Development and clinical application of a rapid IgM-IgG combined antibody test for SARS-CoV-2 infection diagnosis.

The outbreak of the novel coronavirus disease (COVID-19) quickly spread all over China and to more than 20 other countries. Although the virus (severe acute respiratory syndrome coronavirus [SARS-Cov-2]) nucleic acid real-time polymerase chain reaction (PCR) test has become the standard method for diagnosis of SARS-CoV-2 infection, these real-time PCR test kits have many limitations. In addition, high false-negative rates were reported. There is an urgent need for an accurate and rapid test method to quickly identify a large number of infected patients and asymptomatic carriers to prevent virus transmission and assure timely treatment of patients. We have developed a rapid and simple point-of-care lateral flow immunoassay that can detect immunoglobulin M (IgM) and IgG antibodies simultaneously against SARS-CoV-2 virus in human blood within 15 minutes which can detect patients at different infection stages. With this test kit, we carried out clinical studies to validate its clinical efficacy uses. The clinical detection sensitivity and specificity of this test were measured using blood samples collected from 397 PCR confirmed COVID-19 patients and 128 negative patients at eight different clinical sites. The overall testing sensitivity was 88.66% and specificity was 90.63%. In addition, we evaluated clinical diagnosis results obtained from different types of venous and fingerstick blood samples. The results indicated great detection consistency among samples from fingerstick blood, serum and plasma of venous blood. The IgM-IgG combined assay has better utility and sensitivity compared with a single IgM or IgG test. It can be used for the rapid screening of SARS-CoV-2 carriers, symptomatic or asymptomatic, in hospitals, clinics, and test laboratories.

A new manganese superoxide dismutase identified from Beauveria bassiana enhances virulence and stress tolerance when overexpressed in the fungal pathogen.

A superoxide dismutase (SOD) was characterized from Beauveria bassiana, a fungal entomopathogen widely applied to insect control. This 209-aa enzyme (BbSod2) showed no more than 71% sequence identity to other fungal Mn-SODs, sharing all conserved residues with the Mn-SOD family and lacking a mitochondrial signal. The SOD activity of purified BbSod2 was significantly elevated by Mn(2+), suppressed by Cu(2+) and Zn(2+) but inhibited by Fe(3+). Overexpressing the enzyme in a BbSod2-absent B. bassiana strain enhanced its SOD activity (107.2 +/- 6.1 U mg(-1) protein) by 4-10-fold in different transformants analyzed. The best BbSod2-transformed strain with the SOD activity of 1,157.9 +/- 74.7 U mg(-1) was 93% and 61% more tolerant to superoxide-generating menadione in both colony growth (EC(50) = 2.41 +/- 0.03 versus 1.25 +/- 0.01 mM) and conidial germination (EC(50) = 0.89 +/- 0.06 versus 0.55 +/- 0.07 mM), and 23% more tolerant to UV-B irradiation (LD(50) = 0.49 +/- 0.02 versus 0.39 +/- 0.01 J cm(-2)). Its virulence to Spodoptera litura larvae was enhanced by 26% [LT(50) = 4.5 (4.2-4.8) versus 5.7 (5.2-6.4) days]. Our study highlights for the first time that the Mn(2+)-cofactored, cytosolic BbSod2 contributes significantly to the virulence and stress tolerance of B. bassiana and reveals possible means to improving field persistence and efficacy of a fungal formulation by manipulating the antioxidant enzymes of a candidate strain.

Comparative tolerances of various Beauveria bassiana isolates to UV-B irradiation with a description of a modeling method to assess lethal dose.

The tolerances of 20 Beauveria bassiana isolates derived from host insects worldwide to UV-B irradiation were assessed quantitatively in multi-dose bioassays. Conidial suspensions of the isolates smeared on glass slides were exposed to the gradient UV-B doses of 0.1-1.6 J cm(-2) (D), which generated from 0.75 to 10.17 min irradiation of weighted 312-nm wavelength at 2.0-2.61 mW cm(-2). Irradiated conidia were then incubated for 24 h at 25 degrees C under saturated humidity. The ratio of germination at each dose over that in the blank control was defined as survival index (I (s)). For all isolates, the I (s) - D observations fit well with the survival model I (s) = 1/[1 + exp(a + bD)] (0.94 < or = r (2) < or = 0.99) generated widely spanned lethal doses of 0.154-0.928, 0.240-1.139, and 0.383-1.493 J cm(-2) for their losses of 50%, 75%, and 95% viabilities, respectively. These were far below the solar UV-B dose of 2.439 J cm(-2) measured in a sunny day during the summer. The large variation of UV-B tolerance among the isolates indicates a necessity to select UV-tolerant candidates for formulations applied to insect control during summer. The highly efficient bioassay method was developed to measure accurately the UV-B tolerances of fungal biocontrol agents as lethal doses.