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Questions and Answers
Which of the following statements accurately describes viremia?
Which of the following statements accurately describes viremia?
- It refers to local infections only.
- It signifies a virus’s ability to spread systemically through the blood. (correct)
- It is primarily associated with respiratory infections.
- It indicates that a virus remains localized at the infection site.
Which route of virus entry is least likely to infect the central nervous system (CNS)?
Which route of virus entry is least likely to infect the central nervous system (CNS)?
- Genital tract
- Gastrointestinal tract (correct)
- Abrasion
- Respiratory tract
What is one consequence of alpha herpesviruses infecting pseudo-unipolar sensory neurons?
What is one consequence of alpha herpesviruses infecting pseudo-unipolar sensory neurons?
- They cause widespread inflammation throughout the body.
- They are primarily transmitted through contaminated water.
- They reinfect the neurons only when the immune system is strong.
- They can lead to CNS infections requiring specific transport mechanisms. (correct)
Which virus primarily spreads from muscles into somatic motor neurons?
Which virus primarily spreads from muscles into somatic motor neurons?
Which entry route might allow a virus to reach the brain directly?
Which entry route might allow a virus to reach the brain directly?
How do poliovirus and rabies virus primarily reach the CNS?
How do poliovirus and rabies virus primarily reach the CNS?
Which virus classification typically involves infection through abrasions?
Which virus classification typically involves infection through abrasions?
What characteristic do viruses that cause generalized infection typically share?
What characteristic do viruses that cause generalized infection typically share?
What type of cellular components does hematoxylin specifically stain?
What type of cellular components does hematoxylin specifically stain?
What are inclusion bodies typically associated with in infected cells?
What are inclusion bodies typically associated with in infected cells?
In which part of the brain are Negri bodies primarily found in rabies victims?
In which part of the brain are Negri bodies primarily found in rabies victims?
What characteristic coloration do Negri bodies exhibit, and why?
What characteristic coloration do Negri bodies exhibit, and why?
What type of viral infections particularly induce new surface antigens on infected cells?
What type of viral infections particularly induce new surface antigens on infected cells?
Which event is NOT typically involved in the pathogenesis of viral infections?
Which event is NOT typically involved in the pathogenesis of viral infections?
What immune mechanism must viruses overcome to ensure successful replication?
What immune mechanism must viruses overcome to ensure successful replication?
What does viremia refer to in the context of viral infections?
What does viremia refer to in the context of viral infections?
What primarily allows the virus to spread to the central nervous system (CNS)?
What primarily allows the virus to spread to the central nervous system (CNS)?
Which of the following accurately describes the composition of the blood-brain barrier (BBB)?
Which of the following accurately describes the composition of the blood-brain barrier (BBB)?
What is the primary direction of anterograde transport?
What is the primary direction of anterograde transport?
What type of viral infection is characterized by symptom-free periods followed by reactivation?
What type of viral infection is characterized by symptom-free periods followed by reactivation?
Which of the following is NOT a characteristic of a slow-fatal viral infection?
Which of the following is NOT a characteristic of a slow-fatal viral infection?
Which of the following viruses is associated with acute rapid death?
Which of the following viruses is associated with acute rapid death?
What is a risk factor associated with attenuated live vaccines?
What is a risk factor associated with attenuated live vaccines?
What is the role of dyneins and kinesins in axonal transport?
What is the role of dyneins and kinesins in axonal transport?
In terms of immune response, what distinguishes attenuated live vaccines from inactivated or sub-unit vaccines?
In terms of immune response, what distinguishes attenuated live vaccines from inactivated or sub-unit vaccines?
What was demonstrated by the study on the recombinant modified vaccinia virus Ankara with the SARS spike glycoprotein?
What was demonstrated by the study on the recombinant modified vaccinia virus Ankara with the SARS spike glycoprotein?
What type of viral infection typically has a long incubation period followed by a long illness?
What type of viral infection typically has a long incubation period followed by a long illness?
Which of the following describes the mechanism for virus particles in the bloodstream to infect the brain?
Which of the following describes the mechanism for virus particles in the bloodstream to infect the brain?
How many nucleotides differentiate the Sabin vaccine strain from the wild-type Leon strain of poliovirus?
How many nucleotides differentiate the Sabin vaccine strain from the wild-type Leon strain of poliovirus?
What was the frequency of paralytic disease caused by virulent revertant strains after the administration of the Sabin strain?
What was the frequency of paralytic disease caused by virulent revertant strains after the administration of the Sabin strain?
