Neural invasion of two virulent Suid Herpesvirus 1 strains in neonatal pigs with or without maternal immunity

The neural invasion of two virulent Suid Herpesvirus 1 (SHV1) strains was e xamined in neonatal pigs with or without maternal immunity. One-week-old pi gs with comparable levels of maternal immunity (SN-titer = 12-48) were intr anasally inoculated with 10(7.0) TCID50 of either of the Ka or E21 strains. The invasion of the strains was examined in the nasal mucosa and in three neuronal levels of the trigeminal nervous pathway as well as in three level s of the olfactory nervous pathway by virus titration and immunohistochemis try (IHC). in control pigs without specific antibodies, both strains invade d up to the end level of each neural pathway. In pigs with maternal immunit y, the Ka strain invaded only up to the 2nd level of each pathway with tite rs being significantly lower (p < 0.05) than in the negative controls. Howe ver, the E21 strain invaded up to the end levels in both neural pathways of immune pigs with virus titers being similar to those observed in non-immun e pigs (p > 0.05). IHC revealed that maternal antibodies can protect agains t a fibroblast-mediated spread of the Ka strain in the lamina propria of th e nasal mucosa, as well as against a local spread of the Ka and E21 strains from neurons to their satellite cells in the trigeminal ganglion, in concl usion, the nature of virus strain determines the invasion of SHV1 within th e nervous system of maternally-immune neonatal pigs. (C) 1999 Elsevier Scie nce B.V. All rights reserved.