How many hepatitis viruses are there?
5
What are hepatitis viruses resistant to?
low pH, organic solvents, and detergents
Describe Hep A structure.
• Picornavirus, ss (+) RNA genome, naked (un-enveloped) icosahedral capsid
How is Hep. A transmitted?
Fecal-oral
What causes Hep. A symptoms?
• Symptoms not caused by the presence of HAV in the liver but by the immunological response of the host to its presence
What are Hep A. Symptoms?
o Fever, headache, vomiting
o Jaundice
o Pain in the abdomen due to liver inflammation
Hep. A causes what kind of hepatitis?
Infectious hepatitis
Describe Hep. B structure.
Hepadnavirus- DNA virus and is enveloped
Hep. B causes what kind of hepatitis?
Serum Hepatitis
HBV virions are also known as??
Dane particles
How does HBV replicate?
- Unusual because contains partial dsDNA genome which must be replicated.
- HBV enters the body via blood
- Viral DNA forms complete ds circle
- mRNA in capsid produces DNA using reverse transcriptase
- RNA is degraded leaving partial ds DNA
What are the symptoms of HBV?
Symptoms include jaundice, fatigue, abdominal pain, loss of appetite, nausea, vomiting and joint pain
How does HBV spread.
Blood, semen, saliva, & milk.
Describe Hep. C structure
Flavivirus – Enveloped, icosahedral, + ssRNA virus
Only known reservoirs for Hep. C are?
humans and chimpanzees
Hepatitis D (Delta agent), what is unique about it?
Cannot code for its own surface protein and thus in order to produce more virus particles, it needs a helper virus; HBV
How is HDV acquired?
HDV is either acquired along with HBV (co-infection) or as a super-infection of an already HBV-infected individual
Hepatitis E, describe structure.
• HEV is a small, round, icosahedral, (+)ss RNA naked virus
How does HEV spread?
Fecal-oral route.
How long is the Incubation for HEV?
16 to 60 days
To what family of viruses does influenza belong to?
Orthomyxovirus family
Describe influenza shape.
Enveloped, ssRNA virus consisting of 8 RNA fragments
o Influenza virus A is found in???
• Found in humans and animals
o Influenza virus B is found in???
• Found in humans only, no changes in external antigens
o Influenza virus C is found in???
• Found in humans only
o What are the type-specific proteins that are used to determine whether a particular virus is A, B or C
Internal antigens
Which type of influenza is milder?
B influenza
What is Antigenic Drift?
o Due to mutation
o After a few years strains may accumulate sufficient changes that an individual immune to the original strain is not immune to the drifted one
Antigenic shift is due to what?
Reassortment of antigens in influenza A
How is influenza spread?
Via small particle aerosols
How long is the influenza incubation period?
24 to 48 hours (1-2 days)
What are the symptoms of influenza?
- Fever (38 - 40 degrees C)
- Myalgias (muscle pain), headache
- Ocular symptoms - photophobia, tears, ache
- Dry cough, nasal discharge
What is Reye’s syndrome?
Rare encephalitis, approximately 40% of cases are fatal (non-pulmonary complication.)
Amantadine does what?
Impairs the ability of virus to attach to cells
Relenza and Tamiflu do what?
Prevent new virus particles from being released
What is a complication of the flu vaccine?
- Complications: Guillain-Barre syndrome- body attacks its own nerve cells
- One study suggested that one person out of 1 million vaccinated persons may be at risk of GBS associated with influenza vaccine
What are the charecteristics of Picornaviridae?
- Small (pico = small), spherical, naked, (+) RNA virus
- Respiratory and gastrointestinal (enteroviruses) viruses
Enteroviruses infect what?
• Ingested viruses infect cells of the oro-pharyngeal mucosa and lymphoid tissue
Describe Abortive polymyelitis
- Occurs in about 5% of infected individuals
- First symptomatic result of polio infection is fever and occurs in the first week of infection
- Patient may exhibit a general malaise which may be accompanied by vomiting, a headache and sore throat
Describe Non-paralytic poliomyelitis (aseptic meningitis)
- Patient experiences stiff neck and vomiting, virus has now progressed to the brain and infected the meninges
- Spontaneous recovery
Describe Paralytic poliomyelitis?
