Protective Efficacy of the Conserved NP, PB1, and M1 Proteins as Immunogens in DNA- and Vaccinia Virus-Based Universal Influenza A Virus Vaccines in Mice

Abstract

bThe conventional hemagglutinin (HA)-and neuraminidase (NA)-based influenza vaccines need to be updated most years and are ineffective if the glycoprotein HA of the vaccine strains is a mismatch with that of the epidemic strain. Universal vaccines targeting conserved viral components might provide cross-protection and thus complement and improve conventional vaccines. In this study, we generated DNA plasmids and recombinant vaccinia viruses expressing the conserved proteins nucleoprotein (NP), polymerase basic 1 (PB1), and matrix 1 (M1) from influenza virus strain A/Beijing/30/95 (H3N2). BALB/c mice were immunized intramuscularly with a single vaccine based on NP, PB1, or M1 alone or a combination vaccine based on all three antigens and were then challenged with lethal doses of the heterologous influenza virus strain A/PR/8/34 (H1N1). Vaccines based on NP, PB1, and M1 provided complete or partial protection against challenge with 1.7 50% lethal dose (LD 50 ) of PR8 in mice. Of the three antigens, NP-based vaccines induced protection against 5 LD 50 and 10 LD 50 and thus exhibited the greatest protective effect. Universal influenza vaccines based on the combination of NP, PB1, and M1 induced a strong immune response and thus might be an alternative approach to addressing future influenza virus pandemics.T he conventional influenza vaccines that are available currently to prevent seasonal flu outbreaks depend mainly on the surface glycoproteins hemagglutinin (HA) and neuraminidase (NA) (1, 2). However, HA-and NA-based conventional influenza vaccines sometimes fail to prevent flu epidemics because the HA and/or NA in the vaccine strains is a mismatch with that in circulating virus strains (3-7). Universal influenza vaccines (UIVs) that induce effective and long-term cross-protection and address the risk of mismatch may overcome the shortcomings of conventional influenza vaccines. Therefore, the development of a UIV capable of inducing long-term immunity and cross-protection remains a priority in influenza vaccine research (8).Influenza viruses are classified as type A, B, or C based on their nucleoprotein (NP) and matrix protein (M). Among the three subtypes, influenza A virus has been the target of UIVs, because the diverse influenza A strains frequently trigger influenza epidemics and pandemics. A previous study indicated that humans mount a good response to the highly conserved internal proteins NP, M1, and polymerase basic 1 (PB1) of influenza A virus (9); therefore, these highly conserved influenza A virus antigens are the basis of UIVs. Multiple studies have investigated the potential of NP (10-13), matrix protein 1 (M1) (14-17), and ion channel (M2, mainly M2e) (18-27) as alternative vaccine antigens for the prevention of seasonal and pandemic flu outbreaks. PB1 has also shown protective potential but requires further investigation for inclusion in UIVs. Košík et al. (28) constructed a DNA vaccine based on PB1, which provided some protective immunity in a mouse model. We previously constructed DNA vaccines ...

Identification of Conserved Peptides Comprising Multiple T Cell Epitopes of Matrix 1 Protein in H1N1 Influenza Virus

“…ProPred employs a literature-based amino acid/ position coefficient table, and presents the HLA-DR binding propensity of given protein sequence (43). SMM align and NetMHC II v2.2 employs a position-specific weight matrix and ANN, respectively, for binding affinity to different HLA-DR, and their binding affinity is given as IC 50 values. These T cell epitope prediction tools have been extensively used and their efficacy has been verified experimentally by various studies (9,11,20,41).…”

“…Finally, 10 CD8+ T cell epitopes (class I HLA binding epitopes) and nine CD4+ T cell epitopes (HLA class II binding epitopes) of the M1 protein were considered for further analysis (Table 3). In Net MHCII 2.2 and IEDB-based SMM align, the binding affinity of the CD4+ T epitope to HLA is given as IC 50 . For each predicted epitope, the IC 50 value varies with various combinations of HLA alleles and tools used.…”

“…For each predicted epitope, the IC 50 value varies with various combinations of HLA alleles and tools used. The range of IC 50 values for predicted CD4+ T cell epitopes is given in Table 3 to show their binding affinity with HLA. Epitopes MVLASTTAK and IRHENRMVL of the M1.8 conserved sequence were predicted to bind to both class I and II HLA molecules.…”

Improving Cross-Protection against Influenza Virus Using Recombinant Vaccinia Vaccine Expressing NP and M2 Ectodomain Tandem Repeats

“…Using the TK gene system of the Tiantan strain, this vaccinia virus has been developed successfully as a viral vector for various vaccine applications (Ruan 2013) including hepatitis B virus (Chuai et al 2018), hepatitis C virus , and severe acute respiratory syndrome coronavirus vaccines (Yan et al 2009). We have developed recombinant vaccinia viruses based on NP, M1, M2, and PB1 of influenza A virus Wang et al 2007Wang et al , 2015. Several of our NP-based recombinant vaccinia viruses have induced a protective immune response in BALB/c mice.…”

Immune responses to highly conserved influenza A virus matrix 1 peptides

“…However studies conducted in recent years have clearly demonstrated the prospects of M1 protein in combination with other influenza proteins as potential targets for development of a universal influenza vaccine . In one study, mice vaccinated with recombinant vaccinia virus expressing the M1 protein were protected after challenge with a lethal dose of influenza virus A Puerto Rico/8/1934 H1N1 strain . Similarly, significant humoral response was observed in mice immunised with Pichia pastoris expressing rHA and rM .…”