Emerging Viral Pathogens

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Emerging Viral Pathogens
The Nipah Virus Experience
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• 9/98
• First cluster of patients
• with acute febrile encephalitis.
• Outbreak preceded by occurrence
• of respiratory illness and
• encephalitis in pigs
• Initial detection of JE-specific IgM
• led to suspicion of Japanese
• encephalitisvirus as causal agent

• 2/99
• Disease spread south to Nipah.
• 3/99
• Cluster of 11 human cases of
• respiratory and encephalitic illness
• in abbatoir workers in Singapore,
• but only in those who handled pigs from outbreak
• regions in Malaysia

Final Toll 265 human cases of acute
encephalitis, 105 deaths (40 mortality
rate) Culling of gt 1 million pigs
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Nipah Virus

• Novel paramyxovirus
• Negative sense, non-segmented RNA virus
• Natural host are fruit bats
• Bats urinate on pigs, pigs urinate on humans
• Virus can be isolated from urine of
  wild-free-roaming fruit bats,
• serological evidence of Nipah virus infection in
  many animal species

• Isolation of Emerging Viruses
• Vero Cells
• African Green Monkey Kidney Fibroblast Cells
• Especially susceptible to the cytopathic effect
  of many viruses
• Spontaneous gene deletions leading to lack of
  interferon response make cells more permissive
  for virus growth

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Nipah Virus Epidemiological features

• Mortality in pigs is only 5 but transmission is
  100
• Mortality in humans is 40, but no reported case
  of nosocomial transmission (human to human)
  transmission in healthcare workers) in 1st
  outbreak
• Strong evidence of human-to-human transmission in
  Bangladesh outbreaks (2004) mortality rate is up
  to 70
• Transmission is attributed to direct contact with
  excretions and secretions (urine, saliva,
  pharyngeal and lung secretions)
• Mechanical transmission to dogs and cats(?)

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Order
Mononegavirales
Family
Filoviridae
Paramyxoviridae
Bornaviridae
Rhabdoviridae
Sub-family
Paramyxovirinae
Pneumovirinae
Genus
Pneumovirus
Metapneumovirus
Respirovius
Morbillivirus
Henipahvirus
Rublavirus
Species
(Newcastle disease virus)
(Measles)
(Nipah virus) (Hendra virus)
(Mumps)
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Nipah Virus Genome
Intergenic region
3 and 5 UTR
3 Leader
5 Trailer
1.6 kb
2.2 kb
6.8 kb
18 kb
Multiple open reading frames
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Bioterrorism Concerns

• Extreme pathogenicity (40) latest outbreak in
  Bangladesh (April, 2004) has mortality rates up
  to 74 (similar to smallpox-30 and Ebola-40-90)
• 3-7 experience late or relapsed encephalitis
  increased community exposure
• No effective anti-virals, limited diagnostic
  capability
• Paramyxoviruses can be grown to high titers in
  vitro (1011 IU/ml) without concentration
• Aerosolization of other paramyxoviruses has been
  demonstrated
• Symptoms take a week or two to develop during
  which time, asymptomatic carriers can be
  infectious
• Prodromes of fever, headaches, myalgia (muscle
  ache), dizziness, areflexia, hypotonia etc. are
  relatively non-specific and not as dramatic as
  those caused by viral hemorraghic fevers (e.g.
  Ebola)

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Economic Bioterrorism

• NiV outbreak in Malaysia (1999)
• 265 affected individuals
• gt 1 million pigs were culled (military operation)
• economic losses totaled far more than their
  export value of US100 million
• In U.S.A.
• Production value of hogs/pigs in 2002, US8.6
  billion
• Farms in just 3 states (Iowa, Minnesota, North
  Carolina) accounts for 50 of value (gt4 billion)
• If Nipah-like agents released in any one of those
  States, loss of production alone could cost more
  than 1 billion
• Needed
• Effective vaccine compatible with goals of
  efficient animal husbandry
• Vaccine that can protect animals and handlers
• Better understanding of pathogenesis of disease

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Classsical herringbone morphology of
paramyxoviral nucleocapsid
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Virus Emergence
(El Nino)
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Nipah Virus (BSL-4 )Category C Priority Pathogen

• 40-74 mortality from fatal encephalitis
• Pathognomonic features Endothelia syncytia
  formation
• Mediated by envelope glycoproteins
• (F and G)

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NiV also infects
Smooth Muscle Cells (surrounding small arteries)
Neurons
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Fusion of ectodomain of NiV-Gopt allows for
immunoadhesin that binds to NiV receptor
Fusion
Fc-NiV-G blocks fusion mediated by NiV FG
Permissive
Permissive
Permissive
Non-Permissive
ectodomain
huIgG1-Fc
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Fc-NiV-G can IP cognate NiV receptor

• Biotinylate cell surface proteins
• Pre-clear with Fc-only coated Protein-G Dynal
  beads
• IP pre-cleared supernatant with Fc-only construct
  or Fc-NiV-G
• Blot IPed lysate with Streptavidin-HRP

kDa
64
48
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Receptor identity must explain NiV tropism

• Receptor is expressed on endothelial cells and
  neurons and smooth muscle cells surrounding small
  arteries
• (contrast and compare with CCR5 on macrophages
  and CXCR4 on T-cell lines)

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Other exotic emerging viruses (hemorrhagic
fevers)
All RNA viruses