AB Vector - Cytopathic effect at different times post-infection

  Cytopathic effect at different times post-infection  
  The appearance of Sf9 cells during infection is sometimes a cause for concern, especially for new users who are keen to see something happening but are unsure what to look for. Signs of infection are usually visible within 24 hours, certainly by 48 h if all the cells are infected in the cell culture (high multiplicity of infection or MOI). However, sometimes amount of virus is insufficient to infect majority the cells. In partially infected culture uninfected cells will continue to divide and look normal, while infected cells will produce virus progeny that will eventually infect all the cells. In this case baculovirus infection may take up to 5-6 days to show extensive cytopathic effect (cpe). However the level of cpe does vary between recombinants; expression of proteases is invariably highly cytotoxic with most cells dead within 2 days, while with the expression of secreted glycoproteins or non-toxic cytoplasmic proteins most of the cells are alive after 3 days. However, telltale signs of infection such as cellís increase in size, rounding up and enlargement of the cell nucleus are common and act as a good guide to a successful infection. Overall, less then 10% of proteins are cytotoxic. To help you here are some typical views following a high MOI (non-toxic protein expression) infection.
 
 
Day 0
Cells with tight junctions.
Many "diamond" cells apparent.
Day 1
Cells have rounded up.
Few if any "diamond" cells.
Day 2
All cells rounded and increased in size. Swollen nuclei. "Grainy" appearance in some cells.
Day 3
All cells separated. "Grainy" appearance in many cells, some cells collapsed, some cells floating. Time to harvest for protein expression study.


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