Abstract
Avian influenza viruses can be efficiently transmitted through mucous membranes, and conventional vaccines are not effective in protecting against mucosal infection by influenza viruses. To induce multiple immune responses in an organism, we constructed a recombinant Lactobacillus plantarum expressing the influenza virus antigen HA1 with the adjuvant dendritic cell-targeting peptide (DCpep). The recombinant L. plantarum strains NC8Δ-pWCF-HA1 and NC8Δ-pWCF-HA1-DCpep were used to immunize mice via oral administration, and the humoral, cellular and mucosal immune responses were evaluated. In addition, the serum levels of specific antibodies and hemagglutination inhibition (HI) levels were also measured. Our results showed that recombinant L. plantarum activated dendritic cells in Peyer’s patches (PPs), increased the numbers of CD4+IFN-γ+ and CD8+IFN-γ+ cells in the spleen and mesenteric lymph nodes (MLNs), and affected the ability of CD4+ and CD8+ cells to proliferate in the spleen and MLNs. Additionally, recombinant L. plantarum increased the number of B220+IgA+ cells in PPs and the level of IgA in the lungs and different intestinal segments. In addition, specific IgG, IgG1 and IgG2a antibodies were induced at high levels in the mice serum, specific IgA antibodies were induced at high levels in the mice feces, and HI potency was significantly increased. Thus, the recombinant L. plantarum strains NC8Δ-pWCF-HA1 and NC8Δ-pWCF-HA1-DCpep have potential as vaccine candidates for avian influenza virus.
Highlights
Avian influenza viruses (AIVs) have broken the genetic barrier and acquired the ability to directly infect birds and humans, causing substantial economic damage to the poultry industry and posing a serious risk to human health and public health (1)
Synthesis of pWCF-HA1 and pWCF-HA1-dendritic cell-targeting peptide (DCpep) Expressed on L. plantarum
To further determine whether HA1 and HA1-DCpep are localized on the surface of L. plantarum, detection was performed by flow cytometry and immunofluorescence staining
Summary
Avian influenza viruses (AIVs) have broken the genetic barrier and acquired the ability to directly infect birds and humans, causing substantial economic damage to the poultry industry and posing a serious risk to human health and public health (1). The genome of avian influenza virus contains eight single-stranded negative-sense RNA fragments, and the unique fragmented genomic features make the virus highly susceptible to recombination and often lead to the creation of new viruses (2). H7N9 subtype avian influenza virus is a highly pathogenic avian influenza virus, first emerged in China in 2013, resulting in 1,568 human infections and causing 615 deaths (4). Vaccines based on AIV surface proteins are the most effective means of controlling the spread of AIVs. Hemagglutinin is an important multifunctional protein in influenza viruses. The HA0 protein is cleaved into the HA1 and HA2 subunits by cytosolic proteases, and the HA1 subunit, which forms the globular head, is highly variable among isoforms and contains the major neutralizing epitope (5). Oral vaccines based on the HA1 protein have rarely been reported
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