Lecture 2: Pathogenesis of Viral Material

Question 1

Pathogenesis:

Answer 1

Pathogenesis is the process by which a disease develops or originates in an individual.

It refers to the sequence of events and mechanisms that lead to the development and progression of a disease from its initial cause or trigger, such as an infection, genetic mutation, environmental factor, or other underlying conditions.

Question 2

RNA Viruses
Review

Answer 2

RNA viruses are a type of viruses that use RNA (ribonucleic acid) as their genetic material.

Unlike DNA viruses, they need to encode or bring their own RNA-dependent RNA polymerase, an enzyme that’s essential for copying their RNA.

These viruses replicate their genetic material and produce new virus particles in the cell’s cytoplasm, which is outside the cell’s nucleus.

RNA viruses are known for having faster mutation rates compared to DNA viruses, which can make them more adaptable and sometimes harder to treat with vaccines or drugs.

Examples of RNA viruses include the flu virus, HIV, and the common cold virus.

Question 3

DNA viruses Review

Answer 3

DNA viruses are a type of viruses that have genetic material made of DNA. When they infect a cell, they tend to stick around for a long time, causing what’s called a persistent infection. Most DNA viruses like to work inside the cell’s control center, which is the nucleus, to copy their DNA and reproduce.

These viruses are also smart in the way they turn their genes on and off at specific times to make more viruses without being noticed by the cell’s defenses.

Common examples of DNA viruses include herpes and chickenpox viruses.

Question 4

Virulence Factors

Answer 4

Things viruses do to make themselves more harmful, like attaching to cells, spreading, and hiding from the body’s defenses.

Essentially, virulence factors help the virus become more effective at causing disease and spreading to new hosts.

Question 5

Attenuated virus

Answer 5

Weakened versions of viruses with their harmful traits removed, used to make vaccines.

Question 6

Acquisition

Answer 6

Acquisition often relates to the initial exposure to a pathogen or the process by which a microorganism or virus enters the body, which is a critical step in the development of an infection.

Question 7

Initiate primary site infection

Answer 7

The beginning or starting of an infection at the initial or primary location in the body where a pathogen enters and establishes itself.

In many cases, the primary site of infection occurs through either the mouth (oral) or the respiratory system, where pathogens are commonly introduced into the body.

Question 8

How does the body react?

Answer 8

Innate immune reponse will be activated, phagocytes and interferon response

Question 9

Incubation Period

Answer 9

The time between exposure to a pathogen or disease and the appearance of the first symptoms, during which the pathogen is replicating and the individual is not yet symptomatic.

EX: Testing positive for COVID with no symptoms happens during the incubation period

Question 10

Secondary Site

Answer 10

Only happens in some cases.

Replication happens at this second site & the adaptive immune response is triggered.

Sometimes, the adaptive immune system is able to clear out the infection.

Other times, this can develop into immunopathology, where the immune system’s activity causes harm to the host’s own tissues and results in symptoms or disease.

Question 11

How can a viral infection cause immunopathology?

Answer 11

In some cases, the immune system may overreact to a virus, causing excessive inflammation and damage to healthy tissues.

This is often seen in diseases like COVID-19, where a hyperactive immune response can lead to severe lung damage.

& Some viruses trigger autoimmune reactions, where the immune system mistakenly attacks the body’s own cells

Question 12

Resolution of a virus

Answer 12

After an infection, the outcome can be one of two possibilities: resolution, where the infection is successfully cleared by the immune system, or…

Question 13

Persistence of a virus

Answer 13

or persistence, where the pathogen remains in the body and the infection continues over time.

Question 14

HIV initially targets immune response cells and then can target and replicate in lymph nodes. What is this an example of?

Answer 14

Spread to secondary site

Question 15

Asymptomatic

Answer 15

When an individual is infected but shows no symptoms. In some cases, the infection can even progress to secondary sites in the body without noticeable symptoms.

Question 16

Prodrome

Answer 16

The initial phase of an illness marked by early, non-specific symptoms such as fever, aches, and chills that precede the characteristic symptoms of the disease.

Question 17

What is causing the symptoms of prodrome?

Answer 17

Infection:
The presence of a virus, bacteria, or other pathogens in the body can stimulate the immune system and lead to symptoms like fever, aches, and chills.

