The Role of Neutrophils during Mild and Severe Influenza Virus Infections of Mice

Michelle D Tate,Patrick C Reading,Ben Croker,Lorena E Brown,Lisa J Ioannidis,Andrew G Brooks,Ron Fouchier

doi:10.1371/journal.pone.0017618

Abstract

Neutrophils have been implicated in both protective and pathological responses following influenza virus infections. We have used mAb 1A8 (anti-Ly6G) to specifically deplete LyG6high neutrophils and induce neutropenia in mice infected with virus strains known to differ in virulence. Mice were also treated with mAb RB6-8C5 (anti-Ly6C/G or anti-Gr-1), a mAb widely used to investigate the role of neutrophils in mice that has been shown to bind and deplete additional leukocyte subsets. Using mAb 1A8, we confirm the beneficial role of neutrophils in mice infected with virus strains of intermediate (HKx31; H3N2) or high (PR8; H1N1) virulence whereas treatment of mice infected with an avirulent strain (BJx109; H3N2) did not affect disease or virus replication. Treatment of BJx109-infected mice with mAb RB6-8C5 was, however, associated with significant weight loss and enhanced virus replication indicating that other Gr-1+ cells, not neutrophils, limit disease severity during mild influenza infections.

Highlights

Neutrophils are recruited to the respiratory tract following influenza virus infections of humans and mice [1] and large numbers infiltrate the airways following infection of mice with highly pathogenic viruses such as the reconstructed 1918 H1N1 virus and strains of H5N1 [2,3]
Given that neutrophils have been implicated in both protective and pathological responses following influenza virus infections, we investigated the role of neutrophils in vivo following infection with virus strains known to differ in virulence in mice
Influenza virus strains differ in their virulence for mice HKx31 (H3N2) and BJx109 (H3N2) are high-yielding reassortants of PR8 with A/Aichi/2/68 (H3N2) and A/Beijing/353/89 (H3N2), respectively, and bear H3N2 surface glycoproteins and internal components derived from PR8

Summary

Introduction

Neutrophils are recruited to the respiratory tract following influenza virus infections of humans and mice [1] and large numbers infiltrate the airways following infection of mice with highly pathogenic viruses such as the reconstructed 1918 H1N1 virus and strains of H5N1 [2,3]. Extending the findings of Daley et al [11], we have demonstrated that mAb RB68C5 is not highly specific for neutrophils but binds a range of additional leukocyte populations in the lung of influenza virusinfected mice, including CD8+ T cells, macrophages, NK cells and conventional and plasmacytoid dendritic cells (cDC and pDC, respectively). We showed that mAb 1A8 binds exclusively to Ly6Ghigh neutrophils in the airways of influenza virus-infected mice and specific depletion of Ly6G+ cells with mAb 1A8 lead to exacerbated disease in mice infected with virus strain HKx31 (H3N2)

Methods

Results

Conclusion