Patho Test 4

Millions of viruses

• 5000 described in detail

• NCBI viral genome database has about 15k complete sequences

  • 1000s remain to be annotated

• Think there are 320k that infect mammals alone

  • 219 known to infect humans

• 10³¹ viruses exist on earth

Human virome

over 380 trillion viruses inhabiting us

1995 Congo Ebola Outbreak

• syringes reused, no isolation procedures

• centuries of tradition

  • dying and dead cleansed by washing performed by family members

• spread to local villages

  • 254 deaths

  • 80% mortality

Reston ebolavirus

appears to be restricted to monkeys NOT humans

Human reaction to Ebola (scary)

• as the virus starts replicating in earnest, the victim’s capillaries clog with dead blood cells, causing the skin to bruise, blister, and eventually dissolve like wet paper

• By the sixth day, blood flows freely through the eyes, ears, and nose, and the sufferer starts vomiting the black sludge of his disintegrating internal tissues

• Scary bc thought it wouldnt come to USA… 2014

  • even though global deaths are low, very scary

  • Near miss in DC b4 2014

African tribes knew about outbreaks through history

• Marburg Hemorrhagic Fever (MHF)

  • 1967 in Marburg and Frankfurt Germany at vaccine facilities

  • 25 lab people working with monkeys

  • spread to 6 family members

  • 7 deaths

  • 28% mortality

• Ebola Hemorrhagic Fever (EHF)

  • 1976 dual outbreaks in Congo and Sudan

  • 550 cases

  • 88% mortaility in Congo

  • 53% mortality in Sudan

Most Ebola outbreaks are in

Central Africa

Western Awareness of Ebola 1976

• Blood of nun given to Institute of Tropical Medicine in Beligium

• Saw it under microscope, huge virus

• Mistaken for Marburg - found Ebola

Ebola virus is relentless

The virus works as a molecular shark or a terminator in that it will not stop until every cell in the body is destroyed

Symptoms of Ebola

• onset 2-21 after viral entry into body

• early noticeable symptoms, sudden onset

  • fever

  • fatigue

  • Joint and muscle pain

  • headache

  • sore throat

  • cough

• Disease progression symptoms

  • vomiting

  • diarrhea

  • rash

  • unexplained bruising

  • internal and external bleeding

    • gums

    • blood in stool

  • weight loss

Progression of Ebola

• Blood clots shut off the blood supply to various parts of the body, causing dead spots to appear in the brain, liver, kidneys, lungs, intestines, testicles, breast tissue (of men as well as women) and all through the skin

• attacks connective tissue & multiplies in collagen and turns it into mush and liquefies

• Tiny white blisters mixed with red spots (maculopapular rash) appear & spontaneous rips cause hemorrhagic blood to pour out.

• The red spots become spontaneous bruises; the skin can tear off if it is touched with any kind of pressure. Your mouth bleeds around your teeth and the salivary glands - literally every opening in the body bleeds, no matter how small.

• The brain becomes clogged with dead blood cells.

Final stages of ebola

• epiletptic convulsions: the whole-body twitches and shakes, the arms and legs thrash around, and the eyes, sometimes bloody, roll up into the head. The tremors and convulsions of the patient may smear or splatter blood around

• Disease transmission?

  • it makes the victim go into a flurry of seizures as he/she dies, spreading blood all over the place, go into aerosols thus giving the virus a chance to jump to a new host.

