The Pathogenesis of Saffold Virus in AG129 Mice and the Effects of Its Truncated L Protein in the Central Nervous System

Abstract

Saffold Virus (SAFV) is a human cardiovirus that has been suggested to cause severe infection of the central nervous system (CNS). Compared to a similar virus, Theiler’s murine encephalomyelitis virus (TMEV), SAFV has a truncated Leader (L) protein, a protein essential in the establishment of persistent CNS infections. In this study, we generated a chimeric SAFV by replacing the L protein of SAFV with that of TMEV. We then compared the replication in cell cultures and pathogenesis in a mouse model. We showed that both SAFV and chimeric SAFV are able to infect Vero and Neuro2a cells well, but only chimeric SAFV was able to infect RAW264.7. We then showed that mice lacking IFN-α/β and IFN-γ receptors provide a good animal model for SAFV infection, and further identified the locality of the infection to the ventral horn of the spine and several locations in the brain. Lastly, we showed that neither SAFV nor chimeric SAFV causes persistence in this model. Overall, our results provide a strong basis on which the mechanisms underlying Saffold virus induced neuropathogenesis can be further studied and, hence, facilitating new information about its pathogenesis.

Immunohistochemical insights into Saffold virus infection of the brain of juvenile AG129 mice

“…We however showed no gross demyelination in the brains of the infected animals. We hence provided important insights, extending the findings of our previous paper [15], and provided a strong basis on which the mechanisms of neuropathogenesis of SAFV can be further examined.…”

“…We further attempted to elucidate the effects of the infection. In order to do that, we used AG129 mice which we have previously shown to be a good model for SAFV infection in the CNS [15]. We used previously isolated genotype 3 SAFV [16] as a model of SAFV infection due to its high prevalence [7].…”

“…We used previously isolated genotype 3 SAFV [16] as a model of SAFV infection due to its high prevalence [7]. Infectious clone used in this study was obtained as previously described in Tan et al [15]. We then studied brain tissue of infected animals using immunohistochemical methods to elucidate some of the mechanisms involved in the pathogenesis of SAFV.…”

“…Briefly, tissue sections were incubated with rabbit anti-SAFV VP1 [15] and guinea pig anti-glial fibrillary acidic protein (GFAP) (Synaptic Systems, Goettingen, Germany) or guinea pig anti-neuronal nuclei (NeuN) (Synaptic Systems) overnight at 4 °C. Tissue sections were then further incubated with secondary antibody Alexa Fluor 594 conjugated anti-rabbit IgG and Alexa Fluor 488 conjugated anti-guinea pig IgG (Invitrogen, Gaithersburg, USA) and counterstained with DAPI (Invitrogen, Gaithersburg, USA) before coverslipping with anti-fade mounting medium (DAKO, Copenhagen, Denmark).…”

“…3). In order to see if SAFV infection can cause demyelination subsequently, we infected 3–4 week-old AG129 mice with SAFV, an age which we have previously shown that mice initially only show minor symptoms, but subsequently are able to survive infection, showing no further observable symptoms [15]. Mice were then sacrificed at 35 dpi and brain tissue underwent immunohistochemistry using anti-MBP (Abcam, Cambridge, UK), which similarly revealed no signs of gross demyelination (Fig.…”