Microbiology - Viruses Flashcards
What is the only single stranded DNA virus?
Parvovirus
What are the two types of RNA viruses?
Positive(+) stranded RNA viruses - being just like mRNA
Negative(-) stranded RNA viruses - carrying RNA polymerase which transcripe the negative strand into a positive(+) strand, making it ready for translation.
Difference between positive(+) and negative(-) stranded RNA viruses?
Positive(+) RNA viruses are ready for translation immediately after infecting host cell.
Negative(-) RNA viruses carry RNA polymerase that transcribe the negative strand into a positive(+) strand before it is able to translate its genome into structural proteins.
What are the two types of capsids?
1 Icosahedral - capsomers are first arranged in triangles. 20 triangles are placed together to form an icosahedron.
2 Helical capsids - protein capsomers are bound to RNA(always RNA) and coiled into a spherical nucleoprotein capsid.
Viruses that do not have membranes are called?
naked viruses
Viruses that have a membrane are called?
enveloped
What are the HHAPPPy viruses?
Herpes Hepadna Adeno Papova Parvo Pox
All are DNA viruses
Virus that replicates in the cytoplasm?
Poxviridae
Singlestranded DNA virus?
Parvoviridae
Three naked DNA viruses?
Papova
Adeno
Parvo
= PAP
Six positive(+) stranded RNA viruses?
TOGA FLAVI CORONA RETRO - CALICI PICORNA
What are the four steps of viral replication?
1 Adsorption and penetration - virus enters host cell
2 Uncoating - nucleic acid is release from capsid into cytoplasm
3 Synthesis and assembly - production of viral proteins
4 Release of virions from host cell
Four outcomes(for host cell) of viral infection?
1 Death - host cells own function shuts down
2 Transformation - infection activate oncogenes = uninhibited growth
3 Latent infection - virus survive in a sleeping state.
4 Chronic slow infection - disease after many years of indolent infect.
Orthomyxoviridae causes this famous disease?
The flu
What is the role of Neuraminidase and Hemagglutinin in the pathogenesis of infleunza?
Neuraminidase cleaves neuraminic acid and disrupts the mucin barrier.
Hemagglutinin attach to host sialic acid receptors = adsorption.
What is antigenic drift?
During viral replication mutations occur in HA or Na, due to poor proofreading. The antigenic drift is the reason for why influenza reccurs every year. The small alterations makes so that host immune system do not recognize orthomyxoviridae = sesonal flu.
What is antigenic shift?
Co-infection of host cell with two different influenza viruses. When the two viruses undergo replication, their proteins “mix” and creates a new virus that has never before been exposed to human immune system.
Reye’s syndrome?
Giving aspirin to children with viral infection may induce severe hepatitis and encephalopathy.
H5N1?
Avian influenza
H1N1?
Swine flu
Croup?
Parainfluenza infection of larynx an upper respiratory tract. Swelling of these structure produce airway narrowing.
Fusion (F) protein?
protein present in paramyxovirus that causes infected cell to fuse into multinucleated giant cells.
Respiratory Syncytial Virus?
Paramyxovirus. Number one cause of pneumonia in young children, especially in infants less than 6 months.
Measles clinical picture?
1 Prodrome - fever, photophobia, conjunctivitis, rhinitis ++
2 Koplik’s spots - red-based lesions in mouth, 1or 2 days before the rash.
3 Rash - starts on the head and spreads downward
What is the Dane particle?
Active, Intact and infective HBV
HBsAg indicates?
Live virus and infection
Anti-HBsAg?
Immune, cure, no active disease!!
Retroviridae: explain the 3 big concepts RETRO, GROW and BLOW
Retro - reverse transcriptase(RNA dependent DNA polymerase)
Grow - retroviruses my activate oncogenes
Blow - some retroviridae are cytotoxic to certain cells, blowing them up.
What are “sticky ends”?
DNA sequences that are recognized by integrase, that are inserted into the host DNA. Seen in HIV
HIV contain nef virulence factor. What is it?
nef downregulates expression of CD4 and MHC I on infected CD4 cell, therby making it unvisible to host cytotoxic T cell mediated killing.
Kaposi’s sarcoma is associated with … ?
HHV-8 infection in patients with AIDS.
Two common fungal infections seen in HIV-infected patients?
1 Candida albicans - causing oral trush and esophagitis.
2 Cryptococcus neoformans - causing meningitis
Due to the lowered immunity, AIDS patients may have a raging meningitis without the classic meningeal signs.
