Magnesium Functions as Superior Co-factor for Measuring Reverse Transcriptase Activity of HIV-1, HIV-2, and SIV

This study compared different detection methods of human/simian immunodeficiency virus (HIV/SIV) infections in the cell line systems; notably, i) Indirect immunofluorescence assay (IFA), ii) integrated proviral DNA detection, iii) detection of syncytia, iv) measurement of reverse transcriptase (RT) activity. RTs of various retroviruses require cations, including Mg2+, Mn2+, Ni2+, and Cu2+, for their enzyme-activities. The study further compared the roles of Mg2+ and Mn2+ as cofactors for RT activities of freshly harvested HIV-1, HIV-2, and SIV. The NP-2/CD4/coreceptor cells were seeded for overnight and infected with viral inoculums at a multiplicity of infection (MOI) 1.0. The cells were passaged regularly in a 2-3 days interval and maintained up to 2 weeks. Infected cells were detected by indirect immunofluorescence assay (IFA). Multinucleated giant cells (MGC) in syncytia were quantified by Giemsa-staining. Proviral DNA was detected by PCR, and reverse transcriptase (RT) activity was measured. Two different cations, Mg2+ and Mn2+ were used as cofactors for RT assay. We found all the strains of HIV-1, HV-2 and SIV to infection in the cell line conveniently. IFA had identified all the viral infections in the infected cells. Proviral DNA detection, syncytia formation was observed in the infected cells. We found a better performance of Mg2+ as cofactor over Mn2+ in RT assay for HIV-1, HIV-2, SIV. Different four detection techniques of HIV/SIV infections show high level of agreement in the NP-2-based cell line system. Mg2+ remains a better cofactor for RT.