How Is Viral Tropism Measured?
Viral tropism is measure by genetic testing of a blood sample. The blood and virus sample is amplified. Then it is tested against cells that express the CCR5 molecule or the CXCR4 molecule. If the sample is active only in the CCR5 cells, then the virus is R5 tropic. If it is active only in the CXCR4 cells, the virus is X4 tropic. Finally, the sample can be active in both the R5 and X4 cells. This would indicate D/M (dual/mixed) tropism. It takes about two weeks to get tropism test results after a sample is sent in.
