A new recombinant rabies virus expressing a green fluorescent protein: A novel and fast approach to quantify virus neutralizing antibodies.

The Rapid Fluorescent Focus Inhibition Test (RFFIT) is a standard assay used to detect and assess the titers of rabies virus neutralizing antibodies (RVNA) in blood sera. To simplify the multistep RFFIT procedure by eliminating the immunostaining step, we generated a new recombinant RV expressing a green fluorescent protein (rRV-GFP) and assess its suitability for quantifying RVNA. We rescued the rRV-GFP virus from plasmid DNA carrying a full-length genome of the CVS-N2c strain of RV in which the eGFP gene was inserted between the glycoprotein and RNA-polymerase genes. The recombinant virus was genetically stable and grew efficiently in appropriate cells expressing sufficient GFP fluorescence to detect directly 20 h post infection (hpi). We evaluated the feasibility of using rRV-GFP in RFFIT by comparing RVNA titers in 27 serum samples measured by conventional RFFIT and RFFIT-GFP. A linear regression analysis of the data demonstrated a good agreement between these two methods (r = 0.9776) including results with samples having RVNA titers close to the minimally acceptable vaccine potency threshold (0.5 IU/ml). Study results showed that the rRV-GFP virus could replace the CVS-11 challenge virus currently used in the conventional RFFIT and enabling more rapid, simpler, and less expensive detection and quantitation of RVNA.

Evaluating the diagnostic and prognostic value of lone anti-Sm for autoimmune diseases using Euroimmun line immunoassays.

To investigate the value of lone anti-Smith antibody (anti-Sm) using Euroimmun line immunoassay (LIA) in a Chinese population. One thousand two hundred eight of 39,766 patients who were analyzed for anti-Sm had positive anti-Sm, and were divided into true group (having both positive Sm and nRNP/Sm bands) and lone group (only having Sm band without nRNP/Sm band). The proportions of clinical diagnosis of autoimmune diseases (AIDs), non-autoimmune diseases (NAIDs), concentration of C3, C4, and rheumatoid factor (RF), positive rate of autoantibodies of antinuclear antibody (ANA) profile, and titer of anti-Sm and ANA in systemic lupus erythematosus (SLE) patients were analyzed. Lone anti-Sm was evident in 271/1208 (22.42%) of all positive cases. One hundred seventy-five of them had definitive diagnoses with AIDs being the most prominent (69.71%, 122/175). Compared to the true group, SLE patients in the lone group showed significantly lower ANA and anti-Sm titers (both P < 0.001). There was no difference in frequency of other autoantibodies or C3, C4, and RF levels of SLE patients between the two groups. In NAIDs patients, lone anti-Sm indicates less incidence of kidney injury than true anti-Sm (P = 0.05). Lone anti-Sm has great diagnostic value in AIDs, especially SLE. Lone anti-Sm has relationship with mild kidney impairment. Positive anti-Sm patients with no clinical findings or SLE diagnosis should be submitted to new testing to identify changes in anti-Sm, because turning of lone anti-Sm to true anti-Sm indicates evolving kidney injury.