After death ebola

• cadaver deteriorates: the internal organs, having been dead or partially dead for days, have already begun to dissolve

• The corpse's connective tissue, skin, and organs, already peppered with dead tissue begin to liquefy, and the fluids that leak from the cadaver are saturated with Ebola-virus particles

• evert particle ready to do it again and again

Ebola morphology

• Filoviridae viral family

• unlike other viruses, resembles a thread instead of the more normally

  • Tubular virus

• “the shepherd’s rod”

• helical ssRNA genome

• Important proteins

  • Nucleoprotein (N)

  • Glycoprotein (GP)

  • Viral Proteins (VP35 and VP30)

  • Polymerase L protein.

filoviruses origin

• Outbreaks began with animal to human spillover

• Egyptian fruit bats are attributed as an established natural reservoir of Marburg virus

• Bats are also suspected to be a natural reservoir for Ebola virus

filoviruses transmission

• Direct contact with infected blood or bodily fluids (e.g. semen, vomit)

• Entry through broken skin or mucous membranes

• Contact with contaminated materials

• This means that unsafe medical care or funerary practices can result in larger outbreaks, amplifying infection rate

Zoonotic Ebola

• Monkeys have infected many doctors, scientists, and monkey handlers

• Many primate populations such as gorillas have been seriously affected in parts of Africa

• However, compared to other infectious diseases, global deaths are relatively low

  • Symptoms are so scary so human psyche effect

Ebola targets these cells

1. blood vessels and connective tissue

2. immune cells

• early targers: macrophages, monocytes, and dendritic cells

  • infection of these cells leads to viral dissemenation

3. The virus then subsequently spreads to organs such as the liver and spleen before moving on to other organs

• whole body affected

Mode of dissemnation for ebola in the body

• replication overwhelms protein synthesis of infected cells and host immune defenses with the production of 2 glycoproteins

1. GP1 which binds the virus to the endothelial cells lining the interior surface of blood vessels.

• This reduces specific integrins responsible for cell adhesion to the inter-cellular structure

As the blood vessel walls become damaged and leak, the platelets are unable to coagulate, patients succumb to hypovolemic shock

2. A secretory form called GP2 interferes with neutrophil signaling (C5) which allows the virus to evade the immune system by inhibiting early steps of neutrophil activation.

• Viral particles and cell damage resulting from budding causes the release of cytokines, which result in fever and inflammation

• cadaver's internal organs have been compared to black and red tapioca pudding

3. Immune system failure

• interferons are not being made because VP35 interferes with nearly every step in the immune process

• White blood cells are trapped inside the circulatory system because sGP limits their movement

• Macrophages and monocytes are releasing a cocktail of pro-inflammatory cytokines that destroy the vascular endothelium, but also activate the coagulation cascade.

• Lymphocytes themselves don’t become infected with the virus, but a lack of stimulation from some cells and toxic signals from others—prevent these primary immune cells from putting up a fight and producing antibodies.

2026 Flu mutated strain

• H1N1 influenza strain

• new G155E gene mutation

  • helping it partially evade existing immunity and causing early case surges

  • West Coast

  • younger children

No cure for ebola

Treatment for Ebola was limited to intensive supportive care:

• Balancing the patient's fluids and electrolytes

• Maintaining their oxygen status and blood pressure

• Treating a patient for any complicating infections

Surviving ebola?

• Patients fare better with supportive care, including oral or intravenous rehydration that can buy time for the body to fight off infection

• identified genes and other markers that seem to be predictive of survival

  • higher levels of activated T cells in their blood and had certain variants of a gene that codes for surface proteins that white blood cells use to communicate.

  • Convalescence plasma

Convalescence plasma

Plasma transfusions from survivors of the disease but need to screen for other diseases

2014 African outbreaks led to

vaccine pushes

• 2019 2 main Ebola vaccines lincensed and prequalified by WHO

  • single dose Ervebo

    • for outbreak response

  • two dose Zabdeno/Mvabea regimen

    • preventative vaccination of high risk groups

Antibody treatment for Zaire ebolavirus

1. FDA-Approved Monoclonal Antibody Treatments (For Zaire ebolavirus)

• Inmazeb:

  • A combination of three monoclonal antibodies (atoltivimab, maftivimab, and odesivimab-ebgn) approved for adult and pediatric patients

2. Ebanga:

• A single monoclonal antibody (ansuvimab-zykl) used to block the virus from entering cells

