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Questions and Answers
What is the term used to describe the increase in antibody titer to a virus?
What is the term used to describe the increase in antibody titer to a virus?
Which method is used to identify viruses based on their size and morphology?
Which method is used to identify viruses based on their size and morphology?
What does IgM in a patient's blood indicate?
What does IgM in a patient's blood indicate?
What is required for the growth of viruses?
What is required for the growth of viruses?
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How can viral nucleic acids be detected in a patient's sample?
How can viral nucleic acids be detected in a patient's sample?
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What does a 4-fold increased concentration of IgG indicate?
What does a 4-fold increased concentration of IgG indicate?
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Which method is used to amplify viral nucleic acids when only small amounts are present?
Which method is used to amplify viral nucleic acids when only small amounts are present?
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How are viral antigens typically detected in a patient?
How are viral antigens typically detected in a patient?
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What is the primary purpose of a vaccine?
What is the primary purpose of a vaccine?
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Antiviral therapies target specific steps in the virus lifecycle. Which of the following is NOT a targeted step?
Antiviral therapies target specific steps in the virus lifecycle. Which of the following is NOT a targeted step?
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What are the primary components used for the classification of viruses?
What are the primary components used for the classification of viruses?
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Which of the following statements is true about positive-sense RNA viruses?
Which of the following statements is true about positive-sense RNA viruses?
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What is one of the five main effects of virus infection on a cell?
What is one of the five main effects of virus infection on a cell?
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What is the significance of inclusion bodies in infected cells?
What is the significance of inclusion bodies in infected cells?
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Most DNA viruses are characterized by their structure. Which of the following is correct?
Most DNA viruses are characterized by their structure. Which of the following is correct?
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What effect does cell lysis have on virus-infected cells?
What effect does cell lysis have on virus-infected cells?
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Which group commonly refers to HHAPPPy viruses?
Which group commonly refers to HHAPPPy viruses?
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What is the primary reason for using cell cultures in virus identification?
What is the primary reason for using cell cultures in virus identification?
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Which microscopic technique is specifically noted for revealing characteristic inclusions or giant cells?
Which microscopic technique is specifically noted for revealing characteristic inclusions or giant cells?
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How do negative-sense RNA viruses operate before protein production can begin?
How do negative-sense RNA viruses operate before protein production can begin?
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What cytopathic effect (CPE) is typically associated with virus growth in cell cultures?
What cytopathic effect (CPE) is typically associated with virus growth in cell cultures?
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Which microscopy technique uses fluorescent antibody staining for virus identification?
Which microscopy technique uses fluorescent antibody staining for virus identification?
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What is the main function of electron microscopy in virus detection?
What is the main function of electron microscopy in virus detection?
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What is typically examined in clinical specimens for virus identification?
What is typically examined in clinical specimens for virus identification?
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What characteristic findings can suggest a presumptive viral identification in cell cultures?
What characteristic findings can suggest a presumptive viral identification in cell cultures?
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Which of the following does NOT represent a direct method of identifying viruses?
Which of the following does NOT represent a direct method of identifying viruses?
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What is the correct order of the clinical stages of a typical viral infection?
What is the correct order of the clinical stages of a typical viral infection?
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Which of the following is NOT a category of host defenses against viruses?
Which of the following is NOT a category of host defenses against viruses?
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Which types of immunity are included in the specific (adaptive) immune response?
Which types of immunity are included in the specific (adaptive) immune response?
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What are virokines primarily secreted by?
What are virokines primarily secreted by?
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What is the primary function of interferons in the immune response?
What is the primary function of interferons in the immune response?
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Which of the following best describes the function of cytokine decoys?
Which of the following best describes the function of cytokine decoys?
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Which of the following techniques can be used for the microscopic identification of viruses?
Which of the following techniques can be used for the microscopic identification of viruses?
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What is one of the mechanisms by which viruses maintain their presence in the host cell?
What is one of the mechanisms by which viruses maintain their presence in the host cell?
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What is the most common method for processing viral specimens?
What is the most common method for processing viral specimens?
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Which approach is NOT included in the five techniques for diagnosing viral diseases?
Which approach is NOT included in the five techniques for diagnosing viral diseases?
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What does antigenic variation allow viruses to do?
What does antigenic variation allow viruses to do?
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What characteristic is particularly noted when performing microscopic identification of viruses?
What characteristic is particularly noted when performing microscopic identification of viruses?
