Search

Influenza vaccine effectiveness could be improved by combination with an adjuvant with the potential to enhance the host-vaccine response both quantitatively and qualitatively. The goal of this study was to explore a RIG-I agonist (SDI-nanogel) and a TLR7/8 agonist (Imidazoquinoline (IMDQ)‐PEG‐Chol) as adjuvants, when co-administered with a licensed quadrivalent inactivated influenza vaccine (QIV), and to determine the role of these adjuvants in directing helper T (Th) cell responses for their role in the immunoglobulin (Ig) class switching. Administration of QIV with the two adjuvants, individually or combined, resulted in enhanced HA-specific serum ELISA IgG titers, serum hemagglutination inhibition (HAI) titers and splenic T cell responses as examined by IFN-γ and IL-4 enzyme-linked immunosorbent spot (ELISPOT) assays, 4-weeks post-prime and post-boost vaccination in BALB/c mice. While QIV+SDI-nanogel largely induced antigen-specific IgG1 responses, QIV+IMDQ-PEG-Chol predominantly induced IgG2a antibody isotypes post-prime vaccination, suggesting efficient induction of Th2 (IL-4) and Th1 (IFN-γ) responses, respectively. Combination of the two adjuvants not only skewed the response completely towards IgG2a, but also resulted in induction of HAI titers that outperformed groups that received single adjuvant. Moreover, enhanced IgG2a titers correlate with antibody-mediated cellular cytotoxicity (ADCC) that targets both the highly conserved H1 hemagglutination (HA) stalk domain and N1 neuraminidase (NA). A booster vaccination with QIV+IMDQ-PEG-Chol resulted in a more balanced IgG1/IgG2a response in animals primed with QIV+IMDQ-PEG-Chol but increased only IgG2a titers in animals that received the combination adjuvant during prime vaccination, suggesting that class switching events in germinal centres during the prime vaccination contribute to the outcome of booster vaccination. Importantly, IMDQ-PEG-Chol, alone or in combination, always outperformed the oil-in-water control adjuvant Addavax. Vaccine-induced antibody and T cell responses correlated with protection against lethal influenza virus infection. This study details the benefit of adjuvants that target multiple innate immune receptors to shape the host vaccine response.

Developing effective cancer vaccines is thought to require the strong activation of cytotoxic T cells (CTLs) to kill transformed cells. Initiation of such CTL responses requires DCs presenting the antigen via the MHCI route, a feature hardly achievable using soluble antigens. Internalization of particulate antigens in contrast has been shown to strongly promote MHCI mediated antigen presentation. In this study, ovalbumin (OVA) was encapsulated in polyelectrolyte microcapsules (PEM), a new class of particles allowing efficient antigen encapsulation under non-denaturing conditions. OVA-loaded PEM strongly promoted MHCI mediated OVA presentation by DCs in vitro and in vivo. Being attractive tools to enhance antigen presentation, PEM however fail to activate DCs, a prerequisite for the initiation of potent CTL responses. To cope with this issue, we coated the surface of cationic PEM with oligonucleotides containing unmethylated CpG motifs, which are strong activators of DCs by triggering TLR9. Co-delivery of CpG and OVA-loaded microcapsules synergistically increased the strength of the CTL response, indicated by a dramatic increase in the number of IFN-γ secreting CTLs and a strongly enhanced killing of OVA peptide-pulsed splenocytes after adoptive transfer. Finally, immunisation with CpG-modified capsules was able to confer protective immunity against a lethal challenge with the highly aggressive OVA-transduced B16 melanoma, clearly demonstrating the potential of this approach.

The present study was set up to investigate the fate of connexin32 and its channels in hepatocellular apoptosis. Primary hepatocyte cultures were exposed to Fas ligand and cycloheximide, and modifications in connexin32 expression and localization, and gap junction functionality were studied. We found that gap junction functionality rapidly declined upon progression of cell death, which was associated with a decay of the gap junctional connexin32 protein pool. Simultaneously, levels of newly synthesized connexin32 protein increased and gathered in a hemichannel configuration. This became particularly evident towards the end stages of the cell death process and was not reflected at the transcriptional level. We next either silenced connexin32 expression or inhibited connexin32 hemichannel activity prior to cell death induction. Both approaches resulted in a delayed termination of the cell death response. We conclude that connexin32 hemichannels facilitate the apoptotic-to-necrotic transition, which typically occurs in the final stage of hepatocellular apoptosis.