In 1954 the Hazara virus, one of the 34 tick-borne viruses of the genus '' Orthonairovirus'', was discovered in Pakistan in the ''

Ixodes ''Ixodes'' is a genus of hard-bodied ticks (family Ixodidae). It includes important disease vectors of animals and humans ( tick-borne disease), and some species (notably '' Ixodes holocyclus'') inject toxins that can cause paralysis. Som ...

'' tick native to that region. Today this virus is studied in mice in an attempt to develop treatments for the highly pathogenic Crimean-Congo Hemorrhagic Fever virus.

Characteristics

Hazara virus is part of the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''Orthonairovirus'' of the '' Nairoviridae'' family of viruses, which are a family of enveloped negative-stranded

RNA Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...

viruses with a

genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

split into three parts—Small (S), Middle (M) and Large (L). The L RNA segment encodes an RNA-dependent

RNA polymerase In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that catalyzes the chemical reactions that synthesize RNA from a DNA template. Using the e ...

(L protein), the M RNA segment encodes two surface

glycoprotein Glycoproteins are proteins which contain oligosaccharide (sugar) chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known a ...

s (Gc and Gn), and the S RNA segment encodes a nucleocapsid protein (N). The three genomic RNA segments are encapsidated by copies of the N protein in the form of

ribonucleoprotein Nucleoproteins are proteins conjugated with nucleic acids (either DNA or RNA). Typical nucleoproteins include ribosomes, nucleosomes and viral nucleocapsid proteins. Structures Nucleoproteins tend to be positively charged, facilitating inter ...

(RNP) complexes. The N protein is the most abundant viral protein in ''

Bunyaviridae ''Bunyaviricetes'' is a class of segmented negative-strand RNA viruses with mainly tripartite genomes. Member viruses infect arthropods, plants, protozoans, and vertebrates. The name ''Bunyaviricetes'' derives from Bunyamwera, where the virus B ...

'' virus particles and infected cells and, therefore, the main target in many serological and molecular diagnostics.

Transmission

Hazara virus is spread by the '' Ixodes redikorzevi'' tick. The tick is commonly found on an alpine

vole Voles are small rodents that are relatives of lemmings and hamsters, but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars (high-crowned with angular cusps instead of lo ...

inhabiting the

Hazara District Hazara District was a district of Peshawar Division in the North-West Frontier Province of Pakistan. It existed until 1976, when it was split into the districts of Abbottabad and Mansehra, with the new district of Haripur subsequently splitti ...

of Pakistan.

Signs and symptoms

Hazara virus does not cause disease or symptoms in humans. In laboratory mice, symptoms can mirror those of Crimean-Congo Hemorrhagic Fever virus.

Diagnosis

Diagnosis in

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

s is made by detecting Hazara virus

antibodies An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that caus ...

in the serum.

Clinical importance

Hazara virus is in the same nairovirus serogroup as Crimean-Congo hemorrhagic fever virus (CCHFV), and has similar disease progression to that seen in '' Crimean-Congo Hemorrhagic Fever'' (CCHF) infections in suckling mice and in the interferon receptor

knockout mouse A knockout mouse, or knock-out mouse, is a genetically modified mouse (''Mus musculus'') in which researchers have inactivated, or " knocked out", an existing gene by replacing it or disrupting it with an artificial piece of DNA. They are importan ...

model This indicates that ''Hazara orthonairovirus'' could represent a valid model for CCHFV infection. This finding is particularly important because using the Hazara virus ( biosafety level 2) as a model allows scientists to investigate this serogroup of viruses for the development of antivirals, without having to work in a biosafety level 4 environment, which is the highest available level of biosecurity, and is mandatory when working with intact CCHFV. While CCHFV is the most important human pathogen in this serogroup, Hazara research is potentially useful in the development of antiviral medications for all viruses in the genus '' Orthonairovirus''.

References

{{Taxonbar, from=Q29002579 Nairoviridae