Evaluation of spike protein antigens for SARS-CoV-2 serology

BackgroundSpike protein domains are being used in various serology-based assays to detect prior exposure to SARS-CoV-2 virus. However, there has been limited comparison of human antibody titers against various spike protein antigens among COVID-19 infected patients. MethodsWe compared four spike proteins (RBD, S1, S2 and a stabilized spike trimer (ST)) representing commonly used antigens for their reactivity to human IgG antibodies using indirect ELISA in serum from COVID-19 patients and pre-2020 samples. ST ELISA was also compared against the EUROIMMUN IgG ELISA test. Further, we estimated time appropriate IgG and IgA seropositivity rates in COVID-19 patients using a panel of sera samples collected longitudinally from the day ofonset of symptoms (DOS). ResultsAmong the four spike antigens tested, the ST demonstrated the highest sensitivity (86.2%; 95% CI: 77.8-91.7%), while all four antigens showed high specificity to COVID-19 sera (94.7-96.8%). 13.8% (13/94) of the samples did not show seroconversion in any of the four antigen-based assays. In a double-blinded head-to-head comparison, ST based IgG ELISA displayed a better sensitivity (87.5%, 95%CI: 76.4-93.8%) than the EUROIMMUN IgG ELISA (67.9%, 95% CI: 54.8-78.6%). Further, in ST-based assays, we found 48% and 50% seroconversion in the first six days (from DOS) for IgG and IgA antibodies, respectively, which increased to 84% (IgG) and 85% (IgA) for samples collected [≥]22 days DOS. ConclusionsComparison of spike antigens demonstrates that spike trimer protein is a superior option as an ELISA antigen for COVID-19 serology. HighlightsO_LISpike trimer displays the highest antibody titer in SARS-CoV-2 infections among spike protein antigens. C_LIO_LISpike trimer IgG ELISA displays a sensitivity of 50% within six days and 86.2% after 14 days from onset of symptoms. C_LIO_LIIgA and IgG responses to spike trimer antigen were comparable and concomitant in time after infection. C_LIO_LI16% (IgG) and 15% (IgA) of COVID-19 RT-PCR positive patients did not seroconvert even after 21 days from onset of symptoms. C_LI

Orbital aspergillus infection diagnosed by FNAC.

Fungal infections of the orbit represent a small minority of orbital infections. However, due to the virulent nature of some of the fungal species, they can have a devastating effect on ocular functions. Most of these fungi are saprophytes, which cause opportunistic infections. Aspergillus is one such fungus that can cause infection at various sites in an immunosuppressed individual. Sinonasal aspergillus infection with orbital extension and orbital aspergillus infection progress relentlessly. They can have a precipitous clinical course resulting in total loss of vision. Fine needle aspiration cytology (FNAC) is rarely used as a preoperative diagnostic tool in the investigation of orbital mass lesions. Further, fungal infections of orbit are seldom diagnosed on FNAC. Two cases of fungal infection of the orbital and periorbital tissue diagnosed on FNAC are presented. A 50-year-old diabetic male presented with diminishing vision, pain, and forward protrusion of the left eye. On examination, he had upper eye lid fullness. A 55-year-old diabetic male presented with a swelling on the right upper eye lid. The patients were evaluated radiologically and then subjected to FNAC. The smears showed giant cells, histiocytes, epithelioid granulomas, and fungal hyphae. A diagnosis of fungal infection was arrived at which was subsequently confirmed by culture and biopsy. Orbital aspergillus infection can have a precipitous course. Computerized tomography and magnetic resonance imaging of the orbit provide crucial information. However, FNAC can help in making an early definitive diagnosis of fungal infection and thus obviate the need for a biopsy.

Dosimetric comparison of linear accelerator-based stereotactic radiosurgery systems.

Stereotactic radiosurgery (SRS) is a special radiotherapy technique used to irradiate intracranial lesions by 3-D arrangements of narrow photon beams eliminating the needs of invasive surgery. Three different tertiary collimators, namely BrainLab and Radionics circular cones and BrainLab micro multileaf collimator (mMLC), are used for linear accelerator-based SRS systems (X-Knife). Output factor (S(t)), tissue maximum ratio (TMR) and off axis ratio (OAR) of these three SRS systems were measured using CC01 (Scanditronix/ Welhofer) and Pinpoint (PTW) cylindrical and Markus plane parallel ionization chambers as well as TLD and radiochromic film. Measurement results of CC01 and Pinpoint chambers were very close to each other which indicate that further reduction in volume and physical dimensions of cylindrical ionization chamber is not necessary for SRS/SRT dosimetry. Output factors of BrainLab and Radionics SRS cones were very close to each other while output factors of equivalent diameter mMLC field were different from SRS circular cones. TMR of the three SRS systems compared were very close to one another. OAR of Radionics cone and BrainLab mMLC were very close to each other, within 2%. However, OARs of BrainLab cone were found comparable to OARs of Radionics cone and BrainLab mMLC within maximum variation of 4%. In addition, user-measured similar data of other three mMLC X-Knives were compared with the mMLC X-Knife data measured in this work and found comparable. The concept of switching over to mMLC-based SRS/SRT is thus validated from dosimetric characteristics as well.

Allergy diagnosis by Pharmacia Cap System.

From September 1995 to September 1998, sera from 959 suspected allergy patients have been tested by the new Pharmacia Cap System. Of these, 80 per cent were diagnosed to suffer from some allergy while 20 per cent reacted negative. It was found that the CAP system gave accurate and clear cut results to the satisfaction of the patient and referring physician.