Download Hepatitis A Virus - BMC Dentists 2011

Batterjee Medical College
Batterjee Medical College
Classification of DNA Viruses
Virus Family
Envelope
Present
No
No
Papillomavirus No
Icosahedral
Adenovirus
Hepadnavirus
No
Yes
Icosahedral
Icosahedral
Herpesvirus
Yes
Icosahedral
DNA
Structure
SS, linear
DS, circular,
supercoiled
DS, circular,
supercoiled
DS, linear
DS,
incomplete
circular
DS, linear
Poxvirus
Yes
Complex
DS, linear
Parvovirus
Polyomavirus
1SS
= single-stranded; DS = double-stranded.
Capsid
Symmetry
Icosahedral
Icosahedral
Medically Important
Viruses
B19 virus
JC virus, BK virus
Smallpox virus,
molluscum
contagiosum virus
Human papilloma virus
Adenovirus
Hepatitis B virus
Herpes simplex virus,
varicella-zoster virus,
cytomegalovirus,
Epstein-Barr virus
Batterjee Medical College
1-Herpesviruses
Virus
Primary Infection
Usual Site
Recurrent
of Latency
Infection
HSV-1
Gingivostomatitis
Cranial
Herpes labialis,
Vesicular lesions above sensory
encephalitis,
the waist
ganglia
keratitis
HSV-2 • Herpes genitalis
Lumbar or Herpes genitalis
• Vesicular lesions
sacral
below the waist
sensory
• Perinatal
ganglia
disseminated disease
VZV
Varicella
Cranial or
Zoster
• Initial infection in thoracic reactivate years
oropharynx.
sensory later, in older and
• It spreads via blood to ganglia
immunoliver then to skin.
compromised
individuals.
Route of Transmission
Via respiratory
secretions, direct
contact with virus
vesicle & saliva
Sexual contact,
perinatal infection
Via respiratory
secretions
Batterjee Medical College
1-Herpesviruses
Virus
Primary Infection
Usual Site of Recurrent Infection
Route of
Latency
Transmission
B lymphocytes
None
Via respiratory
secretions &
saliva
•Infectious
mononucleosis
•It start in pharyngeal
epithelium, spreads to
cervical lymph nodes,
then travels via blood
to liver & spleen.
CMV •Congenital infection •Uncertain
(in utero)
•Mononucleosis in
transfusion recipients.
•Pneumonia & hepatitis
in immunocompromised patients
•Retinitis & enteritis, in
AIDS patients
HSV-8
Uncertain
•Uncertain
EBV
•Asymptomatic
shedding
•Dissemination in
immunocompromised
patients
•Intrauterine
infection
•transfusions,
•sexual contact,
& secretions
Kaposi's sarcoma
in AIDS patients
Sexual or organ
transplantation
Batterjee Medical College
1-Herpesviruses
Herpes viruses-1
Batterjee Medical College
Herpesviruses
Varicella viruses
Batterjee Medical College
Herpesviruses
Zoster viruses
Batterjee Medical College
Herpesviruses
Epstein-Barr virus
Batterjee Medical College
Adenovirus
• Upper & lower tract
(pharyngitis & pneumonia).
respiratory
disease
• Enteric strains cause diarrhea.
• Transmitted by respiratory droplet , iatrogenic in
eye disease & fecal–oral with enteric strains.
• Live vaccine against types 3, 4, & 7 is used in
military to prevent pneumonia
Batterjee Medical College
Papillomavirus
Human Papillomavirus
•Papillomas (warts); condylomata acuminata (genital
warts); carcinoma of cervix & penis.
•Transmitted by direct contact of skin&genital lesion
•Two early viral genes, E6 & E7, encode proteins that
inhibit activity of proteins encoded by tumor
suppressor genes, p53 gene & retinoblastoma
gene, respectively.
•Vaccine containing capsid proteins of four HPV
types (6, 11, 16 and 18) is available.
Batterjee Medical College
Papillomavirus
Human Papillomavirus
Batterjee Medical College
Hepadnavirus
Hepatitis B Virus
•Hepatitis B & hepatocellular carcinoma.
•Transmitted by blood, during birth & sexual intercourse.
• Hepatocellular injury due to immune attack by cytotoxic
(CD8) T cells.
