أسئلة ريتين السابعة ميكرو دمياط (قبل التعديل)
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Questions and Answers

What is the definition of a virus?

A virus is defined as a sub-microscopic, obligate intracellular parasite that is only active inside viable dividing host cells.

What are virions and how do they form?

Virions are virus particles that do not grow or divide; they form through the assembly of pre-formed viral protein components.

Explain the role of envelope glycoproteins in viral infection.

Envelope glycoproteins help viruses attach to target cells, defining the specificity of the interaction with the host's receptors.

What are the three mechanisms by which viral penetration occurs?

<p>Viral penetration can occur via translocation of the entire virion, endocytosis into vacuoles, or fusion of the viral envelope with the cell membrane.</p> Signup and view all the answers

What is a nucleocapsid in the context of a virus?

<p>A nucleocapsid is the structure formed by the capsid together with its enclosed nucleic acid.</p> Signup and view all the answers

Describe how viruses with an RNA genome replicate.

<p>Viruses with an RNA genome must either make or bring their own polymerases to replicate, as mammalian cells only produce DNA and RNA in the nucleus.</p> Signup and view all the answers

What differentiates 'early' and 'late' viral proteins?

<p>Early proteins are typically DNA or RNA polymerases, while late proteins include structural components like capsid or envelope proteins.</p> Signup and view all the answers

How does the specificity of the viral protein and host receptor interaction affect viral infections?

<p>The specificity determines the host species and cell tropism, influencing which cells and tissues the virus can infect.</p> Signup and view all the answers

What can transcriptional errors during viral replication lead to?

<p>New mutants with clinical importance.</p> Signup and view all the answers

Where can assembly of viral proteins occur within a host cell?

<p>In the nucleus, cytoplasm, or at the cell surface while budding.</p> Signup and view all the answers

What are inclusion bodies and why are they significant in viral diagnosis?

<p>They are accumulations of virions at assembly sites, useful for diagnosing viral infections.</p> Signup and view all the answers

What are the three basic types of tests for diagnosing viral infections?

<p>Viral genome detection by PCR, viral antigen detection, and detection of antibodies to the virus.</p> Signup and view all the answers

What is the role of exocytosis in viral release from infected cells?

<p>It allows virus particles enclosed in vesicles to exit by fusing with the cell membrane.</p> Signup and view all the answers

How can a latent viral infection manifest, and what triggers reactivation?

<p>The viral genome remains in the host cell without effect; reactivation occurs due to changes in the host's immune status.</p> Signup and view all the answers

What distinguishes PCR or antigen detection tests from antibody tests in viral diagnostics?

<p>PCR and antigen tests assess acute infection, while antibody tests provide evidence of prior infection.</p> Signup and view all the answers

What methods are commonly used for viral antigen detection?

<p>Immunofluorescence, ELISA, and rapid tests.</p> Signup and view all the answers

What are the main differences between bacteria and viruses?

<p>Bacteria are single-celled organisms that can reproduce independently, while viruses are much smaller and require a host cell to replicate.</p> Signup and view all the answers

What types of influenza viruses exist and what are their sources of infection?

<p>The main types of influenza viruses are A, B, and C, with sources of infection often being respiratory droplets from infected individuals or contaminated surfaces.</p> Signup and view all the answers

List some antiviral agents and the diseases they treat.

<p>Acyclovir treats herpes virus infections, Zidovudine (AZT) is used for HIV, and Tamiflu is used for influenza.</p> Signup and view all the answers

Why do we have different vaccines for influenza each year?

<p>Different vaccines are necessary each year because influenza viruses constantly mutate, leading to new strains that escape the immune response.</p> Signup and view all the answers

Can viruses be cultured and isolated from pathological samples?

<p>Yes, viruses can be cultured and isolated using specific laboratory techniques on appropriate cell cultures.</p> Signup and view all the answers

What role do public health measures play in controlling viral infections?

<p>Public health measures, such as vaccination and hygiene practices, help minimize the spread of viral infections in populations.</p> Signup and view all the answers

What are live attenuated and inactivated vaccines, and how do they differ?

