Virology Lecture Notes

Virology Lecture Notes

• Viruses are acellular, obligate intracellular parasites.
• Viruses lack organelles and ribosomes.
• Viruses hijack the host cell's machinery for replication.
• Viruses are filterable agents (0.01-0.3 um).
• Viral structure includes a capsid (protein coat) and a nucleic acid core (DNA or RNA).
• Some viruses are enveloped, with an outer lipid layer.
• Replication strategies differ between DNA and RNA viruses.
• DNA viruses typically replicate in the host cell's nucleus, while RNA viruses usually replicate in the cytoplasm.
• Some viruses replicate through a lytic cycle, rapidly producing new virus particles and lysing the host cell.
• Other viruses have a lysogenic cycle, where the viral DNA integrates with the host DNA and replicates with the host cell.
• Viral replication steps generally involve: attachment, penetration, uncoating, viral replication and gene expression, viral assembly, and release.
• Vaccines and drugs are used to combat viral infections.
• There are different types of vaccines: inactivated, subunit, RNA vaccines.
• RNA vaccines work by introducing mRNA that encodes viral proteins to the host, and they promote an immune response to combat the virus in the future.
• Viral structure and replication processes play a role in virus identification.
• Different types of viruses exist (helical, icosahedral, enveloped)
• Viruses can be broadly categorized as DNA or RNA viruses based on their genetic material.
• Many viruses are responsible for worldwide pandemics.
• Understanding virus replication strategies is key to combating infections.
• Seasonal flu and SARs-CoV-2 are examples of pandemic-producing respiratory viruses.

History of Vaccines

• Edward Jenner discovered the smallpox vaccine in 1796.
• Smallpox was eradicated globally by 1980.
• Louis Pasteur developed the first rabies vaccine in 1885.
• Jonas Salk invented the first polio vaccine in 1955.
• Albert Sabin developed the oral polio vaccine in 1961.
• Significant strides have been made in vaccine development, targeting various infectious diseases.
• The development and deployment of COVID-19 vaccines highlight the fast-paced progress in this field.

Strategies for Fighting Pandemic Viruses

• Respiratory viruses like influenza and SARS-CoV-2 cause widespread pandemics.
• Influenza seasonal viruses cause significant yearly deaths.
• Knowledge of international surveillance systems, virology, and ecology is crucial to combatting viral pandemics.
• Specific understanding of immune responses is vital for rational drug development.
• Lipid-based nanocarriers are potentially useful drug delivery systems for combating respiratory infections.
• Effective drugs and delivery systems are required to overcome viral pandemics.

Viral Structure and Replication

• Viruses are composed of either DNA or RNA, with protein capsids.
• Enveloped viruses also have an outer lipid membrane.
• Different viruses have different structures, which affects their transmission, infectivity, and disease presentation.
• The steps in viral replication vary depending on the virus type.
• Understanding viral replication is vital to preventing and treating infections.

Viral Replication

• Viral replication involves the virus's integration into the host cell to utilize its cellular machinery.
• The viral genome is then used to produce viral proteins that are crucial in viral assembly.
• New virus particles are assembled and released from the host cell.

Viral Classification

• Viruses are classified based on their genetics, structure, and replication strategies.
• Different classes of viruses have different modes of transmission and disease presentations.
• Knowledge of viral classification is critical in understanding the spread and potential for pandemic viral infections.

Viral Cultivation

• Various methods exist for culturing viruses, including cell culture and embryonated chicken eggs.
• Determining which method is appropriate depends on the type of virus being studied.
• These techniques are crucial for research, vaccine development, and diagnostic testing.

Viral Cultivation: Cell Culture

• Primary cells are taken directly from an organism and used to culture viruses.
• Secondary cells are derived from primary cells for a limited number of passages.
• Continuous cell lines are artificially transformed cells that can be propagated indefinitely.
• Different types of cell cultures offer advantages depending on the application or type of virus being studied.

Viral Transformation and Oncogenesis

• Certain viruses can induce uncontrolled host cell growth, potentially leading to cancer.
• Viral oncogenes can contribute to cellular transformation.
• Viral transformation pathways and interactions with host cellular machinery must be understood.

Viral Modes of Transmission

• Respiratory transmission is common for influenza and coronaviruses
• Fecal-oral transmission is involved in the spread of some viruses.
• Sexual transmission is important in the spread of certain viruses that are directly transferred via bodily fluids during sexual activity .
• Transmission can occur through contaminated objects, tissue transplants, or animal bites.
• Some viruses can be transmitted across the placenta.