• Antigen–antibody complexes
glomerulonephritis.
cause
arthritis,
rash,
&
• 5% of HBV infections result in a chronic carrier.
• Chronic hepatitis, cirrhosis & hepatocellular carcinoma can
occur (integration of part of viral DNA into hepatocyte DNA).
Batterjee Medical College
Hepadnavirus
Hepatitis B Virus
Laboratory Diagnosis
Three serologic tests are commonly used:
1- Surface antigen (HBsAg)
2- Surface antibody (HBsAb)
3- Core antibody (HBcAb).
• Detection of HbsAg ≥6 months
• Presence of e antigen
chronic carrier.
infectious chronic carrier.
• “Window" phase : HBV-infected person has neither
detectable HBs antigen nor HBs antibody & diagnosed by
detecting HB core antibody.
Batterjee Medical College
Hepadnavirus
Hepatitis B Virus
Treatment
• Alpha
interferon
&
lamivudine
reduce
inflammation
associated with chronic hepatitis B but does not cure
carrier state.
Prevention
(1) vaccine that contains HBsAg as immunogen
(2)hyperimmune serum globulins obtained from donors with
high titers of HBsAb
Batterjee Medical College
Classification of RNA Viruses
Virus Family Envelope
Present
Picornavirus
No
Capsid
Symmetry
Icosahedral
Hepevirus
No
Icosahedral
Calicivirus
No
Icosahedral
Reovirus
No
Icosahedral
Flavivirus
Yes
Icosahedral
Togavirus
Yes
Icosahedral
RNA Structure
•SS linear,
•nonsegmented,
•positive polarity
•SS, linear
• non-segmented
• positive polarity
•SS linear,
•nonsegmented,
•positive polarity
DS linear, 10 or 11
segments
•SS linear,
•nonsegmented,
•positive polarity
•SS linear,
•nonsegmented,
•positive polarity
Medically Important
Viruses
•Poliovirus
•Rhinovirus
• hepatitis A virus
Hepatitis E virus
Norwalk virus
Rotavirus
•Yellow fever virus,
•dengue virus
• West Nile virus,
•hepatitis C virus
Rubella virus
Batterjee Medical College
Classification of RNA Viruses
Virus Family Envelope
Capsid
Present
Symmetry
Retrovirus
Yes
Icosahedral
Orthomyxovirus Yes
Helical
Paramyxovirus Yes
Helical
Rhabdovirus
Yes
Helical
Filovirus
Yes
Helical
RNA Structure
Medically Important
Viruses
SS linear, 2 identical •HIV
strands (diploid), •human T-cell
positive polarity leukemia virus
SS linear, 8
•Influenza virus
segments, negative
polarity
SS linear,
•Measles virus,
nonsegmented, • mumps virus,
negative polarity •respiratory syncytial
virus
SS linear,
•Rabies virus
nonsegmented,
negative polarity
SS linear,
• Ebola virus
nonsegmented, • Marburg virus
negative polarity
Batterjee Medical College
Picornavirus
Enteroviruses: Poliovirus
• Range of responses to poliovirus infection includes:
(1) inapparent, asymptomatic infection
(2) abortive poliomyelitis
(3) nonparalytic poliomyelitis
(4) paralytic poliomyelitis.
• Transmission
by fecal–oral route & humans are natural
reservoir.
• Virus replicates in pharynx & GI tract & spread to local
lymph nodes & then through blood to CNS.
Batterjee Medical College
Picornavirus
Enteroviruses: Poliovirus
• Most infections are asymptomatic or very mild.
• Aseptic meningitis is more than paralytic polio.
• Paralysis is the result of death of motor neurons, anterior
horn cells in the spinal cord.
• Virus in spinal fluid indicates CNS infection .
• Virus
in stools indicates infection ( not necessarily
disease) as it is found in GIT of asymptomatic carriers.
Batterjee Medical College
Picornavirus
Enteroviruses: Poliovirus
• Disease can be prevented by:
- Salk: inactivated vaccine
- Sabin: live, attenuated vaccine
both induce humoral antibody that neutralizes virus in
bloodstream.
Sabin vaccine has been preferred vaccine as :
• Oral vaccine
• Induces intestinal IgA, that prevent GIT infection
• Induces immunity of longer duration
Batterjee Medical College
Picornavirus
Enteroviruses: Hepatitis A Virus
• Hepatitis A.
