Recognition of extremophilic archaeal viruses by eukaryotic cells: a promising nanoplatform from the third domain of life

Abstract

Viruses from the third domain of life, Archaea, exhibit unusual features including extreme stability that allow their survival in harsh environments. In addition, these species have never been reported to integrate into human or any other eukaryotic genomes, and could thus serve for exploration of novel medical nanoplatforms. Here, we selected two archaeal viruses Sulfolobus monocaudavirus 1 (SMV1) and Sulfolobus spindle shaped virus 2 (SSV2) owing to their unique spindle shape, hyperthermostable and acid-resistant nature and studied their interaction with mammalian cells. Accordingly, we followed viral uptake, intracellular trafficking and cell viability in human endothelial cells of brain (hCMEC/D3 cells) and umbilical vein (HUVEC) origin. Whereas SMV1 is efficiently internalized into both types of human cells, SSV2 differentiates between HUVECs and hCMEC/D3 cells, thus opening a path for selective cell targeting. On internalization, both viruses localize to the lysosomal compartments. Neither SMV1, nor SSV2 induced any detrimental effect on cell morphology, plasma membrane and mitochondrial functionality. This is the first study demonstrating recognition of archaeal viruses by eukaryotic cells which provides good basis for future exploration of archaeal viruses in bioengineering and development of multifunctional vectors.

Interaction of extremophilic archaeal viruses with human and mouse complement system and viral biodistribution in mice

“…SSV2 was propagated in S. solfataricus strain 5E6, whereas SMV1 was propagated in S. islandicus CRISPR deletion mutant delta C1C2 as described in detail elsewhere (Gudbergsdottir et al, 2011; Okutan et al, 2013; Uldahl et al, 2016b). Procedures for cultures, ultrafiltration and viral purification by ultracentrifugation through a 10–40% (w/ v) continuous Iodixanol gradient were as before (Uldahl et al, 2016b).…”

“…Procedures for cultures, ultrafiltration and viral purification by ultracentrifugation through a 10–40% (w/ v) continuous Iodixanol gradient were as before (Uldahl et al, 2016b). The virus preparations were stored at 4 °C until used.…”

“…The virus preparations were stored at 4 °C until used. Viral morphology was confirmed by transmission electron microscopy, whereas Nano-Sight LM20 Nanoparticle Tracking Analysis (Malvern Instruments, Malvern, UK), equipped with a sample chamber with a 405 nm blue laser and a Viton fluoroelastomer O-ring, was used for determination of the hydrodynamic size distribution and viral particle concentration as described in detail earlier (Uldahl et al, 2016b). The approximate virus titer was determined by a plaque assay as described previously (Uldahl et al, 2016b).…”

“…Archaeal viruses also appear in distinct morphologies to include bottle, spindle and droplet shapes (Pina et al, 2011). These unique features, together with their nanosize ranges, offer attractive traits for exploration of their potential in bionanotechnology and bioengineering arenas as well as for development of nanotherapeutics (Steinmetz et al, 2008; Uldahl et al, 2016b). However, to the best of our knowledge, there are no reports on interaction of archaeal viruses with elements of the mammalian innate immune system, and such studies would be of safety and performance importance for potential new therapeutic developments.…”

“…It is also conceivable that unlike virulent pathogens and from an evolutionary point of view, archaeal viruses may have not developed strategies to combat the mammalian innate immune system. Here, we have selected two previously characterized spindle-shaped hyperthermostable and acid-resistant archaeal viruses ( Sulfolobus monocaudavirus 1, SMV1 and Sulfolobus spindle-shaped virus 2, SSV2) (Uldahl et al, 2016a, 2016b) and studied their interaction with human and mouse complement system. We have further examined viral clearance and biodistribution on intravenous injection into wild type (WT) and C3 knockout (C3 KO) mice in C57/BL6J background.…”