{HEAD ~ The modified complexes} retain {TAIL ~ their ability} to stimulate interferon release by the cells but are rendered more vulnerable to destruction within the cells, the modified complexes being significantly less toxic than the original complexes 
retain
{ HEAD ~ The modified complexes } retain { TAIL ~ their ability } to stimulate interferon release by the cells but are rendered more vulnerable to destruction within the cells , the modified complexes being significantly less toxic than the original complexes
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH