Coronavirus and respiratory outbreaks Flashcards
What is the genomic size range of Coronaviruses, making it the largest among RNA viruses?
26-32 kb
What is the unique structure that encapsulates the RNA genome of Coronaviruses?
Helical nucleocapsid
What are the three main structural proteins present in all Coronaviruses?
Spike (S), Envelope (E), Membrane (M)
What is the function of the Nucleocapsid (N) protein in Coronaviruses?
Binds to the RNA genome to form the helical nucleocapsid
Aside from its role in host cell binding, what is another important application of the Spike (S) protein?
Utilized in vaccine development
What is the function of the Membrane (M) protein in Coronaviruses?
Serves as a matrix protein embedded in the envelope, interacts with the nucleocapsid, and organizes CoV assembly
What is the name of the third glycoprotein present in some Coronaviruses, such as HCoV-OC43?
Hemagglutinin Esterase (HE)
What are the two activities associated with the HE protein in Coronaviruses?
Hemagglutination and acetylesterase activity
What is the postulated role of the acetylesterase activity of the HE protein?
Acts as a receptor-destroying enzyme by removing acetyl groups from O-acetylated sialic acid
What is the principle behind viral hemagglutination caused by some Coronaviruses?
Interaction between viral surface proteins and carbohydrate groups on erythrocyte membranes
How can hemagglutination be utilized in virology?
To determine the titers of some viruses
What type of RNA genome do Coronaviruses possess?
Single-stranded, positive-sense RNA
What are the three main gene categories in the genome of Coronaviruses?
Replicase genes, Structural protein genes, Accessory genes
What is the specific order of genes encoding for proteins in all Coronaviruses?
Pol-S-E-M-N-3’
What are Open Reading Frames (ORFs) in the context of the Coronavirus genome?
Sections that encode nonstructural proteins and the HE protein, translated from a single mRNA species
What is the receptor binding site for SARS-CoV and SARS-CoV-2 on host cells?
Angiotensin Converting Enzyme 2 (ACE-2) receptor
Where is the ACE-2 receptor primarily found in the human body?
Surface of cells in the respiratory tract, lungs, and other tissues
What role does the Spike (S) protein play in the interaction with the ACE-2 receptor?
Binds with high specificity, triggering fusion of the viral envelope with the host cell membrane
What is the first step in the replication cycle of Coronaviruses?
Attachment and entry into the host cell
Describe the process of attachment and entry of Coronaviruses into host cells.
Spike protein binds to the host cell receptor, followed by fusion with the host cell membrane and release of genetic material into the cytoplasm
What is the first viral protein translated after uncoating in the Coronavirus replication cycle?
RNA-dependent RNA polymerase (RdRp)
What are the two types of RNA synthesized during the replication of Coronaviruses?
Genomic RNA and Subgenomic RNA
What is the function of the genomic RNA in Coronavirus replication?
Used to make copies of the entire viral genome
What is the function of the subgenomic RNA in Coronavirus replication?
Encodes for various viral proteins
What cellular compartments are involved in the assembly of viral components in Coronavirus replication?
Endoplasmic reticulum and Golgi apparatus
Describe the formation of the helical nucleocapsid during Coronavirus assembly.
Newly synthesized genomic RNA interacts with the Nucleocapsid (N) protein
How are mature Coronavirus particles released from the host cell?
Through exocytosis
What is the preferred binding site of the Nucleocapsid (N) protein, and what process is it more closely associated with?
Within the leader RNA; transcription and translation phase
What are the two families within the order Nidovirales that are significant to humans?
Coronaviridae and Arteriviridae
Name the two sub-families of Coronaviridae.
Torovirinae and Coronavirinae
What are the three genera under Coronavirinae that can infect humans?
Alphacoronavirus, Betacoronavirus, and Torovirus
What disease is Torovirus associated with, and in what animal group is it widespread?
Diarrheal disease; ungulates (cloven-hoofed animals)
List the two human Coronaviruses belonging to the genus Alphacoronavirus.
229E and NL63
List the five human Coronaviruses belonging to the genus Betacoronavirus.
OC43, HKU1, SARS-CoV, SARS-CoV-2, MERS-CoV
What is the term for the ability of a pathogen to cross the species barrier and infect humans?
Zoonotic
Towards which cells do most known animal Coronaviruses exhibit tropism?
Epithelial cells of the respiratory and gastrointestinal tract
What are the two main types of Coronavirus infections observed in vivo?
Disseminated infections and Localized infections
What are some common clinical findings associated with Coronavirus infections in humans?
Afebrile common colds, wheezing attacks in asthmatic children, pneumonia, exacerbated respiratory symptoms in adults with chronic pulmonary disease
What is the typical incubation period for common Coronavirus infections?
2-5 days
What is a distinctive feature of SARS-CoV infection regarding the immune response?
Cytokine storm with elevated chemokines and cytokines for about 2 weeks
What is the incubation period for SARS-CoV?
~6 days
List some early symptoms commonly observed in SARS-CoV infection.