• Transmission by fecal–oral route. Blood-borne transmission
is uncommon because viremia is brief & of low titer.
• Virus replicates in GIT then spreads to liver during brief
viremic period.
• Virus is not cytopathic for hepatocyte & hepatocellular
injury is caused by immune attack by cytotoxic T cells.
• Vaccine contains killed virus. Administration of immune
globulin during incubation period
Batterjee Medical College
Picornavirus
Enteroviruses:Coxsackie Viruses
• It causes the following diseases:
-Aseptic meningitis, Myocarditis, pericarditis
-Herpangina (fever, sore throat & tender vesicles in
oropharynx)
-Pleurodynia (fever & severe pleuritic-type chest pain due to
an infection of the intercostal muscles not of pleura
- Hand, foot &mouth disease (vesicular rash on hands &
feet & ulcerations in mouth, mainly in children).
- Coxsackie virus B4 may cause juvenile diabetes
• Transmission by fecal–oral route.
• Initial site of infection is oropharynx, but main site is GI
tract then spreads through blood to various organs.
Batterjee Medical College
Picornavirus
Rhinoviruses
• Common cold.
•There are more than 100 serotypes,which explains why the
common cold is so common.
•They are destroyed by stomach acid
•Transmission by aerosol droplets &
hand-to-nose contact
•Infection is limited to mucosa of upper respiratory tract &
conjunctiva.
•Virus replicates best at low temperatures of nose & less well
at 37°C.
Batterjee Medical College
Orthomyxovirus
Influenza Virus
• Influenza. Influenza A cause worldwide epidemics.
• It has two major antigens ; hemagglutinin (HA) &
neuraminidase (NA) on separate surface spikes.
• Antigenic shift in these proteins as a result of reassortment
of RNA segments accounts for the epidemics of influenza
• Antigenic drift due to mutations
also contributes.
Batterjee Medical College
Orthomyxovirus
Influenza Virus
• Antigenicity of internal nucleocapsid protein determines
virus is A, B or C influenza virus.
• Transmission by respiratory droplets.
• Infection limited to epithelium of respiratory tract.
• Neuraminidase inhibitor, oseltamivir (Tamiflu, drug of
choice) & Zanamivir is used in treatment.
Batterjee Medical College
Orthomyxovirus
Influenza Virus
Two types of vaccines are available:
1-killed (subunit) vaccine:
purified HA & NA.
2- Live, temperature-sensitive mutant of influenza virus.
The virus replicates in cool nasal passages & induces
secretory IgA, but not in warm lower respiratory tract.
Batterjee Medical College
Paramyxovirus
Measles Virus
• Measles & Subacute sclerosing panencephalitis.
• Transmission by respiratory droplets.
• Initial site of infection is upper respiratory tract & spreads
to local lymph nodes then via blood to other organs & skin.
• Maculopapular rash is due to cell-mediated immune attack
by cytotoxic T cells on virus-infected vascular endothelial
cells in the skin.
• Vaccine contains live, attenuated virus,
combination with mumps & rubella vaccines.
given
in
Batterjee Medical College
Paramyxovirus
Mumps Virus
• Mumps. Bilateral orchitis & sterility is rare
• Transmission by respiratory droplets.
• Initial site of infection is upper respiratory tract &
spreads to local lymph nodes then via blood to
other organs, especially the parotid glands, testes,
ovaries, meninges & pancreas.
• Vaccine contains live, attenuated virus, given in
combination with measles and rubella vaccines
Batterjee Medical College
Paramyxovirus
Respiratory Syncytial Virus
• Bronchiolitis &pneumonia in infants & otitis media in older
children.
• Transmission by respiratory droplets.
Paramyxovirus
Parainfluenza Virus
• Bronchiolitis in infants, croup in young children & common
cold in adults.
• Transmission by respiratory droplets.
Batterjee Medical College
Togavirus
Rubella Virus
• Rubella & Congenital rubella syndrome (congenital
malformations, affecting cardiovascular & CNS)
• Transmission by respiratory droplets & across the placenta
from mother to fetus (during first trimester)
• Initial site of infection is nasopharynx, then to local lymph
nodes & disseminates to skin via blood. Rash due to viral
replication & immune injury.
