Presence of broadly reactive and group-specific neutralizing epitopes on newly described isolates of Crimean-Congo hemorrhagic fever virus

Abstract

Crimean-Congo hemorrhagic fever virus (CCHFV), a member of the genus Nairovirus of the family Bunyaviridae, causes severe disease in humans with high rates of mortality. The virus has a tripartite genome composed of a small (S), a medium (M) and a large (L) RNA segment; the M segment encodes the two viral glycoproteins, G N and G C . Whilst relatively few full-length M segment sequences are available, it is apparent that both G N and G C may exhibit significant sequence diversity. It is unknown whether considerable antigenic differences exist between divergent CCHFV strains, or whether there are conserved neutralizing epitopes. The M segments derived from viral isolates of a human case of CCHF in South Africa (SPU 41/84), an infected tick (Hyalomma marginatum) in South Africa (SPU 128/81), a human case in Congo (UG 3010), an infected individual in Uzbekistan (U2-2-002) and an infected tick (Hyalomma asiaticum) in China (Hy13) were sequenced fully, and the glycoproteins were expressed. These novel sequences showed high variability in the N-terminal region of G N and more modest differences in the remainder of G N and in G C . Phylogenetic analyses placed these newly identified strains in three of the four previously described M segment groups. Studies with a panel of mAbs specific to G N and G C indicated that there were significant antigenic differences between the M segment groups, although several neutralizing epitopes in both G N and G C were conserved among all strains examined. Thus, the genetic diversity exhibited by CCHFV strains results in significant antigenic differences that will need to be taken into consideration for vaccine development.

Mice Orally Immunized with a Transgenic Plant Expressing the Glycoprotein of Crimean-Congo Hemorrhagic Fever Virus

“…Since neutralizing antibodies play a pivotal role in protection against CCHF virus, some evidence demonstrated immunogenic epitopes within G N (G2) and G C (G1) parts of the viral glycoprotein. Systemic IgG has previously been found to increase in mice immunized by the DNA vaccine of the CCHFV glycoprotein (43), and some neutralizing epitopes on this protein have been identified by monoclonal antibodies (1). When the viral glycoprotein of the Ebola virus, a very lethal hemorrhagic fever virus, was expressed in mammalian cells, it was able to elicit an efficient immune response (24,45).…”

“…The entire G1 (G C ) and G2 (G N ) portions of the CCHFV glycoprotein gene were derived from the M segment of the Iranian strain (GenBank accession number DQ446215) on the basis of previously published reports (1,41). A plant-optimized G1/G2 (G C /G N ) glycoprotein gene (HM537014) was genetically engineered into one reading frame, chemically synthesized, cloned into pBI121 (Novagen) at the Cfr9I and SacI restriction enzyme sites, and introduced into Agrobacterium tumefaciens strain LBA4404 and Agrobacterium rhizogenes (ATCC 15834) by a standard freeze-thaw method (40).…”

“…The CCHF virus (CCHFV) belongs to the family Bunyaviridae and the genus Nairovirus and contains a three-segment RNA genome, including S (small), M (medium), and L (large) segments which encode a viral nucleoprotein, a precursor glycoprotein, and an RNA-dependent RNA polymerase, respectively (18,23). Subsequently, the precursor is matured to G N and G C glycoproteins by proteolytic cleavages (1,41). In addition to transmission via tick bite and nosocomial infections, humans are mainly infected by exposure to the tissue and blood of infected livestock, which are asymptomatic.…”

Crimean-Congo hemorrhagic fever: History, epidemiology, pathogenesis, clinical syndrome and genetic diversity

“…There in fact appears to be little variation in antigenic sites among CCHF viruses, which form a single antigenic group, by which they are distinguished from other nairoviruses, such as HAZV (Buckley, 1974;Foulke et al, 1981). More subtle antigenic difference within the CCHFV group have been defined using monoclonal antibodies (Ahmed et al, 2005), but it is unclear how such variation affects cross-protection among viruses in vertebrate hosts. Improved understanding of cross-protection among CCHFV strains is needed for vaccine development; such data may be difficult to derive from naturally occurring infections of humans or animals, but could potentially be obtained through studies in recently developed mouse models of CCHF (see below).…”

Genetic Analysis of the Partial M RNA Segment of Crimean-Congo Hemorrhagic Fever Viruses in Turkey

“…The S segment codes for the nucleoprotein (NP) 13 , the M segment encodes for a glycoprotein precursor which gives rise to two structural glycoproteins Gn (37 kDa) and Gc (75 kDa) and also encodes for a non-structural protein (NS m ) [13][14][15] . The glycoproteins, Gn and Gc, encoded by M-RNA segment, are responsible for virus attachment and induction of virus neutralizing antibodies 16 . Therefore, M segment is considered critical to the elicitation of immunopathologic responses in humans 17,18 .…”