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.