Is some white matter damage in preterm neonates induced by a human pestivirus?

Neuro-invasion by a 'Trojan Horse' strategy and vasculopathy during intrauterine flavivirus infection

The central nervous system (CNS) is a major target of several important human and animal viral pathogens causing congenital infections. However, despite the importance of neuropathological outcomes, for humans in particular, the pathogenesis, including mode of neuro-invasion, remains unresolved for most congenital virus infections. Using a natural model of congenital infection with an RNA virus, bovine viral diarrhoea virus in pregnant cattle, we sought to delineate the timing and mode of virus neuro-invasion of and spread within the brain of foetuses following experimental respiratory tract infection of the dams at day 75 of pregnancy, a time of maximal risk of tissue pathology without foetal death. Virus antigen was first detected in the foetal brains 14 days postinfection of dams and was initially restricted to amoeboid microglial cells in the periventricular germinal layer. The appearance of these cells was preceded by or concurrent with vasculopathy in the same region. While the affected microvessels were negative for virus antigen, they expressed high levels of the type I interferon-stimulated protein ISG15 and eventually disappeared in parallel with the appearance of microcavitary lesions. Subsequently, the virus spread to neurons and other glial cells. Our findings suggest that the virus enters the CNS via infected microglial precursors, the amoeboid microglial cells, in a 'Trojan horse' mode of invasion and that the microcavitary lesions are associated with loss of periventricular microvasculature, perhaps as a consequence of high, unrestricted induction of interferon-regulated proteins.

Absence of pestivirus antigen in brains with white matter damage

We previously suggested that antenatal pestivirus infection might play a role in the pathogenesis of perinatal brain white matter damage (WMD) in preterm infants. We have now examined 22 brains from stillborns and deceased newborns (both preterm and term) for the presence of bovine virus diarrhoea virus (BVDV) antigen. The brains of five females and five males with WMD (median gestational age 36.5wks), and nine female and three male controls (median gestational age 36.5wks) were used in the study. No BVDV antigen was detected in any of the 22 brains. We conclude that brain infection with BVDV is unlikely to play a role in WMD pathogenesis among preterm or term newborns. Further research is needed to test the hypothesis that intrauterine exposure to pestivirus antigen elicits a fetal inflammatory response which then contributes to WMD.

Infection remote from the brain, neonatal white matter damage, and cerebral palsy in the preterm infant

This review synthesizes the literature supporting the hypothesis that infection during or even before pregnancy remote from the fetal brain leads to neonatal white matter damage (NWMD) and its long-term sequelae, including cerebral palsy. First, a framework of five dimensions is presented, including the spectrum of NWMD, its relationship with gestational age, its clinical spectrum, the expressions and correlates of infection, and the mother/child dyad. Second, a summary of the plethora of support for the remote infection/NWMD-hypothesis is presented by drawing on studies published over the past three decades. Although an epidemiological perspective is prominent, we invoke molecular explanations (especially the cytokine hypothesis) for observed associations. Third, the article concludes with a section on future studies needed to characterize and eliminate (pre-) pregnancy infections in the mother and to identify and evaluate potentially neuroprotective strategies in the fetus.