ReoViruses Characteristics

1
ReoViruses - Characteristics

• non-enveloped, double stranded RNA, segmented
• double layered capsid, icosahedral
• outer capsid consists of mostly structural
  proteins
• this capsid in removed by proteolytic enzymes
  within the GI tract
• thus forming intermediate/infectious subviral
  particles
• inner capsid binds the enzymes required for
  transcription and replication
• capping enzymes
• RNA dependent RNA polymerase
• Reo Respiratory, Enteric, Orphan
• for many years there was not human diseases
  associated with these viruses
• now viruses have been associated with UR T
  infections and GI infections
• very resistant to environment and
  gastrointestinal conditions
• remain active within the host and outside of the
  host
• of the three orders of Reoviruses only the
  Rotaviruses cause significant human diseases most
  in the form of acute gastroenteritis

2
ReoViruses - Characteristics

• non-enveloped, double stranded RNA, segmented
• double layered capsid, icosahedral
• outer capsid consists of mostly structural
  proteins
• this capsid in removed by proteolytic enzymes
  within the GI tract
• thus forming intermediate/infectious subviral
  particles
• inner capsid binds the enzymes required for
  transcription and replication
• capping enzymes
• RNA dependent RNA polymerase
• Reo Respiratory, Enteric, Orphan
• for many years there was not human diseases
  associated with these viruses
• now viruses have been associated with UR T
  infections and GI infections
• very resistant to environment and
  gastrointestinal conditions
• remain active within the host and outside of the
  host
• of the three orders of Reoviruses only the
  Rotaviruses cause significant human diseases most
  in the form of acute gastroenteritis

3
Rotavirus - Cycle

• Adsorption
• Intestinal protease cleave and remove portions of
  the outer capsid
• this creates an infectious subviral particle
  with an exposed VP4 that binds the virus to
  sialic acid receptors on intestinal epithelial
  cells
• VP4 is antigenic
• Penetration
• the ISVP penetrates the cells directly via the
  fusion action of VP4
• the remainder of the outer capsid is removed
  during penetration
• the inner capsid/nucleic acid is released into
  the cytoplasm
• virus transcription and replication occur via the
  nucleoprotein core

4
Rotavirus - Cycle

• Transcription and Replication
• double stranded RNA strands(10 - 12) are
  transcribed within the core producing a
  m-RNA(from the negative sense template) which
  leaves the core and associates with the
  ribosomes setting the stage for early and late
  proteins
• viral glycoproteins are incorporated into the
  membrane of the ER
• within the core, the positive sense RNA strands
  serve as templates for the negative sense
  strands
• Assembly
• the double stranded RNA replicas are released
  from the core and associate with late structural
  proteins giving nucleocapsids
• these nucleocapsid bud through the ER membrane
  thus acquiring outer capsid and a temporary
  membrane which is cleaved within the ER.
• Release
• Since early proteins shut down the cellular
  macromolecular synthesis, the cell dies and
  lysis thus releasing the viruses

5
RotaVirus Clinical Disease

• Gastroenteritis mostly in infants and children
• diarrhea, vomiting, fever, dehydration
• no fecal leucocytes or blood
• follows a 48 hour incubation period
• Due to gastrointestinal mucosal cell death
• Due to adenylate cyclase activation by viral
  products

6
RotaVirus - Diagnosis

• symptoms cannot be distinguished from other viral
  diarrheas
• laboratory
• antigen detection large quantities of rotavirus
  particles are present with the feces and can
  easily be found via antigen detection methods
• EIA
• Latex agglutination
• Electron microscopy
• serology
• since most people have antibody against
  rotavirus, this is not always diagnostic but a
  detectable four fold increase in serum antibody
  is diagnostic

7
RotaVirus - Epidemiology

• Reservoir infected humans symptomatic and
  asymptomatic
• Sources fomites in developed countries i.e.US,
  etc
• also contaminated water in under developed
  countries
• mode of transmission
• person-to-person, indirect, fecal-oral,
  food-water, fomites
• statistics
• rotaviruses account for 50 of all cases of
  diarrhea in children requiring hospitalization
• 70,00 cases in the U.S. annually
• gt 1 million cases worldwide annually