Question 18

Immune Response

Answer 18

The body’s defense mechanism against infections. Innate immunity can often resolve infections, but if not, it triggers adaptive immune responses, involving antibodies and specific immune cells.

Question 19

Convalescence

Answer 19

The period following an illness when symptoms are improving due to tissue repair mechanisms. During this time, the body also develops immunological memory, which provides protection against future infections.

Question 20

Day 1 of infection:

Answer 20

Acquisition Stage: This is the initial phase where the virus enters the body. It involves the exposure to the pathogen and its entry into the host. The acquisition stage is when the virus gains access to the body.

Disease Course: After the virus gets in, you might start feeling early symptoms like fever, tiredness, and mild aches. This phase happens before you get the full-blown symptoms of the illness.

Question 21

Day 2 of infection

Answer 21

The virus continues to replicate at the primary site.
Some immune cells arrive at the site of infection.
Host response: The innate immune response intensifies.
Disease course: Still no specific symptoms, but the virus is spreading within the primary site.

Question 22

Day 3 of infection:

Answer 22

localized inflammation at the primary site.

Immune cells work to contain the infection.

Virus replication continues.

Host response: Innate immunity remains active.

Disease course: Non-specific prodromal symptoms may appear, like mild fever and fatigue.

Question 23

Day 4 of infection:

Answer 23

The virus continues to replicate at the primary site.

Some viral particles may spread to secondary sites.

Immune response: Adaptive immune responses, involving antibodies and specific immune cells, begin to develop.

Disease course: Prodromal symptoms, such as fever and muscle aches, may intensify. The virus may spread to other tissues.

Question 24

Day 5: Spread to Secondary Sites:

Answer 24

Virus particles may spread to secondary sites, affecting different tissues.

The adaptive immune response becomes more targeted.

Host response: Adaptive immune responses are in full swing.

Disease course: Specific symptoms related to the affected tissues may become noticeable.

Question 25

Day 6: Target Tissues affected

Answer 25

Virus replication and immune response are active in various tissues. Immune cells are actively fighting the infection. Host response: Adaptive immunity is strong. Disease course: Specific symptoms may intensify or begin to subside, depending on the overall balance between virus replication and the immune response.

Question 26

Day 7 and Beyond - Resolution or Persistence:

Answer 26

The disease can follow one of two paths: resolution (where the immune system successfully clears the infection) or persistence (where the virus continues to reside in the body). Convalescence: After the infection is resolved, symptoms may persist due to tissue repair mechanisms. Immunological memory develops to provide protection against future infections.

Question 27

Modes of Viral Transmission

Answer 27

---

Question 28

What is the most common route of entry for viruses?

Answer 28

Inhalation

Question 29

Inhalation

Answer 29

Infects oral and respiratory mucosa The specific cells in your mouth and respiratory tract, called epithelial cells, have the right receptors that the virus can latch onto to enter and infect them. The virus carries the tools it needs to make copies of itself once it's inside these cells, allowing it to multiply and cause infection

Question 30

Gastrointestinal

Answer 30

Virus sheds in feces The virus is found in the stool, and it can be transmitted to others through contaminated food, water, or surfaces. This is often referred to as the "fecal-oral" route of transmission.

Question 31

What cells in the gastrointestinal tract can help the virus spread and transport throughout the body?

Answer 31

M cells in Peyer's patches

Question 32

How do M cells assist with viral transmission?

Answer 32

M cells have a unique ability to capture viruses, bacteria, and other particles from the gut lumen. They have a specialized structure that allows them to sample the contents of the gut. Once M cells capture viruses, they transfer these captured particles to immune cells located in the underlying lymphoid tissue.

Question 33

What kind of virus would be more likely to be shed in the feces: naked or enveloped?

Answer 33

Naked viruses are more likely to be shed in the feces compared to enveloped viruses. Enveloped viruses are surrounded by a lipid membrane (envelope) that is typically derived from the host cell's membrane. This envelope is sensitive to environmental conditions and can be easily damaged by the harsh conditions in the gastrointestinal tract, such as stomach acid and digestive enzymes.

Question 34

Sexual Transmission

Answer 34

Infections can be transmitted through sexual contact, such as during sexual intercourse, oral sex, or through contact with genital fluids.

Question 35

Blood

Answer 35

Infections can be spread through contact with contaminated blood. This can occur through sharing needles (as seen in intravenous drug use), blood transfusions with infected blood, or contact with open wounds.

