Comparison of oral and nasal immunization with inactivated porcine epidemic diarrhea virus on intestinal immunity in piglets

Abstract

Porcine epidemic diarrhea virus (PEDV) has proven to be a major problem for the porcine industry worldwide. Conventional injectable vaccines induce effective systemic immune responses but are less effective in preventing PEDV at mucosal invasion sites, including the nasal or oral mucosa. Additionally, antigens delivered orally are easily degraded. Nasal immunization induces intestinal mucosal immune responses, which can aid in blocking viral invasion, and requires fewer antigen inoculation doses. Therefore, nasal immunizations are considered to be a potential approach to overcome viral infections. In the present study, nasal immunization of piglets was performed using inactivated PEDV combined with Bacillus subtilis as an immunopotentiator and the efficacy of nasal immunization was assessed. The results demonstrated that compared with oral immunization, piglets from the nasal immunization group exhibited higher levels of neutralizing antibodies (P<0.01) in the intestine, PEDV-specific immunoglobulin (Ig)G (P<0.01) in serum and PEDV-specific secretory IgA (SIgA) in saliva (P<0.01) and nasal secretions (P<0.01). An increased number of intestinal CD3 + T cells, IgA-secreting cells and intraepithelial lymphocytes (P<0.05) were also observed. Furthermore, the protein expression levels of interleukin-6 and interferon-γ, relative to the control PEDV infection, were also significantly elevated (P<0.05). The results of the present study indicate that nasal immunization is more effective at inducing the intestinal mucosal immune response, and provide new insights into a novel vaccination strategy that may be used to decrease the incidence of PEDV infections.

Re-emergence of porcine epidemic diarrhea virus in a piglet-producing farm in Jiangxi province in China in 2020

“…Inactivated vaccines mainly act through humoral immunity and can produce a large amount of IgA. IgA antibodies are considered the most important protective antibodies in pig colostrum and provide a protective effect for piglets (En Zhang, 2020). Our research results show that although the vaccine could produce high titers of IgA antibody, some pigs still shed virus in the milk.…”

The New Porcine Epidemic Diarrhea Virus Outbreak May Mean That Existing Commercial Vaccines Are Not Enough to Fully Protect Against the Epidemic Strains

“…Inactivated vaccines mainly act through humoral immunity and can produce a large amount of IgA. IgA antibodies are considered the most important protective antibodies in pig colostrum and provide a protective effect for piglets ( 19 ). Our research results show that although the vaccine could produce high titers of IgA antibody, some pigs still shed virus in the milk.…”

Oral administration of PEDV-dissolved Alg-CS gel induces high and sustained mucosal immunity in mice

“…Levels of IFN-γ in intestinal tissue were measured as previously described [8]. Intestinal tissues were collected on day 24 after immunization, placed in 1.5 ml cryogenic vials containing 500 µl PBS and triturated using a multi-sample tissue grinder.…”

“…An effective measure to protect sows and piglets is to stimulate higher levels of IgA in the intestinal mucosa and milk of sows [4][5][6]. The available PEDV vaccines are administered intramuscularly or subcutaneously and are not effective in preventing PEDV infection in the intestinal mucosa [7,8]. Therefore, a novel and effective method to induce an intestinal mucosal immune response and promote the production of intestinal mucosal IgA is of great significance for the prevention and treatment of PED [9].…”