Other strains of ebola treatment

Other strains like the Bundibugyo virus or Sudan virus do not have universally licensed commercial treatments, though clinical trials evaluate experimental antivirals, antibody cocktails (such as remdesivir or MBP134) and vaccines during active outbreaks through organizations like the WHO

Flu virus morphology

• enveloped - the outer layer is a lipid membrane which is taken from the host cell in which the virus multiplies

• protein shell gives strength and rigidity to the lipid envelope

• ssRNA segmented genome

• A and B most common infect humans

  • differentiated by their serotype, based upon their surface antigens

Antigenic Shift and Antigenic Drift of the flu

May cause variations of surface proteins, increasing the spectrum of animals in which they infect and/or the virulence of the virus by rapidly overcoming the protective immunity of the cell. Also, leads to non-reaction with vaccine

• the genome is separated into 8 segments of vRNA, allowing for rapid reassortment, which furthers both antigenic shift and antigenic drift.

antigenic shift and antigenic drift contribute to

pandemics and epidemics

Protein Hemagglutin of Flu

• Hemagglutinin (denoted as H or HA)

• is a glycoprotein that attaches to sialic acid sugars on the surface of epithelial cells

  • nose throat lungs

• 18 H subtypes have been discovered so far (probably many more)

• Plays a critical role in fusion of the viral envelope, which leads to the injection of viral RNA

• The protein is also used for strain typing e.g. H1 of H1N1 of influenza

Protein Neurainidase of Flu

• (denoted as N or NA)

• 11 types identified to date (probably many more)

• enzymes that cleave glycoproteins from sialic acid on the surfaces of cells

• allows for the detachment of the newly formed virus, making it easier for the progeny virions to diffuse away from the cell once they exit

• These enzymes are also used in typing of strains (i.e. N1 H1N1)

Equine influenza

highly contagious respiratory disease of horses and other equidae. It is caused by two subtypes of the influenza A virus, which are related to, but distinct from, influenza viruses in other species

Seal influenza

Five autopsies revealed that the seals died from infectio with a type of flu known as H3N8. The report pointed out that the seal flu is very similar to a flu strain found in North American birds since 2002. But seals don't just pass the seal flu between each other

Canine influenza

H3N2 is a highly contagious upper respiratory infection that not only affect dogs, but it can also affect cats too. Fortunately, it isn't known to spread to humans. The symptoms in dogs include fever, sneezing, nasal discharge, loss of appetite and lack of energy

Swine Flu

Swine Flu. In a 2012 study, the CDC estimated more than 284,000 possible fatalities worldwide, with range from 150,000 to 575,000. In August 2010, the WHO declared the swine flu pandemic officially over.

Influenza background

• “The Flu” 10,000 virus particles can fit on a period at the end of a sentence!

• Influenza was discovered not by human illness, but rather studies on animal diseases

  • observed in pigs by a vet

• first human strain isolated in 1933 england

• 1940 Flu B was isolated

• grown in chicken embryos, used to be ferrets and dogs

  • allowed for large growth and production for vaccine

  • 
    

Flu deaths

1 billion global cases

• 290k to 650k deaths per year

• 36k deaths avg in USA

spanish flu

• higher morbdity and mortality for young and middle aged

• cytokine storm

• first wave in pigs

• then troops in frnace

• half of WW1 soldiers died from flu

Type A Flu reservoir

animal reservoir that consists of wild birds, mainly aquatic, although it has been noted that it has potential to cross species barriers – to poultry

• Humans and pigs are also known to carry and transmit various strains of the virus.

Type B Flu reservoir

Almost exclusively infects humans, seals are the only other known animal susceptible

Influenza symptoms

Flu life cycle

• In humans, the virus’ replication is restricted to the respiratory tract

  • These versions can replicate in pigs as well, but not very well in birds.

    • Birds have changed this

    • the virus replicates in the epithelial cells of the GI tract and are excreted into the environment.

    • Furthermore, wild waterfowl migrate, thus exposing domestic animals to the virus over great areas.

