Chapter 7 – Viral Infections Flashcards
1
Q
How are viruses distinct from cell-based life?
A
They have non-cellular structures and are parasites that require a host cell to reproduce.
2
Q
What do viruses contain that is similar to living cells?
A
They contain genetic material and biomolecules (e.g., proteins).
3
Q
How many types of viruses infect vertebrates?
A
Around 200–300 have been identified as human pathogens.
4
Q
What are the two main systems used to classify viruses?
A
- The International Committee on Taxonomy of Viruses
- The Baltimore Classification System
5
Q
What criteria are used to classify viruses?
A
- Structural Features
- Functional Features
6
Q
What type of genetic material do viruses contain?
A
DNA or RNA.
7
Q
Why are viruses incapable of metabolism or reproduction?
A
Because viruses are dependent on host cells to replicate.
8
Q
What are the key components of a virion (virus particle)?
A
- Outer Protein or Glycoprotein
- Core w/ Genetic Material
- Enzymes
9
Q
How do viruses reproduce?
A
- Viruses insert their genome into host cells.
- Hijack the host’s cellular machinery to synthesize viral components.
- Assemble and release new virions.
10
Q
e.g., What tissue does the influenza virus infect?
A
Mucosa of the respiratory tract.
11
Q
e.g., What tissue does the rabies virus infect?
A
Nerve and salivary gland tissue.
12
Q
What causes tissue damage during a viral infection?
A
When viruses reproduce and hijack the host cell’s machinery.
13
Q
What steps are involved in viral reproduction?
A
- Absorption
- Penetration
- Reproduction
14
Q
How do viruses escape the host cell after reproduction?
A
They rupture the cell membrane or budding from it’s surface.
15
Q
What is viral absorption?
A
When a virus contacts and adheres to the host cell by containing capsule proteins that bind to specific receptors on the cell surface.
16
Q
What is viral tropism?
A
Ability of a virus to infect specific cell types based on receptor binding.
17
Q
e.g., What cell type does Epstein-Barr virus target?
A
B Lymphocytes.
18
Q
e.g., What cell types does HIV target?
A
Helper T Lymphocytes and Dendritic Cells.
19
Q
What is viral penetration?
A
Process by which a virus passes through the host cell membrane to release its genetic material.
20
Q
What are the three main methods of viral penetration?
A
- Endocytosis
- Fusion
- Adherence and Translocation
21
Q
How does endocytosis help a virus penetrate the host cell?
A
The virus is internalized into a vesicle, uncoated, releasing the viral genome into the cell.
22
Q
How does fusion help a virus penetrate the host cell?
A
The viruses fuses with the host cell membrane, allowing the genome to enter the cell.
23
Q
How does adherence and translocation help a virus penetrate the host cell?
A
Mechanism is unknown but viral material stays inside the host cell (e.g., Poliovirus).
24
Q
What happens to the viral genome during the lysogenic cycle?
A
The viral genome is inserted into the host genome.
25
Does the lysogenic cycle immediately cause disease?
No, the viral genome remains in a latent state until permissive conditions trigger activation.
26
What triggers activation of the viral genome in the lysogenic cycle?
1. Carcinogens
2. Hormones
3. Temperature Changes
4. UV Light
27
What happens when the viral genome is activated?
The viral genome directs the production of new viruses, leading to cell lysis and the release of new virions.
28
How is the viral genome passed on to future generations of the host organism?
It is copied along with the host genome during cell replication.
29
What is the lytic cycle?
When a virus directs the host cell to produce new viral capsid proteins and copy the viral genome.
30
Where are new viruses assembled during the lytic cycle?
In the cytoplasm of the host cell.
31
How are new viruses released from the host cell in the lytic cycle?
By budding from the cell surface or erupting en masse, killing the host cell.
32
What is the result of the lytic cycle?
1. Death of the host cell.
2. Release of thousands of new viruses.
33
What is budding?
When viruses exit the host cell while retaining a piece of the host cell membrane.
34
How do viruses exit the host cell during budding?
1. By hijacking Golgi bodies to form vesicles and exiting via exocytosis.
2. By virion particles emerging directly through the host membrane.
35
What damage does the budding process cause to the host cell?
1. Leakage
2. Osmotic Shock
3. Cell Death
36
Where are pathogenic viruses found?
