MICB Final Exam: Lecture 23 Viral Disease

What are the categories of Viral Diseases?

Airborne

Arthropod-Borne

Direct Contact

Food and Water

Zoonotic

(broken down by major mode of transmission)

What are the types of vaccines?

Inactivated (killed)

Attenuated (live but avirulent)

How do we make inactivated vaccines? What rxn does it have in the body? Drawbacks? Ex?

Treat viral pathogens with chemicals or heat

Rxn: Induce humoral immune response

Drawback: Requires booster

Ex: Rabies, Flu shot

How do we make attenuated vaccines? What rxn does it have in the body? Drawbacks? Ex?

Treat pathogens by inactivating specific genes (can reproduce but weakened)

-Rxn: Humoral (produce antibody B Cells) and T-cell mediated immune response

-Drawback: May Revert

-Ex: Chickenpox, MMR, Flu (intranasal)

How are vaccines made?

Eggs are incoulated with the virus

Herd Immunity

Protection of unvaccinated people in a population where most people are vaccinated due to lessened risk of disease transmission

What % population is needed to achieve herd immunity?

Depends on pathogen

-Highly contagious diseases like Pertussis (whooping cough) and Meases require 80-90%

Chicken Pox (Viral Category, Virus Name, Virus Family, Mode for Spread, Symptoms)

Catagory: Airborne

Cause: Varicella-Zoster Virus

Family: Herpesviridae (Envalope, Iscohedreal Capsule)

Spread: Inhalation or conjunctiva of eye (eye rubbing)

-Spread via blood, neuronal

Symptoms: ~10 days infection of skins leads to vesicular rash

Treatment and Prevention of Chicken Pox

Treatment: No specific med, use regular OTC for inflammatory

Prevention: Attenuated (live) Vaccine

Who are protected and vulnerable to shingles?

Protected: Individuals who recover from chicken pox

Vulnerable: Immunocompromised patients can reactive virus, leading to shingles

Shingles (Zoster) Latency

Viral DNA in dormant state in nuclei of nerves, sensory neurons

What happens in the primary and recurrence infection of chicken pox/shingles?

Primary: Chicken pox virus migrate up sensory nerve to spinal cord and dorsal root ganglion holds latent viral DNA

Recurrence: Activation of latent viral DNA due to environmental stress in dorsal root ganglion of spinal cord.

-Viruses migrate down sensory nerve

Shingles Vaccines

Zostavax: Live Attenuated

Shingrix: Viral Glycoprotein of Virus

Flu (Viral Category, Virus Name, Virus Family)

Category: Airborne

Cause: Influenze

Family: Orthomyxoviridae

Replication Cycle of the Flu

Attachment: Hemagglutinin

Entry: Endocytosis

Release Via Budding: Neuraminidase

What are the structural features of the Flu?

-Spike Proteins on envelope

-Envelope from host cell

-Segmented DNA genome

What must the flu virus bring in to read its mRNA? Why?

Segment genome needs DNA replicase

-Converts negative ssRNA to positive so it can be used as mRNA

Antigenic Drift (what, why, causes)

What: Minor mutations in viral genes in single strand

Why: Viral RNA replicase is error prone

Causes: An epidemic typically in a localized area

Ex: The Flu

Epidemic

Sudden increase in disease

Antigenic Shift

What: Major mutations in viral genome

Causes: New strains of disease, Pandemics

Pandemic:

Increase in disease in large, geographically widespread pop.

How does antigenic shifts lead to new strains of diseases?

Differential strains (animals or humans) infect cell

-Genome reassort leading to new strains

-New strain may spread to humans who have no immunity

-Ex: Spanish flu

Covid-19 (Viral Category, Virus Name, Virus Family, Mode for Spread)

Category: Airborne

Cause: Corona Virus strain SARS-CoV-2

Family: Coronaviridae

Spread: Respiratory Droplets

Corona virus structure

Enveloped

Linear +ssRNA

Uses host receptors to translate mRNA

How does COVID replicate its genome?

Own viral RNA replicase to replicate

How do we test for COVID?

