A new immunoassay of serum antibodies against Peste des petits ruminants virus using quantum dots and a lateral-flow test strip.

A fast and ultrasensitive test-strip system combining quantum dots (QDs) with a lateral-flow immunoassay strip (LFIAS) was established for detection of Peste des petits ruminants virus (PPRV) antibody. The highly luminescent water-soluble carboxyl-functionalized QDs were used as the signal output and were conjugated to streptococcal protein G (SPG), which was capable of binding to immunoglobulin G (IgG) from many species through an amide bond to capture the target PPRV IgGs. The PPRV N protein, which was immobilized on the detection zone of the test strip, was expressed by transfecting recombinant Bacmid-PPRV-N with Lipofect into Sf9 insect cells. When exposed to PPRV IgG, QD-SPG bound to PPRV N protein, resulting in the formation of a complex that subsequently produced a bright fluorescent band in response to 365 nm ultraviolet excitation. Sensitivity evaluation showed that the QD-LFIAS limit of detection (LOD) for PPRV antibody was superior to competitive enzyme-linked immunosorbent assay (c-ELISA) and the immunochromatographic strip. No cross reaction was observed when the positive sera of bluetongue virus, canine distemper virus, goat pox virus, and foot-and-mouth disease virus were tested. Further evaluation using field samples indicated that the diagnostic specificity and sensitivity of the QD-LFIAS was 99.47 and 97.67 %, respectively, with excellent agreement between QD-LFIAS and c-ELISA. The simple analysis step and objective results that can be obtained within 15 min indicate that this new method shows great promise for rapid, sensitive detection of PPRV IgG for onsite, point-of-care diagnosis and post vaccination evaluation (PVE). Graphical Abstract Ultrasensitive fluorescent QD immunochromotography in combination with recombinant PPRV N protein could be used to detect PPRV antibody in serum.

Complete sequence of a viral nervous necrosis virus (NNV) isolated from red-spotted grouper (Epinephelus akaara) in China.

A nodavirus isolated from red-spotted grouper (Epinephelus akaara) larvae in China has been subjected to genome analysis. The full-length genome sequences of RNA1 and RNA2 were determined, and the 5'-non-coding region (NCR) and 3'NCR sequences were determined by 5' rapid amplification of cDNA ends (RACE) and 3'RACE. RNA1 is 3,103 nt in length and contains a 982-amino-acid open reading frame (ORF) encoding protein A with a calculated molecular mass of 110.74 kDa. RNA2 is 1,433 nt long and contains a 338-amino-acid major ORF encoding coat protein with a calculated molecular mass of 37.059 kDa. Multiple alignment and phylogenetic analysis clearly supported including this virus in the species Redspotted grouper nervous necrosis virus, genus Betanodavirus, family Nodaviridae.