Physicochemical Properties of the Ljungan Virus Prototype Virion in Different Environments: Inactivated by Heat but Resistant to Acidic pH, Detergents and Non‐Physiological Environments Such as Virkon®‐Containing Solutions

Abstract

It is of great importance to know how a virus particle is affected by environmental conditions. Physicochemical properties of the virion will affect the virus viability in different environments, viral transmission between hosts, and will also be important for safe handling of the virus. The physicochemical properties of the Ljungan virus (LV) prototype, 87-012, adapted to grow in cell culture were evaluated using both LV in crude cell extracts and purified virions. Replication of LV was completely inhibited by heat. Titers of LV were unaffected by acidic pH, reduced but not completely abolished by alkaline pH, and unaffected by exposure to the detergents Triton ® X-100 and SDS. Surprisingly, viable LV was still detected after incubation in the acidic, oxidising and detergent-containing environment produced by the commonly used disinfectant Virkon ® . In conclusion, LV is resilient to extreme pH, detergents and also to oxidising environments, but is sensitive to heat treatment.

Structure of Ljungan virus provides insight into genome packaging of this picornavirus

“…3 ) show that genomic RNA becomes exposed at a significantly lower temperature (∼60 °C) with little variation in stability with pH, this being ∼10 °C lower than the capsid dissociation temperature of HAV. In fact, this is broadly in line with previous experiments with purified LV 24 , which suggests that an exogenous factor may stabilize the particles in infected cells. In enteroviruses, capsid protein melting occurs in two distinct steps indicative of a two-stage transition in protein conformation, whereas LV only undergoes the higher-temperature conformational transition, consistent with the observation that alternative particles of parechoviruses cannot be produced by heat treatment 22 .…”

“…Furthermore, LV particles are reported to be resistant to acidic pH, detergents and oxidizing environments with complete inactivation of crude extracts requiring heating to 90 °C (ref. 24 ).…”

An outbreak of severe infections among Australian infants caused by a novel recombinant strain of human parechovirus type 3

“…HPeV4 identical to that seen in humans, and like HPeV3 lacking the RGD receptor motif, has been detected in pigs with anecdotal evidence of neurological disease in Bolivia17. The related rodent viruses Ljungan virus and Sebokele virus68 and a ferret parechovirus69 also lack the RGD motif and Ljungan virus is known to infect and cause disease in people151670717273747576. Furthermore, related viruses in the genus Pasivirus (Parechovirus sister clade), also lacking the RGD motif have been detected in swine and although apparently not associated with disease in humans, a serosurvey suggested that these or closely-related viruses may infect people7778.…”

Ljungan Virus Detected in Bank Voles (Myodes glareolus) and Yellow-Necked Mice (Apodemus flavicollis) from Northern Italy

“…Intriguingly, in Sweden it has been shown that the incidence of type 1 diabetes, GuillainBarré syndrome, and myocarditis in the human population is correlated with rodent population cycles (Niklasson et al, 1998), and children newly diagnosed with type 1 diabetes have significantly increased levels of LV antibodies compared to controls (Niklasson et al, 2003a). More recently, this virus has also been associated with intrauterine fetal deaths in humans (Niklasson et al, 2007b), and it is resistant to extreme pH, oxidizing environments, and detergents, although it is sensitive to heat (Ekströ m et al, 2007). Hence, it has been hypothesized that the bank vole as well as other small rodents could act as reservoirs and/or vectors of LV that may be a zoonotic agent of several widespread and economically important diseases, including type 1 diabetes (Niklasson et al, 1998;2003a).…”