AimsAnalysis of the stability and safety of Sulfolobus monocaudavirus 1 (SMV1) during passage through the mammalian GI tract. Methods and ResultsA major challenge of using nano-vectors to target gut microbiome is their survival during passage through the extremely acidic and proteolytic environment of the mammalian GI tract. Here, we investigated the thermo-acidophilic archaeal virus SMV1 as a candidate therapeutic nano-vector for the distal mammalian GI tract microbiome. We investigated the anatomical distribution, vector stability and immunogenicity of this virus following oral ingestion in mice and compared these traits to the more classically used Inovirus vector M13KE. We found that SMV1 particles were highly stable under both simulated GI tract conditions (invitro) and in mice (invivo). Moreover, SMV1 could not be detected in tissues outside the GI tract and it elicited a nearly undetectable inflammatory response. Finally, we used human intestinal organoids (HIOs) to show that labelled SMV1 did not invade or otherwise perturb the human GI tract epithelium. ConclusionSulfolobus monocaudavirus 1 appeared stable and safe during passage though the mammalian GI tract. Significance and Impact of the StudyThis is the first study evaluating an archaeal virus as a potential therapeutic nanoparticle delivery system and it opens new possibilities for future development of novel nanoplatforms.