Erratum: An advanced workflow for single-particle imaging with the limited data at an X-ray free-electron laser. Corrigendum.

[This corrects the article DOI: 10.1107/S2052252520012798.].

Diffraction data from aerosolized Coliphage PR772 virus particles imaged with the Linac Coherent Light Source.

Single Particle Imaging (SPI) with intense coherent X-ray pulses from X-ray free-electron lasers (XFELs) has the potential to produce molecular structures without the need for crystallization or freezing. Here we present a dataset of 285,944 diffraction patterns from aerosolized Coliphage PR772 virus particles injected into the femtosecond X-ray pulses of the Linac Coherent Light Source (LCLS). Additional exposures with background information are also deposited. The diffraction data were collected at the Atomic, Molecular and Optical Science Instrument (AMO) of the LCLS in 4 experimental beam times during a period of four years. The photon energy was either 1.2 or 1.7 keV and the pulse energy was between 2 and 4 mJ in a focal spot of about 1.3 µm x 1.7 µm full width at half maximum (FWHM). The X-ray laser pulses captured the particles in random orientations. The data offer insight into aerosolised virus particles in the gas phase, contain information relevant to improving experimental parameters, and provide a basis for developing algorithms for image analysis and reconstruction.

An advanced workflow for single-particle imaging with the limited data at an X-ray free-electron laser.

An improved analysis for single-particle imaging (SPI) experiments, using the limited data, is presented here. Results are based on a study of bacteriophage PR772 performed at the Atomic, Molecular and Optical Science instrument at the Linac Coherent Light Source as part of the SPI initiative. Existing methods were modified to cope with the shortcomings of the experimental data: inaccessibility of information from half of the detector and a small fraction of single hits. The general SPI analysis workflow was upgraded with the expectation-maximization based classification of diffraction patterns and mode decomposition on the final virus-structure determination step. The presented processing pipeline allowed us to determine the 3D structure of bacteriophage PR772 without symmetry constraints with a spatial resolution of 6.9 nm. The obtained resolution was limited by the scattering intensity during the experiment and the relatively small number of single hits.

Immunization with phage virus-like particles displaying Zika virus potential B-cell epitopes neutralizes Zika virus infection of monkey kidney cells.

Zika virus (ZIKV) is a mosquito-borne flavivirus that has re-emerged and is associated with many debilitating clinical manifestations. Research is currently being conducted to develop a prophylactic vaccine against the virus; however, there has not been any licensed ZIKV vaccine. Recent studies have identified potential B-cell epitopes (amino acids 241-259, 294-315, 317-327, 346-361, 377-388 and 421-437) on the envelope protein of ZIKV, which could be explored to develop peptide vaccines against ZIKV infection. Nevertheless, the immunogenicity of these epitopes has never been assessed. Here, we displayed these epitopes on highly immunogenic bacteriophage virus-like particles (VLPs; MS2, PP7 and Qß) platforms and assessed their immunogenicity in mice. Mice immunized with a mixture of VLPs displaying ZIKV envelope B-cell epitopes elicited anti-ZIKV antibodies. Although, immunized mice were not protected against a high challenge dose of ZIKV, sera - albeit at low titers - from immunized mice neutralized (in vitro) a low dose of ZIKV. Taken together, these results show that these epitopes are B-cell epitopes and they are immunogenic when displayed on a Qß VLP platform. Furthermore, the results also show that immunization with VLPs displaying a single B-cell epitope minimally reduces ZIKV infection whereas immunization with a mixture of VLPs displaying a combination of the B-cell epitopes neutralizes ZIKV infection. Thus, immunization with a mixture of VLPs displaying multiple ZIKV B-cell epitopes is a good strategy to enhance ZIKV neutralization.