Structure and Function of HLA-A*02-Restricted Hantaan Virus Cytotoxic T-Cell Epitope That Mediates Effective Protective Responses in HLA-A2.1/K(b) Transgenic Mice.

Ying Ma,Yun Zhang,Chunmei Zhang,Lihua Chen,Bin Yuan,Ran Zhuang,Kun Yang,Kang Tang,Yusi Zhang,Fanglin Zhang,Boquan Jin,Linfeng Cheng

doi:10.3389/fimmu.2016.00298

Ying Ma, Yun Zhang + Show 10 more

Open Access

https://doi.org/10.3389/fimmu.2016.00298

Copy DOI

Abstract

Hantavirus infections cause severe emerging diseases in humans and are associated with high mortality rates; therefore, they have become a global public health concern. Our previous study showed that the CD8+ T-cell epitope aa129–aa137 (FVVPILLKA, FA9) of the Hantaan virus (HTNV) nucleoprotein (NP), restricted by human leukocyte antigen (HLA)-A*02, induced specific CD8+ T-cell responses that controlled HTNV infection in humans. However, the in vivo immunogenicity of peptide FA9 and the effect of FA9-specific CD8+ T-cell immunity remain unclear. Here, based on a detailed structural analysis of the peptide FA9/HLA-A*0201 complex and functional investigations using HLA-A2.1/Kb transgenic (Tg) mice, we found that the overall structure of the peptide FA9/HLA-A*0201 complex displayed a typical MHC class I fold with Val2 and Ala9 as primary anchor residues and Val3 and Leu7 as secondary anchor residues that allow peptide FA9 to bind tightly with an HLA-A*0201 molecule. Residues in the middle portion of peptide FA9 extruding out of the binding groove may be the sites that allow for recognition by T-cell receptors. Immunization with peptide FA9 in HLA-A2.1/Kb Tg mice induced FA9-specific cytotoxic T-cell responses characterized by the induction of high expression levels of interferon-γ, tumor necrosis factor-α, granzyme B, and CD107a. In an HTNV challenge trial, significant reductions in the levels of both the antigens and the HTNV RNA loads were observed in the liver, spleen, and kidneys of Tg mice pre-vaccinated with peptide FA9. Thus, our findings highlight the ability of HTNV epitope-specific CD8+ T-cell immunity to control HTNV and support the possibility that the HTNV-NP FA9 peptide, naturally processed in vivo in an HLA-A*02-restriction manner, may be a good candidate for the development HTNV peptide vaccines.

Highlights

As widespread emerging zoonotic pathogens, hantaviruses, which belong to the Bunyaviridae family, have significant and growing impacts on global public health [1]
The synthesized peptide FA9 increased the surface expression of human leukocyte antigen (HLA)-A*0201 molecules, corresponding to a fluorescent index (FI) value of 2.77, indicating that peptide FA9 had a high affinity for binding with HLA-A*0201 molecules, whereas the HLA-B*35-restricted peptide aa131–aa139 (VPILLKALY, VY9) on Hantaan virus (HTNV)-NP used as a negative control showed an FI of 0.14, indicating no binding with HLA-A*0201 (Figure 1A)
We reported that the HTNV-NP FA9 peptide could be an immunogenic epitope, which was determined based on its binding with HLAA*0201 molecules and its in vivo functional validation

Summary

Introduction

As widespread emerging zoonotic pathogens, hantaviruses, which belong to the Bunyaviridae family, have significant and growing impacts on global public health [1]. In the U.S, based on the Centers for Disease Control and Prevention report, the total HPS cases from the years of 1993–2015 reached 659, with a higher case-fatality rate of ~36%, thereby raising the concern of the World Health Organization. This situation is further exacerbated by the periodic emergence of novel species of hantaviruses, leading to a disruption of the healthcare systems in epidemic areas and a major health concern worldwide [10,11,12]. Some live attenuated or inactive vaccines have been used in some parts of the world and have partially prevented hantaviruses infections, there remains an urgent need for more effective therapeutic or prophylactic vaccines to better control the epidemic situation [13, 14]

Methods

Results

Conclusion