Systematic evaluation of suspension MDCK cells, adherent MDCK cells, and LLC-MK2 cells for preparing influenza vaccine seed virus.

Suspension Madin-Darby canine kidney (MDCK) cells (MDCK-N), adherent MDCK cells (MDCK-C), and adherent rhesus monkey kidney LLC-MK2 cells (LLC-MK2D) were systematically evaluated for the preparation of influenza vaccine seed viruses for humans on the basis of primary virus isolation efficiency, growth ability, genetic stability of the hemagglutinin (HA) and neuraminidase (NA) genes, and antigenic properties in hemagglutination inhibition (HI) test of each virus isolate upon further passages. All the subtypes/lineages of influenza viruses (A(H1N1), A(H1N1)pdm09, A(H3N2), B-Victoria, and B-Yamagata) were successfully isolated from clinical specimens by using MDCK-N and MDCK-C, whereas LLC-MK2D did not support virus replication well. Serial passages of A(H1N1) viruses in MDCK-N and MDCK-C induced genetic mutations of HA that resulted in moderate antigenic changes in the HI test. All A(H1N1)pdm09 isolates from MDCK-C acquired amino acid substitutions at the site from K153 to N156 of the HA protein, which resulted in striking antigenic alteration. In contrast, only 30% of MDCK-N isolates showed amino acid changes at this site. The frequency of MDCK-N isolates with less than two-fold reduction in the HI titer was as high as 70%. A(H3N2) and B-Yamagata isolates showed high antigenic stability and no specific amino acid substitution during passages in MDCK-N and MDCK-C. B-Victoria isolates from MDCK-N and MDCK-C acquired genetic changes at HA glycosylation sites that greatly affected their antigenicity. When these cell isolates were applied to passages in hen eggs, A(H1N1), B-Victoria, and B-Yamagata viruses grew well in eggs, while none of the cell isolates of A(H3N2) viruses did. Thus, we demonstrate that MDCK-N might be useful for the preparation of influenza vaccine seed viruses.

Rapid discrimination of oseltamivir-resistant 275Y and -susceptible 275H substitutions in the neuraminidase gene of pandemic influenza A/H1N1 2009 virus by duplex one-step RT-PCR assay.

Pandemic influenza A/H1N1 2009 (A/H1N1pdm) virus caused significant outbreaks worldwide last year (2009). A number of oseltamivir-resistant A/H1N1pdm viruses possessing an H275Y substitution in the neuraminidase (NA) protein were reported sporadically in several countries, including Japan, but they were sensitive to zanamivir and did not spread in the community. In this study, to monitor rapidly and simply oseltamivir-resistant A/H1N1pdm viruses possessing H275Y, a duplex one-step RT-PCR assay (H275Y RT-PCR assay) was developed based on an endpoint genotyping analysis method. H275Y RT-PCR assay evaluated using several subtypes/types of influenza A and B viruses and other respiratory pathogenic viruses and shown to have high sensitivity and high specificity. Forty-four clinical specimens were tested after RNA purification using the H275Y RT-PCR assay, resulting in one clinical specimen being found to contain a virus possessing the H275Y mutation. Seventy-three clinical isolates were then tested with the H275Y assay by using clinical isolates in the cultured supernatants of cells directly, without RNA purification, and the results were consistent with the NA sequencing. Since the H275Y RT-PCR assay could detect the H275Y mutation in clinical isolates without RNA purification, as well as a H275Y mutated virus in clinical specimens after RNA purification, the assay was considered a powerful tool for surveillance screening of oseltamivir-resistant A/H1N1pdm virus activity.

Detection of HPV DNA in cervical specimens collected in cytologic solution by ligation-dependent PCR.

