Definition of rna viruses

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Except where otherwise stated, drug dosages and recommendations are for the non-pregnant adult who is not breastfeeding. Paramyxoviruses [link]. Hendra and Nipah viruses [link]. Measles [link]. Severe acute respiratory syndrome coronavirus SARS [link]. Middle east respiratory syndrome coronavirus MERS [link]. Picornaviruses [link]. Hepatitis A virus HAV [link]. Rotavirus [link]. Human immunodeficiency virus HIV [link].

Hepatitis C virus HCV [link]. Hepatitis E virus HEV [link]. Rabies [link]. Ebola virus disease EVD [link]. Marburg virus [link]. Lassa fever [link].

Lymphocytic choriomeningitis virus LCMV [link]. Japanese encephalitis JE [link]. West Nile fever [link]. Yellow fever [link]. Dengue fever [link]. Zika virus [link]. Equine encephalitis viruses [link]. Chikungunya [link]. Bunyaviruses [link]. Rift valley fever and Crimean-Congo haemorrhagic fever [link].

Hantavirus [link]. Histopathology: multinucleate giant cells with inclusion bodies; pathognomonic for measles. During prodrome, detectable in nasopharyngeal aspirate. Virus detection by PCR, e. Serology: fourfold rise in measles-specific IgM. Pulmonary or extrapulmonary tuberculosis; recurrent pneumonia; Mycobacterium avium disseminated or extrapulmonary ; recurrent Salmonella septicaemia. There may also be a requirement for host cell proteins.

Their genomes are translated shortly after penetration into the host cell to produce the RdRp and other viral proteins required for synthesis of additional viral RNAs. Positive-strand RNA viruses often use large complexes of cellular membranes for genome replication. They actively modify host cell membranes to construct viral replication scaffolds. For each of these groups of viruses, the first synthetic event after genome penetration is transcription.

This is accomplished by viral proteins including the RdRp that enter cell with the genome. RdRp is the key player for all of these processes Fig. Ribbon diagram of flavivirus RdRp. Fingers, palm, and thumb subdomains are colored in blue, green, and red, respectively. Motifs A, C, E, F, the G-loop, and the priming loop are colored in orange, yellow, gray, magenta, cyan, and purple, respectively.

N-ter and C-ter indicate the termini of the RdRp domain. RdRps of RNA viruses probably arose from a common ancestor. The RdRp, in association with other proteins required for viral genome synthesis is often called the replicase complex. The biochemical requirements for genome synthesis may or may not be identical to those required for synthesis of mRNAs.

If the two processes differ, the term transcription complex is sometimes used to describe the particular set of proteins required for viral mRNA synthesis. Upon penetration into the host cell, ribosomes assemble on the genome to synthesize viral proteins.

During the replication cycle of positive-strand RNA viruses, among the first proteins to be synthesized are those needed to synthesize additional genomes and mRNAs. A functional definition of a positive-strand virus is that purified or chemically synthesized genomes are infectious Fig. Schematic representation of replication of positive-strand RNA virus genomes. The genome of a positive-strand RNA virus is an mRNA that is translated, upon entry into the cells, to produce proteins needed for transcription and genome replication for example, RdRp.

After initial rounds of translation, the genome serves as the template for synthesis of copy RNA. RdRp is a nonstructural protein, meaning that it is not found within the assembled virion. Instead it is translated directly from the infecting genome shortly after penetration. RdRp and other viral proteins needed for viral RNA synthesis are encoded as a polyprotein that is cleaved by virally encoded proteases. In the case of the picornaviruses and the flaviviruses, all viral proteins structural and nonstructural are synthesized as part of a single long polyprotein.

Other positive-strand RNA viruses i. For each of these groups of viruses, the first synthetic event after genome penetration is transcription Fig.

This is accomplished by viral proteins including viral RdRp that enter cell with the genome. They associate with the genome through interactions with RNA-binding nucleocapsid N or capsid proteins.

Therefore, naked purified away from protein genomic RNA is not infectious, cannot be translated, and will eventually be degraded if transcription is blocked. Before genome replication can proceed, viral mRNAs must be transcribed and translated. If purified virions are gently lysed under appropriate buffer conditions, with the addition of NTPs, mRNAs will be transcribed in the test tube.

However, genome RNA will not be synthesized under these conditions Table Schematic representation of replication of genomes of minus-strand RNA viruses. Upon entry into the cell, the active transcription complex synthesizes mRNAs. This process can also occur in a test tube see Fig.

Translation of mRNAs produces proteins required for genome replication. Thus if protein synthesis is blocked in the infected cell, mRNAs continue to by synthesized but genome replication does not occur. Newly synthesized proteins provide the switch from transcription to genome replication.

The genomes of viruses in the order Mononegavirales are unsegmented, negative-strand RNA. Note that genome synthesis does not occur under these conditions. In contrast, viruses that use an ambisense coding strategy transcribe some mRNAs from the copy genome. There are virus families in which some members are considered negative-strand RNA viruses while others use an ambisense strategy. Thus these two strategies are closely related. Some ambisense viruses package copy genomes that can be used as templates for transcription, such that the full complement of viral genes can be transcribed soon after infection.

It should be noted that packaged copy genomes are not mRNAs and are not translated. Reoviruses also have segmented genomes, packaging 11—12 segments of dsRNA. Reoviruses are nonenveloped and particles consist of two or three concentric icosahedral capsid layers. So there are many different kinds of retroviruses. Now, the most famous one right at the moment is the human immunodeficiency virus which causes acquired immunodeficiency syndrome, or AIDS. But there are many different kinds of retroviruses that are associated with diseases, including cancer, leukemia, and AIDS, obviously.

Finally, retroviruses have been tamed for use in gene therapy, so it is possible to take out all of the genes that allow the retrovirus to replicate itself and replace that with a gene that the particular cell that you're interested in is missing.

And so using the integrating ability of a retrovirus, you can actually take something that could ordinarily harm people and turn it into something that can be used as a therapeutic vehicle to make them better.