Anthrax: Bacillus anthracis

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Anthrax Bacillus anthracis

• Kimberly Covert
• BIO 488
• 3/14/06

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Basics of Anthrax

• Bacillus anthracis causes anthrax
• Became a growing concern after 5 people died in
  2001 through the bioterrorist attack delivered
  through the US Postal Service
• Found commonly as an environmental pathogen
• Can be weaponized but is expensive and dangerous

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What does it look like?
http//www3.niaid.nih.gov/biodefense/Public/Images
.htm
Electron Micrograph of a monkey RBC and the
rod-shaped B. anthracis
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The Mighty Spore-former

• B. anthracis is a spore-forming bacteria and has
  a polyglutamic acid capsule
• It commonly causes infections in grazing species
  of vertebrates such as cows, goats, and sheep
• Can be transmitted to humans, although rare,
  through ingestion of spores, eating contaminated
  meat, or through a bioterrorist attack

http//www.arches.uga.edu/anniej/anthrax20spores
.jpg
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On the Plus Side

• Anthrax cannot be spread from human to human
• Cases in the Unites States are rare about 2
  cases a year are reported
• Is mostly a disease found in developing countries
• Laboratory growth of B. anthracis is difficult
  and most experts do not forsee it being used as a
  large scale biochemical weapon

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The Types of Infection

• There are three types of infections
• Cutaneous
• Inhalation
• Gastrointestinal

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Cutaneous Infections

• Most common making up 95 of infections
• Bacterium enters the body through a break in the
  skin
• Transmitted though the handling of animal
  products
• Initial infection resembles a bug bite but will
  develop into a painless ulcer
• May also cause swelling of local lymph nodes

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Cutaneous Anthrax

• In cases that go untreated the mortality
  rate is about 20
• Death is rare with the use of antibiotics

http//a248.e.akamai.net/7/248/430/20031008051150/
www.merck.com/mrkshared/mmanual/plates/p157_1.gif
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Inhalation Anthrax

• Transmission is through the inhalation of anthrax
  spores
• This is the type that was used in the 2001
  bioterrorist attack
• Manifests as a common cold and progresses to
  severe breathing problems and shock

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Inhalation Anthrax
Inhalation anthrax is usually fatal This picture
shows the lung tissue of a patient infected with
inhalation anthrax The red arrow points to the
infective spores
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Gastrointestinal Anthrax

• Transmitted through eating of undercooked
  contaminated meat or animal products
• Results in acute inflammation of the gut
• Causes nausea, vomiting, and diarrhea which
  become more severe with time

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Gastrointestinal Anthrax
The mortality rate of patients infected with
Gastrointestinal Anthrax is anywhere from
25-60 This is a picture of the intestines of a
patient that died from Gastrointestinal
Anthrax There is severe edema and hemorrhage
http//www.cdc.gov/ncidod/EID/vol9no5/images/02-05
37_1b.jpg
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The Immune Response

• B. anthracis is an extra-cellular pathogen
• The polyglutamic acid capsule is anti-phagocytic
• Typical anti-body players
• Monoclonal Ab response
• IgG
• IgA (nasal entry for inhalation anthrax)
• IgM

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The Immune Response

• Systemic and mucosal anti-toxin responses are
  typical
• There are high levels of IgG and IgM in the serum
• There are high levels of IgA in the secretions of
  the upper and lower respiratory tracts

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The Immune Response

• The anthrax toxin also induces the release of
  inflammatory cytokines
• IL-1ß
• IL-6
• IL-6 directs a Th2 response promoting B-cell
  proliferation
• IL-1ß activates macrophages and contributes to
  inflammation

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Immune Evasion

• Two of the toxin components edema factor and
  lethal factor can suppress the immune system
• The inhibit
• proliferation of T lymphocytes
• the release of inflammatory cytokines
• the activation of macrophages and dendritic cells
  
• Inhibition is mediated through blocking kinase
  signaling pathways necessary for the activation
  of the cells

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Detection of Anthrax

• Anthrax spores are not able to be seen by the
  naked
• They have no distinct odor or taste
• However in weaponized form, they must be
  suspended in a powder
• Most of the signs and symptoms are flu-like but
  there is no runny nose with an anthrax infection

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Testing for Anthrax Exposure

• There are no definitive testing methods to
  determine if a person has contracted anthrax
• Nasal swabs and environmental testing are done to
  determine exposure but not to determine treatment
• No every exposed person will contract a disease
• Signs and symptoms are what determines treatment

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Laboratory Identification

• Staining of the capsule with methylene blue
• Non-fastidious
• Non-hemolytic on horse blood agar whereas many
  other species of the Bacillus genus are hemolytic

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The Toxin

• The lethal affects of a B. anthracis infection
  are mediated by a toxin
• The toxin has 3 parts
• A lethal factor (LF)
• An edema factor (EF)
• A protective antigen (PA)
• PA transports LF and EF to the cytosol of cells
  where they do their damage
• The protective antigen is used to induce immunity

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The Vaccine

• The vaccine for anthrax is a toxoid vaccine
• The Protective Antigen (PA) is the toxoid
• After injection, immunity to the PA is attained
• Since PA is disabled, the anthrax toxin cannot be
  transported into the cell to do damage
• The vaccine is administered at 0, 2, and 4 weeks.
  Then again at 6, 12, and 18 months with annual
  boosters following.

