ICTV Virus Taxonomy Profile: Nairoviridae 2024.

Nairoviridae is a family for negative-sense RNA viruses with genomes of about 17.2-21.1 kb. These viruses are maintained in and/or transmitted by arthropods among birds, reptiles and mammals. Norwaviruses and orthonairoviruses can cause febrile illness in humans. Several orthonairoviruses can infect mammals, causing mild, severe and sometimes, fatal diseases. Nairovirids produce enveloped virions containing two or three single-stranded RNA segments with open reading frames that encode a nucleoprotein (N), sometimes a glycoprotein precursor (GPC), and a large (L) protein containing an RNA-directed RNA polymerase (RdRP) domain. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) report on the family Nairoviridae, which is available at www.ictv.global/report/nairoviridae.

Purification and characterization of soluble recombinant Crimean-Congo hemorrhagic fever virus glycoprotein Gc expressed in mammalian 293F cells.

BACKGROUND: Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne zoonotic disease that presents with severe hemorrhagic manifestations and is associated with significant fatality rates. The causative agent, Crimean-Congo Hemorrhagic Fever Virus (CCHFV), is a high-priority pathogen identified by the World Health Organization with no approved vaccine or specific treatment available. In addition, there is a critical need for enhanced diagnostic tools to improve public health awareness, prevention measures, and disease control strategies. METHODS: We designed plasmids to enable the purification of soluble CCHFV glycoprotein Gc expressed in mammalian 293 F cells, followed by purification using affinity and size exclusion chromatography. The purified antigen was analyzed by SDS-PAGE and Western blotting to confirm its reactivity to antibodies from CCHF survivors. Additionally, an in-house indirect ELISA was developed using the purified Gc as a coating antigen. RESULTS: The optimized expression system successfully produced soluble and pure Gc antigen after affinity chromatography. The protein showed specific reactivity with CCHFV-positive serum antibodies in Western blot analysis. The indirect ELISA assay demonstrated high efficacy in distinguishing between CCHFV-positive and -negative serum samples, indicating its potential as a valuable diagnostic tool. Size exclusion chromatography further confirmed the presence of aggregates in our protein preparation. CONCLUSIONS: The purified Gc antigen shows promise for developing direct diagnostic assays for CCHFV. The antigen's suitability for subunit vaccine development and its application as bait for monoclonal antibody isolation from survivors could be investigated further. This work lays the foundation for future research into the development of rapid diagnostic tests for field deployment.

Annual (2023) taxonomic update of RNA-directed RNA polymerase-encoding negative-sense RNA viruses (realm Riboviria: kingdom Orthornavirae: phylum Negarnaviricota).

In April 2023, following the annual International Committee on Taxonomy of Viruses (ICTV) ratification vote on newly proposed taxa, the phylum Negarnaviricota was amended and emended. The phylum was expanded by one new family, 14 new genera, and 140 new species. Two genera and 538 species were renamed. One species was moved, and four were abolished. This article presents the updated taxonomy of Negarnaviricota as now accepted by the ICTV.

Identification of T cell responses to the nonstructural glycoproteins in survivors of Crimean-Congo hemorrhagic fever in South Africa.

Crimean-Congo hemorrhagic fever orthonairovirus (CCHFV) is listed as a priority pathogen by the World Health Organization due to the severity of disease, propensity for spread to nonendemic regions, and absence of a vaccine or specific treatment. The immune correlates of protection are not clearly defined and hence the importance of investigating host immune responses in survivors. We have previously shown that survivors generate memory T cell responses that are long-lived and this study aimed to further define specific viral proteins targeted by the T cell response. The NSM , GP38, highly variable mucin-like domain, and N-terminus of GC regions in CCHFV are considered immunogenic regions and were investigated using peptide libraries representing regions of interest. An interferon gamma ELISpot assay was used to identify responses in peripheral blood mononuclear cells isolated from 12 survivors of laboratory confirmed CCHFV infections. IFN-γ responses were detected from eight survivors, against nine peptides, including four peptides located in the NSM region and five peptides located in the GP38 protein. No response was detected against peptides representing the mucin-like domain. In conclusion, the results suggest the presence of a long-lasting T cell memory response upon stimulation with viral epitopes in survivors of infection.