OBJECTIVE: To determine the feasibility and sensitivity of detecting human papillomavirus (HPV) in specimens collected in Cytyc PreservCyt fluid (Boxborough, Massachusetts, U.S.A.) using ligation-dependent polymerase chain reaction (LD-PCR) and to demonstrate the diagnostic value of HPV DNA testing as an adjunct to cytology in the detection of cervical squamous intraepithelial lesions (SIL), especially in cases of atypical squamous cells of undetermined significance (ASCUS). STUDY DESIGN: LD-PCR is a recently invented DNA amplification technology that utilizes a capture probe for target isolation and 2 hemiprobes for target detection. The hemiprobes are designed in such a way that when they hybridize to their target, the 5' end of one probe and the 3' end of the other probe are brought together. Two hemiprobes can then be ligated into a full probe that can serve as a template for PCR amplification. A total of 94 cervical specimens were collected in cytologic fluid and tested with LD-PCR. The results were compared with those of the Digene Hybrid Capture II assay (HC II) (Beltville, Maryland, U.S.A.) and consensus PCR. RESULTS: The overall sensitivity for detecting HPV was 41.5% (39/94) by LD-PCR, 50% (47/94) by consensus PCR and 37.2% (35/94) by HC II. The prevalence of HPV by HC II, consensus PCR and LD-PCR were 87.5%, 100% and 87.5% in the high grade SIL group; 100%, 90.9% and 90.9% in the low grade SIL group; 30%, 52.5% and 40% in the ASCUS group; and 14.2%, 22.8% and 17.1% in women with normal cytology. These results indicate that all 3 methods have similar sensitivity in patients with SIL. However, there is greater variation in detection rates in the ASCUS and normal cytology groups. CONCLUSION: LD-PCR is a useful method of detecting HPV in liquid-based gynecologic cytologic preservatives, and HPV testing as a method adjunct to the liquid-based Pap test could be useful in detecting SILs, especially for the management of patients with ASCUS.

Comparison of DNA and RNA extraction methods for mummified tissues.

Nucleic acids extracted from mummified tissues are valuable materials for the study of ancient human beings. Significant difficulty in extracting nucleic acids from mummified tissues has been reported due to chemical modification and degradation. The goal of this study was to determine a method that is more efficient for DNA and RNA extraction from mummified tissues. Twelve mummy specimens were analyzed with 9 different nucleic acid extraction methods, including guanidium thiocyanate (GTC) and proteinase K/detergent based methods prepared in our laboratory or purchased. Glyceraldehyde 3-phosphate dehydrogenase DNA and beta-actin RNA were used as markers for the presence of adequate DNA and RNA, respectively, for PCR and RT-PCR amplification. Our results show that 5 M GTC is more efficient of releasing nucleic acids from mummified tissue than proteinase K/detergent, and phenol/chloroform extraction with an additional chloroform step is more efficient than phenol/chloroform along. We were able to isolate DNAs from all 12 specimens and RNAs from 8 of 12 specimens, and the nucleic acids were sufficient for PCR and RT-PCR analysis. We further tested hepatitis viruses including hepatitis B virus, hepatitis C virus, hepatitis G virus, and TT virus DNA, and fail to detect these viruses in all 12 specimens.

Detection of mycobacterial DNA in Andean mummies.

The identification of genetic material from pathogenic organisms in ancient tissues provides a powerful tool for the study of certain infectious diseases in historic populations. We have obtained tissue samples from the genital areas of 12 mummies in the American Museum of Natural History collection in New York, N.Y. The mummies were excavated in the Andes Mountain region of South America, and radiocarbon dating estimates that the mummies date from A.D. 140 to 1200. DNAs were successfully extracted from all tissues and were suitable for PCR analysis. PCRs were carried out to detect Mycobacterium tuberculosis complex and mycobacteria other than M. tuberculosis (MOTB). M. tuberculosis complex was detected in 2 out of 12 samples, and MOTB were detected in 7 samples. This study confirmed the adequate preservation of genetic material in mummified tissues and the existence of mycobacteria, including M. tuberculosis, in historic populations in South America.