Cross-protection against H5N1 influenza virus infection is afforded by intranasal inoculation with seasonal trivalent inactivated influenza vaccine

Abstract

Background: Avian H5N1 influenza A virus is an emerging pathogen with the potential to cause substantial human morbidity and mortality. We evaluated the ability of currently licensed seasonal influenza vaccine to confer cross-protection against highly pathogenic H5N1 influenza virus in mice.

Methods: BALB/c mice were inoculated 3 times, either intranasally or subcutaneously, with the trivalent inactivated influenza vaccine licensed in Japan for the 2005-2006 season. The vaccine included A/NewCaledonia/20/99 (H1N1), A/NewYork/55/2004 (H3N2), and B/Shanghai/361/2002 viral strains and was administered together with poly(I):poly(C(12)U) (Ampligen) as an adjuvant. At 14 days after the final inoculation, the inoculated mice were challenged with either the A/HongKong/483/97, the A/Vietnam/1194/04, or the A/Indonesia/6/05 strain of H5N1 influenza virus.

Results: Compared with noninoculated mice, those inoculated intranasally manifested cross-reactivity of mucosal IgA and serum IgG with H5N1 virus, as well as both a reduced H5N1 virus titer in nasal-wash samples and increased survival, after challenge with H5N1 virus. Subcutaneous inoculation did not induce a cross-reactive IgA response and did not afford protection against H5N1 viral infection.

Conclusions: Intranasal inoculation with annual influenza vaccine plus the Toll-like receptor-3 agonist, poly(I):poly(C(12)U), may overcome the problem of a limited supply of H5N1 virus vaccine by providing cross-protective mucosal immunity against H5N1 viruses with pandemic potential.

Figures

Table 1.

Titers of antibodies specific for the trivalent vaccine.

Table 2.

Titers of IgA and IgG antibodies cross-reactive with A/Vietnam/1194/2004 (H5N1), and virus titer after challenge, in immunized mice.

Figure 1.

Cross-protective effect of inoculation with trivalent inactivated influenza vaccine and Ampligen against highly pathogenic H5N1 influenza viruses. Mice were inoculated, intranasally (in) or subcutaneously (sc), with trivalent inactivated vaccine and Ampligen, as described in table 1. At 14 days after the final inoculation, the mice were challenged by in administration of 1000 pfu of A/Vietnam/1194/04 virus (A), A/HongKong/483/97 virus (B), or A/Indonesia/6/05 virus (C). At 3 days after challenge, nasal-wash samples were collected, and the titer of each virus was determined (left panels); data are means ± SEs 5 mice/group. White circles indicate values for individual mice. Survival rates of the mice in each group (n=5 or n=10) also were monitored, for 14 days after challenge with H5N1 (right panels). *P < .05 vs. noninoculated (Naive) mice.

Figure 2.

Interferon (IFN)—γ (left panels) and [3H]thymidine incorporation (right panels) by T cells from mice inoculated intranasally (in) with the trivalent vaccine and Ampligen (A), mice inoculated with the trivalent vaccine alone (B), and noninoculated mice (C), as described in table 1. Splenic T cells were isolated from the mice 10 days after the final inoculation and were cultured with irradiated antigen-presenting cells in the absence or presence of A/NewCaledonia (A/NC), A/NewYork (A/NY), B/Shanghai (B/Shan), or A/Vietnam/1194/04 (A/VN) antigens, at concentrations of 0.1 μ/mL and μ/mL. After 4 days of culture, the concentration of IFN-γ in culture supernatants was measured by ELISA; the minimum detectable dose of mouse IFN-γ is <1 pg/mL. Data are means ± SDs for 2 independent experiments, each performed with T cells from 5 mice/group.