Friday, 29 November 2013

Stuff from the literature: very SARS-like coronavirus in Chinese horsehoe bats...

The smoking bat for SARS-CoV?
Xing-Yi Ge and colleagues from China, USA, Australia and Singapore described some new severe acute respiratory syndrome (SARS)-like coronaviruses (SL-CoVs) in bats, publishing in Nature last month.

These discoveries were especially notable (not that any new virus discovery isn't) because they displayed more "SARS-like" properties than many earlier so-called SARS-like CoVs. One could grow in the same line of lab cells and also in human cells, it could be visualized by electron microscopy and it could use the same receptor as the SARS-CoV (angiotensin converting enzyme II; ACE2) . Plus, they were genetically very similar.

The bat species was confirmed by gene sequencing to be Rhinolophus sinicus, family Rhinolophidae; the Chinese rufous horseshoe bat.

Throat and faecal samples (anal swabs and faeces) were screened using RT-PCR with primers towards the conserved RNA-dependent RNA polymerase region (RdRp) and new primers were designed to detect other regions of any discoveries. 27 of 117 samples were CoV POS and had sequences determined.

Two novel (and 5 previously identified) SL-CoVs, each with a 29,787+ base pair RNA genome and sharing 95% nucleotide identity with the Tor2 strain of the SARS-CoV which is higher than previous SL-CoVs from China. The receptor binding domain (RBD) of the new CoVs shared 85-96% amino acid identify with the SARS-CoV. These were called:

  1. RsSHC014
  2. Rs3367

Vero cells were used to attempt growth of SL-CoV virions that were first concentrated from samples. This succeeded for one sample, a variant of Rs2267 (99.9% nucleotide identity with Rs3367) and they named this isolate SL-CoV-WIV1. This success is something that hasn't been achieved with the majority of recently identified bat CoVs.

WIV1 also grew, although less efficiently, in:

  • human alveolar basal epithelial (A549) cells
  • pig kidney (PK-15) cells
  • R.sinicus kidney (RSKT) cells
...but not in...

  • Human cervix (HeLa) cells
  • Syrian golden hamster kidney (BHK21) cells
  • Myotis davidii kidney (BK) cells
  • Myotis chinensis kidney (MCKT) cells
  • Rousettus leschenaulti kidney (RLK) cells
  • Pteropus alecto kidney (PaKi) cells
So we have much more convincing evidence that the SARS-CoV is likely to have originated from a bat.

h/t to @MERS_inSAUDI