Things to Remember about DNA Viruses
DNA Viruses Remember HHAAPPPIC for:
- Herpesviruses
- Hepadnaviruses
- Adenoviruses
- Asfarviruses
- Papova = Polyomaviruses and Papillomaviruses
- Parvoviruses
- Poxviruses
- Iridoviruses
- Circoviruses
All DNA viruses replicate in the nucleus except POX replicate in the cytoplasm
All DNA viruses are dsDNA except PARVO and CIRCO ssDNA
All DNA viruses are icosahedral except POX is complex
Below is a summary of DNA virus families based on criteria for classification and their properties. The detail for each DNA virus family is covered on separate topics.
EXTENSIVE SUMMARY OF DNA VIRUSES
| Family name | Poxviridae | Asfarviridae (Asfar=African swine fever and related viruses) | Circoviridae | Parvoviridae | Herpesviridae | Adenoviridae | Hepadnaviridae (Hepadna=hepatitis DNA virus) | Iridoviridae | Papillomaviridae | Polyomaviridae |
| Genome | ds linear DNA | ds linear DNA | ss circular DNA, ambisense (+/-) | ss linear DNA (+) or (-) sense | ds linear DNA | ds linear DNA | ds circle gapped DNA | ds linear DNA | ds circular DNA | ds circular DNA |
| Genome size | 130-280 kbp | 190 kbp | 1.7 kb | 5 kb | 120-200 kbp | 36-38 kbp | 3.2 kbp | 150-350 kbp | 5-8 kb | 5-8 kbp |
| Symmetry of capsids | Complex | Icosahedral | Icosahedral | Icosahedral | Icosahedral | Icosahedral | Icosahedral | Icosahedral | Icosahedral | Icosahedral |
| Naked or enveloped | Enveloped | Enveloped | Naked | Naked | Enveloped | Naked | Enveloped | Naked/Enveloped | Naked | Naked |
| Baltimore class | I | I | II | II | I | I | VII | I | I | I |
| Baltimore class I: ds DNA viruses: These viruses usually must enter the host nucleus before it is able to replicate (except Poxviridae). These viruses require host cell DNA polymerases to replicate the viral genome and hence are highly dependent on the cell cycle. Proper infection and production of progeny require that the cell is in mitosis as that is when the cell’s polymerases are active. The virus may induce the cell to forcefully undergo cell division, and chronically, this may lead to the transformation of the cell and ultimately, cancer. dsDNA → mRNA | Baltimore class II: ssDNA viruses: Replicate within the nucleus using host cell DNA polymerases and form a dsDNA intermediate during replication ssDNA → dsDNA → mRNA | Baltimore class VII: gapped ds DNA viruses: They have gapped genome and they undergo reverse transcription during maturation as opposed to retroviruses. RNA is formed as intermediate product then DNA. dsDNA → RNA → DNA | ||||||||
| Virion | 170-200×300-450nm | 200nm | 20 nm | 18-26nm | 150-200nm | 70-100 nm | 42nm | 125-300 nm | 40-45 nm | 45-55nm |
| DNA polymerase | + | – | – | – | – | – | + | – | – | – |
| Genus and species | Orthopoxvirus: Cowpox virus, Camelpox virus Parapoxvirus: BoPS, Orf virus, pseudocowpox virus Avipoxvirus: Fowlpox virus, turkeypox virus Capripoxvirus: Goatpox virus, LSD virus, sheeppox virus Leporipoxvirus: Rabbit fibroma Suipoxvirus: Swinepox | Asfarvirus: African swine fever virus | Circovirus: PCV1, PCV2, BFDV Gyrovirus CAV | Parvovirus: CPV, PPV, ChPV Erythrovirus: AAAV, BAAV, CAAV | Simplexvirus: BoHV1, BoHV2, SuHV1, EHV1, EHV3, CaHV1, FeHV1 Mardivirus: GaHV1, GaHV2 Rhadinovirus: AlHV1 | Aviadenovirus: Fowl adenovirus A-E Atadenovirus: Ovine adenovirus D Canine adenovirus, Caprine adenovirus Bovine adenoviruses A-C, Human adenoviruses A-F | Orthohepadnavirus: Hepatitis B virus Avihepadnavirus: Duck hepatitis B virus | Lymphocystivirus: Lymphocystis disease virus of fish
Ranaviruses of fish, amphibians, and reptiles | Bovine polyoma virus (BPyV) BK virus (human)
Simian virus 40 (SV40) | Bovine papillomavirus (BPV) type 1; Human Papillomavirus |
| Disease | Lumpy skin disease | African swine fever | PMWS caused by PCV2 | Canine parvovirus caused by CPV | Pseudorabies (Aujeszky disease) caused by SuHV1 | Duck hepatitis B | Lymphocystis disease in fish Ranaviral disease | Bovine papillomavirus caused by BPV1 | ||
| Hosts | Cattle (Bos taurus, zebus, domestic buffaloes) | Wild and domestic pigs | Domestic pigs | Dogs | Domestic pigs | Fish, amphibians and reptiles | Cattle | |||
