Abstract
In order to compare the mechanisms of resistance to viral infections present in fetal, neonatal, and adult animals, we developed a model infection in sheep utilizing Semliki Forest virus (SFV), a group A arbovirus. Following IV inoculation of adult sheep with 107.0 to 107.5 PFU of virus, initial viral replication as reflected in the serum occurred by 12-16 hrs, with peak titers of 102-104 PFU/ml present at 16-24 hrs. Virus was completely cleared from the blood by 2 days as antibody became detectable in the serum. Neutralizing antibody titers reached levels of 1/2000-1/8000 by 6 to 7 days. Serum interferon was apparent by 16-24 hrs, reached peak levels of 60 to 600 units/ml, and disappeared by 2 days. Although the pattern of SFV pathogenesis following IV inoculation was similar in both fetal and neonatal lambs to that in adult sheep, virus titers in the serum reached higher levels (103-105 PFU/ml) and lasted longer. Antibody did not become detectable until 5 days and titers were generally lower (1/100-1/600) than in the adult. Interferon levels, however, were higher (2000-6000 units/ml) in parallel with the higher virus titers. The results indicated that in the fetal and neonatal animals: 1) virus replication, as reflected in the serum, occurred to a greater degree, 2) the higher interferon levels appeared to reflect the amount of virus replication, and 3) antibody appeared later in the serum and reached lower levels.
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Overall, J., Glasgow, L. PATHOGENESIS OF AN ARBOVIRUS INFECTION IN FETAL, NEONATAL, AND ADULT SHEEP. Pediatr Res 8, 427 (1974). https://doi.org/10.1203/00006450-197404000-00525
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DOI: https://doi.org/10.1203/00006450-197404000-00525