Virology Lecture 8 - RNA Viruses Summer 2023 PDF

Intro to Micro: Virology Lecture 8 – RNA viruses Anne A.M.J. Becker, DVM, MSc, PhD Associate Professor of Microbiology [email protected] Disclaimer The material used in this presentation has been obtained from different sources including books, published papers and online resources. It is in...

Intro to Micro: Virology Lecture 8 – RNA viruses Anne A.M.J. Becker, DVM, MSc, PhD Associate Professor of Microbiology [email protected] Disclaimer The material used in this presentation has been obtained from different sources including books, published papers and online resources. It is intended only for educational purposes. Most of the presented material comes from the following books: § Veterinary Microbiology and Microbial Diseases, Quiin et al., 2nd ed. § Veterinary Microbiology, Scott et al., 3rd ed. § Infectious diseases of the Dog and Cat, Greene, 4th ed. Figure and material acknowledgement to Dr. David Bemis and Dr John Prescott. RNA viruses Virus taxonomy Overview of DNA & RNA viruses What to know/family?! Ø Ø Ø Ø Virus DNA or RNA? Specific characteristic Important members Diseases RNA viruses Reoviridae § Characteristics § Linear ds RNA § Double capsid § Non-enveloped § Transmission: fecal-oral route § Hosts: (in) vertebrates § “Respiratory Enteric Orphan” § Tropism for mucosal gut and respiratory cells § Disease: respiratory tract disease, gastroenteritis Reoviridae Bluetongue § Genus Orbivirus, species Bluetongue virus § Host: sheep § Transmission: arthropode bite § Acute disease with high morbidity and mortility in susceptible breeds, but non-contagious § Torticollis à “Dancing disease” Reoviridae Viral diarrhea § Genus Rota virus, different species § Host: children, infants, young of many animals § Transmission: fecal-oral § Economic losses due to rota viral enteritis in intensively-reared piglets and calves RNA viruses Paramyxoviridae § Characteristics § Linear (-)sense ss RNA § Enveloped § Release by budding § Transmission: inhalation of small droplets § Hosts: vertebrates, humans § Difference between orthomyxo- and paramyxoviruses! § Orthomyxo: segmented genome allows for antigenic shift § Paramyxo: non-segmented genome, one serotype à long-term immunity § Epidemiology § Humans: measles, mumps § Animals: Canine distemper, Rinderpest, Newcastle disease Paramyxoviridae Canine distemper § Genus Morbillivirus, species Canine distemper virus § Hosts: dogs (puppies!!), coyotes, wolves, foxes, ferrets, skunks, raccoons and other wild carnivores § Transmission: airborne (through sneezing or coughing) § Attacks respiratory, gastrointestinal & nervous system § Symptoms: fever, loss of appetite, vomiting, nasal discharge, coughing, circling behaviour,muscle twitches, seizures, convulsion § Hardening of foot pads à “hard pad disease” § Vaccination is essential for prevention! (no cure for disease) Paramyxoviridae Canine distemper Ø Asymptomatic Ø Pattern of symptoms Ø Neurological disease (<> Rabies!) Paramyxoviridae Rinderpest § Genus Morbillivirus, species Rinderpest virus § “can wipe out a cattle herd in a matter of days” § 3 D’s: Dead, Discharge, Diarrhea § Host: cattle § Measles virus emerged from rinderpest as a zoonotic disease between 11th and 12th centuries. § Global eradication! (2011) - stamping out & vaccination Paramyxoviridae Rinderpest To keep or not to keep?! Video: http://www.oie.int/en/for-the-media/rinderpest Paramyxoviridae Newcastle Disease § Genus Avulavirus, species Newcastle disease virus § Hosts: poultry and other bird species § Transmission: respiratory discharges and feces § Contagious bird disease (domestic and wild avian species): acute respiratory disease, with depression, nervous manifestations, or diarrhea in the clinical form (e.g. tremors, torticollis, swelling of tissue) Reduced egg production and misshapen eggs § Control: Vaccination and sanitary measures RNA viruses Coronaviridae § Characteristics § Linear (+)sense ss RNA § Enveloped with “peplomers” (petal-shaped spikes) § Release by exocytosis § Hosts: vertebrates, humans § Transmission: § Inhalation of small droplets § Fecal-oral route § Primary site of infection: epithelial cells of respiratory or intestinal tract § Epidemiology § Feline enteric coronavirus (FECV) & Feline infectious peritonitis virus (FIPV) § Transmissible gastroenteritis virus swine (TGEV) Coronaviridae Coronaviridae Coronaviridae Feline infectious peritonitis (FIP) § Genus Alphacoronavirus, species Feline coronavirus (FCoV) § Two forms of the virus § Feline Enteric Coronavirus (FECV) § Feline Infectious Peritonitis virus (FIPV) § Transmission: fecal-oral (catteries, animal shelters!) à highly contagious § Hosts: Felidae Coronaviridae FIP Just because you can’t see... doesn’t mean it isn’t there! Asymptomatic carriers shed the virus in faeces Fecal-oral FECV Within body mutation FIP Incurable & fatal FIPV -> tropism for macrophages Coronaviridae Feline infectious peritonitis (FIP) Coronaviridae Feline infectious peritonitis (FIP) Dry or non-effusive FIP Wet or effusive FIP § Loss of appetite § Damaged and leaking blood vessels § Weight loss § Ascites § Yellowing inside eyes § Difficult breathing § Iris color change § 15% neurological signs Coronaviridae Severe Acute Respiratory Syndrome (SARS) § Genus Betacoronavirus, species SARS coronavirus § Initial flu-like symptoms: fever, headache, muscle pain followed within 14 days by respiratory symptoms e.g. dyspnea, pneumonia § Not recorded in humans before outbreak in China end of 2002 Coronaviridae Covid-19 § Genus Betacoronavirus, species SARS coronavirus 2 (SARS-CoV-2) § Hosts: humans, some animals (?) § Not recorded in humans before outbreak in China in dec 2019 § Transmission via droplets and indirect contact with droplet contaminated materials Coronaviridae Covid-19 § Mutating virus Omicron has many times more mutations on its spike protein than the Delta variant, raising fears about whether it can evade currently available vaccines more easily. Coronavirus variants due to gene mutations are COMPARISON OF SPIKE PROTEIN OF DELTA AND OMICRON VARIANTS Areas with mutations: not new nor unexpected More than 70% 40% to 70% An image of the new variant by the Bambino Gesu hospital in Rome shows a greater amount of mutations on the Omicron variant compared with the Delta variant. 32 out of 50 mutations of Omicron are on the spike STRUCTURE OF THE VIRUS Spike Any change on the spike can potentially affect how easily a virus infects a cell Membrane Envelope Sars-CoV-2 HOST CELL ACE2 receptor The Sars-CoV-2 spike protein attaches to the human receptor ACE2, found notably on lung cells 5% to 15% 1% to 5% Omicron B.1.1.529 Delta B.1.617.2 Nucleocapsid Holds RNA – the genetic code for replicating the virus 15% to 40% Once attached, the virus infects the cell NOTE: A high number of mutations does not automatically mean that these variants are more dangerous. Antibodies Antibodies, acquired through previous infection or vaccination, recognise the spike protein and prevent it from attaching to the host If there are enough changes to the spike, it could become unrecognisable to antibodies, and therefore enable the variant to evade immunity Source: AGENCE FRANCE-PRESSE STRAITS TIMES GRAPHICS Coronaviridae Covid-19 § Mild symptoms: fever, cough § Severe symptoms: shortness of breath, pneumonia, heart and kidney failure, death Coronaviridae Covid-19 & animals RNA viruses Flaviviridae § Characteristics § Linear (+)sense ss RNA § Enveloped § Surface proteins organized in icosahedral-like symmetry § Release by exocytosis § Hosts: humans, mammals § Transmission via vector (mosquitoes, ticks) § Flavus = yellow (Latin) § Diseases in humans include Japanese encephalitis, Dengue fever, Hepatitis C virus, West Nile fever, Yellow fever, Zika fever Flaviviridae West Nile Fever § Genus Flavivirus, species West Nile virus § Natural host: birds § Can cause fatal neurological symptoms in humans (encephalitis meningitis, meningoencephalitis, poliomyelitis, neuroinvasive disease) § Can cause severe death or disease in horses Human infection ‘iceberg’ Flaviviridae West Nile Fever ZOONOSIS Flaviviridae Bovine