Conditionally viable (ts) CA mutants exhibit defects only when assembled at the non-permissive temperature.

(A) Measurement of infectious virion titer from 293T cells transfected with either the parental or the ts single residue mutant proviral plasmids, and placed at either 35°C (filled circles), 37°C (filled squares), or 39.5°C for virion production (filled triangles), as indicated by distinct plot lines. The titer of infectious virus in the resulting supernatants from each mutant was measured in MT-4 cells at 35, 37, or 39.5°C as indicated on the x-axis, with the addition of dextran sulfate at approximately 16 h post-infection to limit replication to a single cycle. Note that some single ts mutants were resolved from double or triple mutants (see Materials and Methods) so do not appear in Table 1 or 2. (B) As in (A), however, here the temperature of virus production is indicated on the x-axis, and inoculations were done in MT-4 cells at 37°C only.