Lecture 15: Reovirus, (Toga,Flavi), (Bunya, Arena) - Chap 51, 52, 53 Flashcards
What is the structure of the Reovirus genome?
Double-stranded RNA with 10-12 segments.
Which capsid protein in rotaviruses is a target for neutralizing antibodies?
VP4 and VP7.
How does rotavirus enter cells and initiate infection?
Through endocytosis or fusion after acid cleavage activates it in the stomach.
What are common symptoms of rotavirus infection in infants?
Watery diarrhea, vomiting, and dehydration.
What is the function of the NSP4 protein in rotavirus?
Acts like a toxin, causing electrolyte loss and fluid imbalance.
How is Colorado Tick Fever Virus primarily transmitted?
By the wood tick, Dermacentor andersoni.
Which diagnostic method can confirm a rotavirus infection?
ELISA on stool samples or RT-PCR.
What is the genome structure of togaviruses and flaviviruses?
Single-stranded, positive-sense RNA.
Where do togaviruses and flaviviruses replicate in host cells?
Togaviruses at the plasma membrane; flaviviruses at intracellular membranes.
Which mosquitoes are main vectors for arboviruses?
Aedes and Culex mosquitoes.
What is the role of the polyprotein in flavivirus replication?
It is cleaved into structural and non-structural proteins needed for viral assembly.
What are common symptoms of Dengue Fever?
High fever, severe joint pain (‘breakbone fever’), and rash.
What complication can arise from a second dengue infection?
Dengue Hemorrhagic Fever or Dengue Shock Syndrome.
How is West Nile Virus typically transmitted?
By mosquitoes, primarily Culex species.
What are common symptoms of West Nile Virus?
Flulike symptoms, sometimes progressing to encephalitis.
How is Yellow Fever controlled in endemic regions?
Vaccination with the live-attenuated yellow fever vaccine.
What is a significant birth defect risk associated with Zika virus?
Microcephaly in infants born to infected mothers.
How is Zika virus primarily spread?
Aedes mosquito bites and sexual transmission.
What unique feature do Bunyaviruses lack in their structure?
Matrix proteins.
How is Hantavirus transmitted to humans?
Inhalation of aerosols from rodent urine or feces.
What disease does Hantavirus cause in humans?
Hantavirus Cardiopulmonary Syndrome (HCPS).
What is the genome structure of arenaviruses?
Ambisense, segmented single-stranded RNA.
What is the primary vector for Lassa Fever?
Rodents, particularly Mastomys species.
Which arenavirus can cause hemorrhagic fever?
Lassa virus.
What are the main symptoms of Lassa Fever?
Fever, coagulopathy, hemorrhage, and shock.
What is the primary means of preventing Lassa Fever?
Controlling rodent populations and avoiding exposure to their excretions.
What virus is commonly found in blood cells and causes biphasic fever?
Colorado Tick Fever Virus.
Which bunyavirus commonly affects people in forested areas?
California Encephalitis Virus.
What does ‘arbovirus’ stand for?
Arthropod-borne virus.
How does the immune response contribute to Dengue’s severity?
Non-neutralizing antibodies can enhance infection in a second exposure.
What type of genome does Reovirus have?
Double-stranded RNA (dsRNA)
Describe the capsid structure of Reoviruses.
Double-layered capsid with icosahedral symmetry
How are Reoviruses resistant to environmental factors?
Resistant to acidic pH, detergents, and drying
Where does Reovirus replication take place in the host cell?
Cytoplasm
Outline the major steps in the Rotavirus lifecycle.
1) Activated in stomach, 2) Forms ISVP in acidic environment, 3) Enters small intestine, 4) Replicates in enterocytes, 5) New virions released by cell lysis
What protein in Rotavirus acts as a toxin, leading to diarrhea?
NSP4 protein
How does Rotavirus infection typically spread?
Fecal-oral route, possible respiratory route
What key symptoms characterize Rotavirus infection?
