Bat mumps orthorubulavirus, formerly Bat mumps rubulavirus (BMV), is a member of genus Orthorubulavirus, family Paramyxoviridae, and order Mononegavirales. Paramyxoviridae viruses were first isolated from bats using heminested PCR with degenerate primers. This process was then followed by Sanger sequencing. A specific location of this virus is not known because it was isolated from bats worldwide. Although multiple paramyxoviridae viruses have been isolated worldwide, BMV specifically has not been isolated thus far. However, BMV was detected in African fruit bats, but no infectious form has been isolated to date. It is known that BMV is transmitted through saliva in the respiratory system of bats. While the virus was considered its own species for a few years, phylogenetic analysis has since shown that it is a member of Mumps orthorubulavirus.
Classification
The Paramyxoviridae family can be divided in several genera, all negative strand RNA viruses. They include Rubulavirus, Henipavirus, Respirovirus, Morbillivirus, Ferlavirus, Aquaparamyxovirus, and Abulavirus. The rubulavirus genus can then be divided into two main groups, based on the type of pathogen. Rubulavirus genus contains human pathogens, as well as bat-borne pathogens. Examples of the human viruses include the following: parainfluenza virus (hPIV) and mumps virus (MuV), and examples of the bat-borne viruses are: Mapuera (MapV), Bat Mumps Rubulavirus (BMV), and Menangle (MenPV).
Virus structure
Bat mumps rubulavirus (BMV) is a spherical shaped negative sense single stranded RNA virus. Some researchers have noted a pleomorphic structure. BMV is about 15kb in size, with a diameter of about 150nm. This virus also contains an envelope, derived from the host cell. In addition, Rubulavirus has cell attachment glycoprotein, important in mediating viral entry, with neuraminidase and haemagglutinin capability. A ribonucleocapsid is present inside the virus.
Virus genome
The BMV is composed of a linear genome, with a monopartite segmentation, meaning there is a single molecule of nucleic acid, as opposed to multiple molecules. In other words, the genome is non-segmented since it only has the one molecule. Because of this, the genome cannot undergo generic reassortment, so no antigenic shift can occur. RNA-dependent RNA polymerase does not have a function to be able to check for errors in coding, so many mutations are possible in the transcription process. It was initially assumed by researchers that antigenic stability would not be possible due to having these mechanisms occurring, but it has been noted that there is antigenic stability due to the fact that there are so many proteins, each having their own roles. So, any mutation would lead to a reduced ability to function, then creating a less efficient virus, which is not favorable for the virus.
BMV encodes a nucleoprotein, encoded by gene N; a phosphoprotein, encoded by gene P; a V protein, a matrix protein, encoded by M; a fusion protein, encoded by F; and a large polymerase subunit, encoded by L. In addition, the unedited P gene contains the V protein. The order from left to right is the leader region, followed by the nucleocapsid, then the phosphoprotein, then the matrix protein, followed by the fusion protein, then the large polymerase, and finally the trailer sequence. The addition of 2 non-templated G residues of the RNA-dependent RNA polymerase is necessary for expressing the phosphoprotein, in order for viral replication and synthesis to occur since it is a negative single-stranded RNA virus. BMV (as well as a parainfluenza virus known as PIV5) contain short hydrophobic proteins, which have a role in blocking the TNFalpha-mediated apoptosis pathway. In terms of gene expression, the viral RNA-dependent RNA polymerase binds the encapsulated genome at the leader region, which starts the transcription process. The 3’ leader sequence is approximately 50 nucleotides in length, and this is the area acting as the transcriptional promoter. The 5’ trailer sequence (at the opposite end of the leader sequence) is between 50 and 161 nucleotides in length. There are intergenomic regions between each gene, which are usually between 1 and 56 nucleotides long for BMV. mRNAs are capped and polyadenylated by the L protein, and the V protein is created through editing the P mRNA gene, as mentioned earlier.
Virus replication cycle and interaction with the host
The replication cycle for BMV has not been studied; however, the replication cycle of the rubulavirus genus as a whole has been studied, so the information listed below is regarding the entire rubulavirus genus. The replication cycle is cytoplasmic.