Novel HLA-B7-restricted human metapneumovirus epitopes enhance viral clearance in mice and are recognized by human CD8+ T cells

Margot Miranda-Katz,Yu Zhang,Jie Lan,John V Williams,Sebastian Joyce,John J Erickson,Alwyn Ecker

doi:10.1038/s41598-021-00023-0

Abstract

Human metapneumovirus (HMPV) is a leading cause of acute lower respiratory tract illness in children and adults. Repeated infections are common and can be severe in young, elderly, and immunocompromised persons due to short-lived protective humoral immunity. In turn, few protective T cell epitopes have been identified in humans. Thus, we infected transgenic mice expressing the common human HLA MHC-I allele B*07:02 (HLA-B7) with HMPV and screened a robust library of overlapping and computationally predicted HLA-B7 binding peptides. Six HLA-B7-restricted CD8+ T cell epitopes were identified using ELISPOT screening in the F, M, and N proteins, with M195–203 (M195) eliciting the strongest responses. MHC-tetramer flow cytometric staining confirmed HLA-B7 epitope-specific CD8+ T cells migrated to lungs and spleen of HMPV-immune mice. Immunization with pooled HLA-B7-restricted peptides reduced viral titer and protected mice from virulent infection. Finally, we confirmed that CD8+ T cells from HLA-B7 positive humans also recognize the identified epitopes. These results enable identification of HMPV-specific CD8+ T cells in humans and help to inform future HMPV vaccine design.

Highlights

Human metapneumovirus (HMPV) is a pneumovirus discovered in 2001 and a major cause of acute respiratory infection[1]
HLA-B7tg mice were infected with HMPV via the respiratory tract and splenocytes collected on day 10 were plated with predictope peptides in triplicate in an IFNγ ELISPOT assay
Testing of splenocytes collected on day 8, 9, or 10 post-infection confirmed that stimulation with M195 and N198-206 (N198) peptides produced a significantly increased number of HMPV-immune splenocytes releasing IFNγ (Fig. 1B)

Summary

Introduction

Human metapneumovirus (HMPV) is a pneumovirus discovered in 2001 and a major cause of acute respiratory infection[1]. Programmed Cell Death-1 (PD-1) and other inhibitory receptors mediate impairment of lung C D8+ T cells following HMPV infection in mice and h umans[18,19], providing further evidence of the importance of T cells in viral clearance. CTL epitope vaccines reduced viral titers in m ice[22], and virus-like particles (VLP) generated both antibody and T cell responses against H MPV23,24. To track and study C D8+ T cell responses to vaccines and to natural HMPV infection in humans, it is necessary to map MHC I-restricted viral epitopes. We used transgenic mice expressing human HLA-B*07:02 and lacking the classical mouse MHC class I molecules H-2 Kb and D b (Kb−/−/Db−/−), to identify novel C D8+ T cell epitopes recognized during HMPV infection. Our results show that the transgenic mouse is a useful model for identification of HLA-B*07:02-restricted HMPV epitopes and suggest novel targets for vaccination against HMPV

Methods

Results

Conclusion