8
RotaVirus - Control

• Sanitation
• Sewage Disposal
• Water Treatment
• Fomite Disinfection
• Immunization
• Active Attenuated Vaccine
• RotaTeq pentavalent five serotypes

9
Reoviruses - ColtiVirus

• Colorado Tick Fever
• Clinical Disease
• sudden onset of fever, chill, headache,
  photophobia, myalgia, arthralgia, and lethargy
  acute disease many mild or subclincal infections
• accompanied by biphasic fever, conjunctivitis,
  lymphadenopathy, hepatospenomegaly, and
  maculopapular rash
• must be distinguished from Rocky Mountain Spotted
  Fever
• Pathogenesis
• CTF virus infected the erythroid precusor cells,
  which mature into RBC that are released into the
  circuclation the virus is protected from immune
  clearance within the cells (viremia) for weeks or
  months
• the infected RBCs seed the vascular endothelial
  and smooth muscle cells which often results in
  hemorrhage

10
ReoViruses - ColtiVirus

• Diagnosis
• detection of viral antigens on the surface of
  erythrocytes with immunofluorence
• fourfold increase in IgM for 45 days following
  infection
• Epidemiology Many mammalian reservoirs through
  the western U.S. serve to infect wood tick
  vectors to humans

11
Rhabdoviruses - Characteristics

• bullet shaped, enveloped, virions containing a
  helical nucleocapsid
• envelope contains a glycoprotein spike composed
  of G protein
• G protein in the viral attachment protein
  (VAP)
• G protein is antigenic
• nucleocapsid contains
• one single stranded negative sense RNA
• L and NS proteins RNA dependent RNA polymerase
• N protein major caspid structural protein
  which protect the RNA
• M(matrix) protein between the envelope and the
  capsid
• Lyssavirus is the major pathogen in the family
• etiological agent of rabies
• virus replication occurs in the cytoplasm

12
Rhabdoviruses Viral Cycle

• Adsorption
• G protein attaches virus to the host cell
• virus is primarily neurotrophic but also
  replicates in muscle cells
• Penetration
• virus enter the host cell by endocytosis
• viral envelope then fuses with the endosomal
  membrane via acidification
• nucleoprotein is released into the cytoplasm
• Replication
• transcription of the viral RNA occurs through the
  action of viral RNA dependent RNA polymerase
• five m-RNAs are transcribed each translated
  into a different protein
• the polymerase also produces the positive sense
  RNA template required for the replication of new
  negative sense RNA strands
• the G protein is process by the Golgi and
  delivered to the cell membrane
• Matrix protein is also bound to the membrane

13
RhabdoViruses Viral Cycle

• Assembly
• replicas of the genome associate with the
  N(structural) and L/NS (polymerase) to form the
  nucleocapsid
• nucleoprotein bind to the Matrix protein at the
  cell membrane this caused condensation and
  coiling of the particle
• Release
• Virus buds through the cell membrane and acquires
  its envelope

14
Rhadoviruses - Pathogenesis

• most cells infected with rhabdoviruses exhibit
  cell death and lysis
• the major exception to this is rabies virus
  which causes little discernible cell damage
• virus has affinity for nicotinic acetylcholine
  receptors on nerve cells
• virus also multiples in muscles cells at
  inoculation site
• virus remains at inoculation site for several
  days to weeks
• virus reaches the CNS by retrograde axoplasmic
  transport to the dorsal root ganglia and the
  spinal cord virus moves from the spinal cord to
  the brain

15
LyssaVirus Clinical Disease

• Rabies - neurological disease manifested by
  hydrophobia, generalized seizures,
  disorientation, and hallucinations accompanied by
  various degrees of paralysis these symptoms lead
  to coma, respiratory paralysis, and death (
  disease is 100 fatal in humans and animals)
• long incubation period ( 60 - 365 day) avg about
  80 days
• prodromal period consist of fever, malaise,
  headache, paresthesia, gastrointestinal upset,
  fatigue, and anorexia
• the disease itself is an Encephalitis accompanied
  by neuron degeneration
• symptoms are due to the replication of virus
  within cells of the hippocampus, brainstem,
  cerebellum(Purkinjes cells) and pons
• virus disseminates from the CNS via afferent
  neurons to skin of the head and neck, salivary
  glands, retina, cornea, nasal mucosa, etc

