(-)Strand RNA Viruses Flashcards
all (-)strand RNA viruses are [nonenveloped/enveloped]
all (-)strand RNA viruses are enveloped (from host membranes) with glycoprotein spikes
what is the function of the M1 and M2 proteins of influenza (-)ssRNA viruses?
M1: interacts with glycoproteins
M2: forms ion channel, which lowers pH to allow for viral uncoating
what must (-)ssRNA viruses carry with them in order to replicate?
must carry RNA-dependent RNA polymerase in the virion, which can create mRNA transcripts from (-)RNA genome
[in contrast to +ssRNA viruses which do not contain any enzymes, use host instead]
what is the shape of influenza (-)ssRNA viral nucleocapsids?
helical !
contrast the function of hemagglutinin and neuraminidase of influenza (-)ssRNA viruses and the effectiveness of antibodies against each of them, respectively
HA (hemagglutinin): binds sialic acid on human cells for receptor-mediated endocytosis - antibodies against HA are neutralizing
NA (neuraminidase): cleaves sialic acid so that newly formed viruses exiting the cell do not reattach - antibodies against NA stop spread but do not eliminate infection
how is viral protein production regulated in +strand vs -strand RNA viruses?
(+)ssRNA viruses regulate protein at translational level (transcribe long polypeptides which are cleaved into multiple proteins)
(-)ssRNA viruses regulate protein at transcriptional level (segmented transcripts, each will be made into a separate protein)
what is different about viral transcription in Influenza Virus as compared to other RNA viruses?
Influenza (-ssRNA virus) replicates viral genome in the nucleus, while most RNA viruses replicate in the cytoplasm
*note that envelope comes from plasma membrane upon exit from cell though
(DNA viruses replicate in the nucleus)
what 2 viral infections is Reye’s Syndrome linked to?
Varicella (chickenpox) and Influenza
accumulation of fat in liver, brain swelling and acute brain damage
occurs in children, highly fatal, cause unknown
*Tylenol now given to children instead of aspirin (and other drugs containing salicylic acid)
what class of antibody is most effective against Influenza (-ssRNA virus)?
IgA in nasal secretions
also high IgG in serum, but not as protective
*recall that anti-HA (hemagglutinin) Abs are neutralizing, while anti-N (neuraminidase) Abs only stop the spread
which human influenza strain (-ssRNA virus) is associated with endemics?
Influenza A, which is then subdivided by HA and N subtypes
(there is also Influenza B and C)
antigenic drift vs shift
antigenic drift: point mutations in virus cause annual epidemics
antigenic shift: recombination of different HA and N cause creation of a new subtype of virus, cause pandemics - Influenza A only
(when 2 Influenza A viruses from different animals co-infect one cell and genetic exchange occurs)
*note that segmented transcripts of influenza allow for genetic recombination that facilitates antigenic shift
what kind of Influenza (-ssRNA virus) has potential to cause serious illness in humans and pandemics (because it easily mutates), but rarely spreads human-human?
Asian Avian Influenza: rare human-human spread, but can cause serious illness (respiratory, death)
Paramyxoviridae are (-)ssRNA viruses which include Parainfluenza, Mumps, Measles, RSV, Nipah, and Hendra. How do Paramyxoviridae affect infected cell morphology?
Paramyxoviridae cause syncytia (cell fusion), via glycoprotein spikes on their envelope —> multi-nucleated giant cells with inclusion bodies
Which Paramyxoviridae infects the lower respiratory tract of infants and children and presents with a croup, or “barking cough”?
Parainfluenza (1-4): (-)ssRNA virus, infects infants and children, causes lower respiratory tract infection with croup
where does Mumps (Paramyxoviridae, -ssRNA virus) infection originate, and how does it progress?
via respiratory secretions, replicates in parotid gland, causes primary infection in upper respiratory tract
can spread to any organ - CNS, gonads, deafness (sequelae), fetal complications
infection confers immunity for life, prevent with MMR live attenuated vaccine
which Paramyxoviridae (-ssRNA) does this describe?