In the human reservoir, as well as animal reservoirs that can be transmitted to humans via vectors.
37
What determines the specificity of a virus for its target cells?
The presence of specific receptors on the target cells that allow the virus to attach and infect the cell.
38
How can viruses "jump the species barrier" to infect humans?
Through the presence of compatible viral receptor proteins or mutations in the viral docking proteins.
39
What are zoonotic viruses?
Viruses transmitted from animals to humans via vectors (e.g., Zika, Yellow Fever, Nile Fever, Nipah, Dengue).
40
What is the course of a viral infection?
1. Invasion at Portal of Entry
2. Infecting Local Site
3. Replication
4. Spreading Into Circulation to Infect Other Tissues
41
What are the cytopathic effects of viruses on host cells?
1. Host Cell Swelling
2. Changes in Morphology (e.g., size, shape, organization)
3. Fusion of Cells (e.g., multinucleate cells, cell lysis, tissue death)
42
What are inclusion bodies in host cells?
Aggregates of viral proteins that are found in the cytoplasm or nucleus of infected host cells.
43
How do viruses affect host cells when inserting in DNA?
1. Gene Mutations
2. Abnormal Cell Division
3. Cessation of Normal Cell Division
4. Hyperplasia
3. Tumor Cells (e.g., Epstein-Barr Virus, Hepatitis B)
44
Where do DNA viruses bud from in the host cell?
From the nucleus.
45
Where do RNA viruses multiply and release?
They multiply and are released in the cytoplasm.
46
What are common symptoms of viral infection?
1. Fever
2. Myalgia
3. Fatigue
4. Rash
5. Respiratory Symptoms
6. Lymph Swelling
Due to the activation of innate defenses and the release of inflammatory mediators.
47
What are severe symptoms of viral infections?
1. Acute Respiratory Distress
2. Disseminated Intravascular Coagulation
3. Hemorrhage
4. Shock
5. Mortality
48
How do oncogenic viruses affect host cells?
They cause transformation of host cells into tumor cells, leading to malignancies (e.g., Hepatitis B, Hepatitis C).
49
How do viral infections affect pregnancy?
Viruses are able to cross the placental barrier, causing developmental damage to the embryo/fetus from infected mothers.
50
What factors affect the severity of viral infections in individuals?
1. Immune Responses
2. Co-Morbidities
3. Environmental Stressors
4. Viral Load
5. Genetics
6. Age
51
What role does the innate immunity play in viral infection?
The recognition of the virus by macrophages/dendritic cells and the release of inflammatory mediators.
52
What role does the adaptive immunity play in viral infection?
The production of antibodies that neutralize the virus and promote cytotoxicity to destroy infected cells, mediated by CTLs.
53
What was observed in immune responses and clinical manifestations with COVID-19?
Inflammatory responses with respiratory and cardiovascular symptoms.
54
What was identified as the receptor for the COVID-19 Virus?
ACE2 Protein, which is abundant in lung and cardiovascular tissues.
55
How are DNA Viruses Sub-Classified?
1. Enveloped DNA Viruses
2. Non-Enveloped DNA Viruses
56
Enveloped DNA Viruses
Have a viral particle that retains a patch of host cell membrane when it buds from the host, assisting in integration into new host cells.
57
Non-Enveloped DNA Viruses
Consist of a naked protein capsid.
58
Enveloped DNA Virus Infections – Poxviruses
Pox refers to skin pustules that affect subcutaneous connective tissue and epidermal cells, leaving lesions called pockmarks after healing.
59
e.g., Smallpox
Caused by the variola virus, the most infamous/lethal poxvirus. It's reservoir are exclusively humans.
60
What is the significance of smallpox in terms of vaccines?
It was the first viral disease for which a vaccine was developed.
61
How is smallpox transmitted?
Via fomites or direct contact with encrusted pocks of infected persons.
62
What does the variola virus target?
Targets the respiratory tract, moving to the circulatory system, then taking residence in lymph nodes, where multiplication occurs.
63
What are the symptoms of smallpox?
1. Fever
2. Malaise
3. Prostration
4. Rash/Pustules
64
Enveloped DNA Virus Infections – Herpesvirus
1. HSV1
2. HSV2
3. VZV
4. CMV
5. EBV
6. HHV6
7. HHV7
8. HHV8
65
What triggers the reactivation of herpesvirus infections?
