Differential neurovirulence of Usutu virus lineages in mice and neuronal cells

Abstract

Background Usutu virus (USUV) is an emerging neurotropic arthropod-borne virus recently involved in massive die offs of wild birds predominantly reported in Europe. Although primarily asymptomatic or presenting mild clinical signs, humans infected by USUV can develop neuroinvasive pathologies (including encephalitis and meningoencephalitis). Similar to other flaviviruses, such as West Nile virus, USUV is capable of reaching the central nervous system. However, the neuropathogenesis of USUV is still poorly understood, and the virulence of the specific USUV lineages is currently unknown. One of the major complexities of the study of USUV pathogenesis is the presence of a great diversity of lineages circulating at the same time and in the same location. Methods The aim of this work was to determine the neurovirulence of isolates from the six main lineages circulating in Europe using mouse model and several neuronal cell lines (neurons, microglia, pericytes, brain endothelial cells, astrocytes, and in vitro Blood-Brain Barrier model). Results Our results indicate that all strains are neurotropic but have different virulence profiles. The Europe 2 strain, previously described as being involved in several clinical cases, induced the shortest survival time and highest mortality in vivo and appeared to be more virulent and persistent in microglial, astrocytes, and brain endothelial cells, while also inducing an atypical cytopathic effect. Moreover, an amino acid substitution (D3425E) was specifically identified in the RNA-dependent RNA polymerase domain of the NS5 protein of this lineage. Conclusions Altogether, these data show a broad neurotropism for USUV in the central nervous system with lineage-dependent virulence. Our results will help to better understand the biological and epidemiological diversity of USUV infection.

SARS-CoV-2 Poorly Replicates in Cells of the Human Blood-Brain Barrier Without Associated Deleterious Effects

“…As previously published ( 40 ), the in vitro human BBB model ( Figure 1E ) is based on CD34 + blood-derived endothelial cells cultured on Matrigel-coated Transwell filters (Costar, 0.4 µm). Collection of human umbilical cord blood was done after infants’ parents signed consent form in compliance with French legislation.…”

“…In this study, we aimed to monitor potential direct SARS-CoV-2 infection of BBB cells and the permissivity of a human in vitro model of BBB to infection and systemic inflammatory environment. We employed a cellular BBB model using human brain-like endothelial cells (hBLECs) differentiated from hematopoietic stem cells, presenting the main characteristics of the human BBB (36)(37)(38)(39) and previously used to explore other virus infection and replication mechanisms (40)(41)(42). Finally, we investigated the role of the inflammatory environment in plasma of COVID-19 patients on the BBB integrity.…”

Pathology and Pathogenesis of Eurasian Blackbirds (Turdus merula) Naturally Infected with Usutu Virus

“…Regarding USUV tissue and cell tropism, the same reports highlight the presence of the viral antigen in the major affected organs (liver, spleen, heart, brain) [ 5 , 21 , 22 , 23 ]. Despite the identification of different circulating virus lineages [ 17 ], studies investigating their pathogenetic potential in naturally-infected birds are lacking and it has only been partially studied in vitro and in experimental in vivo studies in mice [ 24 , 25 , 26 , 27 , 28 ]. Consequently, due to the small number of animals examined in previous studies, knowledge on the pathology and the complete cell and tissue tropism of the virus, as well as the pathogenetic potential of different circulating viral lineages, are still fragmentary.…”

Usutu virus escapes langerin-induced restriction to productively infect human Langerhans cells, unlike West Nile virus

“…For example, whereas WNV grown in mammalian cells was shown to preferentially use DC-SIGNL as a receptor [22], the introduction of a glycosylation site at position 67 into WNV E protein conferred the capacity to also use DC-SIGN [47]. From the sequence of its USUV E protein, it can be predicted that USUV has, like WNV, a unique glycosylation at N154 [44], so this cannot explain why only USUV can bind langerin and not WNV. Although most CLRs bind mannosylated antigens, they all have ligand specificity [48,49].…”

“…Among the viral strains that we tested, USUV EU2 showed the fastest and most efficient replication in both DCs and LCs, and also triggered the most intense innate immune response. Interestingly, this viral strain was previously described as being involved in several clinical cases, and was recently shown to be particularly neurovirulent and lethal in mice [36,37,44].…”