Sindbis Virus Antibody Seroprevalence in Central Plateau Populations, South Africa.

We report a higher percentage of Sindbis virus-specific IgG in serum from patients attending a rheumatology clinic (18.8%) compared with healthy residents (9.6%) and patients with acute febrile illness (9.4%) in Free State Province, South Africa. Sindbis virus infection should be considered a potential cause of arthritis in South Africa.

History and classification of Aigai virus (formerly Crimean-Congo haemorrhagic fever virus genotype VI).

Crimean-Congo haemorrhagic fever virus (CCHFV) is the medically most important member of the rapidly expanding bunyaviral family Nairoviridae. Traditionally, CCHFV isolates have been assigned to six distinct genotypes. Here, the International Committee on Taxonomy of Viruses (ICTV) Nairoviridae Study Group outlines the reasons for the recent decision to re-classify genogroup VI (aka Europe-2 or AP-92-like) as a distinct virus, Aigai virus (AIGV).

2022 taxonomic update of phylum Negarnaviricota (Riboviria: Orthornavirae), including the large orders Bunyavirales and Mononegavirales.

In March 2022, following the annual International Committee on Taxonomy of Viruses (ICTV) ratification vote on newly proposed taxa, the phylum Negarnaviricota was amended and emended. The phylum was expanded by two new families (bunyaviral Discoviridae and Tulasviridae), 41 new genera, and 98 new species. Three hundred forty-nine species were renamed and/or moved. The accidentally misspelled names of seven species were corrected. This article presents the updated taxonomy of Negarnaviricota as now accepted by the ICTV.

Mammarenaviruses of Rodents, South Africa and Zimbabwe.

We conducted a survey for group-specific indirect immunofluorescence antibody to mammarenaviruses by using Lassa fever and Mopeia virus antigens on serum specimens of 5,363 rodents of 33 species collected in South Africa and Zimbabwe during 1964-1994. Rodents were collected for unrelated purposes or for this study and stored at -70°C. We found antibody to be widely distributed in the 2 countries; antibody was detected in serum specimens of 1.2%-31.8% of 14 species of myomorph rodents, whereas 19 mammarenavirus isolates were obtained from serum specimens and viscera of 4 seropositive species. Phylogenetic analysis on the basis of partial nucleoprotein sequences indicates that 14 isolates from Mastomys natalensis, the Natal multimammate mouse, were Mopeia virus, whereas Merino Walk virus was characterized as a novel virus in a separate study. The remaining 4 isolates from 3 rodent species potentially constitute novel viruses pending full characterization.

2021 Taxonomic update of phylum Negarnaviricota (Riboviria: Orthornavirae), including the large orders Bunyavirales and Mononegavirales.

In March 2021, following the annual International Committee on Taxonomy of Viruses (ICTV) ratification vote on newly proposed taxa, the phylum Negarnaviricota was amended and emended. The phylum was expanded by four families (Aliusviridae, Crepuscuviridae, Myriaviridae, and Natareviridae), three subfamilies (Alpharhabdovirinae, Betarhabdovirinae, and Gammarhabdovirinae), 42 genera, and 200 species. Thirty-nine species were renamed and/or moved and seven species were abolished. This article presents the updated taxonomy of Negarnaviricota as now accepted by the ICTV.

Persistence of Crimean-Congo Hemorrhagic Fever Virus RNA.

Crimean-Congo hemorrhagic fever virus (CCHFV) causes severe disease with fatalities. Awareness of potential sources of infection is important to reduce risk to healthcare workers and contacts. We detected CCHFV RNA in formalin-fixed, paraffin-embedded tissues from a spontaneous abortion that were submitted for histology 9 weeks after a suspected CCHFV infection in the mother.

Basic insights into Zika virus infection of neuroglial and brain endothelial cells.

