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.

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.

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.

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 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.

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.

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.

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 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.

Bacteriophages can induce bacterial production of harmful toxins, such as:
- Diphtheria toxin
- Cholera toxin from Vibrio cholerae
- Botulism toxin

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.

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.

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.

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