- About 4 days after the end of the first minor symptoms, the virus spreads from the blood to the anterior horn cells of the spinal cord and to the motor cortex of the brain
- The degree of paralysis depends on the which neurons are affected and the amount of damage
Describe Postpolio syndrome
• This afflicts victims of an earlier polio virus infection but the virus is no longer present, involves further loss of function in affected muscle
Describe the Salk Vaccine.
- Formalin-killed preparation of normal wild type polio virus
- Vaccine is given by injection (IPV)
- Elicits good humoral (IgG) immunity and prevents transport of the virus to the neurons where it would otherwise cause paralytic polio
What is a Sabin Vaccine?
- Live viral vaccine
- Given orally (OPV)
- Grows in human gut where the wild type virus grows. It cannot, however, migrate to the neurons
- Replicates a normal infection since the virus actually grows in the vaccinee and it elicits both humoral and cell-mediated immunity
Describe Coxsackie virus Type A
o Type A usually is associated with rashes, can cause
• Herpangina
• Hand, foot and mouth disease
• Hemorrhagic conjunctivitis
• Aseptic meningitis- enteroviruses are the major cause of viral meningitis
Describe Coxsackie virus Type B
o Type B typically causes internal symptoms
• Localized internal lesions
• Also can cause meningitis, rashes and fever like type A
• Pluerodynia – the Devil’s Grip
• Myocarditis and pericarditis
An Echovirus is?
An enteric cytopathic human orphan virus
Echoviruses have since been identified with various diseases, which ones?
- Aseptic meningitis
- Respiratory infection
- Gastroenteritis
- Skin rashes, fever
A Rhinovirus is?
The common cold (1/3 of all colds caused by this)
Describe the Coronavirus structure.
o Enveloped viruses with a (+)ss RNA genome
Colds are caused by which two viruses?
Rhinovirus & Coronavirus
What is SARS?
SARS- atypical pneumonia caused by a coronavirus (SARS-CoV)
What is the shape of Reoviruses?
• Non-enveloped, icosahedral, (ds) RNA viruses
List the Rhabdoviridae Characteristics
- Bullet shaped enveloped virus
* Single stranded negative RNA genome
Describe Pathology of Rabies.
o Virus binds to nerve or muscle cells at the site of the inoculation via nicotinic acetylcholine receptors
o Virus then moves along the nerve axons to the dorsal root ganglia and the spinal cord. From here, spread to the brain occurs, infection of the brain leads to encephalitis
Describe rabies prodrome.
o Prodrome - pain or itching at the site of the wound, fever, headache, GI
Describe the Furious form of rabies.
- animals can exhibit symptoms such as agitation and increased aggressiveness early on, followed by depression, paralysis, and eventually death
Describe the Dumb form of rabies.
- animals are lethargic, depressed, and eventually die
How is rabies diagnosed?
• Diagnosis- histologically = Negri bodies (eosinophilic intracytoplasmic inclusions formed by aggregates of nucleocapsids in neurons of about 50 to 80% of infected humans)
Arboviruses =
Arthropod Borne
Describe Togaviridae structure
o Enveloped, icosahedral capsid symmetry,
ssRNA genome
Describe Togaviridiae resevoir
• Reservoir of infection = birds, small mammals, horses
Describe Togaviridiae transmission
- Transmission is via Aedes and Culex mosquitoes
* Humans are a dead end host
Describe Togaviridiae symptoms
- Many cases result in mild flu-like symptoms but children are more likely to have severe clinical symptoms that adults.
- If there is clinical disease, death may occur relatively frequently
Yellow Fever occurs where and is transmitted by what?
- Occurs only in Africa and South America
* Transmitted by Aedes aegypti mosquito
Describe yellow fever pathology.
- Pathology
- In some cases there is involvement of internal organs - liver, kidneys and the heart.
- Hemorrhage from the digestive tract (bloody vomit).