<p>Live attenuated vaccines contain weakened forms of the virus, while inactivated vaccines contain killed viruses; the difference affects immune response and safety.</p> Signup and view all the answers

What is the function of protease inhibitors in antiviral therapy?

<p>Protease inhibitors block the protease enzyme, which is crucial for viral replication, thereby inhibiting the virus's ability to reproduce.</p> Signup and view all the answers

Explain the importance of seasonal vaccines for influenza.

<p>Seasonal vaccines are important as they prepare the immune system to fight against the most recent circulating strains of the influenza virus.</p> Signup and view all the answers

What is the significance of antiviral agents being specific to certain viruses?

<p>The specificity of antiviral agents ensures that they target only the intended virus, reducing the risk of harming host cells and other beneficial bacteria.</p> Signup and view all the answers

What defines the specificity of viral infection in terms of host interaction?

<p>The specificity of viral infection is defined by the interaction between viral surface proteins and specific receptors on suitable host cells.</p> Signup and view all the answers

How do viruses that replicate in the cytoplasm manage to produce their own nucleic acids?

<p>Viruses replicating in the cytoplasm must carry their own polymerases since mammalian cells can only produce DNA and RNA in the nuclear compartment.</p> Signup and view all the answers

What role do viral capsomers play in the structure of a virus?

<p>Capsomers are clusters of structural units that make up the capsid, providing the protective shell for the viral nucleic acid.</p> Signup and view all the answers

Discuss the difference between segmented and non-segmented viral genomes.

<p>Segmented genomes consist of multiple RNA molecules, while non-segmented genomes contain a single RNA molecule.</p> Signup and view all the answers

What is the importance of the viral envelope in the entry process of a virus into a host cell?

<p>The viral envelope facilitates the attachment and fusion with the host cell membrane, enabling viral entry through active penetration.</p> Signup and view all the answers

Explain how 'early' and 'late' proteins are categorized in a viral life cycle.

<p>'Early' proteins include enzymes like polymerases essential for replication, whereas 'late' proteins are structural proteins like capsid or envelope components.</p> Signup and view all the answers

What distinguishes enveloped viruses from non-enveloped viruses in terms of their assembly?

<p>Enveloped viruses acquire their outer membrane from the host cell, while non-enveloped viruses do not have a membrane and rely solely on their capsid.</p> Signup and view all the answers

How does endocytosis facilitate viral entry into host cells?

<p>Endocytosis allows the virus to be engulfed in a cellular vacuole, eventually delivering it to the cytoplasm for replication.</p> Signup and view all the answers

What might result from transcriptional errors during viral replication?

<p>Transcriptional errors can lead to new mutations that may have clinical significance.</p> Signup and view all the answers

How is the release of some viruses from host cells different from that of others?

<p>Some viruses exit by budding through the cell membrane, while others may cause cell lysis.</p> Signup and view all the answers

What is the main purpose of using PCR or antigen detection tests in viral diagnostics?

<p>PCR or antigen detection tests are designed to identify acute viral infections.</p> Signup and view all the answers

In what condition can a latent virus reactivate within a host cell?

<p>Latent viruses can reactivate due to changes in the immune status of the host.</p> Signup and view all the answers

What role do inclusion bodies play in the context of viral infections?

<p>Inclusion bodies can accumulate at sites of viral assembly and are useful for diagnosing viral infections.</p> Signup and view all the answers

What distinguishes the role of antibody tests from PCR or antigen tests in viral diagnostics?

<p>Antibody tests provide evidence of prior infections, while PCR or antigen tests assess active infections.</p> Signup and view all the answers

Describe the effect of viral infection on host cells that are damaged but not killed.

<p>Damaged host cells may release progeny viruses over time without undergoing cell death.</p> Signup and view all the answers

What is the significance of viral vaccines in the prevention of viral infections?

<p>Viral vaccines are essential for establishing immunity and preventing infection before exposure to the virus.</p> Signup and view all the answers

How do antiviral drugs function differently compared to antibiotics in treating infections?

<p>Antiviral drugs specifically target virus replication and have limited spectra of activity, whereas antibiotics target bacterial functions.</p> Signup and view all the answers

What is the significance of using a seasonal vaccine for influenza?

