Comprehensive response to Usutu virus following first isolation in blood donors in the Friuli Venezia Giulia region of Italy: Development of recombinant NS1-based serology and sensitivity to antiviral drugs

Abstract

Surveillance of Usutu virus is crucial to prevent future outbreaks both in Europe and in other countries currently naïve to the infection, such as the Americas. This goal remains difficult to achieve, notably because of the lack of large-scale cohort studies and the absence of commercially available diagnostic reagents for USUV. This work started with the first identification of USUV in a blood donor in the Friuli Venezia Giulia (FVG) Region in Northern-Eastern Italy, which is endemic for West Nile virus. Considering that only one IgG ELISA is commercially available, but none for IgM, a novel NS1 antigen based IgG/M ELISA has been developed. This assay tested successfully for the detection of Usutu virus in blood donors with the identification of a second case of transmission and high levels of exposure. Furthermore, two pan-flavivirus antiviral drugs, that we previously characterized to be inhibitors of other flavivirus infectivity, were successfully tested for inhibition of Usutu virus with inhibitory concentrations in the low micromolar range. To conclude, this work identifies NorthEastern Italy as endemic for Usutu virus with implications for the screening of transfusion blood. A novel NS1-based ELISA test has been implemented for the detection of IgM/G that will be of importance as a tool for the diagnosis and surveillance of Usutu virus infection. Finally, Usutu virus is shown to be sensitive to a class of promising pan-flavivirus drugs.

Epidemiology of Usutu Virus: The European Scenario

“…ticks are not competent vectors for USUV [ 93 ]. First human cases of USUV neuroinvasive infection caused by USUV Europe 1 lineage were documented in 2009 [ 28 , 29 , 68 ]. A retrospectively conducted survey on CSF and serum samples collected between 2008 and 2011 in Modena showed the presence of USUV RNA in 1.1% and antibodies in 6.57% samples.…”

Differential neurovirulence of Usutu virus lineages in mice and neuronal cells

“…various healthy and sick subjects (serum) ? [ 23 ] 2018 1/44 Blood Healthy Blood donors Europe 1 [ 24 ] 2016–2018 25/73964 Blood Healthy Blood donors ? [ 25 ] 2017–2018 9 Blood Healthy Blood donors Europe 2.…”

“…It has been reported in the literature that among 24 patients presenting neurological symptoms, 13 cases were infected with EU2 [ 20 , 27 , 28 , 30 ], one with AF2 [ 31 ], and one with EU1 [ 19 ], while for the other cases the strains involved were not characterized. USUV isolates have also been identified in asymptomatic infected patients or infected patients with mild clinical signs, such as AF3 [ 18 , 33 ], EU1 [ 24 ], EU2 [ 26 , 32 , 33 ], EU3 [ 26 , 34 , 36 ], and EU4 [ 26 ]. Complete genome sequencing and phylogenetic analyses of African and European lineages have shown genetic diversity among all USUV strains analyzed [ 40 ].…”

Broad‐Spectrum Flavivirus Inhibitors: a Medicinal Chemistry Point of View

“…Compound 18 showed also good activity against a wider panel of flaviviruses, such as the DENV serotypes 1, 3, 4, various genotypes of African YFV, TBEV, and lower potency against JEV and ZIKV, displaying overall a slight better activity than starting 16 (Figure 5B) [113] . More recently, compound 18 was tested also against Usutu virus showing an EC 50 of 1.3 μM (Figure 5B) [115] . In the second series of PBTZs, [38] modification at C‐4 position had a heavy impact on biological activity.…”

“…[113] More recently, compound 18 was tested also against Usutu virus showing an EC 50 of 1.3 μM ( Figure 5B). [115] In the second series of PBTZs, [38] modification at C-4 position had a heavy impact on biological activity. Compounds retaining an aminoacyl moiety were able to inhibit isolated DENV-2 RdRp as well as DENV-1-4 and ZIKV replication in cells, with potency comparable to the starting hit 16 in all the assays.…”