DNA Viruses and Hepadnaviridae

DNA Viruses

• Virus families with DNA genomes include Hepadnaviridae, Herpesviridae, Adenoviridae, Papillomaviridae, Polyomaviridae, Parvoviridae, and Poxviridae.
• Most DNA viruses exhibit an icosahedral shape, except for Poxvirus.

Hepadnaviridae

• Genome: Possesses partially double-stranded DNA (pdsDNA) with a length ranging from 3.0 to 3.4 kilobases (kb).
• Virion: Demonstrates a spherical structure, occasionally pleomorphic, with a diameter of 42-50 nm. Consists of an outer envelope with surface proteins surrounding an icosahedral nucleocapsid.
• Host Range: Infects mammals (including humans), birds, reptiles, and fish.

Genera and Species of Hepadnaviridae

• Orthohepadnavirus: Infects mammals, with Hepatitis B virus (HBV) as the most well-known member.
• Avihepadnavirus: Infects birds.
• Herpetohepadnavirus: Infects reptiles and amphibians.
• Metahepadnavirus: Infects fish.
• Parahepadnavirus: Infects fish.

Mode of Transmission and Diseases of Hepadnaviridae

• HBV is a bloodborne pathogen transmitted through direct contact and exchange of body secretions (semen, saliva, milk, vaginal secretions, amniotic fluid), contaminated blood products, percutaneous injection, and perinatal exposure.
• Diseases: Outcomes range from acute infection with resolution (90%) to fulminant hepatitis (1%), chronic hepatitis, asymptomatic carrier state, chronic persistent or active disease, cirrhosis, and hepatocellular carcinoma.

Diagnosis and Non-Infectious Particles of Hepadnaviridae

• Diagnosis: Diagnosis relies on serological markers, viral antigen detection, and PCR to determine viral load. Note: Best indication of active viral replication is HBV DNA in serum (PCR).
• Non-infectious particles, composed of lipids and virus envelope proteins, are released from infected liver cells without nucleocapsids. These particles include spheres and filaments, both 22 nm in diameter, with filaments up to 200 nm long. They are more abundant than virions in the blood.

Reminders on HBV

• HBV is a DNA virus with a circular genome, belonging to the family Hepadnaviridae, genus Orthohepadnavirus, employing reverse transcriptase (RT) to replicate progeny DNA from an RNA intermediate.
• Transmission occurs through blood or bodily fluids. Sexual intercourse is a ready method of transmission.
• Treatment of chronic hepatitis acquired in adulthood with IFN can be successful; prevention depends on blocking person-to-person transmission and immunization.
• During active infection, the blood contains infectious virions (Dane particles), surface antigen spheres, and tubules. HBeAg presence indicates Dane particles, while HBcAg is undetectable in blood.
• Antibodies appear in the order of anti-HBc, anti-HBe, and anti-HBs, indicating recovery. Failure to form anti-HBe or anti-HBs leads to chronic carrier status.

Herpesviridae

• These are at risk of cirrhosis and HCC if HBe-positive and babies who acquire at birth.
• Infections are common in people due of the high rates of HIV.
• Viruses have an icosahedral capsid surrounded by a lipid envelope containing glycoprotein spikes.
• Viruses have linear, double-stranded DNA genomes.
• Virion size is between 120-200 nm.

Herpesviridae Reproduction

• Viruses can cause latent and lytic infections.
• During latency, the virus is dormant in the host and can reactivate later.

Herpesviridae Subfamilies

• Alphaherpesvirinae: Includes genera like Simplex Virus (e.g., HSV-I and HSV-2) and Varicella Virus (e.g., VZV).
• Betaherpesvirinae: Includes genera like Cytomegalovirus (e g, HCMV) and Roseolovirus (e.g., HHV-6 and HHV-7).
• Gammaherpesvirinae: Includes genera like Lymphocryptovirus (e.g., EBV) and Rhadinovirus (e.g., KSHV).

