Species-Specific Conservation of Linear Antigenic Sites on Vaccinia Virus A27 Protein Homologs of Orthopoxviruses.

Henrike Ahsendorf,Li Gan,Christiane Stahl-Hennig,Claus-Peter Czerny,Sven-Kevin Hotop,Ludwig Hoelzle,Kamal Eltom,Ulrike Beutling,Rachel Roper,Ahmed Abd El Wahed,Mark Broenstrup

doi:10.3390/v11060493

Abstract

The vaccinia virus (VACV) A27 protein and its homologs, which are found in a large number of members of the genus Orthopoxvirus (OPXV), are targets of viral neutralization by host antibodies. We have mapped six binding sites (epitopes #1A: aa 32–39, #1B: aa 28–33, #1C: aa 26–31, #1D: 28–34, #4: aa 9–14, and #5: aa 68–71) of A27 specific monoclonal antibodies (mAbs) using peptide arrays. MAbs recognizing epitopes #1A–D and #4 neutralized VACV Elstree in a complement dependent way (50% plaque-reduction: 12.5–200 µg/mL). Fusion of VACV at low pH was blocked through inhibition of epitope #1A. To determine the sequence variability of the six antigenic sites, 391 sequences of A27 protein homologs available were compared. Epitopes #4 and #5 were conserved among most of the OPXVs, while the sequential epitope complex #1A–D was more variable and, therefore, responsible for species-specific epitope characteristics. The accurate and reliable mapping of defined epitopes on immuno-protective proteins such as the A27 of VACV enables phylogenetic studies and insights into OPXV evolution as well as to pave the way to the development of safer vaccines and chemical or biological antivirals.

Highlights

The genus Orthopoxvirus (OPXV) contains a group of large and closely related DNA viruses within the family Poxviridae, encompassing viruses that replicate in the cytoplasm of vertebrate or invertebrate cells [1,2]
For syncytium formation and fusion experiments, BS-C-1 cells cultured in MEM, supplemented with 10% fetal calf serum (FCS) were used to propagate the vaccinia virus (VACV) strain Western Reserve (WR)
The targets of six anti-A27 monoclonal antibodies (mAbs) were mapped by SPOT synthesis (Table S1)

Summary

Introduction

The genus Orthopoxvirus (OPXV) contains a group of large and closely related DNA viruses within the family Poxviridae, encompassing viruses that replicate in the cytoplasm of vertebrate or invertebrate cells [1,2]. Vaccinia virus (VACV), the prototype of the genus, was applied as the vaccine against the related Variola virus (VARV). This vaccination campaign led to the eradication of smallpox [3,4]. Immunization with VACV elicits potent B- and T-cell mediated immune responses, which provide cross protection against all the other OPXVs [5]. The majority of humans worldwide have no longer a protective immunity against poxviruses because of the termination of the vaccination campaign four decades ago. There is considerable concern about the use of VARV and monkeypox virus (MPXV) as potential biological weapons [6,7], after recent outbreaks of MPXV in the Democratic Republic of Congo, the United States of America, Nigeria and the United Kingdom [8,9,10]

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Results

Conclusion