<p>Seasonal vaccines are updated annually to match circulating virus strains, ensuring effective immunity.</p> Signup and view all the answers

Explain the role of molecular biology techniques in the development of antiviral drugs.

<p>Molecular biology techniques help identify viral targets and mechanisms, facilitating the design of specific antiviral agents.</p> Signup and view all the answers

What distinguishes genetically engineered vaccines from traditional vaccines?

<p>Genetically engineered vaccines use modified genetic material to induce immunity, while traditional vaccines often use live attenuated or inactivated pathogens.</p> Signup and view all the answers

What challenges exist in developing antiviral drugs for emerging viruses?

<p>Emerging viruses often mutate rapidly, making it difficult to create effective antiviral drugs that remain effective over time.</p> Signup and view all the answers

How do public health measures complement the effectiveness of antiviral medications?

<p>Public health measures help prevent virus transmission and reduce infection rates, enhancing the overall impact of antiviral treatments.</p> Signup and view all the answers

What are the potential side effects of using antiviral drugs in treatment?

<p>Side effects may include nausea, diarrhea, and, in some cases, serious allergic reactions.</p> Signup and view all the answers

What role do protease inhibitors play in the treatment of viral infections?

<p>Protease inhibitors block viral proteolytic enzymes, preventing virus maturation and replication.</p> Signup and view all the answers

Describe the importance of antiviral drug specificity in treatment plans.

<p>The specificity of antiviral drugs minimizes off-target effects, allowing for effective treatment with reduced risk of damaging host cells.</p> Signup and view all the answers

How can the understanding of viral genome composition aid in antiviral drug development?

<p>Knowledge of whether a virus has DNA or RNA and its structure can guide the development of drugs that target specific replication processes.</p> Signup and view all the answers

Flashcards

What are viruses?

Viruses are microscopic, obligate intracellular parasites that can only replicate inside living host cells.

What is a virion?

A complete viral particle, consisting of the viral genome enclosed within a protein coat called a capsid.

What is the viral envelope?

The outer membrane of some viruses, derived from the host cell membrane.

What is the capsid?

The protein shell that surrounds the viral genome, made up of repeating protein subunits called capsomers.

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What is the nucleocapsid?

The capsid together with its enclosed nucleic acid.

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What is the viral genome?

The genetic material of a virus, which can be either DNA or RNA.

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How do viruses attach to host cells?

The process by which a virus attaches to a host cell, using specific proteins on its surface to bind to receptors on the host cell.

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How do viruses enter host cells?

The process by which a virus enters a host cell, which can happen through fusion with the cell membrane, endocytosis, or translocation.

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Virus Release Mechanisms

When viruses leave an infected cell, they can do so through various mechanisms, including budding from the cell membrane, exocytosis, and lysis. Budding involves the virus wrapping itself in a portion of the cell's membrane. Exocytosis uses vesicles to release the virus. Lysis involves the destruction of the host cell, releasing the viruses.

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Lytic Infection

This type of viral infection leads to the destruction of the infected host cell and the production of new viral particles. This process is commonly seen in acute viral infections.

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Latent Infection

During this type of viral infection, the viral genome persists within the host cell without causing immediate harm or producing new viruses. The virus can remain dormant until triggered by changes in the host's immune status or other factors, leading to the reactivation of viral replication.

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Viral Infection Diagnosis

Viral infections can be diagnosed using various methods, including detecting the virus's genetic material (RNA or DNA) through PCR, identifying viral antigens in samples, or testing for specific antibodies against the virus in the blood.

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PCR for Viral Detection

Polymerase chain reaction (PCR) is a molecular biology technique used to amplify specific regions of DNA or RNA, enabling the detection of viral genetic material even in small quantities.

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Antibody Detection for Viral Infection

Antibodies are proteins produced by the immune system in response to an infection. Detecting specific antibodies against a particular virus in a blood sample can indicate previous exposure to the virus.

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Viral Antigen Detection

Antigen detection methods rely on identifying specific proteins present on the surface of viruses. These tests can be performed on samples from sites of possible infection.

