Chapter 2
Any links that are marked by an "*" contains material which may be on the test
Nomenclature Order has the suffix "-virales" - this is the highest taxonomic group Families have the suffix "-viridae" Subfamilies have the suffic "-virinae" Genera have the suffix "-virus" General Rules Small DNA viruses must replicate in the nucleus negative-stranded RNA viruses must carry a virion transcriptase viruses that go from RNA to DNA must carry a virion transcriptase Bigger viruses mean bigger genomes, which means more complexity, more proteins Viruses which replicate in the cytoplasm have shorter eclipse periods DNA Virus Families Parvoviridae Subfamily: Parvovirinae Genus: Parvovirus (mammals and birds) Genus: Erythrovirus (human parvovirus B19) Genus: Dependovirus (adeno-associated viruses Characteristics: Table 2-1* Are among the smallest of DNA viruses (20 nm). Typically have a very narrow host range and replicate preferentially in dividing cells. One parvovirus -B19 - is found in humans but has not been positively implicated in any disease. Likewise, there are 5 strains of Dependovirus, but none have been implicated as the causal agent in human disease. Papovaviridae Genus: Papillomavirus Genus: Polyomavirus Characteristics: Table 2.1* PAPOVA = papilloma - polyoma - vacuolating agent Replicate in the nucleus and may transform infected cells. Papillomaviruses cause warts, are slightlyl larger (55 nm), and have a larger genome. Polyoma viruses cause tumors in rodents cells, are slightly smaller (45 nm), have a smaller genome, and may integrate into the host cell DNA Some papillomaviruses may be responsible for human cervical cancer. Human polyoma viruses are apparently responsible for inapparent infections and can be reactivated by immunosuppression. SV40 - a polyoma virus has been particularly useful for studying oncogenesis in monkeys and for analyzing the molecular replication of the virus. Adenoviridae Genus: Mastadenovirus (mammalian adenoviruses) Characteristics: Table 2.1* Adeno = gland Replicate in the nucleus. There are 50 serologically distinct types, but they also share a group antigen (which places them in this genus) Infections of the respiratory tract (URI), the eye, and the intestinal tract (viral diarrhea). Some infections persist a long time. Herpesviridae Subfamily: Alphaherpesvirinae (herpes simplex-like viruses) Genus: Simplexvirus (herpes simplex-like viruses) Genus: Varicellovirus (varicella-zoster virus) Subfamily: Betaherpesvirinae (cytomegaloviruses) Genus: Cytomegalovirus (human cytomegalovirus) Genus: Roseolovirus (human herpesvirus 6) Subfamily: Gammaherpersivrinae (lymphoproliferative herpesviruses) Genus: Lymphocryptovirus (Epstein-Barr virus) Characteristics: Table 2.1 Herpes = creeping (as in cold sores) Replicate in nucleus and mature by budding through the nuclear membrane (envelope) All herpesviruses persist in the body for the life of the host -- many times in a latent state. Excretion of the virus in usually in saliva or genital secretions and occurs independent of whether the individual is experiencing an "episode". The virus can be latent for years (undetectable) and then reoccur when a stressful or immunosuppressive event happens. Some herpesviruses may be responsible for cancers -- Burkitt's lymphoma, nasopharyngeal carcinoma (EB virus) Poxviridae Subfamily: Chordopoxvirinae (poxviruses of vertebrates) Genus: Orthopoxvirus (vaccinia) Genus: Parapoxvirus (orf virus) Genus: Molluscipoxvirus (molluscum contagiosum) Genus: Yatapoxvirus (yaba/tanapox virus) Genus: Avipoxvirus (bird poxviruses) Characteristics: Table 2.1* Poc = pustule Largest and most complex. Can be seen with good light microscope. Parapoxviruses are ovoid, as opposed to the normal brick shape. They have an inner core. Poxviruses replicate in the cytoplasm. They carry their own virion transcriptase. Orthopoxvirus - ectromelia, cowpox, rabbitpox, monkeypox, variola, vaccinia Parapoxvirus - contagious putular dermatitis of sheep, pseudocowpox (milker's node), both of which can cause human skin lesions. Molluscum contagiosum is a disease of humans Yabapox and Tanapox may infect humans Hepadnaviridae Genus: Orthohepadnavirus (Hepatitis B-like viruses) Characteristics: Table 2.1* Hepa = liver, dna = DNA Partially double-stranded DNA for genome. Replication involves an RNA intermediate and require a reverse transcriptase. They replicate preferentially in hepatocytes and cause long term degeneration, usually followed by primary hepatocarcinoma. The most important species is the Human hepatitis B virus?????? Woodchucks, ground squirrels, Peking ducks, and herons. RNA Viruses Picornaviridae Genus: Enterovirus (enteroviruses) Genus: Hepatovirus (hepatitis A-like viruses) Genus: Rhinovirus (rhinoviruses) Characteristics: Table 2.2* pico = small, rna = ribonucleic acid Enterovirus includes polioviruses, echoviruses, and coxsackieviruses and a few human enteroviruses. Most are inapparent enteric infections, but can cause polio, meingoencephalitis, rashes, carditis, myositis, conjunctivitis, and mild upper respiratory tract disease. Only human pathogen in the heptoviruses is Hepatitis A. Rhinovirus is the virus responsible for most human colds. Caliciviridae Genus: Calicivirus (caliciviruses) Characteristics: Table 2.2* calix = cup 32 cups-shaped depressions on the surface. Norwalk agent and related caliciviruses are important cause of gastroenteritis. The other major player is Hepatitis E transmitted by the fecal oral route. Similar to picornaviruses. Astroviridae Genus: Astrovirus (astroviruses) Characteristics: Table 2.2* astron = star Found in