Multiplicity of Scrapie virus in infected mouse spleen cells in vivo

Area of Science:

• Virology
• Immunology
• Neuroscience

Background:

• Scrapie is a fatal neurodegenerative disease caused by prions.
• The rapid increase of scrapie virus titer in lymphoreticular tissues indicates active viral replication.
• Understanding the in vivo virus content is crucial for comprehending disease pathogenesis.

Purpose of the Study:

• To determine the average infectious scrapie virus content per infected spleen cell in vivo.
• To investigate whether the transmissible form of the scrapie virus exists as free nucleic acid.

Main Methods:

• Spleen cells from scrapie virus-infected mice were isolated.
• Intact and lysed spleen cells were compared for mean lethal doses.
• Cytoplasmic nucleic acids were extracted from infected spleen cells for infectivity assays.

Main Results:

• Comparison of lysed to intact spleen cells revealed an average of 2 to 6 infectious units per infected cell.
• No detectable infectivity was found in cytoplasmic nucleic acid preparations from infected spleen cells.

Conclusions:

• The average infectious scrapie virus content in infected spleen cells in vivo is estimated to be 2-6 infectious units.
• These findings suggest that the transmissible form of the scrapie virus is cell-associated and not free nucleic acid.