Oncogenic Viruses and Cancer Types

• Viruses are intracellular, obligate parasites that need a host to survive because they can't self-replicate or metabolize on their own.
• Cancer in a human is a malignant tumor that involves continuous proliferation of cells that come from the body's normal cells.
• Cells undergo changes called transformation due to mutation, gene rearrangement, oncogene activation, or tumor suppressor inactivation.

Oncho-Viruses

• Viruses that can cause cancer are oncogenic viruses.
• Onchoviruses are single-stranded RNA viruses.
• They typically infect vertebrates, including humans.
• Transmission of these viruses occurs via bodily fluids like blood and secretions.
• Severe hemorrhagic fevers can be caused by onchoviruses, leading to high mortality rates.
• The viruses enter the host's bloodstream through damaged skin, mucous membranes, contaminated needles, or medical equipment.

Types of Cancer and Cell Types

• Carcinoma affects epithelium cells

• Leukaemia affects blood-forming cells.

• Lymphoma affects lymphocyte cells.

• Mesothelioma affects mesothelium cells.

• Sarcoma affects Connective Tissue.

• About 20% of total human cancer cases are caused by viruses.

• Only a few viruses that can cause various tumors in animals are linked to human cancers and are considered oncogenic.

List of oncogenic virsues

• Hepatitis B virus (HBV)
• Hepatitis C virus (HCV)
• Human papillomavirus (HPV)
• Epstein Barr virus (EBV)
• Human herpes virus 8 (HHV8)
• Merkel cell polyomavirus (MCPyV)
• Ebola virus
• HTLV-1 (Human T-Lymphocyte Virus 1)

Pathogenesis of Onchoviruses

• Onchoviruses target immune cells, particularly macrophages and dendritic cells, once they enter the bloodstream.
• They interfere with the production of interferons and antiviral molecules to evade host immune defenses.
• These viruses can disrupt blood coagulation pathways, causing disseminated intravascular coagulation (DIC) and hemorrhage.
• It causes dysfunction of endothelial cells lining blood vessels, leading to increased vascular permeability and leakage.

Systemic Inflammation and Multi-Organ Dysfunction

• Infection triggers a systemic inflammatory response with the release of pro-inflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α).
• Severe cases can lead to multi-organ dysfunction syndrome (MODS), affecting the liver, kidneys, and lungs that can often be accompanied by shock and high mortality rates.

Immunology of Onchoviruses

• They evade the host immune response by inhibiting the production of interferons.
• The viruses target immune cells like macrophages and dendritic cells to disrupt immune responses.
• A cytokine storm can be triggered by infections.
• The host produces antibodies in response to infection, but onchoviruses can undergo antigenic variation, altering their surface proteins to evade recognition by antibodies.
• Infections can dysregulate adaptive immune response, impairing T cell function, decreasing virus clearance, and causing apoptosis of lymphocytes.
• The immune response to infection can contribute to tissue damage, such as immune complexes depositing in tissues and triggering inflammation

Epidemiology of Onchoviruses

• Onchoviruses are mainly found in certain regions of Africa, specifically in Central and West Africa.
• Examples include outbreaks of Ebola virus in countries like Democratic Republic of Congo and Sudan.
• The viruses are often zoonotic, meaning they can be transmitted from animals to humans.
• An example of this is the Ebola virus. It is believed to originate in fruit bats, which serve as natural reservoir hosts.
• Human infections occur through contact with infected animals or consumption of contaminated bushmeat.
• Outbreaks are typically sporadic and unpredictable, and can occur in remote areas with limited healthcare infrastructure.
• An Example is the Marburg virus, another member of the Filoviridae family, it has occurred in isolated communities in Africa.
• Nosocomial transmission of Onchovirus infections can occur in healthcare settings during outbreaks due to poor infection control, and inadequate personal protective equipment. The 2014 Ebola outbreak in West Africa was made worse by healthcare-associated infections among medical personnel.
• The 2014-2016 Ebola outbreak in West Africa killed over 11,000.

Management of Onchoviruses

• Management of onchovirus infections primarily involves supportive care to address symptoms and complications.
• Fluid and electrolyte management needed to prevent dehydration and electrolyte imbalances.
• Nutritional support is used to maintain adequate intake and support the body's immune response.
• Strict infection control measures are crucial to prevent the spread of onchovirus infections.
• Isolation precautions and proper disposal of contaminated materials such as medical waste and PPE needed to prevent transmission.
• Healthcare workers should have training in infection control protocols and the use of PPE to prevent nosocomial transmission.

Experimental Therapies

• Therapy options include: antiviral medications, monoclonal antibodies, and convalescent plasma to treat infections.
• Remdesivir,has shown promise in treating infections in clinical trials.
• Monoclonal antibodies targeting specific viral proteins, may help neutralize the virus and reduce disease severity.
• Convalescent plasma that is obtained from individuals who have recovered from onchovirus infections, contains antibodies and can be used as a treatment for active infections.

Vaccine Development

• Vaccine development is a crucial strategy for preventing onchovirus infections and reducing the burden of disease.
• Several candidate vaccines for onchoviruses, including Ebola and Marburg viruses, are currently in development and undergoing clinical trials.
• The rVSV-ZEBOV vaccine has shown efficacy in preventing Ebola virus infection and has been used in outbreak response efforts in Africa.

Public Health Measures

• Public health measures are essential for controlling onchovirus outbreaks and preventing further spread.
• These measures include: surveillance, early detection of cases, contact tracing, isolation.
• Promote awareness about the risks of onchovirus infections and promote preventive measures with health education and communication.