Recording-2025-03-04T22_54_35.211Z

Retroviruses Overview

• Retroviruses are unique as they convert RNA genomes into DNA, defying the usual DNA → RNA → protein sequence seen in most organisms.

• The conversion is facilitated by a poor-quality enzyme called reverse transcriptase, leading to high mutation rates in retroviruses like HIV.

Impact of High Mutation Rates

• Due to its imprecise replication process, one individual can harbor multiple genetic variants of HIV at the same time.

• This variability complicates vaccine development because the viral proteins constantly change.

HIV and Host Genome Integration

• Retroviruses integrate their DNA into the host's genome, which can lead to various complications:

  • Persistent infection even while transcription of the viral RNA is suppressed by antiviral drugs.

  • Integration can disrupt normal genes, including tumor suppressor genes, potentially leading to cancer.

Advances in HIV Treatment

• Modern HIV treatments have significantly improved survival rates and are no longer viewed as a death sentence.

• Drugs like PrEP help prevent the transcription of viral RNA in infected cells, and continuous antiviral therapies effectively control the virus.

Cytopathic Effects of Viruses

• Cytopathic effects refer to visible damage caused by viral infection, exemplified by sore throats stemming from cell lysis.

• Viruses can cause the formation of inclusion bodies, which hinder cellular processes.

Respiratory Syncytial Virus (RSV) and Syncytia

• RSV creates syncytia (giant multinucleated cells) in infected lung tissue, impairing lung function and increasing cancer susceptibility.

• Syncytia result when infected cells combine but lose their normal function.

Viral Latency and Transmission

• Some viruses (e.g., HIV, HPV, HSV) remain latent within host cells, often without symptoms

• This can lead to unaware transmission over extended periods.

  • Herpes Simplex Virus (HSV) can reactivate under stress or trauma, leading to new symptoms.

Oncogenic Viruses

• Certain viruses are known to induce cancer; these are referred to as oncogenic viruses:

  • Epstein-Barr Virus (EBV): Causes mononucleosis and can result in Burkitt's lymphoma.

  • Human Papillomavirus (HPV): Linked to warts and cervical cancer; vaccines like Gardasil have been effective in reducing incidence rates.

  • HIV and Hepatitis B are also associated with increased cancer risk due to genomic integration and chronic infection.

Bacteriophages: Viruses of Bacteria

• Bacteriophages are viruses that infect bacteria, critical in biotechnology and medicine.

• They are often double-stranded DNA viruses and can be either lytic or lysogenic:

  • Lytic Phages: Immediately lyse and kill host cells to produce new viruses.

  • Lysogenic Phages: Integrate into the host genome as a prophage and remain dormant until triggered to replicate, causing cell lysis.

• This has applications in gene transfer and synthetic biology for creating new genetic constructs.

Toxins and Bacteriophages

• Bacteriophages can induce bacterial production of harmful toxins, such as:

  • Diphtheria toxin

  • Cholera toxin from Vibrio cholerae

  • Botulism toxin

Viral Culturing Methods

• Viruses cannot be cultured like bacteria; they require live host cells for propagation.

• Plaque assays are used to visualize viral infectivity, evidenced by clearings in a lawn of infected cells.

Manufacturing Vaccines

• Some viruses, such as flu virus, are cultured in chicken eggs for the development of inactivated vaccines.

  • There may be trace amounts of egg proteins in the vaccine, which can be concerning for those with egg allergies.

Noncellular Infectious Agents

• Prions: Misfolded proteins that induce other proteins to misfold; resistant to most sterilization methods and can lead to fatal neurodegenerative diseases (e.g., Creutzfeldt-Jakob disease).

  • Prion diseases can originate from contaminated food sources, such as in cases of mad cow disease.

• Fibroids: RNA molecules that act like infectious agents in flowering plants, with implications for understanding early life forms and genetic evolution.

Conclusion

• Understanding retroviruses, bacteriophages, prions, and fibroids deepens insights into the complexities of viral infections, treatment, and genetic engineering, and underpins future biotechnology advances.