Hepatitis B virus (HBV) is an enveloped virus containing about 3.2 kb, partially double-stranded DNA genome and can be classified into eight genotypes (A to H) [
1]. Different genotypes have distinct geographic distributions, genotype A is pandemic, B and C are mainly prevalent in Asia, D in southern Europe, E in Africa, F in the USA, and G in the USA and France. The newly discovered genotype H was found in central America [
2]. Some studies indicated that different HBV genotypes revealed different disease profiles. Patients with genotype A had a higher rate of clearance HBV DNA and HBeAg than genotype D, and genotype A was more frequent with liver disease of death than genotype F [
3]. Compared with genotype C, patients with genotype B had less active liver disease as HBV genotype B was more associated with earlier HBeAg seroconversion than genotype C [
4].
Hepatitis B virus infection is a major public health problem worldwide, more than 240 million individuals are infected with chronic HBV, among untreated patients with chronic HBV infection, 15 to 40% may progress to cirrhosis [
5]. As HBV is not eradicable by persons immune response or by antiviral drugs developed so far, the only preventive strategy is vaccination, however vaccine is unsuited with some patients, such as those with chronic kidney disease, human immunodeficiency virus infection, type I diabetes mellitus, and celiac disease [
6] Therefore, development of potent HBV detection methods would provide a better insight into HBV immunopathogenesis and therapy [
7] and guide clinical treatment and affect the prognosis [
8]. To compared with other conventional molecular methods, the recombinase aided amplification (RAA) assay is a new isothermal amplification technology with the advantages of rapidity, simplicity and low-cost and therefore potentially suitable for clinical application. RAA has been successfully used to detect a variety of microbial pathogens [
9,
10] and single nucleotide polymorphisms (SNP) [
11]. In the RAA assay, there are there major proteins: single strand DNA binding protein (SSB), recombinase UvsX (
E. coli) and DNA polymerase. The recombinase UvsX pairs the specific primers to template DNA, the main function of SSB is to protect the single chain template DNA and DNA polymerase is responsible for amplification and extension, and the amplification process is completed within 20–30 min at 39 °C.
In this study, we developed a RAA assay to detect HBV without DNA extraction. To our best knowledge, it is the first time to report RAA assay for detecting microbial pathogens without nucleic acid extraction.