    • The pig is a permissive host for both human and bird strains – which is thought of a “mixing vessel” for genetic exchange between the human and avian strains thus, creating new strains (antigenic shift)

Antigenic drift flu

The pig is a permissive host for both human and bird strains – which is thought of a “mixing vessel” for genetic exchange between the human and avian strains thus, creating new strains (antigenic shift)

Virulence factors influenza

• Influenza can evolve rapidly

• Antigenic shift

• Potentially allows for more virulent strains and broader range of reservoirs

  • Especially a concern for Avian influenza H5N1

  • In Asia people and animals often in very close proximity and thus often a common source of new strains.

Antigenic shift

is the process of two different strains combining to form a new subtype

Antigenic drift

is the natural mutation of strains

Immune responses to flu

• Following infection, rapid humoral response and antibodies are produced to viral hemagglutinin (H)

  • blocks virus binding to the target cell

  • response peaks after several days and lasts for about 6 months

  • prevents reinfection by the same strain

  • Response differs from person to person

    • Amount of viral load, prior exposure so antibodies can be more rapidly produced

How flu goes into body

• Influenza virus causes an infection in the respiratory tract, or nose, throat and lungs.

• It then travels down the respiratory tract and binds to epithelial cells lining the lung airways via specific molecules on the cell surface.

• Cytokines initiate T lymphocytes, specifically recognize influenza virus proteins, they then begin to proliferate in the lymph nodes around the lungs and throat.

• This causes swelling and pain in these lymph nodees

• After a few days, these T cells move to the lungs and begin to kill the virus-infected cells. This process creates a great deal of lung damage similar to bronchitis, which can worsen existing lung disease and make breathing difficult.

• In addition, the buildup of mucus in the lungs, as a result of this immune response to infection, induces coughing as a reflex to try to clear the airways. Normally, this damage triggered by arrival of T cells in the lungs is reversible in a healthy person, but when it advances can lead to death.

Why flu hurts head so much

cytokines and chemokines produced by the innate immune cells in the lungs become systemic

• interleukin-1 is important for developing the killer T cell response against the virus, but it also affects the part of the brain in the hypothalamus that regulates body temperature, resulting in fever and headaches.

Why flu hurts muscles so much - muscle atrophy

• influenza infection leads to an increase in the expression of muscle-degrading genes and a decrease in expression of muscle-building genes in skeletal muscles in the legs

Tumor Necrosis Factor alpha flu

causing fever and appetite loss, fatigue and weakness during influenza and other types of infection

Treatment of the flu

Unless infected persons have underlying/pre-existing health conditions, normal treatment of an infected person as follows

• rest

• liquids

• anti fevers

• abx for secondary bac infections, but not encouraged

Neuraminidase inhibitors

• target neuraminidase, which prevents the release (budding) and progeny of newly formed viruses from the cell

• Do not kill or change immune response

• affective against all strains of influenza A, and are approved for prophylaxis or prevention of the infection

• must be taken within 48 hrs and preferably within 36, of initial symptoms

• tablet or inhaler

• Tamiflu

Amantadine and Rimantadine

• Prevent protein coat being stripped away releasing nucleic acid

• target the highly conserved M2 protein

  • ion channel

  • important component in uncoating of the virus

• by blocking this channel, hydrogen ions are unable to enter the vacuole containing the virus and the protein coat is not removed

• TYPE A, not specific for type B (no M2 in B)

• cheaper and easier to make than neuraminidase inhibitors

Tamiflu and doomsday

• prevention of the scariness of the avian flu (H5N1)

• personal stockpiles, but this is debated

  • logistics, clincinal, and community tradeoffs

Prevention of the flu

• annual vaccines

• new versions twice a year

• trivalent - 3 strains

• strains exhibit antigenic shift and drift - need new vaccines yearly

• Fall administration

Trivalent Inactivated Vaccine (TIV)

• Egg-based flu vaccine

• Cell-based flu vaccine

• Recombinant flu vaccine

Egg-Based Flu Vaccines