BackgroundAnkyrins are cellular mediators of a number of essential protein-protein interactions. Unlike intrabodies, ankyrins are composed of highly structured repeat modules characterized by disulfide bridge-independent folding. Artificial ankyrin molecules, designed to target viral components, might act as intracellular antiviral agents and contribute to the cellular immunity against viral pathogens such as HIV-1.ResultsA phage-displayed library of artificial ankyrins was constructed, and screened on a polyprotein made of the fused matrix and capsid domains (MA-CA) of the HIV-1 Gag precursor. An ankyrin with three modules named AnkGAG1D4 (16.5 kDa) was isolated. AnkGAG1D4 and MA-CA formed a protein complex with a stoichiometry of 1:1 and a dissociation constant of Kd ~ 1 μM, and the AnkGAG1D4 binding site was mapped to the N-terminal domain of the CA, within residues 1-110. HIV-1 production in SupT1 cells stably expressing AnkGAG1D4 in both N-myristoylated and non-N-myristoylated versions was significantly reduced compared to control cells. AnkGAG1D4 expression also reduced the production of MLV, a phylogenetically distant retrovirus. The AnkGAG1D4-mediated antiviral effect on HIV-1 was found to occur at post-integration steps, but did not involve the Gag precursor processing or cellular trafficking. Our data suggested that the lower HIV-1 progeny yields resulted from the negative interference of AnkGAG1D4-CA with the Gag assembly and budding pathway.ConclusionsThe resistance of AnkGAG1D4-expressing cells to HIV-1 suggested that the CA-targeted ankyrin AnkGAG1D4 could serve as a protein platform for the design of a novel class of intracellular inhibitors of HIV-1 assembly based on ankyrin-repeat modules.

Alpha-thalassaemia 1 genetic disorder occurs when there is a deletion of two linked alpha-globin genes. The interaction between these abnormal genes leads to the most severe type of thalassaemia disease, haemoglobin (Hb) Bart's hydrops fetalis. The identification of alpha-thalassaemia 1 carriers and genetic counselling are essential for the prevention and control of severe thalassaemia diseases. In this study, we have developed a rapid screening method for identifying alpha-thalassaemia 1. A sandwich-type immunochromatographic (IC) strip test was developed, using the generated monoclonal anti-Hb Bart's antibody, to trace the Hb Bart's in haemolysates. When assayed by our IC strip test, all alpha-thalassaemia 1, HbH disease, HbH-Constant Spring (H-CS) disease, HbH-CS and heterozygous HbE (CSEA) Bart's disease, and homozygous alpha-thalassaemia 2 showed positive results. No false negative results were observed in these blood samples. In alpha-thalassaemia 2 heterozygotes, 83% of them showed positive reactivity. Among HbE (both homozygotes and heterozygotes), beta-thalassaemia (heterozygotes, homozygotes and beta-thalassaemia/HbE) and normal subjects, the IC strip test revealed negative reactivity of 100, 85 and 97%, respectively. These results indicate that this novel immunodiagnostic kit, in combination with red blood cell indices, is suitable for screening and ruling out mass populations for the presence of alpha-thalassaemia 1.