Frequently Asked Questions - Concentrated Viral Preparations

Generally, ABI recommends the following virus preparations for the following applications:

• ELISA/Western blotting Purified virus or purified viral lysate.
• Infectivity Assays and in vitro applications Direct-pelleted or purified virus.
• Lymphocyte stimulation assays Custom prepared and inactivated purified virus.
• Virus tropism/binding studies Purified virus or custom prepared and inactivated purified virus.

Although SDS-PAGE/Western blot is part of our QC regimen, ABI does not routinely provide SDS-PAGE and Western blot profiles on our viral products.

As a rule, it is not advisable to equate p24 or reverse transcriptase activity in terms of infectious equivalents for HIV, unless repeated infectivity assays of the same stock are performed and correlated with p24 or RT levels. Although the relative p24 or reverse transcriptase activity is positively correlated with virus infectivity in most cases, a true measure of virus infectivity (i.e., TCID₅₀, plaque assay, LD₅₀) as the basis for R&D is the most appropriate way to ensure reproducibility of results.

Fluorometric determinations using PicoGreen^® virtually eliminate any skewing of the absorbance readings by interfering contaminants such as RNA, single-stranded DNA, oligonulcotides or nucleotides.