Oxidative stress induced by HIV-1 reverse transcriptase modulates the enzyme’s performance in gene immunization

Abstract

HIV-1 infection induces chronic oxidative stress. The resultant neurotoxicity has been associated with Tat protein. Here, we for the first time describe the induction of oxidative stress by another HIV-1 protein, reverse transcriptase (RT). Expression of HIV-1 RT in human embryonic kidney cells generated potent production of the reactive oxygen species (ROS), detected by the fluorescence-based probes. Quantitative RT-PCR demonstrated that expression of RT in HEK293 cells induced a 10- to 15-fold increased transcription of the phase II detoxifying enzymes human NAD(P)H:quinone oxidoreductase (Nqo1) and heme oxygenase 1 (HO-1), indicating the induction of oxidative stress response. The capacity to induce oxidative stress and stress response appeared to be an intrinsic property of a vast variety of RTs: enzymatically active and inactivated, bearing mutations of drug resistance, following different routes of processing and presentation, expressed from viral or synthetic expression-optimized genes. The total ROS production induced by RT genes of the viral origin was found to be lower than that induced by the synthetic/expression-optimized or chimeric RT genes. However, the viral RT genes induced higher levels of ROS production and higher levels of HO-1 mRNA than the synthetic genes per unit of protein in the expressing cell. The capacity of RT genes to induce the oxidative stress and stress response was then correlated with their immunogenic performance. For this, RT genes were administered into BALB/c mice by intradermal injections followed by electroporation. Splenocytes of immunized mice were stimulated with the RT-derived and control antigens and antigen-specific proliferation was assessed by IFN-γ/IL-2 Fluorospot. RT variants generating high total ROS levels induced significantly stronger IFN-γ responses than the variants inducing lower total ROS, while high levels of ROS normalized per unit of protein in expressing cell were associated with a weak IFN-γ response. Poor gene immunogenicity was also associated with a high (per unit of protein) transcription of antioxidant response element (ARE) dependent phase II detoxifying enzyme genes, specifically HO-1. Thus, we have revealed a direct link between the propensity of the microbial proteins to induce oxidative stress and their immunogenicity.

Keywords: :

• HIV-1 reverse transcriptase
• oxidative stress
• reactive oxygen species
• transcription factor Nrf2
• DNA immunization

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

The authors gratefully acknowledge financial support from the Swedish Research Council (grant K2011-79X-21744-01-6); the New Visby program (grant 00885/2011), and the Thematic partnership program (grant 09272/2013) of the Swedish Institute; the Russian Foundation for Basic Research (grants 13-04-01523 and 11-04-01569a); the Russian Ministry of Education and Science (agreement 8069); and the program “Molecular and Cellular Biology” of the Presidium of the Academy of Sciences of the Russian Federation.

Supplemental Materials

Supplemental materials may be found here: http://www.landesbioscience.com/journals/vaccines/article/25813/