| Clinical signs | Randomly distributed nodules (5-50 mm) in the skin and subcutaneous tissue. Multifocal, roughly circular necrotic areas on the muzzle, respiratory tract, buccal cavity, forestomachs, abomasum, vagina, teats, udder and testes | High fever (40-42°C), haemorrhages in the reticuloendothelial system and skin. Vomiting and haemorrhagic diarrhoea. Death within 3 to 14 days. | wasting, dyspnea, enlarged lymph nodes, diarrhea, pallor, and jaundice in weaned piglets
| Intestinal form: depletion of lymphocytes in lymph nodes and necrosis and destruction of the intestinal crypts. Vomiting and bloody diarrhoea Cardiac form: sudden death | Asymptomatic, but PRV can cause abortion, high mortality in piglets, and coughing, sneezing, fever, constipation, depression, seizures, ataxia, circling, and excess salivation in piglets and mature pigs. | Transformation and hypertrophy of cells in the dermis, connective tissues of various internal organs forming grossly visible lymphocystis nodules. | Cutaneous warts | |||
| Laboratory diagnosis | EM, Inoculation of primary cell culture of lamb or calf testis cells followed by HE, DIF, virus neutralisation; ELISA | PCR, ELISA, IB, haemadsrption | IPMA, IF, ELISA | Detection of CPV2 in the faeces by EIA, HA, EM or PCR | ELISA, PCR | EM, ELISA, FI, HI, PCR | Cell culture, histopathology, serology, PCR, IF | PCR | ||
| Target cells | macrophages | monocyte/ macrophage lineage and different types of epithelial cells | Rapidly dividing cells e.g. epithelial cells in crypts of Lieberkuhn | Trigeminal ganglion neurons | Basal and parabasal cells of the epidermis (keratinocytes) | |||||
| Cellular Virus receptors | CD163 | GAG: HS and CSB | Transferrin receptors (TfR) | Heparan sulphate, herpesvirus entry mediator (HVEM), Nectin 1 and 2, | GAG heparin sulphate Alpha6beta4 integrins | |||||
| Viral attachment ligand | p72 and p54 in virus attachment and p30 in virus internalization | Capsid protein | Capsid protein | gB, gC, gD, gH and gL | ||||||
| Virus replication | Entry via clathrin-mediated endocytosis | Entry via clathrin-mediated endocytosis, pH-dependent replication, virus assembly in the nucleus | Entry via clathrin-mediated endocytosis, pH-dependent replication, and intact viruses enter the nucleus | Entry by fusion, transport to the nucleus along microtubules, egress by exocytosis | Entry via clathrin-mediated endocytosis, pH-dependent replication, virus assembly in the nucleus | Entry via clathrin mediated endocytosis, genome uncoating in cytoplasm, genome import to nucleus, cytolysis | ||||
| Transmission | mechanical | Contact | faecal-oral route | Oral-nasal infection | oral or nasal contact | Direct contact | ||||
| Reservoir host | wild swine (warthogs and bushpigs) | – | – | – | – | |||||
| Vector | Arthropod bite (stable fly Stomyxos calcitrans and Biomyia fasciata)) | Argasid ticks Ornithodoros moubata and O. erraticus | – | – | – | – | ||||
| Control | Homologous attenuated virus vaccine: Neethling strain Heterologous attenuated virus vaccine: sheep pox vaccine | No vaccine available, hygiene, prevent contact between wild and domestic pigs | Hygiene, Vaccination with recombinant PCV2 capsids | Vaccination: Live attenuated parvovirus | Vaccination | Prophylactic and therapeutic vaccination | ||||
PMWS=Post Weaning Multisystemic Wasting Syndrome; PCV1, porcine circovirus type 1; PCV2, porcine circovirus type 2, BFDV, Beak and feather disease virus; CAV, chicken anaemia virus; CPV, canine parvovirus; PPV, porcine parvovirus; ChPV, chicken parvovirus; AAAV, Avian adeno-associated virus; BAAV, bovine adeno-associated virus; CAAV, canine adeno-associated virus; BoHV1, Bovine herpesvirus 1 ; BoHV2, Bovine herpesvirus 2 ; SuHV1, Suid herpesvirus 1 ; EHV1, Equine herpes virus 1; EHV3, Equine herpes virus 3 ; CaHV1, Canine herpes virus 1; FeHV1, Feline herpes virus 1; GaHV1, Gallid herpes virus 1; GaHV2, Gallid herpes virus 2; AlHV1, Alcelaphine herpes virus 1; BoPS, Bovine papular stomatitis; LSD, Lumpy skin disease; BPV1, IPMA=Immunoperoxidase monolayer assay; IB=Immunoblotting Assay