Fever, malaise, chills, headache, dizziness, cough, sore throat
What are some laboratory findings observed in MERS-CoV infection?
Leukopenia, Lymphopenia, Thrombocytopenia, Elevated lactate dehydrogenase levels
What is the estimated mortality rate for MERS-CoV, and why is it likely an overestimate?
Up to 30%; mild cases are not typically reported
What are two distinctive symptoms often reported in SARS-CoV-2 infection?
Anosmia (loss of smell) and Ageusia (loss of taste)
What serious complication can develop in children infected with SARS-CoV-2?
Multisystemic Inflammatory Syndrome in children (MIS-C)
What is the incubation period for SARS-CoV-2?
2-14 days
What is the current circulating strain of SARS-CoV-2 as of October 2023?
Omicron variant
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What is the estimated immunity to SARS-CoV-2 based on recent seroprevalence studies?
99-100%
Why are vaccines for Coronaviruses other than COVID-19 not currently available?
No proven need due to high seroprevalence and endemicity of COVID-19
What type of viral protein is the focus of most COVID-19 vaccines?
Spike protein
List four recommended infection prevention and control measures for COVID-19.
● Standard precautions ● Respiratory droplets precautions ● Frequent hand washing ● Cough etiquette
What is the first step in host cell invasion by viruses?
Adhesion of viral surface proteins to host cell receptors
What are three mechanisms viruses use for penetration into host cells?
● Receptor-mediated endocytosis ● Direct fusion ● Pore formation
What is antigenic variation
and how does it help viruses evade the immune system?
How does viral latency contribute to immune evasion?
The viral genome persists in the host cell without active replication
What is the direct cytopathic effect of viral replication on host cells?
Damage to host cells leading to cell lysis and tissue destruction
How can the immune response contribute to tissue damage during viral infection?
Excessive inflammation and autoimmune reactions can harm healthy tissues
What are the two main components of the adaptive immune response to viral infections?
● Humoral immunity (B cells and antibodies) ● Cell-mediated immunity (Cytotoxic T cells and Helper T cells)
What is the fundamental principle behind vaccination?
Stimulating the adaptive immune system to generate memory B and T cells specific to a virus
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What distinguishes the genome of coronaviruses from most other RNA viruses?
Coronaviruses have a single-stranded, positive-sense RNA genome, which is unusually large (26-32 kb) compared to other RNA viruses. This large genome allows for a more complex genomic organization and greater coding capacity.
Describe the role of the spike (S) protein in the coronavirus replication cycle.
The spike (S) protein on the surface of coronaviruses mediates attachment to host cell receptors, facilitating entry into the cell. The S protein binds to specific receptors, such as ACE2 for SARS-CoV and SARS-CoV-2, triggering fusion of the viral envelope with the host cell membrane.
Explain the significance of the angiotensin-converting enzyme 2 (ACE2) receptor in the context of SARS-CoV and SARS-CoV-2 infection.
The ACE2 receptor serves as the primary binding site for the spike protein of both SARS-CoV and SARS-CoV-2. This interaction is crucial for the viruses to attach to and enter host cells, particularly in the respiratory tract, leading to infection.
List three clinical features commonly associated with SARS-CoV infection.
SARS-CoV infection is commonly characterized by fever, malaise, and a dry cough. Other symptoms can include headache, dizziness, and sore throat.
How does the hemagglutinin-esterase (HE) protein contribute to the infectivity of some coronaviruses?
The HE protein in some coronaviruses possesses hemagglutinating and acetyl-esterase activities. This contributes to the virus’s ability to bind to and release from host cells, promoting the spread of infection.
What laboratory findings might suggest a coronavirus infection? Be specific.
Laboratory findings suggestive of a coronavirus infection include leukopenia (a decrease in white blood cells), lymphopenia (a decrease in lymphocytes), and thrombocytopenia (a decrease in platelets). Additionally, elevated levels of lactate dehydrogenase (LDH), D-dimer, and serum ferritin might be observed.
Differentiate between the roles of cytotoxic T cells and helper T cells in the adaptive immune response to viral infections.
Cytotoxic T cells directly kill virus-infected cells, preventing the spread of infection. Helper T cells, on the other hand, orchestrate the immune response by activating B cells to produce antibodies and stimulating other immune cells.
Why is real-time reverse transcription polymerase chain reaction (RT-PCR) considered the gold standard for diagnosing COVID-19?
RT-PCR directly detects the genetic material of the SARS-CoV-2 virus in respiratory samples, making it highly sensitive and specific for diagnosing active infection, even in asymptomatic individuals.
Briefly explain the concept of sentinel surveillance in the context of respiratory virus monitoring.
Sentinel surveillance involves strategically selecting specific healthcare facilities or locations to monitor for the occurrence of respiratory illnesses, providing an early warning system for potential outbreaks. Data collected from these sites help track trends and detect unusual patterns.
What are two key challenges to effective respiratory virus surveillance in the Philippines?
Geographic diversity and limited healthcare access in certain areas of the Philippines pose significant challenges to establishing comprehensive and uniform respiratory virus surveillance systems.
