Analysis of Common Issues and Research Progress in Loop Mediated Isothermal Amplification

Lymantria dispar (Linnaeus, 1758), which is commonly known as spongy moth, with two subspecies, is found in Asia: Lymantria dispar asiatica and Lymantria dispar japonica, collectively referred to as the Asian spongy moth (ASM). The subspecies Lymantria dispar dispar occurs in Europe and is commonly known as the European spongy moth (ESM). The ASM is on the quarantine list of many countries because it induces greater economic losses than the ESM. Accurate identification is essential to prevent the invasion of ASM into new areas. Although several techniques for identifying ASMs have been developed, the recent discovery of complex patterns of genetic variation among ASMs in China as well as new subspecies in some areas has necessitated the development of new, improved identification techniques, as previously developed techniques are unable to accurately identify ASMs from all regions in China. Here, we demonstrate the efficacy of an improved technique for the identification of the ASM using ASM-specific primers, which were designed based on cytochrome oxidase I sequences from samples obtained from all sites where ASMs have been documented to occur in China. We show that these primers are effective for identifying a single ASM at all life stages and from all ASM populations in China, and the minimum detectable concentration of genomic DNA was 30 pg. The inclusion of other Lymantria samples in our analysis confirmed the high specificity of the primers. Our improved technique allows the spread of ASMs to be monitored in real time and will help mitigate the spread of ASMs to other areas.

Infectious diseases impose a significant burden on global health systems due to high morbidity and mortality rates. According to the World Health Organization, millions die from infectious diseases annually, often due to delays in accurate diagnosis. Traditional diagnostic methods in clinical microbiology, primarily culture-based techniques, are time-consuming and may fail with hard-to-culture pathogens. Molecular biology advancements, notably the polymerase chain reaction (PCR), have revolutionized infectious disease diagnostics by allowing rapid and sensitive detection of pathogens' genetic material. PCR has become the gold standard for many infections, particularly highlighted during the COVID-19 pandemic. Following PCR, next-generation sequencing (NGS) has emerged, enabling comprehensive genomic analysis of pathogens, thus facilitating the detection of new strains and antibiotic resistance tracking. Innovative approaches like CRISPR technology are also enhancing diagnostic precision by identifying specific DNA/RNA sequences. However, the implementation of these methods faces challenges, particularly in low- and middle-income countries due to infrastructural and financial constraints. This review will explore the role of molecular diagnostic methods in infectious disease diagnosis, comparing their advantages and limitations, with a focus on PCR and NGS technologies and their future potential.

BackgroundHuman papillomaviruses (HPVs), a group of non-enveloped small viruses with double-stranded circular DNA which lead to multiple skin diseases such as benign warts, are commonly seen in clinics. The current HPV detection systems aim mainly at mucosal HPVs, however, an efficient clinical approach for cutaneous HPVs detection is lacking.ObjectivesTo establish a rapid detection system for cutaneous HPVs using a colorimetric loop-mediated isothermal amplification (LAMP) with hydroxynaphthol blue (HNB) dye in combination with microfluidic technology.MethodsL1 DNA sequences of the 30 cutaneous HPVs were chemically synthesized, and LAMP primers against L1 DNA were designed with use of an online LAMP designing tool. Isothermal amplification was performed with use of a water bath and the amplification results were inspected with the naked eye. Using PCR sequencing as a control method, the specificity and sensitivity of the new detection system were obtained by detecting clinical samples.ResultsThe lower detection limit of the LAMP assay was 107 viral DNA copies/μl when tested on synthesized L1 DNA sequences, which was better than the conventional PCR. Compared to PCR sequencing, the sensitivity of HPV27, HPV2, HPV1, HPV57, HPV3, HPV4, HPV7 and HPV75 genotypes detections were 100%, whereas the specificity was 34.55, 45.12, 95.83, 98.59 and 97.62% respectively, when tested on clinical samples.ConclusionsThe new cutaneous type HPV detection system is characterized by both a good sensitivity and specificity compared to conventional methods.

Loop-mediated isothermal amplification (LAMP) is a novel method for nucleic acid detection known for its isothermal properties, high efficiency, sensitivity, and specificity. LAMP employs 4 to 6 primers targeting 6 to 8 regions of the desired sequence, allowing for amplification at temperatures between 60 and 65°C and the production of up to 109 copies within a single hour. The product can be monitored by various methods such as turbidimetry, fluorometry, and colorimetry. However, it faces limitations such as the risk of non-specific amplification, challenges in primer design, unsuitability for short gene sequences, and difficulty in multiplexing. Recent advancements in polymerase and primer design have enhanced the speed and convenience of the LAMP reaction. Additionally, integrating LAMP with technologies like rolling circle amplification (RCA), recombinase polymerase amplification (RPA), and CRISPR-Cas systems has enhanced its efficiency. The combination of LAMP with various biosensors has enabled real-time analysis, broadening its application in point-of-care testing (POCT). Microfluidic technology has further facilitated the automation and miniaturization of LAMP assays, allowing for the simultaneous detection of multiple targets and preventing contamination. This review highlights advancements in LAMP, focusing on primer design, polymerase engineering, and its integration with other technologies. Continuous improvements and integration of LAMP with complementary technologies have significantly enhanced its diagnostic capabilities, making it a robust tool for rapid, sensitive, and specific nucleic acid detection with promising implications for healthcare, agriculture, and environmental monitoring.