FIG 6.
M-tropic viruses do not differ from T-tropic viruses in sensitivity to temperature. The effect of temperature on infectivity was assessed for five pairs of subject-matched T-tropic (closed symbols, solid lines) and M-tropic (open symbols, broken lines) Env-pseudotyped reporter viruses. (a) Viruses were incubated at various temperatures for 1 h prior to infecting TZM-bl cells, and the remaining infectivity was normalized to infectivity after incubation at 25°C. Viruses with M-tropic Env proteins were compared with subject-matched T-tropic Env proteins at five temperatures (−80°C, 4°C, 37°C, 49°C and 68°C) but revealed no significant differences between tropism groups (at −80°C, Wpaired = −3, P value = 0.8; at 4°C, Wpaired = −5, P value = 0.6; at 37°C, Wpaired = −7, P value = 0.4; at 49°C, Wpaired = −1, P value = 1; at 68°C, Wpaired = −1, P value = 1). Viruses were incubated at 49°C (b) or 0°C (c) for various lengths of time prior to infecting TZM-bl cells. The remaining infectivity was normalized to an untreated aliquot of each virus. M-tropic Env proteins differed in some cases from paired T-tropic Env proteins, but these differences were not correlated with tropism (panel b, Wpaired = 7, P value = 0.4; panel c, Wpaired = 3, P value = 0.8).