptors and neutrophil activation marker genes. Sequencing of neutrophils isolated after concomitant 4CMenB identified cells expressing the OMV-associated genes Plek and Lcp1. Immunisation with 4CMenB or OMVs led to increased IL-6 in serum and significant upregulation (p < 0.0001) of prostaglandin-synthesising enzymes on brain tissue. These data demonstrate the suitability of a mouse model for assessing vaccine reactogenicity and strongly indicate that the fever following vaccination with 4CMenB in human infants is induced by endotoxin contained in the OMV component of the vaccine.

Outer membrane vesicle (OMV)- based vaccines have been used to provide strain-specific protection against capsular group B Neisseria meningitidis infections, but the full breadth of the immune response against the components of the OMV has not been established. Sera from adults vaccinated with an OMV vaccine were used to screen 91 outer membrane proteins (OMPs) incorporated in an antigen microarray panel. Antigen-specific IgG levels were quantified pre-vaccination, and after 12 and 18 weeks. These results were compared with IgG levels from mice vaccinated with the same OMV vaccine. The repertoires of highly responding antigens in humans and mice overlapped, but were not identical. The highest responding antigens to human IgG comprised four integral OMPs (PorA, PorB, OpcA and PilQ), a protein which promotes the stability of PorA and PorB (RmpM) and two lipoproteins (BamC and GNA1162). These observations will assist in evaluating the role of minor antigen components within OMVs in providing protection against meningococcal infection. In addition, the relative dominance of responses to integral OMPs in humans emphasizes the importance of this subclass and points to the value of maintaining conformational epitopes from integral membrane proteins in vaccine formulations.

One fifth to one quarter of the human population is asymptomatically, naturally and persistently colonised by Staphylococcus aureus. Observational human studies indicate that although the whole population is intermittently exposed, some individuals lose S. aureus rapidly. Others become persistent carriers, as assessed by nasal cultures, with many individuals colonised for decades. Current animal models of S. aureus colonisation are expensive and normally require antibiotics. Importantly, these animal models have not yet contributed to our poor understanding of the dichotomy in human colonisation status. Here, we identify a single strain of S. aureus found to be persistently colonising the gastrointestinal tract of BALB/c mice. Phylogenetic analyses suggest it diverged from a human ST15 lineage in the recent past. We show that murine carriage of this organism occurs in the bowel and nares, is acquired early in life, and can persist for months. Importantly, we observe the development of persistent and non-persistent gastrointestinal carriage states in genetically identical mice. We developed a needle- and antibiotic-free model in which we readily induced S. aureus colonisation of the gastrointestinal tract experimentally by environmental exposure. Using our experimental model, impact of adaptive immunity on S. aureus colonisation could be assessed. Vaccine efficacy to eliminate colonisation could also be investigated using this model.

The majority of routinely given vaccines require two or three immunisations for full protective efficacy. Single dose vaccination has long been considered a key solution to improving the global immunisation coverage. Recent infectious disease outbreaks have further highlighted the need for vaccines that can achieve full efficacy after a single administration. Viral vectors are a potent immunisation platform, benefiting from intrinsic immuno-stimulatory features while retaining excellent safety profile through the use of non-replicating viruses. We investigated the scope for enhancing the protective efficacy of a single dose adenovirus-vectored malaria vaccine in a mouse model of malaria by co-administering it with vaccine adjuvants. Out of 11 adjuvants, only two, Abisco ® -100 and CoVaccineHT TM , enhanced vaccine efficacy and sterile protection following malaria challenge. The CoVaccineHT TM adjuvanted vaccine induced significantly higher proportion of antigen specific central memory CD8 + cells, and both adjuvants resulted in increased proportion of CD8 + T cells expressing the CD107a degranulation marker in the absence of IFNγ, TNFα and IL2 production. Our results show that the efficacy of vaccines designed to induce protective T cell responses can be positively modulated with chemical adjuvants and open the possibility of achieving full protection with a single dose immunisation.

A persistent goal of vaccine development is the enhancement of the immunogenicity of antigens while maintaining safety. One strategy involves alteration of the presentation of the antigen by combining antigens with a multimeric scaffold. Multi-antigen vaccines are under development, and there are presently far more candidate antigens than antigen scaffolding strategies. This is potentially problematic, since prior immunity to a scaffold may inhibit immune responses to the antigen-scaffold combination. In this study, a series of domains from S. aureus which have been shown to crystallise into multimeric structures have been examined for their scaffolding potential. Of these domains, SAR1376, a 62 amino acid member of the 4-oxalocrotonate tautomerase (4-OT) family, was pro-immunogenic in mice when fused to a range of pathogen antigens from both S. aureus and P. falciparum, and delivered by either DNA vaccination, viral vector vaccines or as protein-in-adjuvant formulations. The adjuvant effect did not depend on enzymatic activity, but was abrogated by mutations disrupting the hexameric structure of the protein. We therefore propose that SAR1376, and perhaps other members of the 4-OT protein family, represent very small domains which can be fused to a wide range of antigens, enhancing immune responses against them.