Banna virus (BAV) is a virus belonging to ''

Reoviridae ''Reoviridae'' is a family of double-stranded RNA viruses. Member viruses have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid envelopes and package their segmented genome within multi-layere ...

'', a family of segmented, non-enveloped,

double-stranded RNA viruses Double-stranded RNA viruses (dsRNA viruses) are a Polyphyly, polyphyletic group of viruses that have Nucleic acid double helix, double-stranded genomes made of ribonucleic acid. The double-stranded genome is used to transcribe a Sense (molecular ...

. It is an

arbovirus Arbovirus is an informal name for any virus that is transmitted by arthropod vectors. The term ''arbovirus'' is a portmanteau word (''ar''thropod-''bo''rne ''virus''). ''Tibovirus'' (''ti''ck-''bo''rne ''virus'') is sometimes used to more spe ...

, being primarily transmitted to humans from the bite of infected mosquitoes of the genus ''

Culex ''Culex'' is a genus of mosquitoes, several species of which serve as vectors of one or more important diseases of birds, humans, and other animals. The diseases they vector include arbovirus infections such as West Nile virus, Japanese encep ...

''. Pigs and cattle have also been shown to become infected. The most common symptom of infection is

fever Fever, also referred to as pyrexia, is defined as having a body temperature, temperature above the human body temperature, normal range due to an increase in the body's temperature Human body temperature#Fever, set point. There is not a single ...

, but in some cases

encephalitis Encephalitis is inflammation of the brain. The severity can be variable with symptoms including reduction or alteration in consciousness, headache, fever, confusion, a stiff neck, and vomiting. Complications may include seizures, hallucinations, ...

may occur. There is no specific treatment for infection, so treatment is aimed at alleviating the severity of symptoms until the immune system has cleared the infection.

Virology

Structure and genome

BAV is a small (72–75 nm in size), non-enveloped, double-stranded RNA virus surrounded by an

icosahedral In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes and . The plural can be either "icosahedra" () or "icosahedrons". There are infinitely many non- similar shapes of icosahedra, some of them being more symmetrica ...

protein coat. Fibre proteins extend outward from the surface of the protein coat. The

genome In the fields of molecular biology and genetics, 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 ge ...

of BAV is about 19,500 base pairs in length, linear and segmented into 12 parts, encoding for genes VP1-12. Seven of these, VP1-4 and VP8-10, are structural proteins. VP4 and VP9 form the outer protein coat. The inner particles of the coat are composed of VP1-3, VP8 and VP10. VP7 serves as a

protein kinase A protein kinase is a kinase which selectively modifies other proteins by covalently adding phosphates to them (phosphorylation) as opposed to kinases which modify lipids, carbohydrates, or other molecules. Phosphorylation usually results in a fu ...

, VP1 as an

RNA-dependent RNA polymerase RNA-dependent RNA polymerase (RdRp) or RNA replicase is an enzyme that catalyzes the replication of RNA from an RNA template. Specifically, it catalyzes synthesis of the RNA strand complementary to a given RNA template. This is in contrast to t ...

, VP3 as a

capping enzyme A capping enzyme (CE) is an enzyme that catalyzes the attachment of the 5' cap to messenger RNA molecules that are in the process of being synthesized in the cell nucleus during the first stages of gene expression. The addition of the cap occ ...

, and VP12 as a dsRNA-binding protein.

Types and evolution

Rotavirus ''Rotavirus'' is a genus of double-stranded RNA viruses in the family ''Reoviridae''. Rotaviruses are the most common cause of diarrhoeal disease among infants and young children. Nearly every child in the world is infected with a rotavirus a ...

es share many physical and genetic characteristics with BAV, indicating a close genetic relation between the viruses. Phylogenetic analysis of the various BAV strains suggests that the BAV-Ch and BAV-In6969 strains were two individual

genotype The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a ...

s at one point in time (A and B), before becoming the prototype species for two distinct

serotype A serotype or serovar is a distinct variation within a species of bacteria or virus or among immune cells of different individuals. These microorganisms, viruses, or cells are classified together based on their surface antigens, allowing the epi ...

s (A and B) among all 38 identified strains.

Diagnosis

Clinical features of BAV infection are non-specific and resemble other arboviral encephalitides, so laboratory diagnosis is required to identify BAV as the cause of illness. Detection of the nucleic acid of BAV can be performed with a

TaqMan TaqMan probes are hydrolysis probes that are designed to increase the specificity of quantitative PCR. The method was first reported in 1991 by researcher Kary Mullis at Cetus Corporation, and the technology was subsequently developed by Hoffmann ...

reverse transcription polymerase chain reaction (RT-PCR)

assay An assay is an investigative (analytic) procedure in laboratory medicine, mining, pharmacology, environmental biology and molecular biology for qualitatively assessing or quantitatively measuring the presence, amount, or functional activity of a ...

by extracting RNA strands from a sample and reverse transcribing them into detectable cDNA. A recombinant VP9-based

enzyme-linked immunosorbent assay The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presence ...

(ELISA) can also be used to identify antibodies to BAV in blood serum and study the seroprevalence of BAV infection in a population.

History

Banna virus was first isolated from the

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the bra ...

of encephalitis patients in

Xishuangbanna Xishuangbanna, Sibsongbanna or Sipsong Panna ( Tham: , New Tai Lü script: ; ; th, สิบสองปันนา; lo, ສິບສອງພັນນາ; shn, သိပ်းသွင်ပၼ်းၼႃး; my, စစ်ဆောင်� ...

Yunnan province Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the C ...

People's Republic of China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

in 1987. Subsequent identification came in the

Xinjiang province Xinjiang Province is a historical administrative area of Northwest China, between 1884 and 1955. Periods during which various boundaries of Xinjiang Province have been defined include: * Xinjiang Province (Qing) (1884–1912). * Xinjiang Provi ...

and the virus has since been found elsewhere in China,

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

, and

Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...

in mosquito populations. Because BAV displays similar symptoms to

Japanese encephalitis Japanese encephalitis (JE) is an infection of the brain caused by the Japanese encephalitis virus (JEV). While most infections result in little or no symptoms, occasional inflammation of the brain occurs. In these cases, symptoms may include he ...

virus (JEV) infection and the two viruses share their method of transmission and geographic distribution, it is possible that some past outbreaks attributed to JEV may have instead been caused by BAV.

References

{{Taxonbar, from=Q16243472 Seadornaviruses