Exam I: Virology II Flashcards
Epstein Barr Virus (EBV) HHV-4
EBV enter B cell by binding complement receptor CR2 (CD21)
Pathogenesis:
Infects B cells and epithelial cells of oropharynx
Lead to viral shedding in saliva, which is contagious
Virus spread to blood, lymph
EBV stimulate B cell mitosis leading to increased number of B cells that harbor EBV in their genome
2 kinds of disease may result:
Overactive immune response to EBV= mononucleosis
Weak immune response= Burkitt lymphoma
EBV: Epidemiology
More than 90% of infected shed virus in saliva asymptomatically for life
Kissing as means of transmission
Disease is usually sub-clinical in children
70% of population infected by 30 years
Many, in US, get it in 1st year of college
EBV: Clinical Syndromes
Mononucleosis: high fever, malaise, pharyngitis, lymphadenopathy, hepatosplenomegaly, fatigue, headache
Hairy leukoplakia: consists of white vertical folds or ridges along the lateral borders of the tongue
Oncogenic: Burkitt lymphoma, nasopharyngeal carcinoma, lymphoma
Cytomegalovirus (CMV; HHV-5): Pathogenesis and Epidemiology
Pathogenesis: Persistent, latent infections Infect mononuclear cells, kidney, heart Replicate in ductal epithelial cells which promotes the excretion of virus in most bodily fluids Less common/less disease
Epidemiology:
Virus can be found in urine, blood, saliva, tears, breast milk, semen, stool, amniotic fluid, vaginal and cervical secretions
Can be spread: orally, sexually, congenital in utero, with blood and organ transplants
HIV infected patients at risk
CMV Common Transmission
- In utero: most common in utero infection
Disease ranges from infected with no defects to cytomegalic inclusion disease: jaundice, hepatosplenomegaly, thrombocytopenic purpura, pneumonitis and CNS damage to death - Birth, milk to nursing babies: mild disease, heterophile negative mononucleosis
- Sexually & blood transfusions: mild, heterophile negative mononucleosis
- Reactivation in transplanted organ: transplant patients
Interstitial pneumonitis and systemic disease - Reactivation in transplanted organ AIDS patient
CMV retinitis, pneumonitis and systemic disease
CMV Retinitis
Cytomegalovirus Retinitis is the most common opportunistic infection in HIV- usually seen when CD4+T<50
Prior to highly active anti-retroviral therapy, CMV retinitis was easily recognized as a “pizza pie” retinopathy
Patients on HAART (Highly Active Antiretroviral Therapy), may be more difficult to diagnose
Retinal detachment frequently complicates CMV retinitis
CMV Treatment
Ganciclovir: synthetic analogue of 2’-deoxy-guanosine
It is first phosphorylated to a dGTP analogue
dGTP analogue inhibits the incorporation of dGTP by viral DNA polymerase
Result: termination of elongation of viral DNA
Give to AIDS patients to make the disease less severe
Foscarnet (Foscavir): is classic inhibitor of herpesviruses
Foscarnet is, a phosphonic acid, a structural mimic of the anion pyrophosphate that selectively inhibits the pyrophosphate binding site on viral DNA polymerases
Because foscarnet is not activated by thymidine kinase (tk), it maintains activity in tk–viruses and gained resistance to acyclovir or ganciclovir
Foscarnet is used in acyclovir- or ganciclovir-resistant disease
Roseolovirus
A genus of the family HERPESVIRIDAE
Subfamily BETAHERPESVIRINAE
Viruses have been isolated from lymphocytes
HUMAN HERPESVIRUS 6 (HHV6) is the type species
6th disease –rash
Exanthem subitum, Roseola infantum
Cause: HHV6-B or HHV7
Hepadnaviridae
Hepatitis B virus (HBV): small, enveloped DNA virus,
partially DS -use a reverse transcriptase and RNA intermediate during replication
B hepatitis: acute, chronic, asymptomatic or symptomatic depending on the person’s immune response to the virus
Virus begins to replicate in the hepatocytes within 3 days of infection where no harm done at first
Symptoms may not appear until 6-7 weeks or later
