IL-15 adjuvanted multivalent vaccinia-based universal influenza vaccine requires CD4 ⁺ T cells for heterosubtypic protection

Abstract

Current influenza vaccines are ineffective against novel viruses and the source or the strain of the next outbreak of influenza is unpredictable; therefore, establishing universal immunity by vaccination to limit the impact of influenza remains a high priority. To meet this challenge, a novel vaccine has been developed using the immunogenic live vaccinia virus as a vaccine vector, expressing multiple H5N1 viral proteins (HA, NA, M1, M2, and NP) together with IL-15 as a molecular adjuvant. Previously, this vaccine demonstrated robust sterile cross-clade protection in mice against H5 influenza viruses, and herein its use has been extended to mediate heterosubtypic immunity toward viruses from both group 1 and 2 HA lineages. The vaccine protected mice against lethal challenge by increasing survival and significantly reducing lung viral loads against the most recent human H7N9, seasonal H3N2, pandemic-2009 H1N1, and highly pathogenic H7N7 influenza A viruses. Influenza-specific antibodies elicited by the vaccine failed to neutralize heterologous viruses and were unable to confer protection by passive transfer. Importantly, heterologous influenza-specific CD4(+) and CD8(+) T-cell responses that were elicited by the vaccine were effectively recalled and amplified following viral challenge in the lungs and periphery. Selective depletion of T-cell subsets in the immunized mice revealed an important role for CD4(+) T cells in heterosubtypic protection, despite low sequence conservation among known MHC-II restricted epitopes across different influenza viruses. This study illustrates the potential utility of our multivalent Wyeth/IL-15/5Flu as a universal influenza vaccine with a correlate of protective immunity that is independent of neutralizing antibodies.

Assessment of enhanced influenza vaccination finds that FluAd conveys an advantage in mice and older adults

“…Blood was collected by cardiac puncture and clotted (MiniCollect, Greiner Bio‐one, Kremsmünster, Austria), and serum was harvested after centrifugation and aliquoted and heat‐inactivated, for 30 min at 56°C, before all in vitro experiments. To quantify virus replication, antibody and cellular responses, the lungs, BAL and lymphoid organs (spleen, mLN for challenged mice or iLN for vaccinated mice) were processed as previously described . Lung viral titres were determined from homogenates by standard TCID 50 assay on MDCK cells, and viral titres were calculated by the Reed–Muench method, as previously described .…”

“…To map HA‐specific antibodies to the length of the HA protein, we used a fragmented YSD HA library to bind immune mouse serum. A H3N2‐1968 HA‐YSD library was constructed as previously described . Yeast surface expressing HA (length 100–500 bp) was constructed from random digestion of the HA fragments derived from the H3N2‐1968 HA gene.…”

Generation of Live Attenuated Influenza Virus by Using Codon Usage Bias

“…The reciprocal of the highest dilution of serum that neutralized at least 50% of virus infectivity was taken as the titer. Immune cell profiling of cells isolated from bronchoalveolar lavage (BAL) fluid harvested at day 7 postinfection was performed as described previously (35). Briefly, after Fc receptor blocking, cells were stained with 2 mixtures of monoclonal antibodies (all BioLegend) for innate and adaptive immune cells.…”

The Influenza Viruses

“…Hence, development of a successful "universal" (i.e. one vaccine protecting against multiple virus subtypes) vaccination strategy is urgently needed and a number of research teams are currently being involved in production of such a vaccine [25].…”