Question 36

Transcutaneous

Answer 36

Infections can enter the body through breaks or cuts in the skin. This can happen when, for example, a person is injured, and infectious agents gain entry through the injured skin.

Question 37

Maternal (fetal/neonatal)

Answer 37

Infections can be transmitted from a pregnant person to the developing fetus during pregnancy or to the newborn during childbirth or breastfeeding. This is often referred to as mother-to-child transmission.

Question 38

Various mechanisms of dissemination from 1° site

Answer 38

This refers to the different ways a virus can spread from its primary (initial) site of infection to other parts of the body. Viruses have various strategies to move from the primary site to secondary sites and cause infection at those locations.

Question 39

Local spread:

Answer 39

This term describes the virus's ability to move and infect nearby tissues or cells at or near the primary site of infection. Local spread is one of the initial steps in the virus's dissemination within the body.

Question 40

Viremia – in the bloodstream:

Answer 40

Viremia means the presence of viruses in the bloodstream. It occurs when viruses have entered the bloodstream and can be carried throughout the body, potentially infecting various organs and tissues.

Question 41

infected leukocytes & lymphocytes:

Answer 41

Some viruses can infect white blood cells (leukocytes) and lymphocytes, which are important components of the immune system. When viruses are present in these immune cells, they can be carried through the bloodstream to other parts of the body, allowing the virus to spread.

Question 42

M cells:

Answer 42

M cells are specialized cells found in the mucosal lining of the intestines, particularly in areas like Peyer's patches. They play a role in capturing and transporting viruses and other particles from the gut lumen to immune cells in the gut-associated lymphoid tissue.

Question 43

Transmission into the CNS:

Answer 43

This refers to the ability of viruses to enter the central nervous system (CNS), which includes the brain and spinal cord. Not all viruses can readily enter the CNS, but some have specific mechanisms that allow them to do so.

Question 44

How can viruses reach the CNS?

Answer 44

Viruses can reach the cerebrospinal fluid (CSF) or the protective meninges around the brain and spinal cord through viremia (presence in the bloodstream), migration by immune cells like macrophages, or transmission from infected peripheral nervous system (PNS) neurons.

Question 45

How does macrophage migration lead to the infection of the CNS?

Answer 45

Once macrophages have captured viruses, they can transport these viruses within their own cellular structures. This provides a means for viruses to be carried throughout the body, including to the central nervous system (CNS).

Question 46

What cell type is this similar to?

Answer 46

Both macrophages and M cells are involved in immune responses and can transport viruses, BUT they operate in different contexts and have distinct roles.

Question 47

How does a rabies virus infect the CNS? (from start to finish)

Answer 47

Peripheral Infection: Rabies virus usually enters the body through the bite of an infected animal, such as a rabid dog or bat. The virus initially infects peripheral tissues near the site of the bite. Nerve Invasion: The virus has a high affinity for nerve cells (neurons). It binds to nerve endings in the peripheral tissues and then travels along the nerves in a retrograde manner, moving toward the spinal cord and brain. This retrograde transport occurs within the axons of neurons. CNS Entry: Once the virus reaches the CNS, it can spread throughout the central nervous system, infecting various parts of the brain and spinal cord. This is when clinical symptoms of rabies typically appear.

Question 48

Abortive:

Answer 48

An infection that fails to establish and reproduce within the host.

Question 49

Inapparent

Answer 49

Refers to an infection that is asymptomatic, causing no noticeable consequences. it is INAPPARENT in the body Ex: Epstein-Barr virus (EBV)

Question 50

Lytic

Answer 50

An infection where the virus kills the host cell during the replicative cycle. Ex: The lytic infection of the influenza virus, where it damages and lyses host respiratory epithelial cells.

Question 51

Non-lytic (Persistent)

Answer 51

An infection in which the host cell is not killed, and the virus does not result in cell death. The non-lytic, persistent infection of Hepatitis B virus (HBV) in hepatocytes, which can lead to chronic hepatitis.

Question 52

What are some advantages of being a lytic virus

Answer 52

Lytic viruses can replicate quickly, producing a large number of viral particles. This can help the virus spread within the host population. When the host cell is lysed (ruptured), it releases numerous viral particles, which can then infect neighboring cells or be transmitted to new hosts, promoting the virus's spread.

