Identification of a Neutralizing Epitope on TOSV Gn Glycoprotein

Abstract

Emerging and re-emerging viral infections have been an important public health problem in recent years. We focused our attention on Toscana virus (TOSV), an emergent neurotropic negative-strand RNA virus of the Phenuiviridae family. The mechanisms of protection against phlebovirus natural infection are not known; however, it is supposed that a virus-neutralizing antibody response against viral glycoproteins would be useful to block the first stages of infection. By using an improved memory B cell immortalization method, we obtained a panel of human mAbs which reacted with TOSV antigens. We identified three epitopes of TOSV Gn glycoproteins by neutralizing mAbs using synthetic peptide arrays on membrane support (SPOT synthesis). These epitopes, separated in primary structure, might be exposed near one another as a conformational epitope in their native structure. In vivo studies were conducted to evaluate the humoral response elicited in mice immunized with the identified peptides. The results underlined the hypothesis that the first two peptides located in the NH2 terminus could form a conformational epitope, while the third, located near the transmembrane sequence in the carboxyl terminus, was necessary to strengthen neutralizing activity. Our results emphasize the importance of identifying neutralizing epitopes shared among the various phleboviruses, which could be exploited for the development of a potential epitope-based diagnostic assay or a polyvalent protective vaccine against different phleboviruses.

The Adaptive Immune Response against Bunyavirales

“…Similar findings were observed using SFTSV human mAbs, binding a linear epitope in the ectodomain of Gn and effectively neutralizing all clinical isolates of SFTSV [ 178 ]. Additionally, a recent study identified two TOSV epitopes within the amino-terminal half of Gn as the primary targets for human nAbs [ 179 ]. In RVFV and TOSV infection, Abs targeting NSs have been reported, albeit in low levels [ 180 , 181 , 182 ].…”

“…Immunoinformatics [32] Glycoproteins YQPTELTRS (716-724) YKAHDKEET (782-790) ILGTGTPKF (1172)(1173)(1174)(1175)(1176)(1177)(1178)(1179)(1180) Immunoinformatics [33] JCV CD8+ N protein AAKAKAALA (26)(27)(28)(29)(30)(31)(32)(33)(34) AALARKPER (152)(153)(154)(155)(156)(157)(158)(159)(160)(161) ADHGESVSL (175)(176)(177)(178)(179)(180)(181)(182)(183) ADHGESVSLS (157)(158)(159)(160)(161)(162)(163)(164)(165) YPLTIGIYRV (108)(109)(110)(111)(112)…”

Humoral immunity to phlebovirus infection

“…Neutralizing mAbs (TVB 27, TVB 73, TVB 147, TVB 161, and TVB 164) have been isolated from a TOSV convalescent donor through the immortalization of memory B cells (Table 1 ). 55 The neutralizing epitopes were mapped using pepscan, which revealed epitopes located in the N‐terminus (domain A) and near to the transmembrane region. Further analysis is required to determine the epitope location in TOSV Gn.…”