Development and evaluation of a rapid immunochromatographic test for mumps-specific IgM in oral fluid specimens and use as a matrix for preserving viral nucleic acid for RT-PCR.

The use of oral fluid specimens for diagnosis of mumps by detection of virus-specific IgM or nucleic acid is now well established. The utility of oral fluids would be improved further if testing could be performed closer to the patient. A near patient test (NPT) for the detection of mumps-specific IgM in oral fluid specimens was developed and evaluated using 196 oral fluid specimens from suspected cases of mumps and measles. Compared to enzyme immunoassay (EIA), the sensitivity, specificity, positive and negative predictive value of the mumps IgM NPT were 79.5%, 100%, 100%, and 72.6%, respectively. On oral fluid specimens with a test to negative control optical density ratio (T/N) > or =10 in the EIA, sensitivity of the NPT increased to 95.2%. To determine whether viral nucleic acid from oral fluid was preserved on the NPT strips used for IgM detection, reverse transcription-polymerase chain reaction (RT-PCR) was performed on 58 oral fluids before and after testing on NPT strips. In RT-PCR-positive oral fluids, mumps virus was detected in 19/21 (90.5%) specimens extracted from NPT strips. Mumps virus RNA was not detected in 37/37 (100%) NPT strips from mumps RT-PCR-negative oral fluid specimens. Mumps IgM NPT is rapid and simple to perform, with an acceptable level of performance for confirmation of a clinical diagnosis outside of the laboratory. The NPT strip is also a suitable matrix for preserving nucleic acid, enabling virus-specific RT-PCR to be performed. J. Med. Virol. 82:485-493, 2010. (c) 2010 Wiley-Liss, Inc.

Development of a measles specific IgM ELISA for use with serum and oral fluid samples using recombinant measles nucleoprotein produced in Saccharomyces cerevisiae.

In order to develop sensitive assays for detecting measles antibodies in oral fluid specimens, we have produced recombinant measles virus nucleoprotein (rMVN) in a yeast expression system and prepared monoclonal antibodies to the protein. Measles nucleoprotein gene from the Schwarz vaccine strain was cloned into a yeast expression vector, pFX7 under the control of the hybrid GAL10-PYK1 promoter. High levels of rMVN (20 mg/litre of yeast culture) were generated. Electron microscopy showed that the purified rMVN assembled into typical herring-bone structures. Monoclonal antibodies produced to the rMVN also reacted with native measles virus N in immunofluorescence tests. The purified rMVN and a monoclonal antibody to the rMVN conjugated to horseradish peroxidase were used to develop a measles specific IgM capture EIA (MACEIA) in both serum and oral fluid specimens. Evaluations of the MACEIA were performed by testing a) serum samples (n=80) and b) paired oral fluid/serum samples from measles cases (n=50, representing 16 cases) and oral fluids from controls with non-measles rash (n=59, representing 48 cases). The samples were also tested for measles IgM, using a reference radioimmunoassay (MACRIA). The sensitivity and specificity of the MACEIA compared with MACRIA for a) the serum samples were 100 and 96.6% respectively and b) for paired serum/oral fluids samples 100 and 100%, respectively.