RNA interference approaches for treatment of HIV-1 infection

Achieving HIV-1 Control through RNA-Directed Gene Regulation

HIV-1 infection has been transformed by combined anti-retroviral therapy (ART), changing a universally fatal infection into a controllable infection. However, major obstacles for an HIV-1 cure exist. The HIV latent reservoir, which exists in resting CD4+ T cells, is not impacted by ART, and can reactivate when ART is interrupted or ceased. Additionally, multi-drug resistance can arise. One alternate approach to conventional HIV-1 drug treatment that is being explored involves gene therapies utilizing RNA-directed gene regulation. Commonly known as RNA interference (RNAi), short interfering RNA (siRNA) induce gene silencing in conserved biological pathways, which require a high degree of sequence specificity. This review will provide an overview of the silencing pathways, the current RNAi technologies being developed for HIV-1 gene therapy, current clinical trials, and the challenges faced in progressing these treatments into clinical trials.

Evaluation of the Efficacy And Toxicity of RNAs Targeting HIV-1 Production for Use in Gene or Drug Therapy

Small RNA therapies targeting post-integration steps in the HIV-1 replication cycle are among the top candidates for gene therapy and have the potential to be used as drug therapies for HIV-1 infection. Post-integration inhibitors include ribozymes, short hairpin (sh) RNAs, small interfering (si) RNAs, U1 interference (U1i) RNAs and RNA aptamers. Many of these have been identified using transient co-transfection assays with an HIV-1 expression plasmid and some have advanced to clinical trials. In addition to measures of efficacy, small RNAs have been evaluated for their potential to affect the expression of human RNAs, alter cell growth and/or differentiation, and elicit innate immune responses. In the protocols described here, a set of transient transfection assays designed to evaluate the efficacy and toxicity of RNA molecules targeting post-integration steps in the HIV-1 replication cycle are described. We have used these assays to identify new ribozymes and optimize the format of shRNAs and siRNAs targeting HIV-1 RNA. The methods provide a quick set of assays that are useful for screening new anti-HIV-1 RNAs and could be adapted to screen other post-integration inhibitors of HIV-1 replication.

Design and validation of small interfering RNA on respiratory syncytial virus M2-2 gene: A potential approach in RNA interference on viral replication

Human respiratory syncytial virus (RSV) is the leading cause of severe lower respiratory tract infection in infants and young children globally and is a significant pathogen of the elderly and immunocompromised. The M2-2 protein of respiratory syncytial virus (RSV) is particularly important in regulation of viral RNA transcription and replication that could be a potential anti-viral candidate against RSV infection. In this study, we designed and validated siRNAs that specifically target the RSV M2-2 gene. Four siRNAs targeting different regions of the M2-2 gene were designed using web tool. In-vitro evaluation of silencing effect was performed by using RSV infected Vero cell line. Viral M2-2 linked GFP recombinant plasmid was co-transfected with non-targeted siRNA, Pooled siRNA, siRNA 1, siRNA 2, siRNA 3 and siRNA 4 using synthetic cationic polymer. The silencing effect of M2-2 gene at the protein level was measured both qualitatively and quantitatively by using fluorescence microscopy and flow cytometry. Meanwhile, the silencing effect at the mRNA level was assessed by using RT-qPCR. This study showed that all four designed siRNAs can effectively and efficiently silence M2-2 gene. siRNA 2 showed the highest (98%) silencing effect on protein level and siRNA 4 with 83.1% at the mRNA level. The viral assay showed no significant cytopathic effects observed after 6days post-infection with siRNAs. In conclusion, this study showed the effectiveness of siRNA in silencing M2-2 gene both at the protein and mRNA level which could potentially be used as a novel therapeutic agent in the treatment of RSV infection. However, further study is warranted to investigate the silencing effect of M2-2 protein and inhibition of RSV infection.

Special Issue: Gene Therapy with Emphasis on RNA Interference

Gene therapy was originally thought to cover replacement of malfunctioning genes in treatment of various diseases. Today, the field has been expanded to application of viral and non-viral vectors for delivery of recombinant proteins for the compensation of missing or insufficient proteins, anti-cancer genes and proteins for destruction of tumor cells, immunostimulatory genes and proteins for stimulation of the host defense system against viral agents and tumors. Recently, the importance of RNA interference and its application in gene therapy has become an attractive alternative for drug development.

Virological Mechanisms in the Coinfection between HIV and HCV

Due to shared transmission routes, coinfection with Hepatitis C Virus (HCV) is common in patients infected by Human Immunodeficiency Virus (HIV). The immune-pathogenesis of liver disease in HIV/HCV coinfected patients is a multifactorial process. Several studies demonstrated that HIV worsens the course of HCV infection, increasing the risk of cirrhosis and hepatocellular carcinoma. Also, HCV might increase immunological defects due to HIV and risk of comorbidities. A specific cross-talk among HIV and HCV proteins in coinfected patients modulates the natural history, the immune responses, and the life cycle of both viruses. These effects are mediated by immune mechanisms and by a cross-talk between the two viruses which could interfere with host defense mechanisms. In this review, we focus on some virological/immunological mechanisms of the pathogenetic interactions between HIV and HCV in the human host.