16
LyssaVirus - Diagnosis

• Diagnosis of Rabies is to late for clinical
  intervention
• Symptoms the neurological pattern gives a
  presumptive diagnosis confirmed if recent
  history of animal bite
• Laboratory Confirmation both animal and human
• cytopathology hallmark of rabies is the
  observation of intracytoplasmic
  inclusions(composed of viral nucleocapsids) in
  affected neurons
• Negri Bodies found in brain of infected animals
  and 70 -90 of humans
• inflammatory lesions characteristic of
  encephalitis are not observed from humans who
  have died of rabies
• antigen detection viral antigens in CNS and Skin
• immunofluorescence reveals rabies antigens
  within and upon cells
• viral isolation cell cultures or infant mice
• serology
• antibody is not detectable until late in the
  disease when its found in cerebrospinal fluid and
  serum rapid fluorescent focus inhibition
• cell mediated immunity plays little or no role in
  protection and recovery from rabies

17
LyssaVirus - Epidemiology

• Reservoir domestic and wild mammals
• Urban Rabies
• the dog is the principal reservoir of rabies
  virus in the world
• rabies control programs in the U.S have reduced
  the significance of dogs
• Sylvatic Rabies
• wild animal reservoirs account for most rabies in
  the U.S.
• Source the bite of infected animals
• Incidence the distribution of human rabies
  parallels the distribution of animal rabies
  therefore countries like India and South America
  that have high incidence of animal rabies have
  high incidence of human rabies
• 1 - 5 cases of human rabies per year in the U.S.
• 20,000 humans bitten by animals annually

18
LyssaVirus (Rabies) - Control

• Since antibody does prevent the spread of virus
  to the CNS and the brain, the induction of both
  active and passive immunity forms the basis of
  control in humans and domestic animals
• Rabies Post Exposure Prophylaxis in the U.S
  there are several cases (20,000) of human
  exposure to rabies each year, but very few cases
  of human rabies this is due to post-exposure
  prophylaxis
• Treatment of the Bite (Wound)
• Active immunization with HDCV
• Five doses of HDCV days 0, 3, 7, 14, 28,
• One large dose of anti-rabies hyper-immune
  globulin
• One-half in the bite Other half in the buttocks
• Immunization Human and Animal
• Basis of Pre-exposure Control in high risk humans
• inactive rabies virus grown in human diploid
  cells(HDCV) is used in humans
• various active and attenuated vaccines grown in
  eggs or tissue culture are available for animal
  use

19
Rotavirus - Cycle

• Adsorption
• Intestinal protease cleave and remove portions of
  the outer capsid
• this creates an infectious subviral particle
  with an exposed VP4 that binds the virus to
  sialic acid receptors on intestinal epithelial
  cells
• VP4 is antigenic
• Penetration
• the ISVP penetrates the cells directly via the
  fusion action of VP4
• the remainder of the outer capsid is removed
  during penetration
• the inner capsid/nucleic acid is released into
  the cytoplasm
• virus transcription and replication occur via the
  nucleoprotein core

20
Rotavirus - Cycle

• Transcription and Replication
• double stranded RNA strands(10 - 12) are
  transcribed within the core producing a
  m-RNA(from the negative sense template) which
  leaves the core and associates with the
  ribosomes setting the stage for early and late
  proteins
• viral glycoproteins are incorporated into the
  membrane of the ER
• within the core, the positive sense RNA strands
  serve as templates for the negative sense
  strands
• Assembly
• the double stranded RNA replicas are released
  from the core and associate with late structural
  proteins giving nucleocapsids
• these nucleocapsid bud through the ER membrane
  thus acquiring outer capsid and a temporary
  membrane which is cleaved within the ER.
• Release
• Since early proteins shut down the cellular
  macromolecular synthesis, the cell dies and
  lysis thus releasing the viruses

