Recombinant canine distemper virus strain Snyder Hill expressing green or red fluorescent proteins causes meningoencephalitis in the ferret

The propensity of canine distemper virus (CDV) to spread to the central nervous system is one of the primary features of distemper. Therefore, we developed a reverse genetics system based on the neurovirulent Snyder Hill (SH) strain of CDV (CDV(SH)) and show that this virus rapidly circumvents the blood-brain and blood-cerebrospinal fluid (CSF) barriers to spread into the subarachnoid space to induce dramatic viral meningoencephalitis. The use of recombinant CDV(SH) (rCDV(SH)) expressing enhanced green fluorescent protein (EGFP) or red fluorescent protein (dTomato) facilitated the sensitive pathological assessment of routes of virus spread in vivo. Infection of ferrets with these viruses led to the full spectrum of clinical signs typically associated with distemper in dogs during a rapid, fatal disease course of approximately 2 weeks. Comparison with the ferret-adapted CDV(5804P) and the prototypic wild-type CDV(R252) showed that hematogenous infection of the choroid plexus is not a significant route of virus spread into the CSF. Instead, viral spread into the subarachnoid space in rCDV(SH)-infected animals was triggered by infection of vascular endothelial cells and the hematogenous spread of virus-infected leukocytes from meningeal blood vessels into the subarachnoid space. This resulted in widespread infection of cells of the pia and arachnoid mater of the leptomeninges over large areas of the cerebral hemispheres. The ability to sensitively assess the in vivo spread of a neurovirulent strain of CDV provides a novel model system to study the mechanisms of virus spread into the CSF and the pathogenesis of acute viral meningitis.

Human Parechovirus Infection in Neonatal Intensive Care

Background: Approximately 5-6% of all infective episodes in NICU are of viral origin. Previous studies suggest that human parechovirus (HPeV) infection presents most commonly in term infants, as a sepsis-like syndrome in which meningoencephalitis is prominent. Our aim was to study the infection rate and associated features of HPeV.

Methods: Blood samples were taken from NICU babies greater than 48 hours old, who were being investigated for late onset sepsis. Clinical and laboratory data were collected at the time of the suspected sepsis episode. Samples were tested using universal primers and probe directed at the 5'-untranslated region of the HPeV genome by reverse transcriptase PCR. Results were confirmed by electrophoresis and DNA sequencing.

Results: HPeV was detected in 11 of 84 samples (13%). These infants had a mean (interquartile range, IQR) gestational age of 28.9 (26.9 - 30.6) weeks and mean birth weight of 1.26 (SD = 0.72) kg. The median day of presentation was 16 (IQR: 11-27). These characteristics were similar to the infants without positive viral detection. Six infants presented with respiratory signs. One infant presented with signs of meningitis. Six of the 11 episodes of HPeV infection occurred during the winter months (December - February). No HPeV positive infants had abnormal findings on their 28-day cranial ultrasound examination.

Conclusions: We found a HPeV infection rate of 13% in infants being tested for late onset sepsis. HPeV should be considered as a possible cause of sepsis-like symptoms in preterm infants.