• Vaccine contains live, attenuated virus,
combination with measles and mumps vaccine.
given
in
Batterjee Medical College
Coronavirus
Coronavirus
• Common cold & SARS (severe acute respiratory
syndrome).
• Transmission by respiratory droplets.
• It Infects mucosal cells of respiratory tract.
Batterjee Medical College
Rhabdovirus
Rabies Virus
• Rabies (encephalitis)
• Transmission by animal bite & aerosols of bat
saliva.
• Viral receptor is the acetylcholine receptor.
• Replication of virus at site of bite, followed by
axonal transport up nerve to CNS then replicating
in brain & migrates to salivary glands & saliva.
• Tissue stained with fluorescent
• antibody to detect cytoplasmic
• inclusions (Negri bodies).
Batterjee Medical College
Rhabdovirus
Rabies Virus
• Preexposure prevention: Rabies vaccine
•Postexposure prevention:
1. Washing wound
2. Giving
rabies
immune
globulins
(passive
immunization) into wound
3. Giving inactivated vaccine (active immunization)
made in human cell culture.
Batterjee Medical College
Hepevirus
Hepatitis E Virus
• Outbreaks of hepatitis in developing countries.
• Similar to hepatitis A virus in the following ways:
- Transmitted by fecal–oral route
- No chronic carrier state
- No cirrhosis
- No hepatocellular carcinoma.
Batterjee Medical College
Calicivirus
Norwalk Virus (Norovirus)
• Gastroenteritis (watery diarrhea).
• Transmission by Fecal–oral route.
• Infection is limited to the mucosal cells of the
intestinal tract.
Batterjee Medical College
Reovirus
Rotavirus
• Gastroenteritis (diarrhea) in young children.
• Rotavirus is resistant to stomach acid
• Transmission by the fecal–oral route.
There are two rotavirus vaccines.
• Live attenuated vaccine contains single most
common rotavirus serotype (G1)
• Live reassortant vaccine contains 5 rotavirus strains.
Batterjee Medical College
Flavivirus
Hepatitis C Virus
•Hepatitis C & hepatocellular carcinoma.
• Transmission is via blood. Sexual transmission &
from mother to child probably occurs.
• Hepatocellular injury caused by cytotoxic T cells &
HCV does not cause a cytopathic effect.
• 50% of infections result in chronic carrier which
predisposes to chronic hepatitis & hepatocellular
carcinoma.
Batterjee Medical College
Flavivirus
Hepatitis C Virus
• Serologic testing detects antibody to HCV.
• PCR-based assay for "viral load" can be used to
evaluate whether active infection is present.
• Alpha interferon plus ribavirin mitigates chronic
hepatitis but does not eradicate carrier state.
• Posttransfusion hepatitis can be prevented by
detection of antibodies in donated blood.
Batterjee Medical College
Deltavirus
Hepatitis D Virus
• Hepatitis D (hepatitis delta).
• Defective virus that uses HBs Ag as its protein coat &
replicate only in cells infected with HBV (HBV is helper
virus).
• Transmitted by blood, sexually & from mother to child.
• Hepatocellular injury caused by cytotoxic T cells.
• Chronic hepatitis & chronic carrier state occur.
• Treatment by Alpha interferon mitigates symptoms but
does not eradicate carrier state.
• HBV vaccine & HBV hyperimmune globulins will
prevent HDV infection also.
Batterjee Medical College
Retrovirus
Human Immunodeficiency Virus
• Acquired immunodeficiency syndrome (AIDS).
• RNA-dependent
DNA
polymerase
(reverse
transcriptase) makes a DNA copy of the genome,
which integrates into host cell DNA.
• Precursor polypeptides cleaved by virus–encoded
protease to produce functional viral proteins.
• Antigenicity of gp120 protein changes rapidly
there are many serotypes.
Batterjee Medical College
Retrovirus
Human Immunodeficiency Virus
• Transmission by body fluids, e.g., blood & semen,
transplacental & perinatal transmission.
Two receptors are required for HIV to enter cells:
1 - CD4 protein :
it is found on helper T cells. HIV infects and kills
helper
T
cells,
which
predisposes
opportunistic infections.
2 - chemokine receptor such as CCR5.
to
Batterjee Medical College
Retrovirus
Human Immunodeficiency Virus
• Detecting antibody with ELISA as screening test
and Western blot as confirmatory test.
