Direct template matching reveals a host subcellular membrane gyroid cubic structure that is associated with SARS virus.

Viral infection can result in alterations to the host subcellular membrane. This is often reported when using transmission electron microscopy (TEM), resulting in a description of tubuloreticular membrane subcellular ultrastructure rather than a definition based on 3-D morphology. 2-D TEM micrographs depicting subcellular membrane changes are associated with subcellular SARS virion particles [Goldsmith CS, Tatti KM, Ksiazek TG et al. Ultra-structural characterization of SARS coronavirus. Emerg Infect Dis 2004; 10: 320-326]. In the present study, we have defined the 2-D membrane pattern and shape associated with the SARS virus infection. This is by using a direct template matching method to determine what the 3-D structure of the SARS virus associated host membrane change would be. The TEM image for our purposes is defined on 2-D information, such as the membrane having undergone proliferation and from pattern recognition suggesting that the membrane-described pattern is possibly a gyroid type of membrane. Features of the membrane were used to compute and match the gyroid structure with an existing 2-D TEM micrograph, where it was revealed that the membrane structure was indeed a gyroid-based cubic membrane. The 2-D gyroid computer-simulated image that was used to match the electron micrograph of interest was derived from a mathematically well-defined 3-D structure, and it is from this 3-D derivative that allows us to make inferences about the 3-D structure of this membrane. In conclusion, we demonstrate that a 3-D structure can be defined from a 2-D membrane patterned image and that a SARS viral associated membrane change has been identified as cubic membrane morphology. Possible mechanisms for this cubic membrane change are discussed with respect to viral severity, persistence and free radical production.