RESUMO
Loop-mediated isothermal amplification (LAMP) is the most popular technique to amplify nucleic acid sequence without the use of temperature cycling. However, LAMP is often confounded by false-positive results, arising from interactions between (hetero-dimer) or within (self-dimerization) primers, off-target hybrids and carryover contaminants. Here, we devised a new LAMP technique that is self-avoiding molecular recognition system (SAMRS) components and antarctic thermal sensitive uracil-DNA-glycosylase (AUDG) enzyme-assisted, termed AUDG-SAMRS-LAMP. Incorporating SAMRS components into 3'-ends of LAMP primers can improve assay's specificity, which completely prevents the non-specific amplification yielding from off-target hybrids and undesired interactions between or within primers. Adding AUDG into reaction mixtures can effectively eliminate the false-positive results arising from carryover contamination, thus the genuine positive reactions are generated from the amplification of target templates. Furthermore, AUDG-SAMRS-LAMP results are confirmed using a new analysis strategy, which is developed for detecting LAMP amplicons by lateral flow biosensor (LFB). Only a single labeled primer is required in the analysis system, thus the false positive results arising from hybridization (the labeled primer and probe, or between two labeled primers) are avoided. Hence, the SAMRS components, AUDG and LFB convert traditional LAMP from a technique suited for the research laboratory into one that has practical value in the field of diagnosis. Human Tuberculosis (TB) is caused by infection with members of Mycobacterium tuberculosis complex (MTC), which are detected by the AUDG-SAMRS-LAMP technique to demonstrate the availability of target analysis. The proof-of-concept method can be reconfigured to detect various nucleic acids by redesigning the specific primers.
Assuntos
Mycobacterium tuberculosis/isolamento & purificação , Técnicas de Amplificação de Ácido Nucleico , Uracila-DNA Glicosidase/química , Técnicas Biossensoriais , DNA , Primers do DNA , Humanos , Ácidos Nucleicos , Sensibilidade e Especificidade , Tuberculose/diagnóstico , UracilaRESUMO
A 948-bp sequence of the UL2 gene was amplified from the pseudorabies virus (PRV) Becker strain genome using polymerase chain reaction, and the gene identity was confirmed through further cloning and sequencing. Bioinformatic analysis indicated that the PRV UL2 gene encodes a putative polypeptide with 315-amino acid residues. Its encoding protein, designated UL2, has a conserved uracil-DNA glycosylase (UDG)_F1 domain, which is closely related to the herpesvirus UDG family and is highly conserved among its counterparts encoded by UDG genes. Multiple nucleic acid and amino acid sequence alignments suggested that the product of PRV UL2 has a relatively higher homology with UL2-like proteins of Alphaherpesvirinae than that of other subfamilies of Herpesviridae. In addition, phylogenetic analysis showed that PRV UL2 had a close evolutionary relationship with members of Alphaherpesvirinae, especially members of the genus Varicellovirus of bovine herpesvirus 1 and bovine herpesvirus 5. Antigen prediction indicated the presence of several potential B-cell epitopes in PRV UL2. In addition, secondary structure and 3-dimensional structure prediction revealed that PRV UL2 consisted predominantly of an α-helix. Taken together, these results provide molecular biological insight for the further study of the function and mechanism of UL2 during PRV infection.