Lesson 5.4. RNA Viruses

Influenza Virus

Myxoviruses:

• enveloped, helically symmetric capsid, segmented RNA

• hemagglutinin and neuraminidase spikes project from the envelope

• only multiplies in the cells lining the upper respiratory tract

extensive antigenic variation

Influenza virus is capable of _________________________, producing new types against which the human population does not have effective immunity, causing pandemics.

Mumps Virus

Paramyxoviruses:

• enveloped, helical capsid

• infection in children produces characteristic swelling of parotid and submaxillary salivary glands

• the disease can have neurological complications (ex: meningitis, especially in adults)

Measles Virus

Paramyxoviruses:

• enveloped, helical capsid

• very common childhood fever

• immunity is lifelong

• second attacks are very rare

Rabies Virus

Rhabdoviruses:

• bullet-shaped, enveloped, helical capsid

• very wide host range, infecting all mammals: dogs, cats and cattle are particularly susceptible

• incubation period is extremely varied, ranging from 6 days up to 1 year

fatal encephalitis

Rabies virus remains localized at the wound site of entry for a while before passing along nerve fibers to central nervous system, where it invariably produces a ____________________.

Rotavirus

Reoviruses:

• segmented, double stranded RNA, inner core is surrounded by two concentric icosahedral shells

• spread through poor water supplies and when standards of general hygiene are low

• in developing countries it is responsible for about a million deaths each year

gastroenteritis

Rotavirus is a very common cause of _______________ in infants

Poliovirus

Picornavirus:

• naked, icosahedral

• one of a group of enteroviruses common in the gut of humans

lymphoid tissue

The poliovirus’ primary site of multiplication is the ________ of the alimentary tract

encephalitis or poliomyelitis

Poliovirus rarely cause systemic infections or serious neurological conditions like ___________________

Rhinovirus

Picornaviruses:

• naked, icosahedral

• common cold viruses

100 antigenically distinct types

There are over ______________________ of Rhinovirus, hence the difficulty in preparing effective vaccines.

watery nasal secretions

Rhinovirus shed copiously in _______________________

Hepatitis A Virus (HAV)

Picornaviruses:

• naked, icosahedral

• ‘infectious hepatitis’ spread by the oral–faecal route especially in children

sewage contamination of food or water supplies

Hepatitis A Virus is also associated with

Rubella

Togaviruses

• spherical, enveloped, icosahedral

• causes German Measles in children

• if contracted in the early stages of pregnancy can induce severe multiple congenital abnormalities, e.g. deafness, blindness, heart disease and mental retardation

Yellow Fever Virus

Flavivirus

• spherical, enveloped

• spread to humans by mosquito bites

liver

The Yellow Fever Virus, the _______ is the main target.

jaundice and fever

In Yellow Fever Virus, the necrosis of hepatocytes leads to ___________________.

Hepatitis C Virus (HCV)

Flavivirus

• spherical, enveloped

• spread through blood transfusions and blood products

• induces a hepatitis which is usually milder than that caused by HBV

Dengue Virus

Flavivirus:

• spherical, enveloped

• spread to people through the bite of an infected Aedes species (Ae. aegypti or Ae. albopictus) mosquito

four

a person can be infected with a dengue virus as many as ____ times in his or her lifetime

fever

Most common symptom of dengue:

Ebola Virus

Filovirus:

• long filamentous rods, enveloped, helical nucleocapsid, 1000 nm long, 80 nm in diameter

• widespread amongst populations of monkeys

• can be spread to humans by contact with body fluids from the primates

haemorrhagic fever

Ebola Virus is characterized by _____________ has 90% case fatality rate

Hepatitis D Virus (HDV)

Deltaviridae

• can only replicate in cells co-infected with HBV

• spherical coat of HDV is composed of HBV capsid protein

• presence of the satellite HDV exacerbates the pathogenic effects of HBV producing severe hepatitis

• transmitted from mother to child during birth and delivery, through contact with blood or other body fluids, including sex with an infected partner, injection-drug use and needle sticks or exposures to sharp instruments

