Two distinct regions of HA2 glycopolypeptide of influenza virus hemagglutinin elicit cross-protective immunity against influenza

Abstract

Summary. -currently, a new trend in development of vaccines against influenza with broader spectrum of efficacy is focused on conserved antigens of influenza virus. The hA2 glycopolypeptide (hA2 gp) is one of conserved antigens, potentially suitable as immunogens inducing cross-protection against influenza. We selected two distinct domains of hA2 gp originating from influenza A virus (IAv) of h3 subtype for induction of antiviral immune response: the ectodomain (ehA2) comprising aa 23-185 and the fusion peptide (FP) comprising n-terminal aa 1-38. BAlB/c mice were immunized with three doses of ehA2 and FP, respectively, and subsequently challenged with 2 lD 50 of IAv of homologous (h3) or heterologous (h7) hA subtype. Both peptides induced significant antibody response and protected mice against the lethal infection. The most efficient protection was achieved with ehA2 against homologous virus.Keywords: influenza A virus; cross-protection; hA2 glycopolypeptide; hA2 ectodomain; fusion peptide; mice; vaccine * corresponding author. e-mail: viruevar@savba.sk; phone: +4212-59302427. Abbreviations: A/chicken/Germany/34 (h7n1) virus, rostock strain; A/Miss = A/Mississippi/1/85 (h3n2) virus; A/rostock = avian hA = hemagglutinin; ehA2 = ectodomain of hA2 gp; FA = Freund΄s adjuvant; FP = fusion peptide; hA0 = hA precursor; hA1 = hA1 glycopolypeptide; hA2 = hA2 glycopolypeptide; IAv(s) = influenza A virus(es); MAb = monoclonal antibody; vrnA = viral rnA; p.i. = post infection

HA2 glycopolypeptide of influenza A virus and antiviral immunity

“…These experiments showed that HA2 can induce specific T c -and B-cell immunity resulting in in vivo cross-protection against IAVs of human (H1, H3) and also avian (H7) origin. The cross-protective immune response was found to be broader than that induced by EHA2 in the presence of the Freund΄s adjuvant (Janulíková et al, 2012). The better cross-protectivity achieved by CyaA-HA2 immunization, in comparison to immunization with purified HA2, could be attributed to the specific T-cell immune response involved thanks to insertion of HA2 into CyaA toxoid enabling its presentation on MHC I molecules.…”

“…It has a complex antigenic structure and is able to induce protective antibody and T-cell immune response. At present, peptides corresponding to HA2 epitopes inserted into the various vectors, or the complex trimer of HA2 stem are examined as inductors of cross-protection (Ekiert et al, 2009;Sui et al, 2009;Wang and Palese, 2009;Steel et al, 2010;Bommakanti et al, 2010;Wang et al, 2010b;Eckert and Kay, 2010;Krammer et al, 2012;Janulíková et al, 2012;Staneková et al, 2013). From these studies it can be proposed that HA2 fulfils the requirements to be a candidate for the construction of influenza vaccine with broader protection efficacy.…”

“…Using an animal model, it has been shown that immunization with HA2, expressed by recombinant vaccinia viruses capable of inducing T-and B-cell immunity posed heteroprotection against infection with IAVs of H3 and H1 subtypes (Gocník et al, 2008). Similarly, repeated immunization with purified HA2 gp, produced in E. coli transformed with plasmids expressing the HA2 ectodomain (EHA2) with aa 23-185 in low pH-conformation (Janulíková et al, 2012) or HA2 peptides in native (neutral pH) conformation (Bommakanti et al, 2010) protected mice against a lethal infection with IAVs of human and also of avian origin. Recently, many other systems expressing HA2 gp or the HA trimer stem leading to stimulation of protective immune response have been described (Steel et al, 2010;Ekiert et al, 2009Ekiert et al, , 2011Ekiert et al, , 2012.…”

Virus-neutralizing antibody response of mice to consecutive infection with human and avian influenza A viruses

“…HA2 gp is a relatively conserved protein, and some HA2 epitopes are even shared among HA subtypes (Kostolanský et al, 2002;Varečková et al, 2008). HA2-specific antibodies recognizing HA stem were shown to be protective (Gocník et al, 2007(Gocník et al, , 2008Prabhu et al, 2009;Sui et al, 2009;Wang et al, 2010;Staneková et al, 2011;Janulíková et al, 2012), though they do not mediate virus neutralization by blocking the receptor-binding site on HA. We therefore suggest that anti-stem HA antibodies could help individuals exposed to dangerous avian IAV to overcome the infection in a subclinical manner.…”

“…The latter originated from A/Aichi/2/1968 (H3N2) virus, kindly provided by Drs D.C. Wiley and J. Chen, Harvard University, Boston, USA. EHA2 was purified as previously described (Janulíková et al, 2012).…”