- one of the most infectious childhood diseases
- viable for hours in respiratory droplets on fomites
- major cause of mortality of children in developing countries
- causes formation of multinucleated giant cells
- presents with Kolik’s spots
Measles: extremely infectious childhood disease (winter/spring epidemics), causes multinucleated giant cells
primary infection in respiratory tract, then dissemination in blood —> Koplik’s spots, maculopapular rash (spreads down body)
complications: punctuate keratitis, Subacute Sclerosing Panencephalitis, Giant Cell Pneumonia
what are the key clinical findings of Measles infection? (Paramyxoviridae, -ssRNA)
Measles: one of the most infectious childhood diseases
multinucleated giant cells, Koplik’s spots, maculopapular rash
Pt is a 3yo F presenting with a respiratory tract infection her mother said has been spreading throughout the kindergarten class during February. PE is significant for Koplik spots and a full-body rash the mother states began on the upper torso.
What is going on?
Measles (Paramyxoviridae, -ssRNA): one of the most infectious childhood diseases, viable for hours in respiratory droplets on fomites (spreads easily), causes winter and spring epidemics
major cause of child mortality in developing countries, MMR vaccine in USA
Which Paramyxoviridae (-ssRNA) has the potential for serious complications including Punctuate Keratitis, Subacute Sclerosing Panencephalitis, and Giant Cell Pneumonia?
Measles: one of the most infectious childhood diseases, viable for hours in respiratory droplets on fomites (spreads easily), causes winter and spring epidemics, Koplik spots
Punctuate Keratitis: inflammation of cornea, synergistic with Vit A deficiency (problem in developing countries were vaccination against Measles is not common)
Subacute Sclerosing Panencephalitis: degenerative CNS disease, hits about 10 years later
what is the single most important cause of viral lower respiratory tract disease in infants and children?
Respiratory Syncytial Virus: Paramyxoviridae (-ssRNA), greater exposure = greater immunity
hand washing! for prevention
what shape is Rhabdoviridae (Rabies) under a microscope, and what would indicate that a cell has been infected with Rabies?
Rhabdoviridae: bullet shaped, helical nucleocapsid
infected cells contain Negri bodies (inclusion bodies - site of viral replication)
what are the clinical phases of rabies infection? (3)
Prodromal (nonspecific)
Acute neurological (neuro dysfunction)
Coma (death due to respiratory arrest)
T/F: Rabies inactivated vaccine can be effectively given after a person is bitten
TRUE: Rabies is a slow developing disease, so the vaccine can be given after being bitten and an immune response can develop in time
multiple doses (4) needed for Rabies vaccine
During rounds, you encounter a farmer from the midwest presenting with hemorrhagic fever. It has been determined to be of -ssRNA viral origin. The patient says there are many field mice on the farm, but there is a lack of rodent control.
What is the causative agent?
Arenaviridae: -ssRNA, rodent host that enter homes in winter or on farms
causes either CNS disease or hemorrhagic fever:
- Lymphocytic Choriomeningitis
- Lassa fever
- Hemorrhagic fever
*rodent control is only reliable way to prevent
you catch Arenavirus from entering an ARENA full of mice
what -ssRNA virus family does this describe?
- mostly arthropod borne with rodent hosts
- can cause meningitis (La Crosse virus), hemorrhagic fevers, cardiac/pulmonary disease (Sin Nombre Virus), Heartland Virus (via Lone Star tick)
Bunyaviridae: -ssRNA viruses, wide range of diseases
Bunyaviridae give ya a BUNYA different diseases
which -ssRNA virus is pleomorphic and has just one molecule of RNA?
Filoviridae - Embola/Marburg viruses
cause severe hemorrhagic fevers, death from shock
what kind of virus is Rotavirus? (features of the virus)
Rotavirus: dsRNA genome, no envelope, 2 icosahedral capsids made of protein spikes (Ab against these are neutralizing)
what is the purpose of the 2 icosahedral capsids of Rotavirus?
Rotavirus: dsRNA virus, no envelope (exits via cell lysis)
dsRNA must remain in capsid because it is a red flag to immune system - outer capsid degrades upon endocytosis but inner capsid hides dsRNA
mRNA leaves inner capsid via small pores
what kind of disease is Rotavirus significant for?
Rotavirus: dsRNA virus, most common diarrheal pathogen in infants/children worldwide
transmitted via fecal-oral, respiratory secretions, fomites
natural immunity increases with exposure (age)
*vaccines are live attenuated
