DEVELOPMENT OF NOVEL DIAGNOSTIC TESTS FOR EMERGING INFECTIOUS DISEASES: THE CASE OF TAHYNA VIRUS

Background: Arboviruses are mainly transmitted by blood-feeding arthropods, and environmental and sociodemographic changes have contributed to their emergence in new geographic areas. Tahyna virus (TAHV) is an emerging arbovirus whose circulation in Italy has been documented but remains poorly characterised. Data on human exposure, seroprevalence, and its potential involvement in febrile and neurological syndromes are limited, and specific diagnostic tools are not routinely available. Aim of the study: to develop and evaluate diagnostic approaches for TAHV infection and investigate human exposure and its potential role in febrile and/or neurological syndromes. Materials and methods: A micro-virus-neutralisation test (MVNT) was established to assess TAHV seroprevalence in Veneto. Serum samples were collected from individuals with potential exposure to TAHV habitats and from patients with febrile and/or neurological syndromes. MVNT-positive samples were further analysed by indirect immunofluorescence assay (IFA) for TAHV-specific IgM and IgG. An in-house RT-qPCR assay was also performed on different clinical matrices to investigate viral RNA detection and shedding. Results: among 188 sera analysed by MVNT, 6 (3.19%) showed TAHV-neutralising antibodies, including four individuals from Veneto and two from other Italian regions. Five were asymptomatic, while one had encephalitis. All MVNT-positive sera showed TAHV-specific IgG by IFA, whereas IgM was detected in two samples collected during summer, suggesting recent infection. However, IFA showed cross-reactivity with TOSV-positive sera. RT-qPCR was performed on samples from 506 patients, but no TAHV RNA was detected. Discussion and conclusions: the detection of TAHV-neutralising antibodies confirms human exposure in northeastern Italy and supports previous evidence of viral circulation. Most seropositive individuals were asymptomatic, but the limited number of positive cases prevents conclusions regarding clinical relevance or neurological involvement. The MVNT, IFA, and RT-qPCR developed here provide useful tools for TAHV investigation, although the IFA requires further optimisation due to cross-reactivity with TOSV. The absence of detectable viral RNA does not exclude infection, given the influence of sampling timing, viral clearance, and specimen type. Further prospective studies integrating serological, molecular, and entomological surveillance are needed to clarify TAHV circulation, infection kinetics, and clinical relevance in Italy.