Fusion of HSP70 gene of Mycobacterium tuberculosis to hemagglutinin (H5) gene of avian influenza virus in DNA vaccine enhances its potency

A series of plasmids containing the HSP70 gene of Mycobacterium tuberculosis fused to the hemagglutinin (H5) gene of H5N1 avian influenza virus (AIV) (H5-HSP70 (heat shock protein 70) vaccine) or individual H5 gene (H5 vaccine) or HSP70 gene (HSP70 vaccine) were constructed based on the plasmid pcDNA3.1.Expression of H5 gene in Vero cells in vitro and in chickens in vivo was confirmed following their transfection and immunization with H5 or H5-HSP70 vaccines.Controls consisted of HSP70 vaccine, empty plasmid pcDNA3.1 and co-administered H5 and HSP70 vaccines.H5-HSP70 vaccine produced in chicken higher hemagglutination inhibition (HI) antibody titer than H5 vaccine.However, the increase was not statistically significant.We have demonstrated for the first time that the H5 DNA vaccine with fused HSP70 gene may produce an enhanced induction of humoral immune response to AIV in chickens.Keywords: avian influenza virus; hemagglutinin H5; HSP70; DNA vaccine; humoral immunity used vaccines contain complete inactivated AIV (Villarreal-Chavez, 2007).However, new technologies have been implemented to produce the advanced vaccines, e.g.reverse genetic-engineered AIV vaccine, baculovirus-derived H5 and H7 subunit vaccines (Johansson, 1999, Hoffmann et al., 2000) and fowl poxvirus recombinant vaccine containing H5 or H7 genes (Boyle et al., 2000).Although these vaccines induce a protection against AIV, they have many limitations including minimal cross-protection to the diverse influenza strains (Swayne et al., 2001).The viruses that cause greatest difficulties in vaccine production are highly pathogenic avian influenza viruses (HPAIVs) H5, H7, and H9 subtypes.These viruses require a biosafety facility of high level for handling.In some cases, these viruses are not able to give a high yield of virus in the embryonated chicken eggs, because HPAIVs are lethal to the chicken embryo and kill the embryo before a virus can be harvested (Wood, 2001).H5N1 DNA vaccines are safe and effective in experimental animals (Liu et al., 2003).There are numerous studies describing DNA vaccination of different animals indicating the ability of DNA vaccines encoding HA, NA, M1, and NP proteins of AIV to induce specific humoral Acta virologica 54: 33 -39, 2010