Zika virus (ZIKV) has recently emerged as an important human pathogen due to the strong evidence that it causes disease of the central nervous system, particularly microcephaly and Guillain-Barré syndrome. The pathogenesis of disease, including mechanisms of neuroinvasion, may include both invasion via the blood-brain barrier and via peripheral (including cranial) nerves. Cellular responses to infection are also poorly understood. This study characterizes the in vitro infection of laboratory-adapted ZIKV African MR766 and two Asian strains of (1) brain endothelial cells (hCMEC/D3 cell line) and (2) olfactory ensheathing cells (OECs) (the neuroglia populating cranial nerve I and the olfactory bulb; both human and mouse OEC lines) in comparison to kidney epithelial cells (Vero cells, in which ZIKV infection is well characterized). Readouts included infection kinetics, intracellular virus localization, viral persistence and cytokine responses. Although not as high as in Vero cells, viral titres exceeded 104 plaque-forming units (p.f.u.) ml-1 in the endothelial/neuroglial cell types, except hOECs. Despite these substantial titres, a relatively small proportion of neuroglial cells were primarily infected. Immunolabelling of infected cells revealed localization of the ZIKV envelope and NS3 proteins in the cytoplasm; NS3 staining overlapped with that of dsRNA replication intermediate and the endoplasmic reticulum (ER). Infected OECs and endothelial cells produced high levels of pro-inflammatory chemokines. Nevertheless, ZIKV was also able to establish persistent infection in hOEC and hCMEC/D3 cells. Taken together, these results provide basic insights into ZIKV infection of endothelial and neuroglial cells and will form the basis for further study of ZIKV disease mechanisms.

ICTV Virus Taxonomy Profile: Nairoviridae.

Members of the family Nairoviridae produce enveloped virions with three single-stranded RNA segments comprising 17.1 to 22.8 kb in total. These viruses are maintained in arthropods and transmitted by ticks to mammals or birds. Crimean-Congo hemorrhagic fever virus is tick-borne and is endemic in most of Asia, Africa, Southern and Eastern Europe whereas Nairobi sheep disease virus, which is also tick-borne, causes lethal haemorrhagic gastroenteritis in small ruminants in Africa and India. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Nairoviridae, which is available at ictv.global/report/nairoviridae.

Human papillomavirus DNA in head and neck squamous cell carcinomas in the Free State, South Africa.

Human papillomaviruses (HPVs) have been associated with a subset of head and neck squamous cell carcinomas (HNSCCs). The aim of this study was to determine the prevalence of HPV DNA in archived formalin-fixed paraffin-embedded tissue from patients with histologically confirmed HNSCCs in a South African cohort. A nested PCR was used for the detection of HPV DNA targeting the L1 gene. Positive samples were confirmed using an in-house hemi-nested PCR targeting the E6 gene and genotyped by sequence determination of amplicons. HPV DNA was detected in 57/780 (7.3%) samples, with the highest prevalence being in the sinonasal tract (16.0%) and oropharynx (10.8%). HPV16 was the most frequently detected type, being found in 26/57 (45.6%) positive samples. The prevalence of HPV DNA in HNSCCs found in this study was lower than that found in developed countries.

2020 taxonomic update for phylum Negarnaviricota (Riboviria: Orthornavirae), including the large orders Bunyavirales and Mononegavirales.

In March 2020, following the annual International Committee on Taxonomy of Viruses (ICTV) ratification vote on newly proposed taxa, the phylum Negarnaviricota was amended and emended. At the genus rank, 20 new genera were added, two were deleted, one was moved, and three were renamed. At the species rank, 160 species were added, four were deleted, ten were moved and renamed, and 30 species were renamed. This article presents the updated taxonomy of Negarnaviricota as now accepted by the ICTV.

Taxonomy of the order Bunyavirales: second update 2018.

In October 2018, the order Bunyavirales was amended by inclusion of the family Arenaviridae, abolishment of three families, creation of three new families, 19 new genera, and 14 new species, and renaming of three genera and 22 species. This article presents the updated taxonomy of the order Bunyavirales as now accepted by the International Committee on Taxonomy of Viruses (ICTV).

Taxonomy of the order Bunyavirales: update 2019.

In February 2019, following the annual taxon ratification vote, the order Bunyavirales was amended by creation of two new families, four new subfamilies, 11 new genera and 77 new species, merging of two species, and deletion of one species. This article presents the updated taxonomy of the order Bunyavirales now accepted by the International Committee on Taxonomy of Viruses (ICTV).

Seroepidemiologic Survey of Crimean-Congo Hemorrhagic Fever Virus in Selected Risk Groups, South Africa.

