Rapid detection of influenza A neuraminidase subtypes by cDNA amplification coupled to a simple DNA enzyme immunoassay

Application of a fluorogenic PCR assay for typing and subtyping of influenza viruses in respiratory samples

A fluorogenic PCR-based method (TaqMan-PCR) was developed for typing and subtyping of influenza virus genomes in clinical specimens. The TaqMan-PCR employs a probe technology that exploits the endogenous 5'-3' nuclease activity of the Taq DNA polymerase to allow direct detection of the amplicon by release of a fluorescent reporter during the PCR. Therefore, post-PCR analysis is avoided since hybridization with the fluorogenic probe and quantification of the amplified product is performed simultaneously during PCR cycling. The specificity of the method was evaluated on 86 influenza A (25 H1N1 and 61 H3N2) and 49 influenza B virus reference strains and isolates. The sensitivity of the technique was found to be at the level of 0.1 50% tissue culture infective dose. This TaqMan-PCR was applied prospectively to surveillance work by community-based sampling in Germany during the last two influenza seasons. Seven hundred five throat swabs were analyzed during the winter of 1997-1998. A total of 195 of 705 samples (28%) were positive by PCR. Influenza viruses could be isolated from 125 specimens (18%). During the 1998-1999 season, 1,840 respiratory samples were received. Influenza viruses were isolated from 281 specimens (15%) out of 525 throat swabs (29%) which were positive for influenza A or B virus by TaqMan-PCR. Further differentiation of influenza A virus-positive swabs revealed an intensive circulation of the subtype H3N2 during both seasons, 1997-1998 and 1998-1999. The TaqMan-PCR was much more sensitive than culture and revealed an excellent correlation for typing and subtyping of influenza viruses when samples were positive by both methods.

Typing and subtyping clinical isolates of influenza virus using reverse transcription-polymerase chain reaction

BACKGROUND

Influenza virus infections are a major cause of morbidity and the identification of the type or subtype of a clinical isolate has important clinical and epidemiological implications.

OBJECTIVES

To evaluate the ability of a reverse transcription-polymerase chain reaction (RT-PCR) assay to type and subtype clinical human isolates of influenza virus.

STUDY DESIGN

Reference strains of influenza A H1N1, A/H3N2, and B viruses and human clinical isolates of influenza virus representing antigenic variants from the last 15 years were evaluated using an RT-PCR assay.

RESULTS

Amplicons of 325, 198 and 365 base pairs in length were obtained from RNA extracted from influenza A/H1N1, A/H3N2 and B viruses, respectively. All human-derived A/H1N1, A/H3N2, and B reference strains and antigenic variants tested were correctly identified.

CONCLUSIONS

RT-PCR is an effective alternative to traditional methods for typing and subtyping influenza viruses.

Comparison of reverse transcription-PCR with tissue culture and other rapid diagnostic assays for detection of type A influenza virus

We applied a reverse transcription (RT)-PCR assay for influenza A virus to combined nasal wash-throat swab specimens previously obtained from an outpatient pediatric population with acute respiratory illness during concurrent epidemics of influenza A virus and respiratory syncytial virus. The results of the RT-PCR assay were compared with those previously reported with virus cultivation and commercially available rapid diagnostic kits (E.A. Dominguez, L.H. Taber, and R.B. Couch, J. Clin. Microbiol. 31:2286-2290, 1993). With virus cultivation as the "gold standard", the RT-PCR assay had a sensitivity, specificity, and efficiency of 95, 98, and 97%, respectively, compared with 75, 100, and 93%, respectively, for the best diagnostic kit (Becton Dickinson Directigen). RT-PCR is an effective alternative to virus isolation for the detection of influenza A virus in clinical specimens.