Development of a pseudovirus assay and evaluation to screen natural products for inhibition of HIV-1 subtype C reverse transcriptase

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal plants are used in the management of Human Immunodeficiency Virus and Acquired Immunodeficiency Syndrome (HIV/AIDS) in many developing country settings where HIV-1 subtype C drives the epidemic. Efforts to identify plant derived molecules with anti-HIV properties require reproducible assay systems for routine screening of selected plant compounds. Although a number of standardized HIV-1 pseudoviruses have been generated to assess infectivity, replicability or reproducibility, HIV-1 subtype C (HIV-1-C) pseudoviruses have not been comprehensively characterized to identify inhibitory plant substances.

AIM OF THE STUDY

The current study aimed at developing an HIV-1-C pseudovirus assay, and evaluate plant substances targeting reverse transcriptase (RT) activity.

MATERIALS AND METHODS

HIV-1 subtype C pseudoviruses containing a luciferase reporter gene were generated by transfection of human 293T cells. HIV-1 subtype B (HIV-1-B) wild type pseudoviruses and mutants resistant to nucleoside and non-nucleoside RT inhibitors were also generated and used as controls. Selected plant substances and the RT inhibitors Zidovudine (AZT) and Nevirapine (NVP), were used to evaluate inhibition. Pseudovirus infectivity was determined by luciferase measurement in CF2/CD4⁺/CCR5 cells, and cytotoxicity was determined using the MTT assay. AZT and NVP inhibited wild type pseudoviruses in a dose dependent manner, with IC₅₀ values in the nanomolar range.

RESULTS

Pseudoviruses harbouring RT drug resistance mutations were poorly suppressed by AZT and NVP. Catechin, obtained from Peltophorum africanum inhibited HIV-1-C and HIV-1-B pseudoviruses with selective indices of 6304 μM (IC₅₀: 0.49 μM, CC₅₀: 3089 μM) and 1343 μM (IC₅₀: 2.3 μM, CC₅₀: 3089 μM), respectively; while the methanol root crude extract of Elaeodendron transvaalense gave IC₅₀ values of 11.11 μg/ml and 16.86 μg/ml, respectively.

CONCLUSION

The developed HIV-1-C pseudovirus assay can be used to screen plant substances for RT inhibition, and may have utility in settings with limited access to high level biosafety facilities.