title: Inactivation of the Tulane virus, a novel surrogate for the human norovirus.
abstract: Human noroviruses (HuNoVs) are the major cause of nonbacterial gastroenteritis epidemics. The culturable feline calicivirus and murine norovirus have been used extensively as surrogates to study HuNoV biology, as HuNoV does not grow in vitro. Additional efforts to identify new surrogates are needed, because neither of these common surrogates are truly intestinal pathogens. The newly described Tulane virus (TV) is a typical calicivirus, it is isolated from macaque stools, is cultivable in vitro, and recognizes human histo-blood group antigens. Therefore, TV is a promising surrogate for HuNoVs. In this study, we evaluated the resistance or stability of TV under various physical and environmental conditions by measuring a 50% reduction of tissue culture infective dose (TCID50) by using a TV cell culture system. Due to the nature of this virus, it is hard to produce a high-titer stock through tissue culture. In our study, the maximal reduction in virus titers was 5D (D = 1 log) in heat-denaturation and EtOH experiments, and 4D in UV, chlorine, and pH-stability experiments. Therefore in this study, we defined the inactivation of TV as reaching a TCID50/ml of 0 (a 4- to 5-D reduction in TCID50, depending on the detection limit). TV was inactivated after incubation at 63 °C for 5 min, incubation at 56 °C for 30 min (5D), exposure to 60 mJ/cm2 of UVC radiation (4D), or incubation at 300 ppm of free chlorine for 10 min (4D). TV was shown to be stable from pH 3.0 to 8.0, though an obvious reduction in virus titer was observed at pH 2.5 and 9.0, and was inactivated at pH 10.0 (4D). TV was resistant to a low concentration of EtOH (40% or lower) but was fully inactivated (5D) by 50 to 70% EtOH after a short exposure (20 s). In contrast, quantitative real-time PCR was unable to detect, or poorly detected, virus titer reductions between treated and untreated samples described in this study.
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, Produce Safety and Microbiology Research Unit, Albany, California 94710, USA. peng.tian@ars.usda.gov
authors.forename: Peng
authors.initials: P
authors.lastname: Tian
authors.forename: David
authors.initials: D
authors.lastname: Yang
authors.forename: Christina
authors.initials: C
authors.lastname: Quigley
authors.forename: Marissa
authors.initials: M
authors.lastname: Chou
authors.forename: Xi
authors.initials: X
authors.lastname: Jiang
mesh_terms: D000818:Animals; D002139:Caliciviridae / Q000187:drug effects* / Q000254:growth & development* / Q000472:pathogenicity; D002415:Cats; D002713:Chlorine / Q000494:pharmacology*; D015169:Colony Count, Microbial / Q000379:methods; D005516:Food Microbiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D051379:Mice; D029322:Norovirus / Q000187:drug effects / Q000254:growth & development / Q000472:pathogenicity; D013045:Species Specificity; D013696:Temperature; D013997:Time Factors; D038301:Virus Inactivation
chemical_list: D002713:Chlorine