viral diarrhea (BVD) § Genus Pestivirus, species Bovine viral diarrhea virus § Immunosuppressive effect § Direct effect on respiratory system & fertility § BVD infection of susceptible dam results in persistent infected fetus -> persistent infected animals recognize intra-cellular BVD virus particles as “self” and shed virus throughout life § Significant economic disease of cattle § Cytopathic and non-cytopathatic biotypes Flaviviridae Bovine viral diarrhea (BVD) Flaviviridae Bovine viral diarrhea (BVD) à Fatal mucosal disease Non-cytopathic BVDV Cytopathic BVDV Fatal mucosal disease Flaviviridae Bovine viral diarrhea (BVD) à Fatal mucosal disease Flaviviridae Bovine viral diarrhea (BVD) à Fatal mucosal disease Flaviviridae Zika Fever § Genus Flavivirus, species Zika virus § Fever, red eyes, rash, joint pain, headache § Transmission: by day-time active mosquito (Aedes aegypti), sexually RNA viruses Togaviridae § Characteristics § Linear (+)sense ss RNA § Enveloped § Release by budding § Hosts: humans, mammals, birds, mosquitoes § Epidemiology § Genus Rubivirus: respiratory transmission § Disease: congenital rubella (humans § Genus Alphavirus: arthropod bite § Diseases: Eastern equine encephalitis, Chikungunya Togaviridae Togaviridae § Arbovirus = Arthropod borne virus = virus that replicates in and is transmitted by arthropods § These viruses maintain in nature by going through a cycle between a host and a vector § Most arboviruses are ZOONOTIC and have a maintenance enzootic cycle in birds, rodents, non-human primates Aedes aegypti Assorted ticks Anopheles Togaviridae Togaviridae § Enzootic = endemic in animal population § Epizootic = epidemic outbreak of a disease in animal population Transmission cycle of Eastern equine encephalitis virus FYI RNA viruses Picornaviridae § Characteristics § Linear (+)sense ss RNA § Non-enveloped § Release by cell lysis § Hosts: vertebrates § Cell tropism § Enteroviruses: gastrointestinal tract § Species Rhinovirus: upper respiratory tract (“common cold”) § Aphtoviruses: epithelium § Hepatoviruses: liver § Cardioviruses: GI tract priamry site of infection, then heart and central nervous system Picornaviridae Foot and Mouth Disease § Genus Aphtovirus, species Foot and Mouth virus § Host: cattle, pigs, sheep, goat (all species of deer, antilope, giraffe and elephant also susceptible) § Highly infectious via excretions and secretions of infected animal § High fever, blisters in mouth and feet, high mortality in young animals § Endemic in most of Africa, Middle East and parts of Asia Picornaviridae Poliomyelitis § Genus Enterovirus, species Poliovirus § Host: humans (young children!) § Chimpanzees and Old World Monkeys can be infected experimentally § Transmission: fecal-oral § Multiplies in intestines à viremia à central nervous system à deformations (<> 95% asymptomatic) § Very rapid replication à overwelming the immune system RNA viruses Caliciviridae § Characteristics § Linear (+)sense ss RNA § Non-enveloped § Release by cell lysis § Not well studied, difficult to grow in cell cultures and no suitable animal models § Epidemiology § Genus Vesivirus: airborne transmission (cats) à respiratory disease § Genus Lagovirus: direct contact (rabbits) à haemorrhagic disease § Genus Norovirus: fecal-oral transmission (humans, mammals) à acute gastroenteritis (very contagious) Caliciviridae Caliciviridae Caliciviridae Feline calicivirus § Genus Vesivirus, species Feline calicivirus § Important viral cause of respiratory infection in cats § Cheetahs can be naturally infected § Latent infections possible § Symptoms: sneezing, nasal discharge, stomatitis, pneumonia Learning objectives 1. Know the different RNA virus families and their basic characteristics 2. Understand the importance of enzootic and epizootic cycle, of carriers and vectors 3. Understand the specific viral features that lead to FIP, fatal mucosal disease 4. Outline the main characteristic of each viral disease RNA VIRUSES § Reoviridae § Paramyxoviridae § Coronaviridae § Flaviviridae § Togaviridae § Picornaviridae § Caliciviridae