Question 53

What are some disadvantages of being a lytic virus

Answer 53

Lytic infections may lead to the death of the host cell. This can be a disadvantage if the virus relies on the host cell for a prolonged period. Immune Response: The destruction of host cells during lytic infections can trigger a strong immune response, making it more challenging for the virus to evade the host's defenses.

Question 54

Chronic

Answer 54

A type of non-lytic, productive infection that persists over an extended period. Ex: HIV

Question 55

Latent

Answer 55

A non-productive infection in which the virus remains dormant within the host cell, without active replication. Example: Herpes Simplex Virus (HSV) can establish a latent infection in nerve cells, causing recurrent cold sores.

Question 56

Recurrent

Answer 56

An infection characterized by on-and-off production of viral particles. Example: Recurrent infections of Varicella-Zoster Virus (VZV) can lead to shingles outbreaks in individuals previously infected with chickenpox. Initial Infection: The virus infects the host and may cause symptoms or an initial outbreak. Latent Phase: After the initial infection, the virus may enter a dormant or latent state, where it remains hidden within host cells and does not actively replicate or produce symptoms. Reactivation: At a later time, the virus may reactivate due to certain triggers, such as stress, illness, or other factors. When reactivation occurs, the virus starts replicating and can lead to the recurrence of symptoms or outbreaks.

Question 57

Transforming

Answer 57

Infections that immortalize host cells, potentially leading to the development of cancer. Example: Infection with some strains of Human Papillomavirus (HPV) can transform host cells and contribute to the development of cervical cancer.

Question 58

Permissive

Answer 58

Host cells that allow the complete replicative cycle of the virus. Example: Influenza A virus is permissive (ALLOWED) to infection in respiratory epithelial cells, allowing the virus to replicate and cause the flu.

Question 59

Semi-permissive

Answer 59

Infections in which replication is slow and inefficient within the host cell. Example: HIV infection in macrophages is semi-permissive, leading to slower viral replication compared to CD4+ T cells.

Question 60

Non-permissive

Answer 60

Host cells that lack essential machinery or actively block virus replication or assembly, preventing a successful infection. Example: Most non-neuronal cells are non-permissive to Rabies virus replication, as the virus requires specific neural machinery for successful infection. But a neuronal cell would be permissive to Rabies virus replication

Question 61

Viral Infection Patterns (Section title)

Answer 61

-----

Question 62

What does the term 'acute infection' refer to?

Answer 62

Acute infections are often associated with a sudden and intense immune response as the body attempts to fight off the invading virus.

Question 63

What does the word latent mean?

Answer 63

Dormant

Question 64

Which virus is most closely associated with the following description? Acute infection which is then followed by viral clearance by the immune system

Answer 64

The flu

Question 65

Which virus is most closely associated with the following description? Acute infection which is then followed by latent infection and periodic reactivation.

Answer 65

Herpes Simplex Virus Type 1

Question 66

Which virus is most closely associated with the following description? Acute infection which is then followed by Chronic Infection

Answer 66

HCV: Hepatitis C Virus.

Question 67

Which virus is most closely associated with the following description? Acute infection which is then followed by persistent infection (set point) and virus overproduction

Answer 67

HIV

Question 68

Which virus is most closely associated with the following description? a slow chronic Infection

Answer 68

Mad cow disease The slow and chronic nature of Mad Cow Disease and other prion diseases is related to the gradual accumulation and spread of misfolded prion proteins within the nervous system, resulting in the characteristic neurological symptoms

Question 69

Lytic Infection Characteristics * section title*

Answer 69

--

Question 70

Kill target cells

Answer 70

Lytic viruses infect and replicate within host cells, ultimately causing the death of these cells.

Question 71

Produce Cytopathic Effects (CPEs)

Answer 71

Lytic infections induce morphological changes in host cells, which are referred to as cytopathic effects. These changes can be visible under a microscope and often involve cell shrinkage, rounding, or the formation of viral inclusions These are alterations or abnormalities in the structure and appearance of host cells that result from viral infection. CPEs are signs that a virus is actively replicating within the host cell and causing damage.

Question 72

inflict damage

Answer 72

Lytic viruses inflict damage on host cells by disrupting their normal functions and structures.

Question 73

Inhibit repair

Answer 73

They can inhibit the host cell's ability to repair or recover from the viral damage.

Question 74

Inhibit DNA & Protein Synthesis:

Answer 74

Lytic infections often interfere with the host cell's ability to synthesize DNA and proteins, which are essential for normal cellular functions.

