Mapping the sensitivity of the resistant viruses towards other HIV inhibitors. The sensitivity against (A) the CD4bs inhibitors M48, M48U1, sCD4, mAb b12, llama nanobody A12, (B) the CD4i mAb 17b, and the V3 mAb 447-52D and against (C) the anti-gp41 mAbs 4E10 and 2F5, and the NNRTI TMC120, were tested in a TZM-bl assay. Fold change in IC50 values was calculated as follows: IC50 values from the resistant viruses divided by the IC50 value from the control wild-type virus. Control viruses are cultured without compound in parallel with the resistance inductions; i.e. each resistant virus has its control wild-type virus which was used as a reference to determine ‘wild-type’ IC50 values. Technical cut-off (TCO) values were used to define the susceptibility of each virus to a given inhibitor. TCOs were defined as the means and standard deviations (SD) of the IC50 values obtained for the control wild-type viruses according to the following formula: TCO = 1 + 2 SD/mean. >; IC50 could not be exactly quantified because maximal nontoxic levels of miniCD4 were reached.