Evaluation of the Protective Efficacy of Poly I:C as an Adjuvant for H9N2 Subtype Avian Influenza Inactivated Vaccine and Its Mechanism of Action in Ducks

Abstract

Current commercial H9 avian influenza vaccines cannot provide satisfactory protective immunity against antigenic variant influenza viruses in ducks. Poly I:C, when used as an adjuvant, improves humoral and cellular immunity in many animals but has not been tested in ducks. In this study, we investigated the protective efficacy of Poly I:C as an adjuvant for an inactivated H9N2 Avian influenza vaccine in ducks. We found that an H9N2 vaccine administered with poly I:C (H9-PIC vaccine) induced a significantly more rapid response with higher anti-influenza antibody titers than those of the vaccine alone (H9 vaccine). Moreover, virus shedding was reduced in ducks immunized with the H9-PIC vaccine after challenge with an H9 subtype antigenic variant viruses. IFN-α, IFN-γ, IL-6 and MHC-II mRNA levels were all elevated in ducks receiving the H9-PIC vaccine. In addition, lower expression level of MHC-I may be a reason for inefficient protective ability against heterologous influenza viruses in H9-PIC vaccination of ducks. In conclusion, poly I:C adjuvant enhanced both humoral and cellular immune responses in ducks induced by immunization of inactivated H9N2 vaccine.

H9 Influenza Viruses: An Emerging Challenge

“…In the same study, the adapted virus showed deletions in the stalk region of the NA, which is consistent with field observations of natural adaptation of influenza viruses in poultry (Hossain et al 2008). A handful of pathogenesis studies have been also conducted in turkeys (Morales et al 2009;Bonfante et al 2013;Umar et al 2015), chukars (Zhu et al 2018b), ducks (Zhang et al 2017a;Zhu et al 2018b;Wang et al 2019;Yang et al 2019), and guinea fowl (Umar et al 2016). In general, nonpoultry-adapted H9 IAVs showed limited replication and transmission in gallinaceous birds (Xu et al 2012;Suarez and Puscha 2019).…”

Avian Toll-like receptor 3 isoforms and evaluation of Toll-like receptor 3–mediated immune responses using knockout quail fibroblast cells

“…The inhibition of the virus replication in poly(I:C)-treated WT cells ( Figure 4 ) is in agreement with previous reports showing poly(I:C)-induced block of IAV and Marek's disease virus replication in chicken cells ( Ahmed-Hassan et al., 2018 ; Bavananthasivam et al., 2018 ). Polyinosinic:polycytidylic acid also has shown promising results in live birds when used as a prophylactic agent or an adjuvant in vaccines against influenza and Marek's disease ( Parvizi et al., 2012 ; St. Paul et al., 2012 ; Zhang et al., 2017 ). Although the level of poly(I:C)-mediated TLR3-dependent virus reduction ( Figure 4 ) corresponded well with the expected sensitivity to type I interferons (high, moderate, and low sensitivity for VSV, IAV, and ARV, respectively) ( Sekellick et al., 2000 ), other cytokines and antiviral mechanisms may have been involved.…”

Evaluation of Immune Responses and Histopathological Effects against Gamma Irradiated Avian Influenza (Sub type H9N2) Vaccine on Broiler Chicken

“…LPAI can break species barrier and cause infection in pig, horse, and human [9]. Vaccination is a good policy for infectious diseases such as avian influenza virus because it reduces complications of AIV in bird [10,11]. The chemically inactivated influenza virus vaccines provide surface antigens or split product.…”