IFN-γ-Based ELISpot as a New Tool to Detect Human Infections with Borna Disease Virus 1 (BoDV-1): A Pilot Study

More than 40 human infections with the zoonotic Borna disease virus 1 (BoDV-1) have been reported to German health authorities from endemic regions in southern and eastern Germany. Diagnosis of a confirmed case is based on the detection of BoDV-1 RNA or BoDV-1 antigen. In parallel, serological assays such as ELISA, immunoblots, and indirect immunofluorescence are in use to detect the seroconversion of Borna virus-reactive IgG in serum or cerebrospinal fluid (CSF). As immunopathogenesis in BoDV-1 encephalitis appears to be driven by T cells, we addressed the question of whether an IFN-γ-based ELISpot may further corroborate the diagnosis. For three of seven BoDV-1-infected patients, peripheral blood mononuclear cells (PBMC) with sufficient quantity and viability were retrieved. For all three patients, counts in the range from 12 to 20 spot forming units (SFU) per 250,000 cells were detected upon the stimulation of PBMC with a peptide pool covering the nucleocapsid protein of BoDV-1. Additionally, individual patients had elevated SFU upon stimulation with a peptide pool covering X or phosphoprotein. Healthy blood donors (n = 30) and transplant recipients (n = 27) were used as a control and validation cohort, respectively. In this pilot study, the BoDV-1 ELISpot detected cellular immune responses in human patients with BoDV-1 infection. Its role as a helpful diagnostic tool needs further investigation in patients with BoDV-1 encephalitis

Antibodies against viral nucleo-, phospho-, and X protein contribute to serological diagnosis of fatal Borna disease virus 1 infections

Borna disease virus 1 (BoDV-1) causes rare but often fatal encephalitis in humans. Late diagnosis prohibits an experimental therapeutic approach. Here, we report a recent case of fatal BoDV-1 infection diagnosed on day 12 after hospitalization by detection of BoDV-1 RNA in the cerebrospinal fluid. In a retrospective analysis, we detect BoDV-1 RNA 1 day after hospital admission when the cell count in the cerebrospinal fluid is still normal. We develop a new ELISA using recombinant BoDV-1 nucleoprotein, phosphoprotein, and accessory protein X to detect seroconversion on day 12. Antibody responses are also shown in seven previously confirmed cases. The individual BoDV-1 antibody profiles show variability, but the usage of three different BoDV-1 antigens results in a more sensitive diagnostic tool. Our findings demonstrate that early detection of BoDV-1 RNA in cerebrospinal fluid and the presence of antibodies against at least two different viral antigens contribute to BoDV-1 diagnosis. Physicians in endemic regions should consider BoDV-1 infection in cases of unclear encephalopathy and initiate appropriate diagnostics at an early stage

Human Infections with Borna Disease Virus 1 (BoDV-1) Primarily Lead to Severe Encephalitis: Further Evidence from the Seroepidemiological BoSOT Study in an Endemic Region in Southern Germany

More than 40 human cases of severe encephalitis caused by Borna disease virus 1 (BoDV-1) have been reported to German health authorities. In an endemic region in southern Germany, we conducted the seroepidemiological BoSOT study (“BoDV-1 after solid-organ transplantation”) to assess whether there are undetected oligo- or asymptomatic courses of infection. A total of 216 healthy blood donors and 280 outpatients after solid organ transplantation were screened by a recombinant BoDV-1 ELISA followed by an indirect immunofluorescence assay (iIFA) as confirmatory test. For comparison, 288 serum and 258 cerebrospinal fluid (CSF) samples with a request for tick-borne encephalitis (TBE) diagnostics were analyzed for BoDV-1 infections. ELISA screening reactivity rates ranged from 3.5% to 18.6% depending on the cohort and the used ELISA antigen, but only one sample of a patient from the cohort with requested TBE diagnostics was confirmed to be positive for anti-BoDV-1-IgG by iIFA. In addition, the corresponding CSF sample of this patient with a three-week history of severe neurological disease tested positive for BoDV-1 RNA. Due to the iIFA results, all other results were interpreted as false-reactive in the ELISA screening. By linear serological epitope mapping, cross-reactions with human and bacterial proteins were identified as possible underlying mechanism for the false-reactive ELISA screening results. In conclusion, no oligo- or asymptomatic infections were detected in the studied cohorts. Serological tests based on a single recombinant BoDV-1 antigen should be interpreted with caution, and an iIFA should always be performed in addition

Acute myeloid leukemia with RAM immunophenotype: a pediatric case with unusual morphologic features

The RAM immunophenotype has been recently described as a subtype of acute myelogenous leukemia (AML) that is characterized clinically by extremely poor prognosis. We present a case of AML with RAM immunophenotype in a 5-year-old patient that resulted in poor outcome despite early hematopoietic cell transplant. We describe the unusual morphologic features that, along with the distinct immunophenotype, may provide initial diagnostic clues and further justify the classification of this AML variant as a rather distinct subtype

Detection of virus-specific T cells via ELISpot corroborates early diagnosis in human Borna disease virus 1 (BoDV-1) encephalitis

Background Within endemic regions in southern and eastern Germany, Borna disease virus 1 (BoDV-1) causes rare zoonotic spill-over infections in humans, leading to encephalitis with a high case-fatality risk. So far, intra-vitam diagnosis has mainly been based on RT-qPCR from cerebrospinal fluid (CSF) and serology, both being associated with diagnostic challenges. Whilst low RNA copy numbers in CSF limit the sensitivity of RT-qPCR from this material, seroconversion often occurs late during the course of the disease. Case presentation Here, we report the new case of a 40 − 50 year-old patient in whom the detection of virus-specific T cells via ELISpot corroborated the diagnosis of BoDV-1 infection. The patient showed a typical course of the disease with prodromal symptoms like fever and headaches 2.5 weeks prior to hospital admission, required mechanical ventilation from day three after hospitalisation and remained in deep coma until death ten days after admission. Results Infection was first detected by positive RT-qPCR from a CSF sample drawn four days after admission (viral load 890 copies/mL). A positive ELISpot result was obtained from peripheral blood collected on day seven, when virus-specific IgG antibodies were not detectable in serum, possibly due to previous immune adsorption for suspected autoimmune-mediated encephalitis. Conclusion This case demonstrates that BoDV-1 ELISpot serves as additional diagnostic tool even in the first week after hospitalisation of patients with BoDV-1 encephalitis