Lecture 8 - Segmented RNA Viruses

Question 1

Of the segmented RNA viruses, ______ is the most common and _____ is the least common.

Answer 1

Influenza

Bunyavirus

Question 2

Keep in mind that ALL segmented RNA viruses encode/package their own ______ for transcription and replication, and co-infection of a host cell by two viruses from the same genus permits _______ of the genome.

Answer 2

Polymerases

Reassortment

Question 3

Influenza is of the ______ family. Vaccines are used to protect again ___ and ___ of the three (A, B, and C strains.)

Answer 3

Orthomixaviridae

A and B

Question 4

Seasonal flu epidemics are caused by Antigenic _____ (a direct result of ______ errors) while Pandemics are caused by Antigenic _____ (due to ______, introducing a segment from an animal source.)

Answer 4

Drift

Polymerase errors

Shift

Reassortment

Question 5

One of the key differences between influenza and rhinovirus infection is the former involves the ______ respiratory tract (without viremia) while the latter involves just the _____.

Answer 5

Entire

Upper

Question 6

Children are the most significant vector for influenza because they shed the virus for _____ as opposed to days for adults.

Answer 6

Weeks

Question 7

The influenza virus is an enveloped virus that encodes 2 envelope glycoproteins which are the basis for the classification into _____. The first is _____ (N) and the second is _____ (H), each of which is encoded in one of the 8 segments of the genome.

Answer 7

Neuraminidase

Hemagglutinin

Question 8

If two H glycoproteins differ by ____% or less of their AAs, they are considered the same subtype. They are typically considered different subtypes if the difference is greater than ____%.

Answer 8

15%

20%

Question 9

Human Abs are targeted against one of the 5 _____ heads (A, B, C, D, and E.)

Answer 9

Globular heads

Question 10

Only when a mutation is made during creation of ___RNA for replication or during the synthesis of vRNA from the ___RNA can the mutation be passed to progeny.

Answer 10

cRNA

cRNA

Question 11

_____ are the reservoirs for ALL influenza viruses.

Answer 11

Water foul

Question 12

____ are thought to be the mixing vessels for reassortment between avian flu and human flu viruses.

Answer 12

Pigs

Question 13

There are 4 key characteristics of a Pandemic:

1. Virus breaks ____ barrier
2. New ____ of virus is detected in Humans
3. Virus is highly _____
4. Virus is easily _____ between humans

Answer 13

Species barrier

Subtype

Pathogenic

Transmitted

Question 14

Avian flu (H__N__) had high _____, but negligible _____ between humans. Wet markets in SE Asia were considered the main reservoirs.

Answer 14

Pathogenicity

Transmissibility

H5N1

Question 15

Swine flu (H__N__) had low ______ but high ______. It was a ___ reassortment, containing Human, Avian, and Swine subunits.

Answer 15

H1N1

Pathogenicity

Transmissibility

Triple

Question 16

Four major viral factors affecting pathogenesis are:

1. _____ specificity (recognition of particular glycosidic bonds)
2. _____ efficiency
3. Transmissibility
4. ____-infection with bacteria.

Answer 16

Receptor

Replication

Co-infection

Question 17

2 major host factors affecting pathogenesis are:

1. overall _____ response (over reaction/more than is helpful.)
2. type ___ interferon response.

Answer 17

Immune response

Type I interferon

Question 18

There are 2 major considerations for replication efficiency of influenza:

1. The influenza polymerase is species specific
2. The H protein must be activated by host _____. Strains that are highly activated are much more pathogenic.

Answer 18

Protease

Question 19

Neuraminidase aids in transmissibility as does the enhanced ____ transmission in lower temp and humidity (explains why flu season is in colder months.)

Answer 19

Aerosol

Question 20

There are 2 considerations for co-infection of influenza with bacteria:

1. Bacterial _____ can contribute to activation of influenza ____ protein.
2. Influenza N protein can cleave ____ ____ which would otherwise work to inhibit bacterial binding to host cells.

Answer 20

Proteases

H protein

Sialic Acid

Question 21

Influenza ___ protein inhibits host ____ response to dsRNA.