Oral hairy leukoplakia is caused by?
Epstein-Barr virus. Oral hairy leuoplakia usuallyndevelop when CD4 counts are < 400
Three general characteristics that the herpesviridae share?
1 Can develop a latent state.
2 May become multinucleated giant syncytial cells w/ intranuclear inclusion bodies.
3 They are held at bay by the cell-mediated immune response.
TORCHES ?
Txoplasmosis Other Rubella CMV HErpes, Hiv Syphilis
are all organisms that can cross the placenta, causing developmental disease.
Varicella Zoster virus causes?
Varicella (chickenpox) and Herpes zoster(shingles)
Chikenpox are not caused by pox viridae
viridae responsible for chickenpox?
herpesviridae
Explain the latent varicella-zoster virus infection, and how reactivation develops?
Latent infection resides in the sensory ganglion begins to replicate and migrate to the peripheral nerves. The diagnosis of zoster is likely when a patient develops a painful skin rash that overlays a specific sensory dermatome(representing the sensory ganglion in which the virus multiplied)
Why is CMV called CMV?
Because infected cells become swollen = cytomegaly
Causative agent of mononuceosis?
Epstein-Barr virus
EBV mechanism of infection?
EBV binds to compliment (C3d) receptor on human B cells. Once internalized, EBV will change the infected cells so that the B cell proliferate and pass on EBV copies to it’s progeny.
Malignancies associated with Epstein-Barr virus?
Nasopharyngeal cancers and Burkitt’s lymphoma
3 disease causing members of PAPOVAVIRIDAE?
1 Papilloma virus - 16 &18 in cervical cancer / 6 & 11 in genital warts
2 Polyomavirus
3 Adenoviridae - responsible for approx 10% of childhood respiratory infections .
Causing fever and “slapped face” rash in kids?
Parvovirus
Causing the common cold?
Rhinovirus and coronaviridae
Two viruses that causes diarrhea?
rotavirus and caliciviridae
Causing rubella?
Rubivirus
part of the TORCHES group
Body areas affected in congenital rubella?
HEART - patent ductus arteriosus, ventricular defects ++
EYE - cataracts, chorioretinitis ++
CNS - mental retardation, microcephaly, deafness ++
Yellow fever and dengue fever is caused by?
flaviviridae
Yellow fever and dengue fever is transmitted by …. ?
mosquitos
PICORNAVIRIDAE: four genera that contain important human pathogens?
Hepatovirus
Enterovirus
Rhinovirus
Parechovirus
Poliovirus infect cells in ….. ?
1 Peyer’s patches of the intestine
2 Motor neurons
Poliovirus infects cells i the Peyers’s patches of the intestines and motor neurons. How is polio transmitted and what is the worst case scenario?
1 Fecal-oral mode of transmission
2 The disease paralytic poliomyelitis
Three disease manifestations of Polio?
1 Mild illness - asymptomatic / mild febrile viral illness.
2 Aseptic meningitis - fever and meningismus.
3 Paralytic poliomyelitis - destroys presynaptic motor neurons.
Hand, foot and mouth syndrome?
Coxackie A cause small tender lesions on the hands, feet and buttocks.
Associated with 50% of viral myocarditis/pericarditis?
Coxackie B virus. Cross-reaction is also associated with development of insulindependent diabetes melitus.
Describe the nucleocapsids of the rhabdoviruses?
Bullet-shaped, enveloped with helical symmetry.
The only virus in the rhabdovirus family that normally infect humans?
The rabies virus!
Pathomechanism of rabies virus?
The virus replicates locally at the wound site for a few days, then slowly migrates up nerve axons to the CNS.
What are Negro bodies?
Neuropathic changes seen in brain cells infected with the rabies virus.
Describe four stages of infections with the rabies virus?
1 Prodrome - nonspecific symptoms
2 Acute encephalitic - hyperactivity, agitation, confusion, seizures++
3 Brainstem encephalitis - CN dysfunction + painful contraction of pharyngeal muscles leading to impaired swallowing and foaming of the mouth.
4 Death - the highest fatality ratio of any infectious disease.
Succesfull treatment of rabies was performed in 2005. How?
Coma was induced using ketamine and midazolam while waiting for the patients immune response to mature. Antiviral medications ribavirin and amantadine was also administer.
Ebola virus cause
Hemorrhagic fever
