Comparing Human Norovirus Surrogates: Murine Norovirus and Tulane Virus

Abstract

Viral surrogates are widely used by researchers to predict human norovirus behavior. Murine norovirus (MNV) is currently accepted as the best surrogate and is assumed to mimic the survival and inactivation of human noroviruses. Recently, a new calicivirus, the Tulane virus (TV), was discovered, and its potential as a human norovirus surrogate is being explored. This study aimed to compare the behavior of the two potential surrogates under varying treatments of pH (2.0 to 10.0), chlorine (0.2 to 2,000 ppm), heat (50 to 75°C), and survival in tap water at room (20°C) and refrigeration (4°C) temperatures for up to 30 days. Viral infectivity was determined by the plaque assay for both MNV and TV. There was no significant difference between the inactivation of MNV and TV in all heat treatments, and for both MNV and TV survival in tap water at 20°C over 30 days. At 4°C, MNV remained infectious over 30 days at a titer of approximately 5 log PFU/ml, whereas TV titers decreased significantly by 5 days. MNV was more pH stable, as TV titers were reduced significantly at pH 2.0, 9.0, and 10.0, as compared with pH 7.0, whereas MNV titers were only significantly reduced at pH 10.0. After chlorine treatment, there was no significant difference in virus with the exception of at 2 ppm, where TV decreased significantly compared with MNV. Compared with TV, MNV is likely a better surrogate for human noroviruses, as MNV persisted over a wider range of pH values, at 2 ppm of chlorine, and without a loss of titer at 4°C.

Comparative Virucidal Efficacy of Seven Disinfectants Against Murine Norovirus and Feline Calicivirus, Surrogates of Human Norovirus

“…It's significant effect on infectious viral titre and genomic copy number confirms results of other studies which also revealed a significant effect on HuNoV genome integrity (Girard et al 2010;Lim et al 2010;Park and Sobsey 2011;Hirneisen and Kniel 2013;Tung et al 2013). …”

“…However Tulane virus does not belong to the genus Norovirus and is less resistant than MNV which is currently considered to be a better surrogate for HuNoV (Hirneisen and Kniel 2013). First isolated in 2003, MNV belongs to genogroup V and infects mice (Karst et al 2003;Wobus et al 2006).…”

Comprehensive Comparison of Cultivable Norovirus Surrogates in Response to Different Inactivation and Disinfection Treatments

“…Because of the importance of low-pH resistance and the need for relatively simple methods to allow the routine use of surrogates, FCV and PEC are inadequate for assessing the efficacies of methods to reduce the public health risk of norovirus infections. Based on our data and those of others, MNV and TuV are the most promising candidates for serving as surrogates for human norovirus (26). However, MNV is significantly more susceptible to alcohols than other nonenveloped viruses, as numerous studies have shown (19,20,22,43).…”

“…Many studies comparing FCV and MNV with or without other surrogates, such as MS2 coliphage and hepatitis A virus, as well as human norovirus (using reverse transcription-quantitative PCR [RT-qPCR]), have been published (4,(18)(19)(20)(21)(22)(23)(24). However, because MNV is highly sensitive to alcohols (18), the focus has expanded to cultivable calici-viruses such as TuV (14,(25)(26)(27)(28) and to porcine enteric calicivirus (PEC), a genogroup III (GIII) sapovirus (29,30).…”

Tulane Virus Recognizes the A Type 3 and B Histo-Blood Group Antigens

“…A challenge of rhesus monkeys with in vitro-cultivated TV resulted in intestinal infection with mild gastroenteritis, indicating that TV is an enteric pathogen (12). Because the TV also recognizes the HBGAs like NoVs (13), it has been used as a surrogate for human NoVs (14)(15)(16)(17)(18).…”