Harnessing mucosal immunity against respiratory viruses using adenoviral vectors encoding cytokines/chemokines as mucosal adjuvants
Creators: name: Vieira Antão, Ana
Publisher: name: Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)
Year: 2024

description: Influenza (IAV) and respiratory syncytial viruses (RSV) are two of the main causes of severe respiratory tract infections; however, developing effective vaccines against these pathogens remains a challenge. Despite the recent approval of two vaccines against RSV, the annual vaccination against IAV has demonstrated that inducing systemic immunity is not sufficient to prevent reinfections. The recent discovery of tissue resident memory (TRM) T cells in mice and human lungs has highlighted the importance of mucosal immunity against these pathogens. In IAV and RSV infected individuals, the induction of lung TRM cells and IgA antibodies was shown to correlate with an improved prognosis and rapid viral clearance in secondary infections. Therefore, vaccines able to improve mucosal humoral and T cell responses against these viruses are considered a promising approach to reduce disease burden. However, as mucosal tissues are the main entry site for different pathogens, these compartments have evolved to rapidly elicit immune responses to counteract replication and the subsequent inflammation. For this reason, antigen delivery by mucosal immunizations can be impaired, resulting in a weak vaccine immunogenicity. Nevertheless, these problems may be overcome with good vaccine platforms as well as the usage of adjuvants. Indeed, our work has elucidated the effect of an adenoviral vector (Ad) expressing IL1β as mucosal adjuvant together with Ad-based influenza and RSV vaccines. The intranasal administration of IL1β showed to improve vaccine immunogenicity and efficacy against these respiratory viruses. However, the pleiotropic effect of this cytokine may induce undesired immune responses. In line with these findings, we aimed to develop and analyse the effect of different chemokines/cytokines encoded in adenoviral vectors as alternative mucosal adjuvants. For this purpose, the innate molecules CCL17, CCL20, CCL21, CXCL9, CXCL13, TGFβ, IL28A and IL28B were chosen based on the observations made in the in vivo experiments with Ad-IL1β as well as on their function described during influenza and RSV infections. Therefore, these chemokines/cytokines are sought to be involved in the generation of the host mucosal immunity against these pathogens. In the first part of this study, adenoviral vectors expressing the different genes were produced and characterized in vitro. Afterwards, their impact on vaccine-specific immune responses were investigated in vivo. Our results showed that Ad-CCL17 and Ad-TGFβ were the two most promising candidates as mucosal adjuvants. Their expression in the lungs of mice resulted in the enhancement of antigen-specific TRM cells, whereas the other chemokine/cytokine did not improve vaccine-induced humoral or T cell responses. The second part of this project aimed to establish a mucosal combinatory vaccine against IAV and RSV, as an advantageous strategy to control and prevent both infections. In vivo studies elucidated the impact of a mucosal adenoviral vector-based vaccine encoding the influenza HA and NP protein as well as RSV-F, in combination with the adjuvants Ad-CCL17 and Ad-TGFβ. The combinatory vaccine induced robust mucosal immune responses and protected mice against heterologous IAV strains or RSV viruses. The additional use of the adjuvants strengthened the formation of antigen-specific TRM cells, but had less impact on the antibody responses against IAV and RSV. In addition, the mucosal administration of these adjuvants did not significantly improve vaccine efficacy. In summary, an effective mucosal vaccine was established against two of the most clinically relevant respiratory viruses. In addition, the co-expression of TGFβ revealed a supportive role in the formation of antiviral lung resident memory T cells, which is an interesting observation for additional basic or mechanistic studies.