Copies of HBV genome are integrated into hepatocytes = latency
From the liver to viremia (blood) then spread to saliva, semen, vaginal secretions and mother’s milk
All these fluids are contagious
HBV Replication
Intracellular mature virus (IMV): represents the majority of infectious progeny and remains inside the host cell
Extracellular enveloped virus (EEV)
HBV Epidemiology
More than 300,000 cases/year with 4,000 deaths in the US Asymptomatic chronic carriers are a reservoir that keep spreading the disease Spread by: sexual contact, blood transfusion and exchange via sharing needles, acupuncture, ear piercing and tattooing Perinatal transmission (vertical transmission)
HBV: Clinical Symptoms
Acute infection:
Long incubation, insidious onset
Prodrome: fever, malaise, fatigue, anorexia, nausea & vomiting and abdominal pain
Icteric/jaundice stage- Bilirubin, the yellow breakdown product of normal heme catabolism is responsible for
Jaundice, yellowing of skin and eye-white, dark urine, pale stools, fulminant disease
1% may progress causing severe liver damage, cirrhosis and bleeding
Chronic infection: 5-10% with HBV
Usually after mild or apparent clinical symptoms
May only be detected by increased liver enzymes
10% with chronic HBV develop cirrhosis and liver failure
Primary hepatocellular carcinoma: major complication attributed to HBV in more than 80% of cases
HBV Treatment
No specific treatment
IFN-alpha for chronic disease
HBV Ig: for newborns and recently exposed patients
Drugs target: polymerase, reverse transcriptase
Lamivudine and anti-herpes drug famciclovir
Vaccine: HBsAG= hepatitis B surface antigen
Subunit vaccine 3 times
Smallpox
The Pharaoh Ramses V died of smallpox in 1157 B.C.
The disease reached Europe in 710 A.D.
It was transferred to America by Hernando Cortez in 1520
3.5 million Aztecs died in the next 2 years.
In the cities of 18th century Europe, smallpox reached plague proportions and was a feared scourge - highly infectious.
Five reigning European monarchs died from smallpox during the 18th century
Poxviruses: Morphology, Pathogenesis, and Transmission
Morphology: virions enveloped, composed of an external coat containing lipid and tubular or globular protein structures
Nucleocapsid brick-shaped to ovoid
Core usually biconcave with two lateral bodies
Largest, most complex virus, linear ds DNA genome
Replication in cytoplasm
Pathogenesis: virus enters the upper respiratory tract by inhalation and disseminates in lymphatics → viremia
After a secondary viremia, the virus infects all dermal tissues and internal organs leading to the classic “pocks” formation
Transmission: acquired via respiratory route and close contact
Smallpox: Clinical Syndromes
Variola major: virus replicates in respiratory tract, travels to lymph glands, then to blood (viremia)
Incubation of 5-17 days
15-40% mortality rate
Variola minor
1% mortality rate
No treatment
Vaccine available but no longer produced in large quantities because disease is eradicated
Encephalitis is an important complication
Pox: Molluscum contagiosum & Orf
Molluscum contagiosum: a minor infectious warty papule of the skin with a central umbilication (depression)
transferred by direct contact, sometimes as a venereal disease
ORF – a worldwide occupational disease associated with handling sheep and goats afflicted with “scabby mouth”.
In humans it manifests as a single painless, papulo-vesicular lesion on the hand, forearm or face
PAINLESS
Paramyxoviridae
Parainfluenza virus, measles, mumps, respiratory syncytial virus (RSV)
RNA virus family
Orthomyxoviridae
Influenza virus types A, B, and C
RNA virus family
Arenaviridae
Lassa fever virus, lymphocytic choriomeningitis virus
RNA virus family
Rhabdoviridae
Rabies virus, vesicular stomatitis virus
RNA virus family
Filoviridae
Ebola virus, Marburg virus
RNA virus family
Bunyaviridae
California encephalitis virus, Hanta virus, hemorrhagic fever virus, Rift valley fever
RNA virus family