1. Fatigue
2. Infection
3. Surgery
4. Immunosuppression
5. Malignancy
6. Intense Sunlight
7. Emotional Stress
66
What is the herpesvirus infection pattern?
They establish latent, recurrent, and persistent infections.
67
How are herpesviruses transmitted?
Through direct mucosal/skin contact or respiratory aerosol from infected persons.
68
What happens when herpesvirus infection activates in sensory nerve endings?
The virus migrates up axons to enter dorsal root ganglia, entering latency. Upon reactivation, the virus moves back along the nerves, causing recurrent infections.
69
What is HSV1?
Herpes Simplex Virus 1 transmitted by direct mucosal/skin contact. They enter through sensory nerve endings and reside in the trigeminal nerve ganglia. Causes cold sores on the oral region.
70
What is HSV2?
Herpes Simplex Virus 2 transmitted by direct mucosal/skin contact. They enter through sensory nerve endings and reside in the dorsal root ganglia in the sacral region. Causes cold sores on the genital region. If infecting the eyes, it can cause corneal damage.
71
What is a specific activation with HSV1 and HSV2?
Through corticosteroid activation of JNK protein, controlling apoptosis and neurodegeneration.
72
What is VZV?
Varicella Virus that causes chickenpox and shingles.
73
What is chickenpox?
A highly contagious infection that is transmitted via respiratory aerosol, direct contact with saliva or infected blister from pustules. It causes lymph node swelling, fever, malaise, rash, macules, and papules. Children who are unimmunized are susceptible. Complications include pneumonia, encephalitis, convulsions, brain injury.
74
What is shingles?
The recurrence of the VZV infections when the virus emerges from latency in individuals who had chickenpox. It causes painful rashes with blisters, headache, fever, nausea, chills, itching, tingling, pain.
75
What is CMV?
Cytomegalovirus that is transmitted via bodily fluids. It can cause hepatosplenomegaly, microcephaly, jaundice, ocular inflammation, damage, mental retardation, hearing and vision loss. It is opportunistic in individuals with AIDS.
76
What is EBV?
Epstein-Barr Virus that resides in human lymphoid tissue and salivary glands, and is transmitted by direct oral contact/contamination with bodily fluids. It causes mononucleosis and can cause autoimmune conditions.
77
Enveloped DNA Virus Infections – Hepadnaviruses
The most significant are the Orthohepadnaviruses, causing Hepatitis B.
78
How is Hepatitis B Virus transmitted?
Through blood, semen, vaginal secretions, and from mother to child during birth. It can also be transmitted via mosquitoes.
79
What complications are associated with HBV?
As they target hepatocytes, it can lead to liver cirrhosis, hepatocellular carcinoma, and liver failure.
80
How does HBV affect liver function?
It causes loss of liver function by including the inability to metabolize toxins and conjugate bilirubin.
81
What are the symptoms of HBV?
1. Malaise
2. Fatigue
3. Nausea
4. Headache
5. Fever
6. Darkened Urine
7. Jaundice
82
Non-Enveloped DNA Viruses – Adenoviruses
Adenoviruses are transmitted through humans via contact with secretions, contaminated objects, or airborne droplets. They infect the respiratory and intestinal epithelia, and the conjunctiva.
83
What are the symptoms of Adenovirus?
1. Fever
2. Acute Rhinitis
3. Pharyngitis
4. Cough
5. Otitis Media
6. Enlarged Lymph Nodes
7. Follicular Lesions of the Conjunctiva
84
What can Adenovirus type 3 and 7 cause?
Pharyngoconjunctival Fever
85
What can Adenovirus cause in children?
Acute Hemorrhagic Cystitis
86
What can Adenovirus cause in immunocompromised individuals?
Bronchiolitis and Pneumonia
87
What type of viral infection pattern do Adenoviruses follow?
Lysogenic, can remain latent, and are oncogenic in animals.
88
Non-Enveloped DNA Viruses – Papovaviruses
Human Papillomavirus is the most significant. It causes plantar and genital warts and are transmitted via sexual contact. It's responsible for cancer cases like cervical, anal, vulvar, vaginal, penile, and oropharyngeal.
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