Question 75

Degrade Host Nucleic Acids:

Answer 75

Some lytic viruses can degrade the host cell's nucleic acids, further impairing the cell's ability to function properly.

Question 76

Disrupt Host Cellular Functions:

Answer 76

These infections disrupt various host cellular functions, leading to cell death and the release of new viral particles.

Question 77

Cytopathic effect under the microscope

Answer 77

Viral CPE induces changes in the cell that can cause cell death

Question 78

Non-lytic Infections

Answer 78

Virus will replicate but not kill the host cell

Question 79

Intracellular Persistence

Answer 79

The state in which viruses remain within host cells for an extended period, often without actively replicating or destroying the host cell.

Question 80

Exocytosis or Budding

Answer 80

Mechanisms by which viruses are released from host cells in non-lytic infections, involving the packaging and release of viral particles without cell lysis.

Question 81

Does a viral gene product transform the host cell?

Answer 81

Yes, the viral genome is integrated into the host nucleus and this disrupts growth regulation

Question 82

Oncogenic transformation

Answer 82

Unregulated growth is promoted by the virus

Question 83

What % of cancers are related to viral oncogenes?

Answer 83

15%

Question 84

What's an example of a virus -> cancer?

Answer 84

HPV and Cervical Cancer HPV can lead to cervical cancer by infecting cervical cells, causing precancerous changes, and, if left untreated, progressing to invasive cancer.

Question 85

What happens if a virus enters a non-permissive cell?

Answer 85

A non-permissive cell will not allow the virus to replicate & the virus will leave the cell through exocytosis or budding

Question 86

DNA viruses that can cause tumors

Answer 86

Papillomaviruses, HEPB, herepes viruses, poxviruses

Question 87

RNA viruses that can cause tumors

Answer 87

Retroviruses & Hep C

Question 88

Innate Immune Responses:

Answer 88

The first line of defense against viral infections that includes detection of viral nucleic acids, activation of Toll-Like Receptors (TLRs), RIG-I-Like Receptors (RLRs), cytokine release, Interferon (IFN) response, and activation of immune cells like macrophages, dendritic cells, and NK cells.

Question 89

Adaptive immune responses

Answer 89

The immune response that involves the production of specific antibodies by B cells and the activation of T cells (cytotoxic and helper T cells) to provide defense against viral infections.

Question 90

Interferon Response

Answer 90

When a host cell detects a viral infection, it can release signaling proteins called interferons (IFNs). These interferons serve as messengers to neighboring cells, alerting them to the presence of a viral invader. In response to interferon signaling, neighboring cells activate various antiviral defense mechanisms, including the inhibition of viral replication. NK cells are among the immune cells that respond to these IFNs by becoming activated. They can then detect and target virus-infected cells for elimination, contributing to the defense against the viral infection. In this way, NK cells and interferons work together to enhance the host's antiviral response.

Question 91

Single-stranded RNA (ssRNA) and double-stranded RNA (dsRNA)

Answer 91

Two common types of RNA found in viruses

Question 92

TLRs can detect __?

Answer 92

Both ssRNA and dsRNA in endosomes

Question 93

What is the significance of TLRs being able to detect both ssRNA and dsRNA ?

Answer 93

TLRs serve as an early warning system for the immune system. When a virus infects a cell and its genetic material (RNA) is released, TLRs within endosomes can detect the viral RNA. This early detection is vital for initiating a rapid immune response to contain the infection.

Question 94

TLRs

Answer 94

Once a TLR has detected viral RNA, it signals to the cell to produce interferon. There are three main types of interferon: alpha (IFN-α), beta (IFN-β), and gamma (IFN-γ). IFN-α and IFN-β are produced by most cells in the body, while IFN-γ is produced by T cells and natural killer cells.

Question 95

RLRs, or RIG-I-Like Receptors

Answer 95

Recognition of Viral RNA: RLRs are specialized in detecting viral RNA in the cytoplasm of infected cells. They can identify certain patterns or structures in the RNA that are typically associated with viral genomes.

Question 96

Two pathways that Interferons can trigger

Answer 96

Both result in protein synthesis being inhibited and no viral production

Question 97

Pathway 1

Answer 97

oligosynthetase -> ribonuclease -> degrades mRNA, which causes no protein synthesis and thus no virus production

Question 98

Pathway 2

Answer 98

Protein kinase -> inhibits the subunits of protein initiation factors -> which causes no protein synthesis and thus no virus production

Question 99

What are some of the most common viral diseases?

