A DNA Vaccine Expressing Consensus Hemagglutinin-Esterase Fusion Protein Protected Guinea Pigs from Infection by Two Lineages of Influenza D Virus

Abstract

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 ( = 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 × 10 50% tissue culture infective dose(s) (TCID)] D/OK ( = 6) or D/600 ( = 6), based on the absence of viral RNA in necropsied tissues (5 and 7 days postchallenge) using quantitative reverse transcription-PCR and hybridization. In contrast, animals that received a sham DNA vaccine ( = 12) had no detectable neutralizing antibodies against IDV, and viral RNA was readily detectable in respiratory tract tissues after intranasal challenge (3 × 10 TCID) with IDV D/OK ( = 6) or D/660 ( = 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. 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.

Emerging Influenza D Virus Threat: What We Know so Far!

“…The study showed that the vaccinated animals showed significant titers of neutralizing antibodies against both lineages of IDV and were protected against the intranasal IDV challenge. Although studies in past have shown the potential of DNA vaccines against IAV [81], this study is claimed to be the first to show the effect of a DNA vaccine against IDV and thus a promising approach to manage infections [82].…”

Antigenic heterogeneity among phylogenetic clusters of influenza D viruses

“…However, the protective effects of these vaccines are unsatisfactory in some cases of respiratory illness, suggesting that the cases may be associated with flu D virus infection. Therefore, vaccine development for flu D should be considered [ 9 , 23 ]. The antigenic heterogeneity among all flu D virus HEFs shown in this study emphasizes that, when developing flu D vaccine in Japan, the D/Japan-lineage virus should be used as a seed virus to yield maximal vaccine efficacy.…”

Novel Synthetic DNA Immunogens Targeting Latent Expressed Antigens of Epstein–Barr Virus Elicit Potent Cellular Responses and Inhibit Tumor Growth

“…We designed consensus optimized DNA vaccines targeting the oncogenic EBV latent proteins commonly seen in malignancies, which are EBNA1, LMP1, and LMP2A. Consensus immunogens can focus the immune response towards conserved regions of important antigens, allowing for increased T cell cross reactivity as well as partially compensating for minor variability in the vaccine targeted antigens [48,49,50]. Consensus sequences using GD1 (type 1), B95-8 (type 1), and AG876 (type 2) EBV genes were generated for all 3 antigens (Figure 1A) to optimize the ability of the vaccines to elicit immune responses against all common viral strains, which are phylogenetically similar [51].…”