A paper published by the Molecular Virology Group, ICGEB Trieste, Italy, presents a new strategy to diagnose flaviviruses infection in patient sera. This work is pivotal for the TBFVnet project as starting point to develop new assays for tick-borne flaviviruses.
The Molecular Virology Group is led by Alessandro Marcello at the partner institution ICGEB. The Group has developed a new assay to detect flaviviruses antibodies in human sera, from which it will be possible to study the development of new assays for other tick-borne flaviviruses.
Diagnosis of flavivirus infection through virus isolation, detection of viral RNA and viral antigens are highly specific but limited to the short time window of the viremic phase of the infection (2-3 weeks). Serological assays provide a longer time-window for testing. IgM antibodies can be detected in most patients by day 3-5 after the onset of symptoms and remain for several months following infection. IgG antibodies are initially detectable at low titers but are stable for longer time periods.
Present serological assays for flaviviruses are mostly based on structural antigens, while the proposed assay suggests the non-structural protein 1 (NS1) as a novel target. This protein is secreted in high amounts during early stages of viral replication and causes an immediate immune response with anti-NS1 IgM (2-3 days after infection). The authors describe a strategy to produce and purify high quality, non-structural protein 1 (NS1) to use in an ELISA test to detect the presence of flavivirus antibodies in patients’ sera. The results clearly show that NS1 is a valid antigen with higher sensitivity as compared to previously available commercial assays. Furthermore, this assay is also able to detect infection in patients with vaccination breakthrough TBE, particularly in older individuals.
The expertise developed at ICGEB during this research will be shared with the partners of TBFVnet through in-site and on-line training. Combined efforts will boost the development of similar assays to help fast monitoring and surveillance of tick-borne flaviviruses.
The article by Marcello and colleagues has been published in PLOS Neglected Tropical Diseases.