Answer 21

NS1

Interferon

Question 22

There are a few antivirals for influenza treatment. Amantadine and Rimantadine target the viral ____ protein which helps with viral uncoating. Oseltamivir and Zanamivir (brand name Tamiflu) target the viral ___ protein to inhibit its ability to cleave sialic acid.

Answer 22

M2 protein

NA protein

Question 23

Bunyaviruses are the least common in humans (most prevalent in Asia), and have a genome comprised of ___ segments. Humans are a dead-end host.

Answer 23

3

Question 24

_____ is the most prevalent encaphalitis-causing Bunyavirus while _____ is the most common hemorrhagic-causing.

Answer 24

La Crosse

Hanta

Question 25

Hantavirus is transmitted to humans via a non-arboviral route: dried rodent _____. Following heavy rain seasons there is more vegetation, so increase in rodent population –> greater chance of infection. Hanta is the only Bunyavirus not transmitted through an arthropod vector.

Answer 25

Feces

Question 26

The key takeaway about Bunyaviral diseases is they result primarily from infections of ____ or ____ cells. Infection of ____ presents as aseptic (non-bacterial) meningits or encephalitis (rare in US with low fatality.) Infection of ____ cells presents with ____ fever and has higher fatality rates.

Answer 26

Neurons

Endothelial

Neurons - aseptic meningitis or encephalitis

Endothelial cells - Hemorrhagic fever

Question 27

Arenaviruses have ___ RNA segments, and like Flu and Bunya, it is an enveloped virus that packages its own _____.

Answer 27

Polymerase

Question 28

Human to human transmission of Arenaviruses is only seen in Lassa (semen transmission), LCMV (in ____) or exposure to infected tissues of hemorrhagic viruses. In most other ways it’s similar to Bunyaviruses (transmission via rodent excreta etc…)

Answer 28

Utero

Question 29

LCMV is a congenital ____, causing birth defects like chorioretinitis or optic atrophy. It is an Arenavirus that affects the ____ (not usually hemorrhagic, but can be in immunosuppresed –> organ transplant recipients.) Early replication occurs in ______ and Dendritic cells and can establish persistent infection.

Answer 29

Teratogen

CNS

Macrophages

Question 30

Big takeaway for the process of pathogenesis in ALL hemorrhagic fevers is as follows:

Initial infection typically occurs in ____ or dendritic cells with a few major outcomes:

1. disruption of ____ that leads to apop of lymphocytes
2. release of chemokines from infected _____ to recruit naive _____ (continue the infection)
3. Initiation of DIC
4. Disruption of porocity of ____ cells –> edema.

Answer 30

Macrophages

Cytokines

Macrophages

Macrophages

Endothelial cells

Question 31

Ribavirin is an antiviral drug that is a _____ analog. The idea is to push viral replication toward _____ catastrophe (accumulation of too many mutations due to Polymerase _____.)

Answer 31

Nucleoside

Error Catastrophe

Polymerase Errors

Question 32

Rotavirus belongs to the _____ family. It has a ____-layered protein capsid and does not have an _____. It is transmitted via ___/___. The capsid contains all the enzymes necessary for mRNA production. Its genome is comprised of ____ segments of ___RNA. It is the primary agent of sever ________ in infants and young children worldwide. It’s the only human virus that encodes a ____. Disease is treated with hydration and electrolytes.

Answer 32

Reoviridae

Double-layered

Fecal/Oral

11 segments

dsRNA

Gastroenteritis

Toxin

Question 33

One of the unique features of Rotavirus infection is the virion retains its ______ capsid layer (protects against host enzymes that degrade dsRNA.)

Answer 33

Inner capsid layer

Question 34

Mechs of Rotavirus-induced diarrhea come from two interactions with the host:

1. Malabsorptive component–> Kills ______ cells of small intestine and alters ____ junctions and actin skeleton (increased permeability.)
2. Secretory component –> virally encoded NSP4 toxin activates ____ nervous system.

Answer 34

Epithelial cells

Tight junctions

Enteric