What symptom characterizes oral herpes caused by the herpes simplex virus?
What symptom characterizes oral herpes caused by the herpes simplex virus?
What was concluded about the rDEN4delta30 dengue vaccine candidate in the study mentioned?
What was concluded about the rDEN4delta30 dengue vaccine candidate in the study mentioned?
What does the abbreviation 'SARS' stand for in the context of vaccines?
What does the abbreviation 'SARS' stand for in the context of vaccines?
Which type of vaccine typically produces a longer-lasting immune response?
Which type of vaccine typically produces a longer-lasting immune response?
What is the role of the E1 protein in viral replication?
What is the role of the E1 protein in viral replication?
Which types of HPV do the Gardasil vaccine target that are associated with cervical cancer?
Which types of HPV do the Gardasil vaccine target that are associated with cervical cancer?
What is the benefit of using Gardasil besides preventing cervical cancer?
What is the benefit of using Gardasil besides preventing cervical cancer?
What type of vaccine is used for chickenpox?
What type of vaccine is used for chickenpox?
What is the significance of the structure of the virus in the context of vaccination?
What is the significance of the structure of the virus in the context of vaccination?
What age group is GARDASIL 9 indicated for vaccination against HPV-related diseases?
What age group is GARDASIL 9 indicated for vaccination against HPV-related diseases?
Which of the following statements about the E2 protein is true?
Which of the following statements about the E2 protein is true?
What component of Gardasil helps it target multiple HPV types?
What component of Gardasil helps it target multiple HPV types?
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Study Notes
Staining in Histology
- Hematoxylin stains nuclear components such as heterochromatin and nucleoli.
- Eosin stains cytoplasmic components, including collagen, elastic fibers, muscle fibers, and red blood cells.
Inclusion Bodies
- Inclusion bodies are aggregates of stainable substances, mainly proteins within cells, often indicating viral replication.
- Common viruses associated with inclusion bodies include Rabies Virus, Herpes Virus, and Measles Virus.
- Negri bodies are eosinophilic inclusion bodies indicating rabies virus infection, primarily found in the cytoplasm of nerve cells.
Viral Interaction with Host Cells
- Viruses induce new antigens on the surface of infected cells, especially enveloped viruses (e.g., herpes, orthomyxoviruses, retroviruses).
- Infected cells become susceptible to cytotoxic T cells, detectable via immunofluorescence staining.
Viral Pathogenesis
- Key events include invading the host, replicating in susceptible cells, evading immune defenses, and spreading through the bloodstream (viremia).
- Respiratory aerosols from infected individuals contain viral particles, contributing to systemic transmission.
Infection Routes
- Viruses can enter the host via various routes, including:
- Abrasion (e.g., cut)
- Inoculation (e.g., contaminated needle)
- Animal bites (e.g., rabies)
- Respiratory tract (e.g., influenza)
- Gastrointestinal tract (e.g., norovirus)
- Conjunctiva (e.g., HSV)
- Genital tract (e.g., HPV)
Nervous System Invasion
- Alpha herpesviruses (e.g., HSV-1, VZV) infect sensory neurons, with rare CNS spread through anterograde axonal transport.
- Rabies and poliovirus spread via neuromuscular junctions into the spinal cord.
- Various viruses can traverse the blood-brain barrier (BBB) via infected leukocytes or BMVECs.
Types of Viral Infections
- Acute infections lead to rapid recovery or death (e.g., influenza, rabies).
- Chronic infections exhibit symptom-free periods with potential reactivation (e.g., herpes).
- Slow-fatal infections, such as HIV, manifest as long incubation periods followed by illness.
Vaccine Development
- Gardasil vaccine targets HPV types 16, 18, 6, and 11, preventing cervical cancer and genital warts.
- Chickenpox vaccine uses a live attenuated virus to provide immunity against varicella-zoster virus.
- Ongoing research includes developing vaccines against HIV and dengue through various innovative approaches.
Live Attenuated vs Inactivated Vaccines
- Live attenuated vaccines typically provide longer-lasting immunity, generating both humoral and cell-mediated responses.
- Inactivated or sub-unit vaccines primarily stimulate humoral immunity.
- Concerns exist regarding the genetic reversion potential of live attenuated vaccines, such as the polio vaccine.
Genetic Variability in Vaccines
- Genetic differences between attenuated (e.g., Sabin polio) and wild-type strains can be minimal but significant for pathogenicity.
- Cases of virulent revertant strains highlight the need for careful monitoring of vaccine-derived strains.
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