A live-attenuated influenza vaccine for H3N2 canine influenza virus

Abstract

Canine influenza is a contagious respiratory disease in dogs caused by two subtypes (H3N2 and H3N8) of canine influenza virus (CIV). Currently, only inactivated influenza vaccines (IIVs) are available for the prevention of CIVs. Historically, live-attenuated influenza vaccines (LAIVs) have been shown to produce better immunogenicity and protection efficacy than IIVs. Here, we have engineered a CIV H3N2 LAIV by using the internal genes of a previously described CIV H3N8 LAIV as a master donor virus (MDV) and the surface HA and NA genes of a circulating CIV H3N2 strain. Our findings show that CIV H3N2 LAIV replicates efficiently at low temperature but its replication is impaired at higher temperatures. The CIV H3N2 LAIV was attenuated in vivo but induced better protection efficacy in mice against challenge with wild-type CIV H3N2 than a commercial CIV H3N2 IIV. This is the first description of a LAIV for the prevention of CIV H3N2 in dogs.

Interplay of PA-X and NS1 Proteins in Replication and Pathogenesis of a Temperature-Sensitive 2009 Pandemic H1N1 Influenza A Virus

“…1B). Both combinations of plasmids (WT and LAIV) resulted in similar Gaussia luciferase (Gluc) expression levels at 33°C; however, Gluc expression was significantly reduced at higher temperatures (37°C and 39°C) in cells transfected with the pH1N1 LAIV plasmids, consistent with previous results shown for other IAV LAIV strains (9)(10)(11). Importantly, Western blot analysis shows similar levels of NP expression at each temperature for WT-and LAIV-transfected cells (Fig.…”

“…First, because a recombinant pH1N1 harboring inhibitory PA-X and NS1 proteins could lead to a more virulent virus (35)(36)(37)(38), we selected, for safety reasons, to use the ca, ts, and att pH1N1 LAIV virus. Second, we and others have previously shown that LAIVs provide a more sensitive approach to study mutations affecting overall viral replication and pathogenicity (5,7,(9)(10)(11)39). Finally, the results obtained from our studies could be used to identify and develop more efficient LAIV candidates with acceptable safety profiles by modulating the virus' ability to control the host immune responses (7,11).…”

“…In order to generate a pH1N1 LAIV virus, we introduced four ts mutations identified in previous studies into the PB2 (N265S) and PB1 (K391E, D581G, and A661T) ORFs of pH1N1 (Fig. 1A) (7,9,10,39). No mutation was introduced into the viral NP, since pH1N1 NP already contains a G at position 34.…”

“…The attenuation mechanisms are not totally understood but could involve several steps in the replication cycle of the virus (4). Importantly, when the ts signature of A/AA/6/60 was introduced into three different viruses (influenza virus A/Puerto Rico/8/34 H1N1 [PR8] [7,8], canine influenza virus H3N8 [9,10], or pandemic influenza virus A/New York/1682/2009 H1N1 [11]), a similar ts viral phenotype was observed in tissue culture cells and in mouse models of infection. Moreover, ca, ts, and att viruses have been previously utilized to evaluate additional mutations that can increase the safety profile of a vaccine candidate (7,11).…”

Canine Infectious Respiratory Disease

“…Parenteral vaccines are available for reduction of clinical signs owing to CIVs, including individual H3N8 or H3N2 vaccines and combination (bivalent) vaccines. 82,83 No commercially available vaccines are available for reduction of clinical signs caused by CRCoV and CHV.…”