Intranasal Immunization with Influenza Virus-Like Particles Containing Membrane-Anchored Cholera Toxin B or Ricin Toxin B Enhances Adaptive Immune Responses and Protection against an Antigenically Distinct Virus.

Xianliang Ji,Na Xu,Zhijun Yu,Yongkun Zhao,Hongli Jin,Yuanguo Li,Yuwei Gao,Jinshan Cao,Na Feng,Nan Li,Shengnan Li,Wensen Liu,Tiecheng Wang,Xianzhu Xia,Xiaoyu Sang,Lingnan Meng,Zhiguang Ren,Hualei Wang,Xiaodong Zheng ,Cuiling Wang

doi:10.3390/v8040115

Abstract

Vaccination is the most effective means to prevent influenza virus infection, although current approaches are associated with suboptimal efficacy. Here, we generated virus-like particles (VLPs) composed of the hemagglutinin (HA), neuraminidase (NA) and matrix protein (M1) of A/Changchun/01/2009 (H1N1) with or without either membrane-anchored cholera toxin B (CTB) or ricin toxin B (RTB) as molecular adjuvants. The intranasal immunization of mice with VLPs containing membrane-anchored CTB or RTB elicited stronger humoral and cellular immune responses when compared to mice immunized with VLPs alone. Administration of VLPs containing CTB or RTB significantly enhanced virus-specific systemic and mucosal antibody responses, hemagglutination inhibiting antibody titers, virus neutralizing antibody titers, and the frequency of virus-specific IFN-γ and IL-4 secreting splenocytes. VLPs with and without CTB or RTB conferred complete protection against lethal challenge with a mouse-adapted homologous virus. When challenged with an antigenically distinct H1N1 virus, all mice immunized with VLPs containing CTB or RTB survived whereas mice immunized with VLPs alone showed only partial protection (80% survival). Our results suggest that membrane-anchored CTB and RTB possess strong adjuvant properties when incorporated into an intranasally-delivered influenza VLP vaccine. Chimeric influenza VLPs containing CTB or RTB may represent promising vaccine candidates for improved immunological protection against homologous and antigenically distinct influenza viruses.

Highlights

Seasonal influenza A viruses are human respiratory pathogens that cause seasonal epidemics and an average of 250,000–500,000 annual deaths globally [1]
A recombinant baculovirus expression system was used to generate virus-like particles (VLPs) consisting of the HA, recombinant baculovirus expression system was used generate consisting of the HA, NA, A
Electron microscopy revealed spherical and pleomorphic VLPs 80–100 nm in diameter, with surface spikes characteristic of influenza virus HA and NA proteins (Figure 1E). These results demonstrate that VLPs containing HA, NA, M1 and either membrane-anchored cholera toxin B (CTB) or ricin toxin B (RTB) are similar to standard influenza VLPs and influenza virions with respect to size and morphology

Summary

Introduction

Seasonal influenza A viruses are human respiratory pathogens that cause seasonal epidemics and an average of 250,000–500,000 annual deaths globally [1]. Emergent influenza viruses are a persistent public health threat, as underscored by the novel 2009 H1N1 pandemic virus and sporadic human cases of avian H5N1 and H7N9 influenza viruses [2]. Humans are highly susceptible to newly emergent pandemic influenza viruses due to a lack of pre-existing immunity. Available influenza vaccines are limited in their capacity to elicit highly cross-reactive immune responses against antigenically novel viruses [3]. The sporadic nature of the pandemic influenza virus emergence poses a logistical problem for vaccine manufacturing due to the time it takes to produce and distribute adequate doses of an effective vaccine. There is a need to develop influenza vaccine formulations that are capable of eliciting protective immunity against antigenically diverse influenza viruses at low doses

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