Answer 99

common cold influenza flulike syndromes gastroenteritis

Question 100

Things that can determine how severe a virus is

Answer 100

exposure/entry viral dose target tissue/tissue tropism permissiveness of cells host status (age, immunity, health) viral structure (naked vs. envelope)

Question 101

Oral & Respiratory Infections

Answer 101

Viruses can enter the body through the mouth and nose, causing infections in the oral and respiratory systems.

Question 102

Flulike & Systemic Symptoms

Answer 102

Some viral infections lead to flu-like symptoms and can affect the entire body.

Question 103

GI Infections

Answer 103

Viruses can infect the gastrointestinal (GI) tract, leading to stomach and intestinal issues.

Question 104

Exanthems (Rashes, Viral-Induced Skin Disease):

Answer 104

Certain viruses cause skin rashes or other skin-related symptoms.

Question 105

Hemorrhagic Fevers

Answer 105

Infections with certain viruses result in severe bleeding and fever.

Question 106

Arthritis

Answer 106

Some viruses can lead to joint inflammation and arthritis.

Question 107

Eye Infections:

Answer 107

Viruses can infect the eyes, causing various eye-related symptoms and issues.

Question 108

Organ & Tissue Infections

Answer 108

Viruses can infect specific organs and tissues, leading to organ-specific symptoms.

Question 109

CNS Infections

Answer 109

Viral infections can affect the central nervous system, leading to neurological symptoms.

Question 110

Hematologic Infections:

Answer 110

These infections involve the blood and can lead to blood-related symptoms.

Question 111

Sexually-Transmitted Viral Infections

Answer 111

: Some viruses are transmitted through sexual contact.

Question 112

Transfusion/Transplantation:

Answer 112

: Viral infections can be transmitted through blood transfusions or organ transplants.

Question 113

Animal Vectors:

Answer 113

Some viruses are transmitted to humans through insect or animal vectors, such as mosquitoes.

Question 114

Polio Virus

Answer 114

Polio, short for poliomyelitis, is a highly contagious viral infection caused by the poliovirus.

Question 115

First step of Polio Virus Pathogenesis

Answer 115

Entry and Initial Infection: The polio virus enters the body through the mouth, often via contaminated water or food. It primarily targets the gastrointestinal (GI) tract and multiplies in the lining of the throat and intestines.

Question 116

How does Polio virus invade the gut-associated lymphoid tissue:

Answer 116

Entry via M Cells: M cells sample and transport antigens, including viruses, from the gut lumen into the underlying lymphoid tissue. Replication in Monocytes: Once the virus has entered the gut-associated lymphoid tissue, it can encounter immune cells, including monocytes. Certain viruses can infect and replicate within monocytes or macrophages. This can lead to viral dissemination and activation of the immune response.

Question 117

How does Polio virus invade the regional lymph nodes?

Answer 117

After initial infection with the polio virus in the gastrointestinal tract, the virus can spread through the bloodstream to regional lymph nodes. In these lymph nodes, the virus may undergo further replication. The lymph nodes serve as sites where the immune system can recognize and respond to the virus, as well as sites of viral multiplication.

Question 118

Plasma Viremia of Polio

Answer 118

As the polio virus progresses through the body, it can enter the bloodstream, allowing it to be distributed to various organs and tissues. Plasma Viremia: Once the virus is in the bloodstream, it can lead to the presence of viral particles in the blood plasma. This is known as plasma viremia and indicates a systemic spread of the virus throughout the body.

Question 119

Polio & the CNS

Answer 119

In some cases, the polio virus can breach the BBB, allowing it to enter the central nervous system (CNS). This is a crucial step in the progression of the infection. Spinal Cord: Once the virus gains access to the CNS, it can specifically target and replicate within the motor neurons. Cell Destruction and Paralysis: The replication of the polio virus in these motor neurons can lead to cell destruction and damage. This damage can result in muscle weakness and paralysis, as the motor neurons are responsible for controlling muscle movement.

Question 120

Where is the polio virus shed? (orally/fecally etc?)

Answer 120

During the course of the infection, the polio virus can be shed and excreted in the feces of infected individuals. This fecal shedding is a significant means by which the virus can be transmitted to other individuals.

