Infectivity Assays

At MDS, we use murine cell lines or hybrid cell lines containing a murine component which are capable of producing infectious mouse retroviruses such as:

• Ecotropic retroviruses
• Xenotropic retroviruses
• Amphotropic and mink cell focus-forming (MCF) retroviruses

The following two protocols are offered:

• Direct focus assays (using one detector cell line) enable direct detection of retrovirus particles. The selected cell line will detect the specific type of retrovirus.
• Extended assays using an initial cell line to amplify the retrovirus (with three and five passages).  These assays are recommended following a direct focus assay.

Remarks:

• These extensive amplifications allow more sensitive detection of retrovirus particles. Hence, if the quantity of retrovirus in the test article is expected to be low, the extended protocol will be chosen.
• If the test articles are supernatants, the inoculation of the test article is directly carried out on the detector cell lines. If the test articles are cells, the latter are co-cultured with the detector cell lines.

Detector Cell Lines:

*The detector cell lines are modified with sarcoma-positive (S+) and leukemia negative (L-) isotypes in order to obtain foci and show the presence of the retrovirus in the cells during the focus assay.

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