Herpesviridae Impact

• Capable of causing both asymptomatic and symptomatic disorders
• Cause latent infections.
• Affect many species of warm- and cold-blooded animals.
• More than 100 known viruses were isolated
• Have 8 human viruses

Herpes Simplex Virus (HSV-1 & HSV-2)

• Modes of transmission: via Direct/Oral-Genital contact leading to oral herpes (cold sores) or genital herpes
• Symptoms: Oral sores, fever, and swollen lymph nodes with potential to cause encephalitis
• Latency: The virus remains dormant in nerve cells (trigeminal/sacral ganglia) and can reactivate, causing recurrent infections.
• Diseases: Causes gingivostomatitis, herpes labialis, conjunctivitis, keratitis, encephalitis, cold sores/fever blisters; herpetic whitlow (hands), herpes gladiatorum (body); genital herpes

Herpes Simplex Virus (HSV)

• Diagnosis: Cell culture, enzyme immunoassay (EIA), immunofluorescence assay (FA), polymerase chain reaction (PCR), aspirates, and conjunctival scrapings.
• Skin and mucous membranes serve as entry points.
• Skin and mucous membranes enter the virus, which multiplies and causes lysis of cells and formation of cells.
• Cells containing eosinophilic intranuclear inclusion bodies are found in scrapings or sections of vesicles.

Immune Response and Epidemiology

• The immune response causes the production of IgM, IgG, and IgA antibodies.
• The antibody response to recurrences is variable
• Most people are infected by the time they are adults.

Varicella Zoster Virus (VZV)

• MOT: Via close personal contact, especially respiratory.
• *Chickenpox transmission: *Via high contagion through respiratory droplets or direct contact with the fluid from blisters.
• Shingles Transmission: Not as contagious but spread by skin contact to those unvaccinated.
• Symptoms include chickenpox (varicella) with fever and maculopapular rash, and shingles (zoster/herpes zoster) rash and vesicular lesions in a dermatomal pattern, with postherpetic neuralgia.
• VZV remains dormant in nerve cells and can reactivate years later, especially when the immune system is weakened.

Epstein-Barr Virus (EBV)

• Most infections cause Varicella (Chicken Pox) or Herpes Zoster.
• Infections cause Varicella (Chicken Pox),
• Herpes Zoster Symptoms: Postherpetic pain or Ophthalmic/Generalized Zoster.

Varicella is obtained via and causes:

• the respiratory Patho genesis.
• There is no animal.
• Model Dissemination of the the blood stream.

VZV Details

• VZV may affect any sensory nerve, it is rare for more than one of these to be involved.
• Antibody appears within the first few weeks.
• T-cell responses are important.

###Human Herpes Virus

• This happens at some points in the persons lifetime.
• They shed into the body.
• Transplantation puts a person in risk because of the transmission.

Diagnosis of EBV

• Dependant on demonstrating specific IgM antibody
• Viral antigen is found in fibroblast cultures
• B-cell Lymphoma
• MOT: High contagious and spread by sharing various forms of saliva.
• Disease: Heterophile-Antibody-positive, which is the infectious and the Progressive Lymphoid disease.

Diagnosis

• Must use a "Serological Test".
• A "Paul-Bunnel" test with Atypical "Lymphocytes" that uses B lymphocytes
• • EBV contains induced virus that are linked to B lymphocytes.

Kaposi's Sarcoma

• MOT: The fluids may occur via breast milk and semen or injection of fluids.   Disease: Kaposi's Sarcoma Primary diagnosis: in STU hybridizations
• They must perform in VIVO to fill the Lytic presence .

Human Papilloma Virus

• Supercoil their genomes
• Long central region that determine the Humans tissue specification
• Structure: circular double-stranded DNA, icosahedral capsid, no envelope.
• MOT. Direct contact.
• Disease: Warts, condylomas, and papillomas

Diagnosis of HPV

• Perform pap smears
• DNA Hybridizations
• Histology of warts

Replication

•  Binds glycoproteins and enter a cell releasing visions to the per nuclear. 
• As. Might be expected from liability and genital wars

Adenovirus

• Is caused by respiratory droplets
• Symptoms are like the common cold

Poxvirus

• Mot Causes respiratory droplets from animals and humans

Prophylaxis and Remedies:

• Causes disruptive effects
• Molecular boilogists have now taken a special interest

Smallpox and Vaccinia

• the differential diagnosis most often needed was between smallpox and chickenpox