Detection of emergent strains of West Nile virus with a blood screening assay.

BACKGROUND: West Nile virus (WNV) is a threat to transfusion safety. WNV Kunjin strain (WNVKUN ) is endemic across parts of Australia; however, human infection is believed to be infrequent and is often associated with relatively minor symptoms. A virulent strain, closely related to WNVKUN (termed WNVNSW2011 ) was recently identified as the etiologic agent of encephalitis in Australian horses. The aim of this project was to investigate whether a commercially available WNV blood screening assay can detect different strains of WNVKUN , including the virulent WNVNSW2011 , in human blood donor samples. STUDY DESIGN AND METHODS: Plasma samples were spiked with four different strains of WNVKUN , as well as a prototype WNV strain, at high, medium, and low viral loads. Spiking was confirmed with real-time reverse transcription-polymerase chain reaction (RT-PCR), before testing with the Procleix WNV transcription-mediated amplification (TMA) blood screening assay (Grifols). RESULTS: All WNV strains used were detectable by RT-PCR after being spiked into plasma. Additionally, all viral spiked samples were reactive by WNV TMA. CONCLUSION: We experimentally demonstrate that a commercially available WNV blood screening assay can detect different strains of WNVKUN . Given that WNV can be transfusion transmissible, it is essential to confirm that emergent strains are detectable by existing blood screening methods.

Seroprevalence of hepatitis E virus (HEV) and detection of HEV RNA with a transcription-mediated amplification assay in blood donors from Catalonia (Spain).

BACKGROUND: Hepatitis E virus (HEV) is an emerging threat to the safety of blood transfusion. The aim of this study was to determine HEV immunoglobulin (Ig)G and RNA prevalence in Catalan blood donors. STUDY DESIGN AND METHODS: Nearly 10,000 samples were collected from anonymized, unpaid donors at the Banc de Sang i Teixits (Barcelona, Spain) from June to December 2013. For the serology study, a subset of 1082 donations was tested in parallel for HEV IgG using Wantai and Mikrogen enzyme-linked immunosorbent assay tests. Samples were tested individually (individual-donation nucleic acid test [ID-NAT]) for HEV RNA using the Procleix HEV assay (95% limit of detection 7.9 IU/mL). Procleix repeat-reactive donations were confirmed by an in-house real-time polymerase chain reaction (PCR) test. RESULTS: The prevalences of IgG anti-HEV in Catalan blood donors were 19.96% (Wantai assay) and 10.72% (Mikrogen assay). Screening of 9998 samples with the Procleix HEV assay yielded three real-time PCR-confirmed and IgM and IgG anti-HEV-positive donations with viral loads of 250, 564, and 2755 IU/mL. The donation with highest viral load was genotype 3f. HEV RNA positivity rate was one per 3333 donations (0.03%; 95% confidence interval, 0.01%-0.09%). CONCLUSION: The Procleix HEV ID-NAT screening system has provided evidence of HEV RNA presence in Catalan blood donors. Further data are needed to assess the impact of HEV infection in at-risk patients to design the best strategy to increase blood safety.

Performance evaluation of the PROCLEIX West Nile virus assay on semi-automated and automated systems.

The PROCLEIX West Nile virus assay (WNV assay) is a qualitative nucleic acid test based on transcription-mediated amplification (TMA). The assay was used under an investigational protocol in the United States to screen blood donations for West Nile virus (WNV) RNA starting in the summer of 2003, and was licensed by the FDA in December 2005 for use on the PROCLEIX System, also known as the enhanced semi-automated system (eSAS). Performance characteristics for the assay were determined on both eSAS and the fully automated PROCLEIX TIGRIS (TIGRIS) System. Detection of both lineage 1 and lineage 2 WNV was demonstrated on both systems. For lineage 1, the 95% detection limit was 8.2 copies/ml for eSAS and 9.8 copies/ml for the TIGRIS system. For lineage 2, > or =95% detection was seen at > or =30 copies/ml on both systems. The overall specificity of the assay was >99.9% in fresh and frozen plasma specimens. Reproducibility studies on the TIGRIS system yielded > or =99.1% agreement with expected results for the 3-member panel tested (0, 30, and 100 copies/ml). The WNV assay exhibited robust performance in cadaveric specimens and specimens representing various donor and donation conditions, including specimens from different plasma collection tubes that were subjected to multiple freeze/thaw cycles; specimens with elevated levels of endogenous substances; specimens containing other viruses and microorganisms; and specimens from patients with autoimmune and other diseases. Overall, these studies demonstrate high sensitivity, specificity, and reproducibility of the WNV assay on both the semi-automated and automated systems.