Mixing NA variants in an antigen presenting cell-targeted DNA vaccine elicits cross-reactive influenza antibody responses

ABSTRACT

Vaccination is a successful tool against influenza. However, antigenic drift of the virus requires an annual update of the vaccine. A universal vaccine approach which can elicit immune responses reactive to ideally all seasonal as well as zoonotic influenza strains is urgently needed. To explore this we used a flexible DNA vaccine platform, increasing immunogenicity by targeting dimeric vaccine molecules to antigen-presenting cells (APCs). We hypothesize that when including multiple antigen variants from different influenza strains in one heterodimeric APC-targeted mix DNA vaccine, antibody responses can be focused on conserved epitopes which are shared between the different variants. Neuraminidase (NA) is the second most abundant surface protein on the influenza virus after hemagglutinin and has been established as an independent correlate of protection. We have previously shown that an APC-targeted DNA vaccine with NA induced highly protective antibody responses. NA is divided into 9 different subtypes (N1-N9), and two NA-like antigens in bats (N10 and N11). Here, we created a NA mix vaccine which successfully expressed heterodimeric vaccine molecules with 8 different NA variants (N2-N9) that were targeted to MHC class II on APCs. Upon intramuscular DNA immunization and electroporation in mice, the NA mix vaccine induced cross-reactive antibody responses towards N1, which was not included in the vaccine. The NA mix approach has the potential to fill knowledge gaps about NA immunity and would be a great advancement in universal vaccine design for influenza as well as for other emerging and rapidly changing viruses. WS5.4 ;SARS-CoV- 2- specific T cell responses to COVID-19 BNT162b2 vaccination in chronic lymphocytic leukaemia patients Lisa Blixt1,2;David Wullimann2;Soo Aleman1,2;Jeanette Lundin1,2;Puran Chen2;Yu Gao2;Angelica Cuapio2;Mira Akber2;Joshua Lange2;Olga Rivera-Ballesteros2;Marcus Buggert2;Hans-Gustaf Ljunggren2;Anders Hansson;Lotta1,2;Österborg1,2 1Karolinska University Hospital;Stockholm, Sweden;2Karolinska Institutet, Stockholm, Sweden Immunocompromised patients have an increased risk for severe disease and mortality from viral infection. Importantly, disease and treatment reduce humoral and cellular immune responses to vaccination, which offer the best protection from severe COVID-19 disease during the ongoing pandemic. We recently reported from a prospective clinical trial that BNT162b2 vaccination in different immunodeficient groups had significantly lower SARS-CoV- 2- specific antibody titers compared to healthy controls. The seroconversion rate observed was 63% in chronic lymphocytic leukaemia (CLL) patients, with a negative impact of ibrutinib treatment. Whether T cells in the absence of sufficient levels of SARS-CoV- 2- specific antibody titers can confer immunity after BNT162b2 vaccination remains unclear. We measured reactive SARS-CoV- 2- specific T cell responses in uninfected (naive) and previously infected CLL patients following BNT162b2 vaccination. Out of 52 naive CLL patients, 12 (29%) had a specific IFN-γ T cell response compared to 24/41 (59%) in controls after two doses. In previously infected CLL patients, mainly spike-specific CD8 T cells expanded after the third dose, at which 11/12 (92%) had detectable responses, and all 12 (100%) had spike-specific CD4 T cell responses. Relative to the Wuhan reference strain (wild-type) variant, the median reduction of antigen-specific CD8 and CD4 T cells to the B.1.1.529 (Omicron) variant were 51% and 13%, respectively. Collectively, these data indicate that CLL patients respond with T-cells specific to SARS-CoV- 2 spike protein after BNT162b2 vaccination or infection. The increased T-cell response rate after the third dose and ability to recognize the Omicron variant of concern demonstrates the importance of a booster dose in this patient group.