ANTIVIRAL AGENTS (Natural and Synthetic agents)

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1. Acyclovir:

·      Treats Herpes Simplex Virus (HSV) infections, such as cold sores and genital herpes, as well as Varicella-Zoster Virus (VZV), which causes chickenpox and shingles.

·      Mechanism: Inhibits viral DNA replication by incorporating into the viral DNA chain, leading to premature chain termination.

2. Oseltamivir (Tamiflu):

·      Treats and prevents influenza A and B.

·      Mechanism: Inhibits the neuraminidase enzyme on the surface of the influenza virus, preventing the release of new viral particles from infected cells.

3. Zidovudine (AZT):

·      Treats Human Immunodeficiency Virus (HIV) infection.

·      Mechanism: Inhibits reverse transcriptase, an enzyme critical for the replication of HIV, thereby reducing the viral load in the body.

4. Sofosbuvir:

·      Treats hepatitis C virus (HCV) infection.

·      Mechanism: Acts as a nucleotide analog inhibitor of the HCV RNA polymerase, essential for viral replication.

5. Remdesivir:

·      Treats COVID-19 caused by the SARS-CoV-2 virus.

·      Mechanism: Inhibits viral RNA-dependent RNA polymerase, disrupting viral replication.

6. Ganciclovir:

·      Treats cytomegalovirus (CMV) infections, especially in immunocompromised patients.

·      Mechanism: Similar to acyclovir, it inhibits viral DNA synthesis.

These agents are crucial for managing viral infections, especially when vaccines are not available or the infection is severe.

ANTIVIRAL AGENTS IN HUMAN BODY

The human body produces several natural antiviral molecules as part of the innate immune system to combat viral infections. Here are some examples:

1. Interferons:

Types: Interferon-alpha (IFN-α), interferon-beta (IFN-β), and interferon-gamma (IFN-γ).

·      Mechanism: These proteins are produced by cells in response to viral infections.

·      They help to inhibit viral replication within host cells,

·      Activate immune cells like natural killer cells and macrophages,

·      They play a crucial role in the defense against viral infections by interfering with viral replication and activating immune cells.

·      There are three main types of interferons: Type I, Type II, and Type III.

i. Type I Interferons

·      Interferon-alpha (IFN-α) and Interferon-beta (IFN-β)

·      Interferon-alpha (IFN-α) Source: Produced by leukocytes (white blood cells).          

·      Functions: Induces the expression of antiviral proteins that inhibit viral replication.

·      Enhances the presentation of viral antigens to T cells, boosting the adaptive immune response.

·      Increases the activity of natural killer (NK) cells and macrophages, which are crucial for eliminating virus-infected cells.

·      Example Use: Used as a treatment for chronic hepatitis B and C infections, and certain cancers like hairy cell leukemia and Kaposi's sarcoma.

ii. Interferon-beta (IFN-β) Source: Produced mainly by fibroblasts and epithelial cells.

·      Functions: Similar to IFN-α, it induces antiviral proteins and enhances immune cell activity.

·      Reduces inflammation by modulating the immune response.

·      Example Use: Used to treat multiple sclerosis (MS), where it helps reduce the frequency and severity of relapses.

2. Type II Interferon

·      Example: Interferon-gamma (IFN-γ)

·      Interferon-gamma (IFN-γ) Source: Produced by T cells and natural killer (NK) cells.

·      Functions: Activates macrophages, enhancing their ability to destroy pathogens.

·      Promotes the presentation of antigens to T cells, aiding in the adaptive immune response.

·      Increases the production of other cytokines and enhances the overall immune response.

·      Example Use: Used in the treatment of chronic granulomatous disease and severe infections.

3. Type III Interferons

·      Examples: Interferon-lambda (IFN-λ1, IFN-λ2, IFN-λ3)

·      Interferon-lambda (IFN-λ) Source: Produced by various cells, including epithelial cells.

·      Functions: Induces antiviral proteins similarly to Type I interferons, but with a more localized effect on mucosal surfaces such as the respiratory and gastrointestinal tracts.

·      Plays a crucial role in defending against viral infections in tissues exposed to the external environment.

·      Example Use: Research is ongoing for its potential use in treating viral infections like hepatitis C and respiratory infections.

·      Interferons are essential for the body's antiviral defense mechanisms.

·      These molecules play critical roles in the body's defense against viral infections by directly inhibiting viral replication and modulating the immune response to enhance the body's ability to fight off infections.

 

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