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Immunizations

• The vaccine is not generally made available to
  the public
• Only those persons who are at a high risk of
  exposure should be vaccinated
• Antibiotics are sufficient post-exposure in most
  cases

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Who is at risk?

• Military personnel
• Laboratory workers who come into contact with the
  organism
• Those who work with imported animal furs and
  hides
• Anyone who handles animal products that are at a
  high potential of contamination

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Treatments

• There are several prescription drugs prescribed
  for anthrax infections
• For inhalation and gastrointestinal anthrax and
  for severe cases of cutaneous anthrax multiple
  antibiotics are taken
• The main drugs are
• Ciprofloxacin (main)
• Doxycycline (main)
• Penicillin
• Erythromycin
• Chloramphenicol

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Doxycycline

• Is part of the tetracycline class of antibiotics
• Inhibits protein synthesis
• Inhibits the normal flora
• Common side effects include upset stomach,
  vomiting, and diarrhea
• Should not be take by children or pregnant women
  because it suppresses bone growth

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Ciprofloxacin

• Belongs to the family of Quinolone antibiotics
• Inhibits nucleic acid synthesis
• Side effects include, nausea, vomiting, diarrhea,
  dizziness, and headache
• Are not recommended for children and pregnant
  women because it suppressed the growth of
  catilage

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Should we stock pile?

• Most experts agree that the risk of a large scale
  bio-terrorist attack is low and stockpiling of
  antibiotics is unnecessary
• A stockpile may be created that will be used
  against numerous bioterrorist agents including
  anthrax
• If a stockpile were to be created, doxycycline is
  recommended over cipro because it is less
  expensive and there is less immunity in B.
  anthracis and other bioterrorist agents

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More Research on the Toxin

• The 3D crystal structure of the PA and one of the
  binding sites on human cells CMG2 bound together
  has recently been determined
• This discover give scientists more of an idea of
  how the two interact and how to shut down the
  interaction
• Another possible outcome of the discovery is the
  using an altered anthrax toxin to attack tumor
  cells

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Tumor Attack

• Researchers believe that the CMG2 receptor is
  very similar to the other receptor on human
  cells, TEM8
• TEM8 is usually found in the cells lining the
  blood vessels of tumors
• If an altered toxin with an affinity only for
  TEM8 could be produced, it would be selectively
  toxic for the tumor cells and have no effects on
  normal cells
• In effect, the toxin would be able to kill the
  tumor

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Whats the big deal?

• Anthrax and bioterrorism are part of a bigger
  controversial issue
• Many people seem to be highly concerned with
  bioterrorism
• The government has restricted access to many
  dangerous pathogens and research has become far
  more restricted

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The Big Deal

• The greatest concern comes from the publishing of
  techniques that could potentially aid terrorists
  in mass producing toxic biological agents
• The paper published on the recreation of the 1918
  strain of influenza raised many ethical questions
  about who should be allowed to reproduce
  dangerous pathogens and if the methods should be
  open the public

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The Big Deal

• The previous terrorist attacks were not exacted
  on a mass scale and not well thought out
• The biggest question remains, do terrorist groups
  have the funding and the personnel to carry out a
  large scale attack?
• Are we aiding them in learning how to created and
  distribute a biochemical weapon?

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References

• Websites
• The Centers for Disease Control
• www.cdc.gov
• The New England Journal of Medicine
• www.nejm.org
• The National Institutes of Health
• www.nih.gov

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References

• Journals
• Brouillard, J.E. et al. 2006. Antibiotic
  selection and resistance issues with
  fluoroquinolones and doxycycline against
  bioterrorist agents. Pharmacotherapy. 133-14.
• Comer, J.E. et al. 2005. Direct inhibition of
  T-lymphocyte activation by anthrax toxins in
  vivo. Infection and Immunity. 73128275-81.
• Hanson, J.F. et al. Neutralizing antibodies and
  persistence of immunity following anthrax
  vaccination. Clinical Vaccine Immunology.
  132208-213.
• McConnell, M.J. et al. Cytokine response and
  survival of mice immunized with an adenovirus
  expressing Bacillus anthracis protective antigen
  domain 4. Infection and Immunity. 7421009-15.

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References

• Petro, J.B., Relman, D.A. 2003. Understanding
  threats to scientific openness. Science.
  3021898-1898.
• Pittman, P.R. et al. 2006. Patterns of antibody
  response in humans to the anthrax vaccine
  absorbed (AVA) primary (six-dose) series.
  Vaccine. Feb 9 (Epub ahead of print).
• Santelli, E. et al. 2004. Crystal structure of a
  complex between anthrax toxin and its host cell
  receptor. Nature. 4307002905-8.
• Sloat, B.R., Cui, Z. 2006. Strong Mucosal and
  Systemic Immunities Induced by Nasal
  Immunization with Anthrax Protective Antigen
  Protein Incorporated in Liposome- Protamine-DNA
  Particles. Pharmaceutical Research. 232262-9.
• Xu, J.J. et al. 2005. Toxin-neutralizing
  monoclonal antibodies to the different domains
  of anthrax protective antigen. Wei Sheng Wu Xue
  Bao. 456947-51.