Introduction to Microbiology: Virology Lecture 5 - DNA Viruses PDF

Introduction to Microbiology: Virology Lecture 5 – DNA viruses Darryn Knobel BVSc MSc PhD [email protected] Asfarviridae Asfarviridae Family properties Asfarviridae = African swine fever and related viruses Currently, only one genus (Asfivirus) and only one species in the genus (African swine f...

Introduction to Microbiology: Virology Lecture 5 – DNA viruses Darryn Knobel BVSc MSc PhD [email protected] Asfarviridae Asfarviridae Family properties Asfarviridae = African swine fever and related viruses Currently, only one genus (Asfivirus) and only one species in the genus (African swine fever virus, ASFV) dsDNA (linear) Icosahedral capsid symmetry Enveloped Large (~200 nm) ASFV virions are stable across a wide temperature and pH range; resistant to protease enzymes Ø Stability in meat and in meat products Ø chilled meat 15 weeks; processed hams 6 months Asfarviridae ASFV transmission ASFV is the only known DNA arbovirus (= arthropod-borne virus) Poxviridae Poxviridae Family properties dsDNA Complex symmetry Enveloped (single or double membrane) Large (~300 nm) Replicate in the cytoplasm Very resistant to drying - scabs contain infectious virus, durable in the environment Highly epitheliotropic but two pathways: Localized infection -> localized skin lesions Systemic infection -> generalized skin lesions 8 genera, multiple species infect animals Poxviridae Poxviridae Systemic infection (e.g. sheeppox virus) Localized infection (e.g. orf virus) Orf virus is zoonotic Herpesviridae Herpesviridae Family properties dsDNA (linear) Icosahedral capsid symmetry Enveloped Large (~150-200 nm) Latent infections, often reactivated by stress Virions do not survive well outside host Three subfamilies (many genera and species): Alphaherpesvirinae Betaherpesvirinae Gammaherpesvirinae Herpesviridae Alphaherpesviruses that infect domestic livestock Virus Diseases caused by infection in livestock Bovine herpesvirus 1 Infectious bovine rhinotracheitis, infectious pustular vulvovaginitis, infectious balanoposthitis and other syndromes Bovine herpesvirus 2 Pseudo-lumpy skin disease/bovine herpesvirus mammillitis Bovine herpesvirus 5 Meningoencephalitis Caprine herpesvirus 1 Gastroenteritis, pustular vulvovaginitis, abortion Equid herpesvirus 1 Neonatal deaths, abortion, rhinopneumonitis, myeloencephalopathy Equid herpesvirus 3 Equine coital exanthema Equid herpesvirus 4 Rhinopneumonitis Equid herpesvirus 6 Vesicular and erosive lesions on muzzle, genitalia and udder Equid herpesvirus 8 Rhinitis Suid herpesvirus 1 Pseudorabies (Aujeszky’s disease) Herpesviridae Epithelial cells at mucosal surface Latency Neurons (sensory or sympathetic) Viral genome ‘silenced’ Multiple copies but no proteins Infection Reactivation Stress UV light Damage to nerves Corticosteroids Rapid replication and lysis of cells Herpesviridae Clinical signs and pathology Complications may result from secondary bacterial infection, such as Mannheimia hemolytica and Pasteurella multocida (Shipping fever) Papillomaviridae Papillomaviridae Family properties dsDNA (circular) Icosahedral capsid symmetry, spherical Non-enveloped Small (~55 nm) Cell transformation Papillomas (keratinocytes) Fibropapillomas (keratinocytes + fibroblasts) Can cause malignant neoplasia (e.g. HPV) Many virus species; most are hostspecific Parvoviridae Cell cycle Papillomaviridae Pathogenesis Infection of basal keratinocytes (microtrauma) Lose nucleus Shed by desquamation Cell division continues Stop dividing Detach from basement membrane Differentiate Force cells to keep dividing Dividing cells Attached to basement membrane Most DNA viruses need cells in S phase so they can replicate their DNA T antigens (proteins encoded by E6 and E7 genes) kick cells into the S phase Papillomaviridae Pathogenesis Papillomaviridae Oncogenesis in HPV Papillomavirus (HPV) E6 & E7 proteins Parvoviridae Parvoviridae Family properties ssDNA (linear) Icosahedral capsid symmetry Non-enveloped Very small (~25 nm) Viruses are very stable - disinfection of contaminated premises is difficult Can only infect actively dividing cells (require host cells to go through S phase) Parvoviridae Parvoviridae taxonomy Genus Name Virus Protoparvovirus Canine parvovirus 2 (CPV-2) Feline panleukopenia virus (FPV) Porcine parvovirus (PPV) Amdoparvovirus Bocaparvovirus Aleutian mink disease virus (AMDV) Canine parvovirus 1 (CPV-1) (Canine minute virus, Canine Bocavirus 1) Parvoviridae Infection of actively dividing cells Canine parvovirus 2 (CPV-2) Feline panleukopenia virus (FPV) Hemopoetic/stem cells in bone marrow & lymph organs Intestinal crypt cells Puppies: (CPV-2) (