Type I and Type III Interferons Differ in Their Adjuvant Activities for Influenza Vaccines

Abstract

Type I and type III interferons (IFNs) can promote adaptive immune responses in mice and improve vaccine-induced resistance to viral infections. The adjuvant effect of type III IFN (IFN-λ) specifically boosts mucosal immunity by an indirect mechanism, involving IFN-λ-induced production of thymic stromal lymphopoietin (TSLP), a cytokine that activates immune cells. To date, it remained unclear whether the previously described adjuvant effect of type I IFN (IFN-α/β) would also depend on TSLP and whether type I IFN stimulates different antibody subtypes. Here, we show that after infection with a live attenuated influenza virus, mice lacking functional type I IFN receptors failed to produce normal amounts of virus-specific IgG2c and IgA antibodies. In contrast, mice lacking functional IFN-λ receptors contained normal levels of virus-specific IgG2c but had reduced IgG1 and IgA antibody levels. When applied together with protein antigen, IFN-α stimulated the production of antigen-specific IgA and IgG2c to a greater extent than IgG1, irrespective of whether the mice expressed functional TSLP receptors and irrespective of whether the vaccine was applied by the intranasal or the intraperitoneal route. Taken together, these results demonstrate that the adjuvant activities of type I and type III IFNs are mechanistically distinct.IMPORTANCE Interferons can shape antiviral immune responses, but it is not well understood how they influence vaccine efficacy. We find that type I IFN preferentially promotes the production of antigen-specific IgG2c and IgA antibodies after infection with a live attenuated influenza virus or after immunization with influenza subunit vaccines. In contrast, type III IFN specifically enhances influenza virus-specific IgG1 and IgA production. The adjuvant effect of type I IFN was not dependent on TSLP, which is essential for the adjuvant effect of type III IFN. Type I IFN boosted vaccine-induced antibody production after immunization by the intranasal or the intraperitoneal route, whereas type III IFN exhibited its adjuvant activity only when the vaccine was delivered by the mucosal route. Our findings demonstrate that type I and type III IFNs trigger distinct pathways to enhance the efficacy of vaccines. This knowledge might be used to design more efficient vaccines against infectious diseases.

Keywords: immunization; interferons; mucosal adjuvants.

FIG 1

Different impacts of type I and type III IFN receptor deficiencies on antibody production after infection with live attenuated influenza virus. Mx1-WT (open symbols), Mx1-Ifnar1^–/– (closed symbols), and Mx1-Ifnlr1^–/– (gray symbols) mice were infected with 10⁵ PFU of NS1-deficient influenza virus (hvPR8-△NS1) by the intranasal route. Levels of influenza virus (Flu)-specific IgG in serum (A, C) and Flu-specific IgA in BAL fluid (B, D) were determined by ELISA on day 21 postinfection. Each symbol represents an individual animal. Data are expressed as mean ± SEM. *, P < 0.05; **, P < 0.01 by Mann-Whitney test; ns = no significant difference.

FIG 2

Exogenous IFN-α stimulates IgG and IgA production after intranasal immunization with M2e fusion construct irrespective of TSLP receptor expression. (A, B) WT mice were immunized by intranasal application of 1 μg CTA1-3M2e-DD (M2e) in the presence or absence of 1 μg IFN-αB/D or 1 μg IFN-λ2. Ten days after a single booster immunization, blood (A) and BAL fluid (B) was analyzed for M2e-specific IgG and IgA by ELISA. Each symbol represents an individual animal. Data are expressed as mean ± SEM. **, P < 0.01 by Mann-Whitney test. (C, D) WT and Tslpr^−/− mice were immunized by intranasal application of 1 μg CTA1-3M2e-DD (M2e) in the presence or absence of 1 μg IFN-αB/D. Ten days after booster immunization, blood (C) and BAL fluids (D) were analyzed for M2e-specific IgG and IgA by ELISA. Each symbol represents an individual animal. Data are expressed as mean ± SEM. **, P < 0.01 by Mann-Whitney test; ns = no significant difference.

FIG 3

IFN-α enhances antibody production after intraperitoneal immunization with influenza subunit vaccines. (A) Mx1-WT mice were immunized by the intraperitoneal route with 1 μg CTA3M2e-DD (M2e) in the presence or absence of 1 μg IFN-αB/D. Ten days later, a single booster immunization was performed. M2e-specific IgG serum levels were determined by ELISA 10 days after the booster immunization. Each symbol represents an individual animal. Data are expressed as mean ± SEM. **, P < 0.01 by Mann-Whitney test. (B) WT mice were immunized by the intraperitoneal route with Influsplit Tetra vaccine (HA) in the presence or absence of 1 μg IFN-αB/D. Booster immunizations were performed 10 and 20 days later. HA-specific IgG serum levels were measured 10 days after the first and 10 days after the second booster immunization. Each symbol represents an individual animal. Data are expressed as mean ± SEM. *, P < 0.05; ***, P < 0.001 by two-way ANOVA with Tukey’s multiple-comparisons test; ns = no significant difference.

FIG 4

Intraperitoneal immunization with M2e vaccine in the presence of IFN-α confers enhanced protection against influenza virus challenge. Mx1-WT mice (n = 6 per group) were immunized by intraperitoneal application of 1 μg CTA1-3M2e-DD (M2e) in the presence or absence of 1 μg IFN-αB/D. A single booster immunization was performed 10 days later. Seven weeks after booster immunization, all animals were infected with 10³ PFU of a highly virulent influenza virus strain (hvPR8). Weight loss (A) and survival (B) were monitored. Animals were sacrificed when body weight reached the 75% limit.