Picornavirus infection in early murine gestation: Significance of maternalillness

To evaluate whether maternal illness following picornavirus infection durin g pregnancy adversely affects placental and fetal health, mice were inocula ted with the GDVII strain of Theiler's murine encephalomyelitis virus or co ntrol cell lysate during days 4-7 of gestation. Gross appearance, histopath ology and viral culture, and in situ hybridization positivity of placentae and fetuses from ill GDVII-infected, healthy GDVII-infected and control mic e mere compared. Twenty of 34 (59 per cent) GDVII-infected darns became cli nically ill. More placenta-fetus pairs from ill mice were grossly abnormal (68 per cent) than from well GDVII-infected (51 per cent; P<0.01) or contro l mice (9 per cent; P<0.001). Virus was detected by in situ hybridization i n 73 per cent of placentae and 29 per cent of fetuses from sick GDVII-infec ted dams, and in 85 per cent of placentae and 19 per cent of fetuses from h ealthy GDVII-infected mice (differences not significant). Histological abno rmalities consisting of necrosis or an increase in hyaline tissue in the va scular labyrinth layer were similarly frequent in placentae from ill and we ll GDVII-infected mice (58 per cent versus 67 per cent, P=0.5). Viral RNA, inflammation and necrosis mere evident in the heart, great vessels, brain a nd spinal cord of GDVII-infected fetuses. Infection with GDVII in early pre gnancy produces a high rate of gross placental and fetal abnormalities. The rate of gross abnormalities exceeds the incidence of fetal infection and m ore closely parallels the rates of infection and histopathology in the plac enta, suggesting that much of the damage to placenta-fetus pairs is a conse quence of placental infection. In addition, the occurrence of viral-induced maternal illness is associated with additive risk to placental and fetal h earth not explained by an increased rate of placental or fetal infection. ( C) 2000 Harcourt Publishers Ltd.