Two lineages of influenza D virus (IDV) have been found to infect cattle and promote
bovine respiratory disease complex, one of the most commonly diagnosed causes of morbidity and mortality within the cattle industry. Furthermore, IDV can infect other economically important domestic livestock, including pigs, and has the potential to infect humans, which necessitates the need for an efficacious
vaccine. In this study, we designed
a DNA vaccine expressing consensus
hemagglutinin-esterase fusion (HEF)
protein (FluD-Vax) and tested its protective efficacy against two lineages of IDV (D/OK and D/660) in guinea pigs. Animals that received FluD-Vax (n = 12) developed appreciable titers of
neutralizing antibodies against IDV lineage representatives, D/OK and D/660. Importantly, vaccinated animals were protected against intranasal challenge with IDV [3 × 105 50% tissue culture infective dose(s) (TCID50)] D/OK (n = 6) or
D/600 (n = 6), based on the absence of
viral RNA in necropsied tissues (5 and 7 days postchallenge) using quantitative reverse transcription-PCR and in situ hybridization. In contrast, animals that received a
sham DNA vaccine (n = 12) had no detectable
neutralizing antibodies against IDV, and
viral RNA was readily detectable in respiratory tract tissues after intranasal challenge (3 × 105 TCID50) with IDV D/OK (n = 6) or D/660 (n = 6). Using a TUNEL (terminal
deoxynucleotidyltransferase-mediated dUTP-
biotin nick end labeling) assay, we found that IDV D/OK and
D/600 infections induced apoptosis in epithelial cells lining alveoli and bronchioles, as well as nonepithelial cells in lung tissues. Our results demonstrate for the first time that the consensus IDV HEF
DNA vaccine can elicit complete protection against
infection from two lineages of IDV in the guinea pig model.IMPORTANCE Influenza D virus (IDV)
infection has been associated with
bovine respiratory disease complex, one of the most devastating diseases of the cattle population. Moreover, with broad host range and high environmental stability, IDV has the potential to further gain virulence or even infect humans. An efficacious
vaccine is needed to prevent
infection and stop potential cross-species transmission. In this study, we designed
a DNA vaccine encoding the consensus
hemagglutinin-esterase fusion (HEF)
protein of two lineages of IDV (D/OK and D/660) and tested its efficacy in a guinea pig model. Our results showed that the consensus
DNA vaccine elicited high-titer
neutralizing antibodies and achieved sterilizing protection against two lineage-representative IDV intranasal
infections. To our knowledge, this is the first study showing that
a DNA vaccine expressing consensus HEF is efficacious in preventing different lineages of IDV
infections.