Human T-Cell Leukemia Virus (HTLV-1)

Retroviridae:

• spherical, enveloped, icosahedral, 2 copies of RNA, reverse transcriptase

• spread inside infected lymphocytes in blood, semen or breastmilk

• most infections remain asymptomatic but after an incubation period of 10–40 years in about 2% of cases, adult T-cell leukemia can result

• may cause Kaposi’s sarcoma

Human Immunodeficiency Virus (HIV)

Retroviridae:

• cone-shaped core

• transmitted from person to person via blood or genital secretions

• principal target for the virus is the CD4+ T-lymphocyte cells

• depletion of these cells induces immunodeficiency

• may also cause Kaposi’s sarcoma

cone-shaped

Structure of Human Immunodeficiency Virus (HIV):

a. enveloped virus with a ___________ nucleocapsid

b. contains two copies of a _____________________ molecule

c. contains the enzyme ___________________

d. has __________________ (gp120) project from the envelope and interact specifically with the CD4 protein receptor on the T-lymphocyte

a = ?

positive-sense ss RNA

Structure of Human Immunodeficiency Virus (HIV):

a. enveloped virus with a ___________ nucleocapsid

b. contains two copies of a _____________________ molecule

c. contains the enzyme ___________________

d. has __________________ (gp120) project from the envelope and interact specifically with the CD4 protein receptor on the T-lymphocyte

b = ?

reverse transcriptase

Structure of Human Immunodeficiency Virus (HIV):

a. enveloped virus with a ___________ nucleocapsid

b. contains two copies of a _____________________ molecule

c. contains the enzyme ___________________

d. has __________________ (gp120) project from the envelope and interact specifically with the CD4 protein receptor on the T-lymphocyte

c = ?

70 glycoprotein spikes

Structure of Human Immunodeficiency Virus (HIV):

a. enveloped virus with a ___________ nucleocapsid

b. contains two copies of a _____________________ molecule

c. contains the enzyme ___________________

d. has __________________ (gp120) project from the envelope and interact specifically with the CD4 protein receptor on the T-lymphocyte

d = ?

two RNA molecules and the reverse transcriptase

HIV Replication Process:

1. the core penetrates the cell cytoplasm following membrane fusion and is uncoated releasing the _______________________________________ into the cytoplasm

2. RNA is copied by __________________ into ss DNA which is then duplicated to form a ds DNA copy

3. DNA moves into the host cell nucleus where it is integrated as a provirus into a host cell chromosome by the enzyme ____________.

1 = ?

reverse transcriptase

HIV Replication Process:

1. the core penetrates the cell cytoplasm following membrane fusion and is uncoated releasing the _______________________________________ into the cytoplasm

2. RNA is copied by __________________ into ss DNA which is then duplicated to form a ds DNA copy

3. DNA moves into the host cell nucleus where it is integrated as a provirus into a host cell chromosome by the enzyme ____________.

2 = ?

integrase

HIV Replication Process:

1. the core penetrates the cell cytoplasm following membrane fusion and is uncoated releasing the _______________________________________ into the cytoplasm

2. RNA is copied by __________________ into ss DNA which is then duplicated to form a ds DNA copy

3. DNA moves into the host cell nucleus where it is integrated as a provirus into a host cell chromosome by the enzyme ____________.

3 = ?

provirus

• can lie dormant in the cell or can be expressed producing viral mRNA and proteins and resuming the multiplication cycle producing virions

• polycistronic, producing polyproteins that need to be cleaved by a specific virus-encoded

virions

In HIV, the ____________ bud off the infected cells

protease

When the provirus is active, it produces a polyproteins which are cleaved by ________

SARS-CoV 2 Virus

Coronaviridae:

• enveloped, single-stranded positive-sense RNA

• causes COVID-19 pandemic

membrane protein (M), spike protein (S), and envelope protein (E)

SARS-CoV 2 is associated with three structural proteins: _____________________

third zoonotic human coronavirus

SARS-CoV 2 is the _____________________________ of the century, following SARS-CoV and MERS-CoV