Antigen Tests: labeled antibody to detect nucleocapsid (N) protein

RT-PCR Serology: Antibody test using reverse transcriptase to convert RNA to DNA for PCR

Vaccines COVID-19

Moderna and Pfizer

mRNA vaccines

What are the components of the Covid vaccine?

mRNA encoding SARS-CoV-2 spike protein

-Too unstable alone need it to be enclosed in a lipid nanoparticle

-Our cells translate mRNA to antigen in form of spike protein

Measles, Mumps, Rubella (Viral Category, Virus Type)

Category: Airborne

Cause: RNA Viruses

Vaccine for Measles, Mumps, and Rubella

MMR attenuated vaccine

Measles, Mumps, and Rubella symptoms

Measles: Rubeola; physically feel bumps at virus site

Mumps: Salivary gland swelling

Rubella: German Measles, immune response of smooth rash patches

Arthropod-Borne Diseases (Cause, Viral Family, Examples)

Cause: Mosquito Vector

Family: Flavivirdae

Examples: Yellow Fever, West Nile Fever, Dengue Fever, Zika Virus Disease

What major symptom is caused by the zika virus during pregnancy?

Microcephaly

Arthropod-Borne Diseases Structure?

Enveloped, icosaheral

+ssRNA

Common Cold (Viral Category, Virus Name)

Viral Catagory: Direct Contact

Virus: Rhinovirus (major), coronaviruses, adenovirsus

Rhinovirus Structure

naked icosahedral (no envelope)

+ssRNA

(over 100 serotypes)

Mononucleosis (Viral Category, Virus Name, Virus Family, Mode for Spread)

Category: Direct Contact

Virus: Epstein-Barr Virus

Family: Herpesviridae

Spread: Saliva

Mono structure

Envelope with spike proteins

Infection process of mono

1. Enters and replicates in throat epithelial cells

2. Infects B cells (can become latent)

3. Engage with MHC II Receptor to attach to host cell

Downey Cells

Enlarged T cells responding to infected B cells with mono

Other than mono, what other disease can the Epstein-Barr Virus cause?

Associated with Burkitts (B cell) lymphoma

What is the most common sexually transmitted disease in the US?

Genital warts

Warts (Viral Category, Virus Name)

Category: Direct Contact

Virus: Human Papillomaviruses (HPV)

Warts virus structure

Naked

DNA

Infection process of Warts

HPV protein E6 targets human p53 tumor suppressor protein which controls cell cycle and programmed cell death

Vaccine against HPV

Gardasil

-Virus like particle (VLP) vaccine

-Receive protein structure capsid but no genome (non-infectious)

Besides warts, what other disease is associated with HPV?

Oncogenic, cervical cancer

Ebola Hemorrhagic Fever (Viral Category, Virus Name, Virus Family, Mode for Spread)

Category: Direct Contact

Virus: Ebola Virus

Family: Filoviridae

Spread: Direct contact with blood or body fluids of infected symptomatic person

Ebola Virus Structure

Enveloped

RNA

Filamentous

Infection process of Ebola Virus

Viral proteins block interferon (antiviral cytokine)

Clot blood

What other viral category can ebola fit into?

Zoonotic: Fruit bats, primates

What is gastroenteritis?

inflammation of the stomach and intestines

What viruses cause gastroenteritis? Viral Category? Viral Structure? How is it spread?

Category: Food and Water Borne

Virus: Rotavirus, Norovirus

Structure: Naked, RNA viruses

Spread: Fecal-oral transmission, also person to person

Polio (Viral Category, Virus Name, Viral Structure, Spread)

Category: Food and Water Borne

Virus: Poliovirus

Structure: Enterovirus (intestinal tract), RNA genome

Spread: Stable in food, water (ingested)

Infection process of Polio

-Multiplies in throat and intestinal cells

-Targets motor nerve cells in spinal cord causing paralysis

(polio also known as infantile paralysis)

Polio Vaccines

Salk (killed) (recommended one b/c no chance of becoming viral)

Sabin (live, oral)

"iron lungs"

large metal tanks that change air pressure to help patients breath due to paralysis from polio

Estimate of infectious diseases that originate with animals

75%

What factors has caused the transmission of diseases from animals to humans?

Habitat changes altering ecosystems

-Deforestation

-Farming

-Climate changes

-Travel and Trade add to the quicker spread

Rabies (Viral Category, Virus Name, Viral Structure, Spread)

Catagory: Zoonotic

Virus: Rabis Virus

Structure: Bullet shaped, enveloped, RNA

Infection Process of Rabies

1. Multiples in salivary glands of animals

2. Viral replication in muscle and neuronal cells (Tropism)

3. Spread via CNS microtubule tracks using dynein and kinesin motor proteins

4. Spread to brain leading to paralysis

How long is the incubation period for rabies? What does this allow for?

2-16 week incubation period

-Slow disease allows for post-exposure vaccination

What kind of vaccine is the rabies vaccine?

Killed vaccine