- Later the disease is sometimes complicated by jaundice with liver failure and/or renal insufficiency
- Delirium, seizures and coma ensue
- Mortality is around 5%; although historically it has been much higher
Describe Dengue Fever
- Dengue fever is caused by four different arboviruses. It is transmitted by the bite of Aedes aegypti, found in tropic and subtropic regions
- It is generally self-limited and although uncomfortable is not fatal
Describe Dengue Hemorrhagic Fever
• Dengue hemorrhagic fever is a severe, potentially fatal infection that occurs when someone with immunity to one type of Dengue virus is infected by a different type
What are the two types of hot viruses?
- Bunyaviridae
* Filoviruses
Filoviruses give general description.
o Filamentous single stranded negative RNA viruses that target primates
o Cause viral hemorrhagic fevers, characterized by massive bleeding from every orifice of the body
o Shockingly lethal, with very high mortality rates
o Endemic to Africa
o Natural host is unknown, very recent evidence points to fruit bat (11/05)
What are the two types of filoviruses?
- Ebola virus (Ebolavirus, with four species)
* Marburg virus (Marburgvirus)
Retroviruses, give general description.
- Enveloped, + ssRNA genome
- Reverse transcriptase to synthesize DNA from RNA
- DNA integrates into host cell DNA
HLTV-I & HLTV-II are what kinds of viruses?
Oncoviruses
How are oncoviruses transmitted?
Sexual contact
List the Lentiviruses
SIV & HIV viruses.
What are the origins of AIDS.
- Evidence suggests that HIV-1 originated in West Africa as SIV cpz was transmitted from chimps (Pan troglodytes troglodytes) to humans in food preparation
- The earliest documented case of HIV infection in humans was identified in a sample of serum from Democratic Republic of Congo that was stored in 1959
Koch’s Postulates what?
It is now apparent that:
- Virtually all AIDS patients are HIV-infected
- HIV can be isolated from virtually all AIDS patients, as well as in almost all seropositive individuals with both early- and late-stage disease
- Health care and laboratory workers accidentally infected with concentrated purified HIV have developed AIDS
- HIV has been isolated from many of these individuals
The River by Edward Hooper
- HIV made the jump from simians to humans via the administration of oral polio vaccine in Africa in the 1950s
What is “Clinical” Latency?
Refers to fact that symptoms of HIV infection do not manifest themselves as AIDS for many years
Describe the structure of the HIV virus.
- Enveloped +RNA virus,
* Cone shaped capsid
How does the HIV virus bind?
• Gp 120 interacts with CD 4 receptor on immune cell (T cell)
In Western countries majority of HIV-1 is subtype B- seen predominantly in which population?
most infections in men who have sex with men (MSM)
Can HIV be transmitted by mosquitoes or ticks?
NO!
What cells are susceptible to HIV infection due to sexual intercourse?
mucosa has dendritic immune cells susceptible to infection called Langerhans cells
What is the most infectios stage of HIV disease.
Primary Viremia. (Virus moves through lymph system)
What is involved in the Adapted (specific) immune response to HIV infection?
- Cytotoxic T-lymphocytes
- Antibody production
- Interferon and other antiviral cytokines
What happens during the Dynamic Equilibrium phase of HIV infection?
• Within six to nine months, a dynamic equilibrium between cell infection, viral replication and CD4 + lymphocyte production and destruction occurs
Describe the Second Phase of Decay of HIV infection.
- Marked by the loss of long lived latently infected CD4+ cells
- The continual loss of CD4+ cells (up to 10 billion a day) eventually overwhelms ability to replace lymphocytes
Describe the onset of AIDS.
- The period of clinical latency varies in length from as little as 1 to 2 years to more than 15 years
- As the T4 cells fall below 200 per cu mm, virus titers rise rapidly and immune activity drops
- It is the onset of HIV-associated opportunistic infections that defines AIDS
In reference to HIV/AIDS, what is the “window period”?
When an infected person does not give a positive western blot HIV test or ELISA, although there is a high viral load and possibly symptoms. This can last for six months before seroconversion
What are the AIDS related cancers?
- Viral induced (herpes 8) Kaposi’s sarcoma
- Hodgkin’s lymphoma (lymph tissue)
- B cell lymphomas (Burkett’s lymphoma)
- HPV cancers – anogenital (anus and genitals
