Table 1. Characteristics of virions analyzed
Virus Cell line* gag/env TM form Estimated env trimers per virion EM counted env trimers per virion ± SD (range) Calculated gag per virion§ Virus diameter, nm Trimer diameter, nm
HIV-1 MN CEM×174 42:1 gp41 10–19 8 ± 2 (3–12) 1,008 135.0 ± 17.4 11.7 ± 1.3
HIV-1 MN Sup-T1-CCR5 56:1 gp41 7–14 10 ± 3 (5–17) 1,512 116.9 ± 8.5 12.6 ± 0.9
SIVmac239 CEM×174 56:1 gp41 7–14 9 ± 5 (2–17) 1,344 128.0 ± 7.1 12.6 ± 1.4
SIVmac239-tail CEM×174 6:1 gp32 67–133 79 ± 12 (61–96) 1,422 134.4 ± 23.0 12.3 ± 1.2
SIVmac239** Sup-T1-CCR5 8:1 gp32 50–100 70 ± 9 (52–84) 1,680 121.1 ± 22.6 11.6 ± 0.8
Overall mean ± SD 1,393 ± 249 126.5 ± 16.4 12.4 ± 1.3
  • * Cell lines in which viruses were propagated. Virus from CEM×174 cells contained MHC-II, and virus from SupT1-CCR5 cells contained no detectable MHC-II molecules

  • Trimer estimation based on HPLC, amino acid analysis, and immunoblot analysis, assuming 1,200–2,400 gag molecules per virion (20)

  • Trimer estimation based on direct counting from 3D EM tomograms, mean value ± SD, for 10–15 independent virions counted for each different virus sample

  • § Gag molecule per virion values calculated based on EM determined per virion trimer counts and biochemically determined gag:env molar ratios for each virus preparation

  • From membrane surface to membrane surface (excluding env spikes)

  • SIVmac239-tail is a variant of SIVmac239 with a truncated TM env glycoprotein (gp32) and increased virion env content

  • ** Propagation of SIVmac239 in Sup-T1-CCR5 cells resulted in truncation of the transmembrane glycoprotein and increased levels of virion env glycoprotein content