21
RotaVirus Clinical Disease

• Gastroenteritis mostly in infants and children
• diarrhea, vomiting, fever, dehydration
• no fecal leucocytes or blood
• follows a 48 hour incubation period
• Due to gastrointestinal mucosal cell death
• Due to adenylate cyclase activation by viral
  products

22
RotaVirus - Diagnosis

• symptoms cannot be distinguished from other viral
  diarrheas
• laboratory
• antigen detection large quantities of rotavirus
  particles are present with the feces and can
  easily be found via antigen detection methods
• EIA
• Latex agglutination
• Electron microscopy
• serology
• since most people have antibody against
  rotavirus, this is not always diagnostic but a
  detectable four fold increase in serum antibody
  is diagnostic

23
RotaVirus - Epidemiology

• Reservoir infected humans symptomatic and
  asymptomatic
• Sources fomites in developed countries i.e.US,
  etc
• also contaminated water in under developed
  countries
• mode of transmission
• person-to-person, indirect, fecal-oral,
  food-water, fomites
• statistics
• rotaviruses account for 50 of all cases of
  diarrhea in children requiring hospitalization
• 70,00 cases in the U.S. annually
• gt 1 million cases worldwide annually

24
RotaVirus - Control

• Sanitation
• Sewage Disposal
• Water Treatment
• Fomite Disinfection
• Immunization
• Active Attenuated Vaccine
• RotaTeq pentavalent five serotypes

25
Reoviruses - ColtiVirus

• Colorado Tick Fever
• Clinical Disease
• sudden onset of fever, chill, headache,
  photophobia, myalgia, arthralgia, and lethargy
  acute disease many mild or subclincal infections
• accompanied by biphasic fever, conjunctivitis,
  lymphadenopathy, hepatospenomegaly, and
  maculopapular rash
• must be distinguished from Rocky Mountain Spotted
  Fever
• Pathogenesis
• CTF virus infected the erythroid precusor cells,
  which mature into RBC that are released into the
  circuclation the virus is protected from immune
  clearance within the cells (viremia) for weeks or
  months
• the infected RBCs seed the vascular endothelial
  and smooth muscle cells which often results in
  hemorrhage

26
ReoViruses - ColtiVirus

• Diagnosis
• detection of viral antigens on the surface of
  erythrocytes with immunofluorence
• fourfold increase in IgM for 45 days following
  infection
• Epidemiology Many mammalian reservoirs through
  the western U.S. serve to infect wood tick
  vectors to humans

27
Rhabdoviruses - Characteristics

• bullet shaped, enveloped, virions containing a
  helical nucleocapsid
• envelope contains a glycoprotein spike composed
  of G protein
• G protein in the viral attachment protein
  (VAP)
• G protein is antigenic
• nucleocapsid contains
• one single stranded negative sense RNA
• L and NS proteins RNA dependent RNA polymerase
• N protein major caspid structural protein
  which protect the RNA
• M(matrix) protein between the envelope and the
  capsid
• Lyssavirus is the major pathogen in the family
• etiological agent of rabies
• virus replication occurs in the cytoplasm

28
Rhabdoviruses Viral Cycle

• Adsorption
• G protein attaches virus to the host cell
• virus is primarily neurotrophic but also
  replicates in muscle cells
• Penetration
• virus enter the host cell by endocytosis
• viral envelope then fuses with the endosomal
  membrane via acidification
• nucleoprotein is released into the cytoplasm
• Replication
• transcription of the viral RNA occurs through the
  action of viral RNA dependent RNA polymerase
• five m-RNAs are transcribed each translated
  into a different protein
• the polymerase also produces the positive sense
  RNA template required for the replication of new
  negative sense RNA strands
• the G protein is process by the Golgi and
  delivered to the cell membrane
• Matrix protein is also bound to the membrane