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Rapid Tests for Viral Detection

Rapid tests are designed to provide quick and easy results for the detection of certain viral antigens or antibodies, often used for initial screening or diagnosis.

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What are antiviral drugs?

Antiviral drugs target and interfere with the replication of viruses inside the host cells.

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What are the main differences between bacteria and viruses?

Viruses are much smaller than bacteria and have a simpler structure. They lack a cellular organization and can only replicate inside living cells. Bacteria are single-celled organisms with their own cellular machinery.

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Is influenza a viral infection? What are the types and sources of infection?

Influenza is caused by the influenza virus. There are three main types: influenza A, influenza B, and influenza C. They spread through respiratory droplets expelled when an infected person coughs, sneezes, or talks.

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Name some antiviral agents and the diseases they treat.

Acyclovir is used for herpes infections, Zidovudine (AZT) and Lamivudine (3TC) are HIV drugs, Protease inhibitors target HIV, Tamiflu is for influenza, Sovaldi and daclatasvir are for Hepatitis C, Remdesivir and Favipravir are antiviral drugs used for COVID-19.

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Why do we need a new influenza vaccine each year?

The influenza virus constantly mutates, leading to new strains. These mutations make the immune system less effective against the new strains, requiring updated vaccines each year.

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What are Live Attenuated Virus Vaccines?

Live attenuated vaccines contain a weakened version of the virus, stimulating the immune system without causing illness.

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What are Inactivated Vaccines?

Inactivated vaccines contain killed viruses, which are safer but may not trigger as strong an immune response as live attenuated vaccines.

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What are Sub-unit Vaccines?

Sub-unit vaccines use only specific parts of the virus, such as proteins, to trigger an immune response.

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What are Genetically Engineered Vaccines?

Genetically engineered vaccines are the latest generation, using DNA or RNA to instruct the body to produce viral proteins, triggering an immune response.

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Can viruses be cultured and isolated from samples?

It is possible to isolate and culture viruses from pathological samples, but methods are complex and require specialized labs and equipment.

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How do viruses replicate?

Viral nucleic acid (DNA or RNA) is replicated using viral or cellular polymerases, creating new viral genomes.

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How are new virus particles released from host cells?

Viruses release new virions through various mechanisms such as budding, exocytosis, or lysis. Budding involves wrapping the virus in a host cell membrane, exocytosis releases them through vesicles, and lysis causes cell destruction.

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What are the possible outcomes of viral infection?

Viral replication can be a complex process with diverse outcomes for the infected cell.

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What is a lytic infection?

This type of viral infection results in the destruction of the infected host cell and the production of new viral particles.

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What is a latent infection?

During this type of viral infection, the viral genome persists within the host cell without causing immediate harm or producing new viruses.

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What are the methods for detecting viral infections?

These tests directly detect the presence of the virus or its components in a sample.

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How do different tests for viral infections differ?

Techniques such as PCR and antigen detection are used to assess acute infection, while antibody tests provide evidence of past exposure.

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What is PCR?

This molecular technique amplifies specific regions of viral nucleic acid, providing sensitive detection of even low viral loads.

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What are antigen detection tests?

These tests detect specific proteins on the virus's surface.

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What are antibody detection tests?

These tests identify antibodies produced by the immune system in response to a viral infection, providing evidence of past exposure.

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Antiviral Drugs

Antiviral drugs are medications specifically designed to treat viral infections.

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What are Bacteria?

Bacteria are single-celled organisms that can multiply outside of host cells. They also have a more complex structure compared to viruses.

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What is Influenza?

Influenza is a respiratory illness caused by the influenza virus. There are three major types: A, B, and C.

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What are some treatments for influenza?

Treatments for influenza include antiviral medications like Tamiflu, which can reduce the severity and duration of the illness.

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Why do we need a new flu vaccine every year?

Influenza viruses constantly mutate, leading to the emergence of new strains. This is why new vaccines are developed annually.

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Live Attenuated Virus Vaccines

Live attenuated vaccines contain a weakened version of the virus, which prompts the immune system to develop immunity without causing disease.

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Inactivated Vaccines

Inactivated vaccines use killed viruses, making them safer but less likely to trigger a strong immune response compared to live attenuated vaccines.

