Exam II - Positive Sense RNA Viruses and Prions

Picornavirus

a family of naked positive sense virus containing single stranded RNA. They have icosahedral symmetry and are very small.

naked

is picornavirus naked or enveloped?

positive sense

is picornavirus positive or negative sense?

Icosahedral symmetry

describe the shape of picornavirus.

Polio virus

picornavirus part of the enterovirus class causing infection of the Peyer's patches of the intestines and motor neurons. Mostly irradicated but still seen in India, Pakistan, and Nigeria.

Fecal oral route

route of transmission of polio virus

Peyers patches and motor neurons

tropism of polio virus

vaccine available and improved sanitation

two reasons for decreased poliovirus infection

flaccid asymmetric paralysis

the main complication of polio virus infection. Occurs due to the destruction of presynaptic motor neurons in the anterior horn of the spinal cord as well as the destruction of postsynaptic neurons exiting the cord.

Coxsackievirus (A and B)

picornavirus part of the enterovirus first identified in New York, but is widely distributed worldwide. Most cases (60%) are subclinical.

Fecal oral, respiratory droplets, saliva, contaminated water

four modes of transmission of coxsackievirus

Coxsackie A

form of coxsackievirus primarily causing skin and mucosal infections. Ie) hand foot mouth disease, herpangina, and acute hemorrhagic conjunctivitis

2-6, 8, 10

three coxsackie A serotypes causing herpangia

5, 10, 16

three coxsackie A serotypes causing hand, foot, and mouth disease

24

coxsackie A serotype causing acute hemorrhagic conjunctivitis.

Coxsackie B

form of coxsackievirus primarily causing pleurodynia and myocarditis/pericarditis.

Rhinovirus

picornavirus which replication in surface epithelium of nasal mucosal and spread via contact with infected secretion. Produces a common cold due to infection.

epithelium of nasal mucosa

where does rhinovirus replicate?

Direct contact, fomites, self inoculation

three routes of transmission for rhinovirus

Togavirus/Rubivirus

family of enveloped positive sense virus containing single stranded RNA. They have icosahedral symmetry

enveloped

is rubivirus naked or enveloped?

positive sense

is rubivirus positive or negative sense?

icosahedral symmetry

describe the shape of togavirus

E1

glycoprotein of togavirus/rubivirus that interacts with host receptors to facilitate viral attachment to the host.

E2

glycoprotein of togavirus/rubivirus that interacts with capsid and E1 to reach the host golgi for assembly.

Acquired infection

infection of rubivirus where the virus enters the repiratory tract. It then disseminates via blood and lymph to other tissues. A rash develops and the virus is shed from the oropharynx.

respiratory tract, blood and lymph, oropharynx

in acquired infection of rubivirus the virus enters the _____. It then disseminates via _____ (2) to other tissues. A rash develops and the virus is shed from the ______

Respiratory tract secretions

transmission of acquired rubella virus infection

Congenital infection

infection of rubivirus that occurs due to maternal viremia. It is spread trans placentally to the fetus. After birth infants excrete the virus in the throat and urine. Infections that occur earlier in pregnancy are more severe.

Cataracts, cardiac abnormalities, deafness

triad of congenital rubella infection

Retrovirus

a family of enveloped positive sense virus containing single stranded linear diploid RNA which is translated in the reverse direction via reverse transcriptase to form double stranded DNA. Has the ability to then incorporate itself into the host genome.

positive sense

is HIV positive or negative sense?

HIV/retrovirus

name one positive sense RNA virus that is unique in that it replicates in the nucleus

enveloped

is HIV naked or enveloped?

Icosahedral symmetry

shape of immature retrovirus/HIV. Become cylindrical shaped when they mature

Plasma membrane

host cell structure that HIV derives its envelope from

Protease

proteins of HIV that destroy host proteins

Reverse transcriptase

protein of HIV that converts viral RNA to DNA which can be incorporated into the host genome.

Integrase

protein of HIV that integrate viral genetic material into the host genetic material

Capsid proteins

protein of HIV that is measurable in serum during early infection

Matrix proteins

protein of HIV that holds glycoprotein spikes in the cell envelope

Sexual contact (via small ulcerations), blood transfusion, needles, transplacental

transmission of HIV

CD4+ T cells

tropism of HIV including other immune cells such as macrophages, monocytes, and CNS dendritic cells.

Clinical latency

HIV infection stage where that is asymptomatic, but there is still viral replication. Occurs for about 8 years.

400-200

levels of CD4 cells in HIV infection where there is a wasting syndrome that occurs. Opportunistic infections also occur.

AIDS

HIV infection stage where CD4 count is less than 200. The immune system fails and severe opportunistic infections occur.

<50

CD4 levels in HIV infection where there is almost no immune response and the patient is highly susceptible to opportunistic infections.