OPTO435 Microbiology II Gamal El-Hiti - PowerPoint Presentation

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OPTO435

Microbiology II

Gamal El-Hiti

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Nonenveloped DNA

Viruses

Lecture Nine

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Learning Outcomes

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Viral Infections

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Nonenveloped DNA

Viruses

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Nonenveloped DNA

Viruses

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

Adenoviruses are members of the family

Adenoviridae

.



They are medium sized viruses (80–90 nm).



Nonenveloped viruses have an icosahedral nucleocapsid containing a double stranded DNA genome.



Their name derives from their initial isolation from human

adenoids

in 1953.

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

A virus is an infectious agent that is minimally constructed of

two components

, genome and capsid.



A

genome consisting of DNA. A capsid which is a protein-containing structure designed to protect the genome. Over 150 types of human papillomaviruses (HPVs) are now recognized, based on DNA sequences of well characterized virus genes.

 HPVs

exhibit great cell specificity, infecting surface of skin and mucous membranes.

Nonenveloped DNA

Viruses

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Nonenveloped DNA

Viruses

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Nonenveloped DNA

Viruses

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Nonenveloped DNA

Viruses

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

Epidemiology of Human

Adenovirus



Transmission of

HPVs

infection requires direct contact with infected individuals (

e.g

. sexual contact or contaminated surfaces).



HPVs

can also be transmitted from mother to infant during passage down the birth canal.



Outbreaks have been more common in

late winter

,

spring

and

early summer

.



All ages are susceptible to adenovirus infection, but commonly during

childhood

.

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Viruses

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

Pathogenicity of Adenovirus



The

HPVs

multiplication and pathogenesis are very specific for the

epithelial cells

.



When an

adenovirus

enters its host, it will typically

replicate

in the

epithelial cells

that line the

lungs

or other enteric organs.



After several replication cycles, the virus will being to

inhibit

host macromolecular synthesis and transport of

mRNA

to the cytoplasm.

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Viruses

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

These cellular disturbances will

kill host cells

and can cause

disease symptoms

.



Studies have implied that the

penton protein

of adenoviruses is

virulent

 to their host

.



The penton protein has caused the cells to

detach

from monolayers.



Even when the disease symptoms disappear, the virus can still

remain latent

in a person's body

for years.



The viruses are found in

lymphoid tissue

.

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Nonenveloped DNA

Viruses

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Viruses

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

Clinical Significance

of Adenovirus



HPVs

cause diseases that cover from simple warts to malignancies.



Warts

can occur on any part of the body, including both

cutaneous

and

mucosal

surfaces.



Specific

HPV

types tend to be associated with specific wart morphology, although a wart morphological type is also related to its location.

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Nonenveloped DNA

Viruses

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Viruses

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

Acute

adenovirus conjunctivitis

is very contagious and transferred by contact.



Common symptom includes swelling of the eyelid, either upper or lower.



Redness of the eye (

pink eye

).



Excess tears, itchy, burning and sensation of a foreign object in the eye.

 A

ccompanied by a pus-like discharge, often causing eyelids to stick together after sleeping.

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Viruses

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Viruses

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

Treatment and Prevention

of Adenovirus



There is no specific treatment for people with adenovirus infection.



Most adenovirus infections are mild and don’t require any medical care.



Cidofovir

has been used to treat severe adenovirus infections in people with immunocompromised systems.



Currently, there is

no adenovirus vaccine

available for the general public.

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

Cidofovir

(brand name

Vistide

) is an injectable antiviral used as a treatment for cytomegalovirus retinitis (an infection of the retina of the eye) in people with AIDS.

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Estimated HPV DNA prevalence in the world region (2007)

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Picornaviridae

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

Picornaviridae

contain a single-stranded, non-segmented RNA genome.



Picornaviruses

are small, naked (nonenveloped) and icosahedral viruses.

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Picornaviridae

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

They cause a broad spectrum of diseases but they share the following features:



They replicate in the cytoplasm.



Genomic RNAs serve as messenger RNAs and are infectious.



Genomic RNAs are nonsegmented.



Virions do not contain any enzymes.



Virus-specified proteins are synthesized as polyproteins that are processed by viral and cellular proteases, giving rise to individual viral proteins.

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Enteroviruses

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

Enteroviruses

are a genus of positive-sense single-stranded RNA viruses associated with several human and mammalian diseases.



More than seventy enteroviruses have been identified.



Enteroviruses

isolated more recently are named with a system of consecutive numbers as

EV68

,

EV69

,

EV70

and

EV71

.



They affect millions of people worldwide, and often found in respiratory secretions.

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Enteroviruses

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

Epidemiology of Enteroviruses



Individuals are infected with

Enteroviruses

by ingestion of contaminated food or water.



Enteroviruses

are stable at the

low pH

of the stomach, replicate in the gastrointestinal (GI) tract and are excreted in the stool.



They can

replicate

in a variety of tissues.



Most infections are

asymptomatic

.



Enteroviruses

account for

ca.

10



15 million

symptomatic infections per year in the

US

.

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Enteroviruses

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

Clinical Significance of Enterovirus Infections



All

Enteroviruses

can cause

CNS disease

.



Enteroviruses

are currently the major cause of acute

aseptic

meningitis

syndrome.



Viral meningitis disease is milder than bacterial meningitis.



Evidence of infection can also be obtained by demonstration of a rise in antibody titer against a specific

enterovirus.

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Enteroviruses

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

Treatment of Enterovirus Infections



Viral meningitis occurs mainly in summer and fall, affecting both

children

and

adults

.



Enteroviruses infection is usually a

benign

self-limiting illness

.



No antiviral drugs

are available for the treatment of infections

caused by

Enterovirus

species.



No vaccine

is currently available for the prevention of enterovirus infections.

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Acute Hemorrhagic Conjunctivitis

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

Acute hemorrhagic conjunctivitis

(AHC) is a derivative of the highly contagious conjunctivitis virus (

pink eye

).



Symptoms include excessively

red

,

swollen eyes

as well as subconjunctival hemorrhaging.



Currently, there is

no known treatment

.



Patients are required to merely

endure the symptoms

while the virus runs its five to seven day course.

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Acute Hemorrhagic Conjunctivitis

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

There are

three main viruses

that have been confirmed as the agents responsible for AHC, including

Enterovirus 70

,

Coxsackievirus A24 variant

(CA24v) and

Adenovirus 11

.

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Acute Hemorrhagic Conjunctivitis

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

Enterovirus 70

and

Coxsackievirus

A24

are members of the genus

Enterovirus

and family of

Picornaviridae

.



They are non-enveloped having a single-stranded positive-sense RNA genome.



Enterovirus 70

is very small.



Coxsackievirus A24

is isolated from human.



Adenovirus 11

is a medium-sized variant that are nonenveloped.



These viruses are some of the largest nonenveloped viruses in existence.

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Enteroviruses

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Enteroviruses

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Weekly case numbers of acute hemorrhagic conjunctivitis reported by the disease surveillance network in Guangdong (China) between July and October of 2007 and 2010.

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Enteroviruses

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The incidence of

acute hemorrhagic conjunctivitis

cases in China. 

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