• Determine the "viral load," i.e., the amount of HIV
RNA in the plasma, using PCR-based assays.
• High viral load predicts more rapid progression to
AIDS
Batterjee Medical College
Retrovirus
Human Immunodeficiency Virus
Treatment
• Highly active antiretroviral therapy (HAART)
consists of two nucleoside inhibitors (inhibit HIV
replication by inhibiting reverse transcriptase) &
one protease inhibitor (prevent cleavage of
precursor polypeptides).
• Clinical improvement occurs, but virus persists.
Batterjee Medical College
Retrovirus
Human Immunodeficiency Virus
• Screening of blood prior to transfusion for the
presence of antibody.
• "Safe sex," including the use of condoms.
• Nucleoside inhibitors (zidovudine) with or without
a protease inhibitor should be given to HIVinfected mothers and their newborns.
• Nucleoside inhibitors (Zidovudine & lamivudine ) &
protease inhibitor should be given after a needlestick injury.
Batterjee Medical College
Arboviruses
Classification of Major Arboviruses
Family
Genus
Viruses of Medical Interest
•Eastern equine encephalitis virus
•western equine encephalitis virus
•St. Louis encephalitis virus
Flavivirus
Flavivirus
• Yellow fever virus
• Dengue virus,
•West Nile virus
Bunyavirus Bunyavirus California encephalitis virus
Colorado tick fever virus
Reovirus
Orbivirus
All arboviruses are transmitted by arthropods (arthropodborne) such as mosquitoes & ticks from the wild animal
reservoir to humans.
Togavirus
Alphavirus
Batterjee Medical College
Arboviruses
Flavivirus: Yellow Fever Virus
• Yellow fever
• "Jungle" yellow fever is transmitted from monkeys to
human by mosquitoes.
• "Urban" yellow fever is transmitted from human (reservoir)
to human by Aedes mosquitoes
• It is severe, life-threatening disease characterized by
jaundice & fever.
• It begins with sudden onset of fever, headache, myalgias, &
photophobia.
• There is a live, attenuated vaccine for humans.
Batterjee Medical College
Arboviruses
Flavivirus: Dengue Virus
• Dengue fever.
• Transmitted by Aedes mosquitoes from one human to
another.
• Classic dengue (worldwide) (breakbone fever) begins
suddenly with influenzalike syndrome consisting of fever,
malaise, cough, & headache.
• Severe pains in muscles & joints (breakbone) occur.
• Enlarged lymph nodes, maculopapular rash & leukopenia
• After a week, symptoms regress but weakness may persist.
Batterjee Medical College
Arboviruses
Flavivirus: Dengue Virus
The diagnosis : Isolation of virus in cell culture & Serologic
tests that demonstrate presence of: IgM antibody & fourfold
or greater rise in antibody titer in acute & convalescent sera.
Outbreaks are controlled by using:
• Insecticides
• Raining stagnant water serves as breeding place for
mosquitoes
• Personal protection includes: Using mosquito repellent &
Wearing clothing that covers the entire body.
Batterjee Medical College
Prions
• Creutzfeldt-Jakob disease (CJD), variant CJD &
kuru (transmissible spongiform encephalopathies)
• There is a hereditary form of CJD called
Gerstmann-Sträussler-Scheinker (GSS) syndrome.
• Prions are composed of protein only.
• They have no detectable nucleic acid & highly
resistant to UV light, formaldehyde & heat.
• They are encoded by a cellular gene.
Batterjee Medical College
Prions
• Pathogenic form (beta-pleated sheet) increases in
amount by inducing conformational change in
normal form (alpha helix).
• In GSS syndrome, a mutation occurs that enhances
conformational change to beta-pleated sheet form.
• CJD is transmitted by pituitary extracts, brain
electrodes & corneal transplants.
• Kuru was transmitted by ingestion or inoculation of
human brain tissue.
• Variant CJD is transmitted by ingestion of cow
brain tissue in undercooked food
Batterjee Medical College
Prions
• Aggregation of prion filaments within neurons
occurs, vacuoles within neurons cause spongi-
form changes in brain, no inflammation or
immune response occurs.
• Brain biopsy shows spongiform changes.
• Prions cannot be grown in culture.