DR. MOHAMMED ARIF.ASSOCIATE PROFESSOR.CONSULTANT VIROLOGIST.HEAD OF THE VIROLOGY UNIT.

Medical virology , Laboratory session-1

Electron micrographs of medically important viruses

DNA - viruses :

1- Herpesviridae. 2- Adenoviridae. 3-Hepadnaviridae. 4- Poxviridae .

1- Family - Herpesviridae .

Enveloped, lose envelope. Icosahedral nucleocapsid.The viral genome is ds-DNA.Eight human herpes viruses.Examples of diseases: HSV-1 : Gingivostomatitis, keratoconjunctivitis,

meningoencephalitis, herpetic whitlow. HSV-2 : Genital herpes, neonatal herpes. varicella –zoster virus ( VZV ) : varicella, zoster.

Family – Herpesviridae.

Cytomegalovirus (CMV) : Infectious mononucleosis like syndrome , congenital infection, severe diseases in the immunocompromized.

Epstein Barr virus (EBV ) : infectious mononucleosis, Nasopharyngeal carcinoma, Burkitts lymphoma.

EM of herpes virus .

EM of herpes virus

2- Family- Adenoviridae

Unenveloped.Icosahdral nucleocapsid ( spherical particle).The viral genome is ds-DNA.Examples of diseases : Pharyngoconjunctival

fever, keratoconjunctivitis, pneumonia, gastroenteritis, hemorrhagic cystitis.

EM of adenoviruses

EM of adenoviruses .

3- Family : Hepadnaviridae ( hepatitis B virus ).

Three forms of particles. The complete hepatitis B virus (HBV )

particle is enveloped with ds-DNA genome ( the large particles)

The free hepatitis B surface antigen particles (HBsAg), 22-nm in diameter.

The filament form of HBsAg particles .Diseases : hepatitis B .

EM of Hepatitis B virus (HBV ) .

4- Family : Poxviridae ( pox viruses ).

Brick shaped .The viral genome is ds-DNA .Complex structure .Diseases : smallpox ( variola).

EM of poxvirus .

RNA viruses .

1- Family : orthomyxoviridae ( Influenza viruses ).

2- Family : Rhabdoviridae ( Rabies virus ).3- Family : Reoviridae ( Rotaviruses).4- Family : Caliciviridae ( Caliciviruses).5- Family : Filoviridae ( Marburg virus &

Ebola virus). 6- Arenaviridae ( Lassa virus ) .

1- Family – Orthomyxoviridae ( influenza viruses ).

Pleomorphic.Enveloped.Covered with two glycoprotein spikes:Hemagglutinin and neuraminidase .The viral genome consists of 8- segments of

ss-RNA.Diseases : Influenza ( flue ), pneumonia .

EM of influenza viruses.

EM of influenza viruses .

2- Family : Rhabdoviridae ( Rabies Virus ).

Bullet shaped.Enveloped.The viral genome is ss-RNA , negative strand.Diseases : Rabies , acute encephalitis .

EM of Rabies virus .

3- Family : Reoviridae ( Rotaviruses).

Unenveloped.The virus particle has a wheel structure

(double capsid).Spherical particles .The viral genome consists of 11- segments of

ds-RNADiseases : The major cause of infantile

diarrhea.

EM of Rotaviruses.

4- Family : Caliciviridae ( caliciviruses ).

Unenvelpoed.Spherical particles with cup- shaped

depressions.The viral genome is SS-RNA with positive

polarity.Diseases : Diarrhea .

EM of caliciviruses .

EM of caliciviruses .

5- Family : Filoviridae. ( Marburg virus & Ebola virus).

The virus is filament in shape. Unenveloped. the viral genome is ss-RNA with negative

polarity.Diseases : Hemorrhagic fever .

EM of Marburg virus & Ebola virus .

Family : Arenaviridae

Sandy appearance .Enveloped .ss-RNA , 2-segments with negative polarity . Lassa virus .Diseases : Lassa hemorrhagic fever .

Family Arenaviridae ( Lassa virus ) .

family : Arenaviridae ( Lassa virus ) .

Egg inoculation routes .

1- Chorio allantoic membrane ( CAM ). 2- Allantoic membrane . 3- Yolk sac . 4- Amniotic cavity .

Chorioallantoic membrane ( CAM ) .

2-Allantoic cavity

3-Amniotic cavity

4-Yolk sac