Watery diarrhea, vomiting, dehydration
What is the main treatment for severe dehydration caused by Rotavirus?
Oral rehydration therapy
Describe the genome of Togaviruses.
Single-stranded, positive-sense RNA
What is the replication site for Togaviruses?
Cytoplasm
How does Togavirus lifecycle proceed in early and late protein synthesis?
1) Early synthesis of nonstructural proteins, 2) Late synthesis of structural proteins
Summarize the steps in Togavirus replication.
1) Entry via receptor-mediated endocytosis, 2) RNA released in cytoplasm, 3) Polyprotein cleaved into functional proteins, 4) Assembly at plasma membrane, 5) Budding and release
How is Rubella, a Togavirus, different in transmission from other members?
Transmitted by respiratory route, not an arbovirus
What are symptoms of Rubella infection?
Mild rash, fever, arthralgia; teratogenic effects in congenital infection
Describe the structure of Flaviviruses.
Enveloped, single-stranded positive-sense RNA
Where do Flaviviruses replicate within the host cell?
Cytoplasm
Explain the Flavivirus replication cycle.
1) Entry via receptor-mediated endocytosis, 2) Genome translated into polyprotein, 3) Polyprotein cleaved into functional proteins, 4) Assembly in endoplasmic reticulum, 5) Budding at intracellular membranes, 6) Release by exocytosis
How do Flaviviruses evade the immune system?
Use Fc receptors on monocytes/macrophages for entry
What are the symptoms of Dengue fever?
High fever, retroorbital pain, rash, severe joint pain (‘breakbone fever’)
How is Dengue transmitted?
By Aedes mosquitoes
What severe condition can occur with a secondary Dengue infection?
Dengue hemorrhagic fever (DHF) and Dengue Shock Syndrome (DSS)
Describe the unique feature of the Bunyavirus genome.
Three segmented RNA strands (L, M, S) with pseudo-circular shape
What is the typical site of Bunyavirus replication?
Cytoplasm
Outline the Bunyavirus replication cycle.
1) Enters via receptor-mediated endocytosis, 2) Genome segments transcribed in cytoplasm, 3) Transcripts used for protein synthesis, 4) Assembly at Golgi apparatus, 5) Released by budding
How are California Encephalitis and La Crosse viruses (Bunyaviruses) transmitted?
By Aedes mosquitoes
What are common symptoms of La Crosse encephalitis?
Headache, fever, nausea, stiff neck, encephalitis
What is the structure and genome of Arenaviruses?
Enveloped, ambisense single-stranded RNA with two segments
Describe Arenavirus ribosomes’ unique role.
Host cell ribosomes are incorporated, giving virions a sandy appearance
Explain the Arenavirus lifecycle.
1) Entry via endocytosis, 2) Ambisense RNA transcribed in cytoplasm, 3) Translation of proteins, 4) Assembly in cytoplasm, 5) Budding from plasma membrane
What severe disease is caused by Lassa virus (Arenavirus)?
Lassa fever, characterized by fever, coagulopathy, visceral hemorrhage
How are Lassa fever and other Arenaviruses primarily transmitted?
Via rodent urine/feces and aerosols from infected rodents
What diagnostic test is used for Rotavirus detection in stool samples?
ELISA
How is Colorado Tick Fever diagnosed?
Detection of virus in red blood cells (RBCs)
How is La Crosse virus transmitted to humans?
Through the bite of Culex mosquitoes
Describe the main mode of prevention for Dengue virus transmission.
Mosquito control, especially eliminating standing water
What is the primary method for diagnosing Flavivirus infections like Dengue?
RT-PCR for viral RNA
How can Rubella infection be confirmed, especially in pregnancy?
IgM antibody test
What is the effect of congenital Rubella syndrome?
Birth defects, particularly with infection during the first trimester
How do Arenaviruses avoid immune detection?
Limited cytolytic activity, persistent infection