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Sub-unit Vaccines

Sub-unit vaccines only include specific parts of the virus, such as proteins, to initiate an immune response.

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Genetically Engineered Vaccines

Genetically engineered vaccines, the latest technology, use DNA or RNA to instruct the body to produce viral proteins, triggering an immune response.

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Study Notes

General Virology

  • Viruses are defined as submicroscopic, obligate intracellular parasites that only replicate inside living host cells.
  • Viral particles (virions) do not grow or undergo cell division.
  • Virions are produced from the assembly of pre-formed viral protein components.
  • Viruses vary in size. Sizes range from 15nm to 300 nm.
  • Viral shapes include helical, icosahedral and complex.

Viral Structure

  • Viruses contain a protein coat called a capsid.
  • The capsid is composed of repeating protein subunits called capsomers.
  • The capsid encloses the viral nucleic acid (either DNA or RNA).
  • Some viruses have an outer envelope made of a lipid bilayer derived from the host cell.
  • The envelope may contain glycoproteins that help the virus attach to host cells.
  • Examples of viral structures include spikes, nucleocapsids, membranes, and envelopes.

Viral Classification

  • Viruses are classified based on their nucleic acid properties.
  • Nucleic acids can be single-stranded or double-stranded, linear or circular.
  • Nucleic acids can be RNA or DNA.
  • The Baltimore classification system groups viruses based on their replication strategy (e.g. DNA viruses, RNA viruses).

Viral Replication

  • Viral replication involves several steps: Adsorption (attachment), uptake, uncoating, genomic and protein synthesis, assembly, and release.
  • Viruses use a variety of mechanisms for gaining entry into cells. These include endocytosis or fusion with the cell membrane.
  • Viral nucleic acid replication may occur by viral or cellular polymerases.
  • Some viruses can cause infection that is latent, with the virus genome present in the host cell without causing any apparent harm, then triggering reactivation.
  • Viral replication includes steps like adsorption, penetration, uncoating, biosynthesis of viral components (RNA or DNA replication and protein synthesis), assembly (making complete virions), and release (releasing virions). This process varies depending on the specific virus structure.

Viral Infections and effects

  • Viral infections can result in cell death and production of new viruses.
  • Some infections are abortive, meaning no cell damage and no progeny virus is produced.
  • Persistent infections involve release of progeny viruses over a period of time.
  • Latent infections involve the viral genome being present in the host cell without causing any apparent harm.
  • Viral infections can have various outcomes depending on several factors including the virus, the host's immune response, and the specific tissues affected.

Laboratory Diagnosis of Viral Infections

  • Viral infections are diagnosed using different methods: Viral genome detection, viral antigen detection, and antibody detection.
  • PCR (Polymerase Chain Reaction) is used for detecting viral genome.
  • Immunofluorescence, ELISA, and rapid tests are used for antigen and antibody detection.
  • These diagnostic methods are used to determine the presence and type of virus, which is helpful in guiding treatment.

Prevention and Treatment

  • Vaccination is a key preventative measure against viral infections.
  • Antiviral drugs are available to treat viral infections, but are often quite specific.
  • Examples presented include antiviral agents used to treat Herpes,AIDS, Influenza, HCV, and COVID-19.
  • Antiviral treatment focuses on inhibiting viral replication, either by targeting specific viral enzymes or by interfering with the viral life cycle.

Clinical case studies

  • Grandfather Ali's symptoms are descriptive of a viral infection like influenza, not a bacterial one. This case highlights the importance of accurate diagnosis for appropriate treatment.

Summary and general information

  • Viruses are responsible for many human infections.
  • Viral genomes can be either RNA or DNA.
  • Viral replication involves a series steps during infection, ranging from attachment to host cells, to cell entry, biosynthesis and release.
  • There are multiple types of viral infections, such as lytic, abortive, persistent and latent infections.
  • Laboratory tests are used for the identification and classification of viruses, including techniques such as polymerase chain reaction (PCR) , and serological tests.
  • Viral infections impact the human body in many ways, ranging from minor inconveniences to severe, life-threatening conditions.

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