Question 121

Live Attenuated Vaccines:

Answer 121

These are vaccines containing weakened forms of a live virus or bacterium that can no longer cause disease in a healthy person. They can replicate in the body, closely resembling a natural infection, and typically provide long-lasting immunity.

Question 122

Killed or Inactivated Vaccines:

Answer 122

These vaccines are made from viruses or bacteria that have been completely inactivated or killed, rendering them unable to cause disease. They primarily stimulate an antibody-based immune response and often require booster shots for sustained protection.

Question 123

Subunit Vaccines:

Answer 123

Subunit vaccines contain only a piece of the virus or bacterium, such as a specific protein or component. They do not include the entire infectious organism. Subunit vaccines are generally safer but may provide shorter-lived immunity and sometimes necessitate multiple doses.

Question 124

Immune Evasion

Answer 124

Strategies employed by viruses to avoid or circumvent the host's immune system, allowing them to establish and maintain infection.

Question 125

Inhibiting IFN Response

Answer 125

Some viruses can inhibit the host's interferon (IFN) response, which is essential for antiviral defense, preventing the production of interferons or blocking their signaling pathways.

Question 126

Modification of Viral Antigens

Answer 126

Viruses can alter their surface proteins or antigens to evade recognition by the immune system, making it challenging for immune cells to target them.

Question 127

Cell-Cell Spreading (Syncytia)

Answer 127

Some viruses cause infected cells to fuse, forming multinucleated syncytia, which can hide infected cells from immune surveillance.

Question 128

Suppress Antigen Presentation

Answer 128

Viruses may interfere with the presentation of viral antigens to immune cells, hampering the activation of an effective immune response.

Question 129

Inhibition of Lymphocytes

Answer 129

Certain viruses can directly target and inhibit immune cells, such as T lymphocytes, leading to immune dysfunction.

Question 130

HIV

Answer 130

Has a high degree of immunosuppression & does it through T-Cell depletion

Question 131

Herpes & immunosupression

Answer 131

Low HSV encoded proteins can function as viroreceptors, facilitating their entry into host cells. Bare minimum for a virus

Question 132

Measles

Answer 132

Moderate immunosuppression Overproduction of cytokines This excessive release of immune signaling molecules can result in severe inflammation and tissue damage, contributing to some of the more serious complications associated with measles.

Question 133

Rubella

Answer 133

Moderate Immune tolerance associated with fetal infection. Rubella virus infection during pregnancy can result in immune tolerance in the developing fetus. This means that the fetal immune system may not mount a strong response against the virus, potentially allowing the virus to persist and cause congenital rubella syndrome (CRS).

Question 134

how can the immune system be a major contributor to disease?

Answer 134

The immune system's RESPONSE to the virus plays a significant role in causing the disease or the symptoms experienced by the infected individual.

Question 135

prodrome: Flu-Like Systemic Symptoms

Answer 135

Before the onset of specific symptoms, many viral infections can lead to a prodrome characterized by flu-like systemic symptoms. These include fever, fatigue, headache, muscle pain, and general malaise. This is caused by the immune response

Question 136

Type IV Hypersensitivity Reactions:

Answer 136

When a viral infection occurs, these T cells trigger an immune response, leading to localized inflammation and sometimes skin reactions like rashes

Question 137

Type III hypersensitivity reactions

Answer 137

Type III hypersensitivity reactions involve the formation of immune complexes composed of IgG antibodies and antigens. In the context of viral infections, these immune complexes can deposit in small blood vessels and lung alveoli, leading to inflammation and tissue damage.

Question 138

Role of CD8 in Immune Mediated viral diseases

Answer 138

While their primary function is to eliminate infected cells, in some cases, an overactive immune response involving CD8 T cells can lead to immune-mediated damage to tissues, which is a feature of certain viral diseases. in some instances, the immune response itself can contribute to the clinical manifestations of the diseases, causing symptoms and tissue damage.

Question 139

Which viruses' immune response involves CD8+ T cells?

Answer 139

Hep B & RSV & Arenavirus

Question 140

Cytokine Storm:

Answer 140

A cytokine storm is an extreme and uncontrolled release of proinflammatory cytokines, such as interferon-γ, TNF-α, IL-1, and IL-6, by the immune system. This phenomenon is typically seen in response to highly virulent viruses like bird flu (H5N1) or swine flu (H1N1), among others.