ABSTRACT
Reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) is a unique gene amplification method that can be completed within 35 min at 62.5 degrees C. In the present study, RT-LAMP was used to develop a rapid and sensitive laboratory diagnostic system for the H5N1 highly pathogenic avian influenza (HPAI). The sensitivity of the system was 0.1-0.01 plaque-forming units per reaction for HPAI-H5N1 viruses belonging to the genetically and antigenically distinct clade 1, represented by A/Vietnam/JP1203/2004, and clade 2, represented by A/Indonesia/JP283/2006. This RT-LAMP sensitivity is 10-fold higher than the sensitivity of standard one-step RT-PCR. By using viral RNAs extracted from avian influenza viruses of H1-H15 hemagglutinin (HA) subtypes and human pathogenic respiratory viruses, it was confirmed that the RT-LAMP system amplifies specifically RNA of the H5 subtype virus. The system detected H5-HA genes in throat swabs collected from humans as well as from wild birds. These results suggest that the present RT-LAMP system is a useful diagnostic tool for surveillance of recent outbreaks of the HPAI-H5N1 virus.
Subject(s)
Influenza A Virus, H5N1 Subtype/isolation & purification , Influenza A virus/isolation & purification , Influenza in Birds/diagnosis , Influenza, Human/diagnosis , Reverse Transcriptase Polymerase Chain Reaction/methods , Adolescent , Adult , Aged , Animals , Antigens, Viral/genetics , Base Sequence , Child , Child, Preschool , Crows , DNA Primers/genetics , Genes, Viral , Hemagglutinin Glycoproteins, Influenza Virus/genetics , Humans , Influenza A Virus, H5N1 Subtype/genetics , Influenza A virus/genetics , Influenza in Birds/virology , Influenza, Human/virology , Middle Aged , Molecular Sequence Data , Sensitivity and Specificity , Species SpecificityABSTRACT
We developed a rapid and sensitive diagnosis system for H5N1 highly pathogenic avian influenza (HPAI) virus infection using an unique gene amplification method, reverse transcriptase loop-mediated isothermal amplification (RT-LAMP). The sensitivity of the system was found to be 100-fold higher than that of ordinary one-step RT-PCR. Moreover, by using viral RNAs extracted from influenza viruses of all 15 HA subtypes, the RT-LAMP system was confirmed to amplify only the RNA of H5 subtype virus. In the surveillance of H5N1 virus infection of wild birds, we detected two positive cases from dead crows found near the affected area with H5N1-HPAI by using RT-LAMP system, although one of two positive cases was missed by RT-PCR. These results suggested that our newly developed RT-LAMP system specific for H5 virus would be a beneficial diagnostic tool for surveillance of recent outbreaks caused by H5N1-HPAI viruses.