29
RhabdoViruses Viral Cycle

• Assembly
• replicas of the genome associate with the
  N(structural) and L/NS (polymerase) to form the
  nucleocapsid
• nucleoprotein bind to the Matrix protein at the
  cell membrane this caused condensation and
  coiling of the particle
• Release
• Virus buds through the cell membrane and acquires
  its envelope

30
Rhadoviruses - Pathogenesis

• most cells infected with rhabdoviruses exhibit
  cell death and lysis
• the major exception to this is rabies virus
  which causes little discernible cell damage
• virus has affinity for nicotinic acetylcholine
  receptors on nerve cells
• virus also multiples in muscles cells at
  inoculation site
• virus remains at inoculation site for several
  days to weeks
• virus reaches the CNS by retrograde axoplasmic
  transport to the dorsal root ganglia and the
  spinal cord virus moves from the spinal cord to
  the brain

31
LyssaVirus Clinical Disease

• Rabies - neurological disease manifested by
  hydrophobia, generalized seizures,
  disorientation, and hallucinations accompanied by
  various degrees of paralysis these symptoms lead
  to coma, respiratory paralysis, and death (
  disease is 100 fatal in humans and animals)
• long incubation period ( 60 - 365 day) avg about
  80 days
• prodromal period consist of fever, malaise,
  headache, paresthesia, gastrointestinal upset,
  fatigue, and anorexia
• the disease itself is an Encephalitis accompanied
  by neuron degeneration
• symptoms are due to the replication of virus
  within cells of the hippocampus, brainstem,
  cerebellum(Purkinjes cells) and pons
• virus disseminates from the CNS via afferent
  neurons to skin of the head and neck, salivary
  glands, retina, cornea, nasal mucosa, etc

32
LyssaVirus - Diagnosis

• Diagnosis of Rabies is to late for clinical
  intervention
• Symptoms the neurological pattern gives a
  presumptive diagnosis confirmed if recent
  history of animal bite
• Laboratory Confirmation both animal and human
• cytopathology hallmark of rabies is the
  observation of intracytoplasmic
  inclusions(composed of viral nucleocapsids) in
  affected neurons
• Negri Bodies found in brain of infected animals
  and 70 -90 of humans
• inflammatory lesions characteristic of
  encephalitis are not observed from humans who
  have died of rabies
• antigen detection viral antigens in CNS and Skin
• immunofluorescence reveals rabies antigens
  within and upon cells
• viral isolation cell cultures or infant mice
• serology
• antibody is not detectable until late in the
  disease when its found in cerebrospinal fluid and
  serum rapid fluorescent focus inhibition
• cell mediated immunity plays little or no role in
  protection and recovery from rabies

33
LyssaVirus - Epidemiology

• Reservoir domestic and wild mammals
• Urban Rabies
• the dog is the principal reservoir of rabies
  virus in the world
• rabies control programs in the U.S have reduced
  the significance of dogs
• Sylvatic Rabies
• wild animal reservoirs account for most rabies in
  the U.S.
• Source the bite of infected animals
• Incidence the distribution of human rabies
  parallels the distribution of animal rabies
  therefore countries like India and South America
  that have high incidence of animal rabies have
  high incidence of human rabies
• 1 - 5 cases of human rabies per year in the U.S.
• 20,000 humans bitten by animals annually

34
LyssaVirus (Rabies) - Control

• Since antibody does prevent the spread of virus
  to the CNS and the brain, the induction of both
  active and passive immunity forms the basis of
  control in humans and domestic animals
• Rabies Post Exposure Prophylaxis in the U.S
  there are several cases (20,000) of human
  exposure to rabies each year, but very few cases
  of human rabies this is due to post-exposure
  prophylaxis
• Treatment of the Bite (Wound)
• Active immunization with HDCV
• Five doses of HDCV days 0, 3, 7, 14, 28,
• One large dose of anti-rabies hyper-immune
  globulin
• One-half in the bite Other half in the buttocks
• Immunization Human and Animal
• Basis of Pre-exposure Control in high risk humans
• inactive rabies virus grown in human diploid
  cells(HDCV) is used in humans
• various active and attenuated vaccines grown in
  eggs or tissue culture are available for animal
  use