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How do virulent strains of viruses differ from non-virulent strains?
How do virulent strains of viruses differ from non-virulent strains?
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What type of proteins do some viruses encode that can manipulate the immune response?
What type of proteins do some viruses encode that can manipulate the immune response?
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Which immune mediators can cytokine decoys specifically neutralize?
Which immune mediators can cytokine decoys specifically neutralize?
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What do virokines compete with in the host?
What do virokines compete with in the host?
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Study Notes
Viral Infections & Pathogenesis
- Viral infections are classified based on chemical and morphological criteria.
- Major components used in viral classification include the nucleic acid (type and structure; DNA vs. RNA), capsid (icosahedral vs. helical), and envelope (naked vs. enveloped).
Viral Pathogenesis
- Viral disease can be studied at two levels: changes within individual cells and processes in the infected patient.
- Classifications of DNA and RNA viruses exist as well as their common diseases.
Viral Family Classification
- Some DNA viruses are double-stranded and show icosahedral symmetry, replicating in the nucleus.
- Some DNA viruses, like Parvovirus, are single-stranded DNA that replicate in the cytoplasm, not icosahedrally.
- Most RNA viruses are single-stranded (+ vs. -) sense, enveloped, and replicate in the cytoplasm.
- Positive-sense RNA (+RNA) viruses can be directly translated into proteins.
- Negative-sense RNA (-RNA) viruses must first be transcribed into complementary positive-sense RNA before protein production can begin.
Infected Cell Effects
- Viral infection can result in cell death (lysis), cell fusion (multinucleated giant cells), malignant transformation, no noticeable change, or persistence (latent infections).
- Inclusion bodies are discrete areas within infected cells containing viral proteins or particles.
Malignant Transformation
- Viral infection can cause certain viruses to exhibit unrestrained growth, prolonged survival, and morphologic changes, leading to malignant transformation of infected cells.
- Oncoviruses carry oncogenes in their genetic material that can be integrated into host cell genomes, activating oncoproteins and driving malignant transformation. HPV and EBV are examples.
- Rapid viral replication and immune destruction can drive accelerated cell division, leading to increased mutagenesis and potentially cancerous changes. HCV and HIV are examples.
Viral Pathogenesis in the Infected Patient
- Viral pathogenesis in humans involves virus transmission, entry, replication and damage to cells, spread to other cells and organs, the immune response, and potential persistence.
- Understanding portals of entry and possible diseases associated with specific viruses is important.
Viral Virulence
- Viral strains vary significantly in their ability to cause disease.
- Some viruses have genes encoding molecules inducing cytopathic effects, promoting malignant transformation, exhibiting antigenic variations, allowing viral latency.
- Viruses may evade the host immune response by using cytokine decoys, virokines, and immunomodulatory proteins.
Multiple Antigenic Types (Serotypes)
- Some viruses, such as rhinoviruses and influenza, have multiple serotypes (antigenic types).
- Having multiple serotypes enhances the virus' ability to cause infection across the population because previous exposure to one serotype does not grant immunity to others.
Persistent Viral Infections
- In some cases, viruses remain in the body after the host recovers, resulting in persistent infections.
- Viral latency can occur through various mechanisms, including the action of latency genes, location of the virus in immunologically sheltered sites, and rapid antigenic variation.
Types of Persistent Viral Infections
- Chronic-carrier infections: These viruses replicate continuously and are constantly shed, serving as a source of infection to others. Chronic hepatitis B and C are one example.
- Latent infections: Virus replication may stop after initial infection, but in some cases, symptoms may reappear, accompanied with virus production.
- Slow virus infections: A prolonged period between infection and disease onset.
Laboratory Techniques (Diagnosis)
- Viral specimens are typically processed in class II biological safety cabinets.
- Diagnosis involves identification of the virus in cell culture, microscopic examination (light or electron microscopy), serologic procedures to detect antibody titers or IgM, or detection of viral antigens or nucleic acids.
Viral Vaccination
- Vaccines are preparations designed to produce immunity against diseases by inducing antibody production.
- Live attenuated and inactivated vaccines are common methods of viral vaccination. They can differ in how long immunity lasts, their efficacy, ease of use, and potential for reversion to virulence.
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Description
This quiz covers the classification and pathogenesis of viral infections, focusing on the criteria used in categorizing viruses based on their nucleic acid, capsid, and envelope. It also delves into the mechanisms of viral disease at cellular and patient levels. Perfect for students studying virology.
