Dna Viruses

DNA VIRUSES DNA ENVELOPED / DNA NON ENVELOPED VIRUSES

DNA ENVELOPED VIRUSES • HEPADNAVIRUS :Icosahedral, DS, incomplete circular DNA Eg Hep B virus

• HERPESVIRUS: Icosahedral, DS, Linear DNA Herpes simplex virus (HSV), Varicella zoster (VZ) , Cytomegalovirus (CMV) • POXVIRUS: Complex virus, DS, Linear eg: smallpox, vaccinia virus

HERPES VIRUS • Important human pathogens: – HSV 1 – HSV 2 – V-Z (Varicella zoster) – CMV (Cytomegalovirus) – EBV (Ebstein Barr virus) – Human herpes virus 8

GENERAL CHARACTERISTICS • • • • • • • •

Large ICOSAHEDRAL Lipoprotein envelope Linear, ds DNA Doesn’t have Polymerase Replicate in nucleus Envelope from nuclear membrane* Latent infection

Virus Replication (enveloped virus) • 1. Attachment – Binding Sites must match receptor sites on host cell

• 2. Penetration – Endocytosis (phagocytosis)

• 3. Uncoating – separation of the Viral Genome from the capsid

Virus Replication (enveloped virus) • 4. Biosynthesis – Genome Replication – Transcription – Translation

• 5. Assembly – Virus particles are assembled

• 6. Release – Budding

Herpesviruses • Alpha herpesvirus – HSV 1 & 2 , VZ --epithelial cells ,neurons • BETA herpesvirus – CMV , Human herpesvirus 6--- variety of tissues • Gamma herpesvirus – EBV, , Human herpesvirus 8 (Kaposi sarcoma) – lymphoid cells.

HERPES SIMPLEX VIRUS (HSV) 1&2 • HSV 1 – vesicular lesions above the waist » » » » »

Gingivostomatitis (primary lesion) Recurrent herpes labialis Keratoconjunctivitis Encephalitis (temporal lobe) Herpetic whitlow– pustular lesion on fingers & hands of medical personnel esp dentists. » Herpetes gladitorum– wrestlers. Site of latency – cranial sensory ganglia Transmission– respiratory / saliva

• HSV 2 – vesicular lesions below waist genital herpes neonatal herpes aseptic meningitis site of latency – lumbar / sacral sensory ganglia Transmission– sexual contact / perinatal infection

Herpes Simplex

LAB DIAGNOSIS • Isolation of virus • ELISA / Flourescent antibody • Tzanck smear of infected skin– multinucleated giant cells. • PCR – spinal fluid – in encephalitis TREATMENT Acyclovir

VARICELLA ZOSTER VIRUS (VZV) • • • • •

Chickenpox – primary disease Zoster (shingles) –recurrent Humans – natural host 1 serotype Transmission – respiratory droplets / direct contact with the lesions • Highly contagious • Childhood • worldwide

VZV • INFECTS mucosa upper respiratory tract --- blood ----- skin– vesicular rash • Multinucleated giant cells & intranuclear inclusions ---- base of lesions • Latent virus – dorsal root ganglia (cytoplasm) – later nerve pain + skin lesions • Life long immunity

VZV • • • •

CLINICAL FEATURES 14-21 days incubation Prodrome Papulovesicular rash in crops on trunk –head & extremeties • Papule– vesicle –pustule– crust • Reyes syndrome (aspirin) • Zoster –pain & vesicles on sensory nerve root of head or trunk

LAB DIAGNOSIS • • • •

Clinical diagnosis Cell changes (tzank smear) Isolation Serological Tests

TREATMENT • • • •

Self limiting Acyclovir PREVENTION Vaccine

CYTOMEGALOVIRUS (CMV) • Cytomegalic inclusion disease in neonates (esp congenital abnormalities) • Pneumonia • Humans – natural host • 1 serotype • Transmission – vertical / saliva in young children , • Sexual transmission , by blood transfusion, organ transplantation • Highly contgaeous • worldwide

CMV • INFECTS many organs in fetus– if mother has primary infection in pregnancy & no antibody • Multinucleated giant cells & intranuclear inclusions in infected cells. • Immunocompetent Children & adults – asymptomatic • Immunocompromised --- latent state in leucocyte

CLINICAL FEATURES • 20 %-- Cytomegalic inclusion disease: microcephaly , seizures , deafness, jaundice ,purpura , hepatospleenomegaly • Immunocompetant – Heterophil negative mononucleosis • Immunocompromised – pneumonia , hepatitis • In AIDS pt – intestinal tract – intractable diarroea, Retinitis-- blindness

LAB DIAGNOSIS • Viral isolation • FTA (FLOURESCENT antibody test) • Tissue staining –owl- eye like inclusion bodies in cells • PCR

TREATMENT & PREVENTION • Ganciclover • No vaccine

EPSTEIN BARR VIRUS (EBV) • Causes Infectious mononucleosis • Associated with Burkitt’s lymphoma, B cell lymphomas , Nasopharyngeal carcinomas, hairy leukoplakia (AIDS). • Viral capsid antigen* • Humans –natural host • Infects B lymphocytes – by receptor site for C3.

EBV • • • • • • • • •

Transmission by exchange of saliva Blood transmission – rare Worldwide Causes Infectious mononucleosis Ass with Burkitts lymphoma, Nasopharyngeal Ca, Hairy cell leukoplakia (AIDS) Epithelium & lymphoid tissue of oropharynx – blood – B cells Cytotoxic T cells , Ig M & Ig G against VCA -- immune Heterophil antibodies found Fever , sore throat, lymphadenopathy, spleenomegaly

Lab diagnosis • Atypical lymphocytes • Immunological tests : – Heterophil antibody , EBV specific antibody TREATMENT & PREVENTION – No treatment required for Infectious Mononucleosis – Acyclovir– high doses– in life threatening infection – No vaccine

HUMAN HERPESVIRUS 8 • Kaposi sarcoma (AIDS)