Development of an Alternative Modified Live Influenza B Virus Vaccine

Abstract

Influenza B virus (IBV) is considered a major human pathogen, responsible for seasonal epidemics of acute respiratory illness. Two antigenically distinct IBV hemagglutinin (HA) lineages cocirculate worldwide with little cross-reactivity. Live attenuated influenza virus (LAIV) vaccines have been shown to provide better cross-protective immune responses than inactivated vaccines by eliciting local mucosal immunity and systemic B cell- and T cell-mediated memory responses. We have shown previously that incorporation of temperature-sensitive (ts) mutations into the PB1 and PB2 subunits along with a modified HA epitope tag in the C terminus of PB1 resulted in influenza A viruses (IAV) that are safe and effective as modified live attenuated (att) virus vaccines (IAV att). We explored whether analogous mutations in the IBV polymerase subunits would result in a stable virus with an att phenotype. The PB1 subunit of the influenza B/Brisbane/60/2008 strain was used to incorporate ts mutations and a C-terminal HA tag. Such modifications resulted in a B/Bris att strain with ts characteristics in vitro and an att phenotype in vivo. Vaccination studies in mice showed that a single dose of the B/Bris att candidate stimulated sterilizing immunity against lethal homologous challenge and complete protection against heterologous challenge. These studies show the potential of an alternative LAIV platform for the development of IBV vaccines.IMPORTANCE A number of issues with regard to the effectiveness of the LAIV vaccine licensed in the United States (FluMist) have arisen over the past three seasons (2013–2014, 2014–2015, and 2015–2016). While the reasons for the limited robustness of the vaccine-elicited immune response remain controversial, this problem highlights the critical importance of continued investment in LAIV development and creates an opportunity to improve current strategies so as to develop more efficacious vaccines. Our laboratory has developed an alternative strategy, the incorporation of 2 amino acid mutations and a modified HA tag at the C terminus of PB1, which is sufficient to attenuate the IBV. As a LAIV, this novel vaccine provides complete protection against IBV strains. The availability of attenuated IAV and IBV backbones based on contemporary strains offers alternative platforms for the development of LAIVs that may overcome current limitations.

Alternative Strategy for a Quadrivalent Live Attenuated Influenza Virus Vaccine

“…Thus, reverse genetics was used to generate the following viruses: Ty/04 att (H3N2), Ca/04 att (H1N1), B/Bris att (Victoria lineage), and B/Wisc att (Yamagata lineage). The Ty/04 att , Ca/04 att , and B/Bris att viruses have been previously described ( 23 – 25 ), while the B/Wis att virus was prepared for this study ( Table 1 ). Like the B/Bris att virus, the B/Wis att virus displayed a ts phenotype in vitro that is typically associated with attenuation in vivo (data not shown).…”

“…QIV-vaccinated mice also survived challenge with the B/Bris strain carrying the PB2 F406Y mutation and by 5 dpc showed no evidence of virus replication in lungs and NTs. We have previously shown that the PB2 F406Y mutation increases the virulence for mice of the wild-type B/Bris strain (it also slightly increases the virulence of B/Wisc) ( 25 ). Unexpectedly, the B/Bris challenge dose (≤10 50% lethal doses [LD 50 ]) was sufficient to cause significant body weight loss in the QIV-vaccinated/challenged mice compared to the PBS-PBS mice.…”

“…A single intranasal (i.n.) dose of the IBV att protected mice against lethal challenge with antigenically matched and mismatched IBV strains ( 25 ). In this study, we used the IAV att and IBV att backbones to generate a quadrivalent LAIV (QIV) containing H3N2 and H1N1 IAV antigenic subtypes and two antigenic IBV lineages.…”

Universal Vaccines and Vaccine Platforms to Protect against Influenza Viruses in Humans and Agriculture

“…More recently, a prototypical influenza B virus engineered with a similar tsHA strategy resulted in a stable virus over multiple passages in tissue culture and eggs, and attenuated in vivo . In mice, a single intranasal dose of the IBV tsHA virus offered protection against lethal homologous and heterologous IBV challenges (Santos et al, 2017a ).…”

FluB-RAM and FluB-RANS: Genome re-arrangement as safe and efficacious live attenuated influenza B virus vaccines.

“…Live attenuated vaccine platforms have been among the most explored over the years (reviewed in [24]). In addition to the coldadapted LAIVs developed in the 60's that form the basis of the current LAIVs approved for human use, alternative LAIV approaches have been developed that include modifications and deletions to the NS1 gene segment, generation of M2 deficient viruses, alternative virus backbones with temperature sensitive phenotypes, among others [25][26][27][28][29][30][31]. We have previously shown that genome re-arrangement is a suitable strategy for the development of influenza A virus LAIVs [32].…”