Crimean Congo hemorrhagic fever virus (CCHFV) is endemic in South Africa, but whether mild undiagnosed cases occur is unclear. In a seroepidemiologic survey, only 2 of 387 adults considered at risk because of occupational or recreational activities had evidence of previous infection. Seroprevalence in South Africa remains low within the groups investigated.

Evaluation of in vitro refolding vs cold shock expression: Production of a low yielding single chain variable fragment.

The development of therapeutic antibodies in their various forms has been a constant challenge since the development of the first monoclonal antibodies in 1975. This is especially true for the development of therapeutic single chain variable (scFv) fragments in Escherichia coli. In a previous study the selection of a tissue factor inhibiting single chain variable fragment (TFI-scFv) isolated from the Thomlinson I + J phage libraries was described. Although the initial findings were promising, additional characterization of the antibody fragment and subsequent application was hampered due low protein yield. This study reports on: i) the improved expression of a previously low yielding TFI-scFv in the cytoplasm of E. coli BL21 (DE3) through modifications to the expression systems in conjunction with codon optimization ii) evaluation of two commercial methods of protein recovery: in vitro refolding and the utilization of cold shock expression systems in conjunction with E. coli SHuffle. Results showed that TFI-scFv could be expressed at higher levels in the cytoplasm of E. coli than previously achieved in the periplasm. Both the in vitro refolding and cold shock strategies were capable of producing functional TFI-scFv with varying degrees of success. These procedures could be applied to improve the production of other problematic low yielding scFv isolated from phage display repositories in order to facilitate their characterization.

Global Genomic Diversity of Human Papillomavirus 11 Based on 433 Isolates and 78 Complete Genome Sequences.

UNLABELLED: Human papillomavirus 11 (HPV11) is an etiological agent of anogenital warts and laryngeal papillomas and is included in the 4-valent and 9-valent prophylactic HPV vaccines. We established the largest collection of globally circulating HPV11 isolates to date and examined the genomic diversity of 433 isolates and 78 complete genomes (CGs) from six continents. The genomic variation within the 2,800-bp E5a-E5b-L1-upstream regulatory region was initially studied in 181/207 (87.4%) HPV11 isolates collected for this study. Of these, the CGs of 30 HPV11 variants containing unique single nucleotide polymorphisms (SNPs), indels (insertions or deletions), or amino acid changes were fully sequenced. A maximum likelihood tree based on the global alignment of 78 HPV11 CGs (30 CGs from our study and 48 CGs from GenBank) revealed two HPV11 lineages (lineages A and B) and four sublineages (sublineages A1, A2, A3, and A4). HPV11 (sub)lineage-specific SNPs within the CG were identified, as well as the 208-bp representative region for CG-based phylogenetic clustering within the partial E2 open reading frame and noncoding region 2. Globally, sublineage A2 was the most prevalent, followed by sublineages A1, A3, and A4 and lineage B. IMPORTANCE: This collaborative international study defined the global heterogeneity of HPV11 and established the largest collection of globally circulating HPV11 genomic variants to date. Thirty novel complete HPV11 genomes were determined and submitted to the available sequence repositories. Global phylogenetic analysis revealed two HPV11 variant lineages and four sublineages. The HPV11 (sub)lineage-specific SNPs and the representative region identified within the partial genomic region E2/noncoding region 2 (NCR2) will enable the simpler identification and comparison of HPV11 variants worldwide. This study provides an important knowledge base for HPV11 for future studies in HPV epidemiology, evolution, pathogenicity, prevention, and molecular assay development.

Biosafety standards for working with Crimean-Congo hemorrhagic fever virus.

In countries from which Crimean-Congo haemorrhagic fever (CCHF) is absent, the causative virus, CCHF virus (CCHFV), is classified as a hazard group 4 agent and handled in containment level (CL)-4. In contrast, most endemic countries out of necessity have had to perform diagnostic tests under biosafety level (BSL)-2 or -3 conditions. In particular, Turkey and several of the Balkan countries have safely processed more than 100 000 samples over many years in BSL-2 laboratories. It is therefore advocated that biosafety requirements for CCHF diagnostic procedures should be revised, to allow the tests required to be performed under enhanced BSL-2 conditions with appropriate biosafety laboratory equipment and personal protective equipment used according to standardized protocols in the countries affected. Downgrading of CCHFV research work from CL-4, BSL-4 to CL-3, BSL-3 should also be considered.