feces of humans calves and lambs suffering from enteritis. Very similar to picornaviruses and caliciviruses. Togaviridae Genus: Alphavirus (used to be known as "Group A" arboviruses) Genus: Rubivirus (rubella virus) Characteristics: Table 2.2* toga = cloak Acquire envelope by budding through cell membranes. All Alpha viruses are transmitted by mosquitoes. May neurotropic strains including - Eastern encephalitis, Western encephalitis, Venezuelan equine encephalitis, Ross river virus, chikungunya virus. The alpha viruses produce inapparent infections in birds, mammals, or reptiles. Virus transmitted to humans by mosquito bite and then causes encephalitis-like disease. Rubella is separated out in its own genus because it is not arthropod-borne. Causes a measles-like disease that is not severe, but which can cause congential defects in fetus. Flaviviridae Genus: Flavivirus (used to be known as "group B" arboviruses Genus: Hepatitis C (hepatitis C virus) Characteristics: Table 2.2* flavus = yellow Flavirus are arthropod-borne, but hepatitis C is transmitted sexually and through human blood. Flaviviruses contain yellow fever, dengue, St. Louis encephalitis, Japanese encephalitis, Murray Valley encephalitis, and Russian tick-borne encephalitis. Coronaviridae Genus: Coronavirus (coronaviruses of mammals and birds) Characteristics: Table 2.2* corona = crown pleomorphic. Contain peplomers. Envelope lacks a matrix protein. Coronaviruses are causative agent of human colds and are implicated in some gastroenteritis (found in feces). Paramyxoviridae Subfamily: Paramyxovirinae Genus: Paramyxovirus (parainfluenza viruses) Genus: Morbillivirus (measles-like viruses) Genus: Rubulavirus (mumps virus) Subfamily: Pneumovirinae Genus: Pneumovirus (respiratory syncytial virus) Characteristics: Table 2.2* para = by the side, myxa = mucus Envelope has two glycoproteins, hemagglutinin and fusion protein. parainfluenza is respiratory disease, measles is generalized infection with rash, mumps is infection that becomes localized in parotid glands, RSV is major cause of respiratory disease in infants.
Rhabdoviridae (Rhabdoviruses)
Genus: Vesiculovirus (vesicular stomatitis-like viruses) Genus: Lyssavirus (rabies-like viruses) Characteristics: Table 2.2 rhabdos = rod Bullet-shaped viruses. Virus matures at plasma membrane. Animal pathogens include Chandipura, Piry, and Isfahan viruses. Lyssavirus includes rabies virus and several relted viruses from Africa, which may cause severe disease in humans following animal bites. Filoviridae (Filoviruses) Genus: Filovirus (Marburg, Evola, and Reston viruses) Characteristics: Table 2.2 filo = threadlike Marburg and Ebola are important human pathogens and have high fatality rates. They cause a severe hemorrhagic fever. Reston virus is not virulent for humans (causing a sublinical infection) but is very virulent for monkeys. Orthomyxoviridae (Influenza viruses) Genus: Influenzavirus A, B Genus: Inluenzavirus C Genus: unnamed Thogoto-like viruses (tick-borne) Characteristics: Table 2.2 orthos = straight, myxa = mucus Bud through plasma membrane to acquire envelope. Two types of envelope proteins: hemagglutinin and neurimindase - (which help confer host specificity) in A and B influenza. One kind of protein - hemagglutinin-esterase - in influenza C. Influenza A infects birds, horses, swine, mink, seals, whales, and humans. Influenza B is only a human pathogen Influenza C is a human and swine pathogen and is a mild disease. Influenza of A undergoes antigenic shift to cause major pandemics. Dhori and Thogoto occasionally infect humans and are in a separate genus because they are tick-borne. Arenaviridae Genus: Bunyavirus (Bunyamwera subgroup) Genus: Phlebovirus (sandfly fever viruses) Genus: Nairovirus (Nairobi sheep disease-like viruses) Genus: Hantavirus (hemorrhagic fever with renal syndrome viruses) Characteristics: Table 2.2 Genome consists of three molecules of minus-strand (ambisense for Phlebovirus) RNA held in circular configuration by hydrogen bonds. Replicate in cytoplasm and bud from the Golgi membranes. They readily undergo genetic reassortment. All except the hantaviruses are arboviruses which have wild animal reservoirs. Some are transovarially transmitted in mosquitoes. Hantaviruses are enzootic in rodents and cause hemorrhagic fever with renal syndrome (pulmonary syndrome in humans). Phlebovirus includes Sandfly fever virus, and Rift Valley fever virus (transmitted by mosquito) that is pathogen of sheep and humans. Bunyaviruses are mostly mosquito-transmitted and include the California encephalitides. Nairovirus are tick-borne and include the Crimean-Congo hemorrhagic fever. Reoviridae (Reoviruses) Genus: Orthoreviruses (reoviruses of animals) Genus: Orbivirus (orbiviruses) Genus: Rotavirus (rotaviruses) Genus: Coltivirus (Colorado tick fever virus) Characteristics: Table 2.2 Reo stands for respiratory enteric orpha virus Orthoreoviruses were the first discovered in respiratory and enteric tract of humans but have not been associated with any disease. The genera are differentiated on the basis of how many segments they contain. 10 for orthoreo or orbi, 11 for rota, 12 for colti Orbiviruses are arboviruses - some of which cause disease in humans. Colorado tick fever is also disease of humans. Rotaviruses are an important human enteric pathogen. Retroviridae (Retroviruses) Genus: Lentivirus (HIV-like viruses, maedi/visna like viruses) Genus: Spumavirus (foamy viruses) Genus: Unnamed; HTLV-BLV viruses (includes human T-cell leukemia) Characteristics: Table 2.2 retro = backwards genome is diploid - inverted dimer of plus RNA