Evaluation of Rta (BRLF 1) antibody for diagnosis of infectious mononucleosis

Abstract

Epstein-Barr virus (EBV) infection is prevalent all over the world. Infectious mononucleosis (IM) is the most common clinical presentation of EBV especially in adolescences. It also causes haematological and epithelial malignancy for example nasopharyngeal carcinoma (NPC). Serological detection with VCA and EBNA antibodies as markers are in used for IM diagnosis. Traditional detection methods include enzyme link immunosorbent assay (ELISA), indirect immunofluorescent antibody (IFA) assay and polymerase chain reaction (PCR). Rta is a protein that is expressed by early lytic gene BRLF 1 and responsible in triggering the reactivation of EBV. Rta-IgG had been proven to be a screening test for NPC. To explore the potential of Rta as an detection marker in IM diagnosis, evaluations was done in 2 approaches, in-house Rta antibody ELISA and a commercial NPCheck Rta IgG ELISA kit. The 96 sera sent to Virology laboratory from Queen Mary Hospital and Pamela Youde Nethersole Eastern Hospital were recruited in this study. The his-tag Rta fusion protein, which was kindly provided by Xiamen University, was used to develop in-house ELISA. The concentration of Rta protein was 120 μg/mL measured by Nanodrop. ND-1000 spectrophotometer. However the in-house method was inconclusive since the optimum amount of Rta used in the test could not be defined and was also lack of specificity. Subsequently trials of this method with patient sera were inconclusive. The commercial kit used was originally designed for NPC screening for Rta-IgG and was used in evaluation for EBV. It was also used to detect Rta IgM in this study. The sensitivity of this kit to Rta IgG and IgM were low (30.8% and 48.2%), while the specificity of the commercial kit to IM was satisfactory (83.3% and 80.0%). Optimization of the test protocol should be performed for further investigation. Rta protein might be a potential marker in addition to the current serological panel to diagnose IM infection.