Virology Lectures 2025 #21: Evolution

Introduction to Viral Evolution00:00:11

An introduction to the Red Queen hypothesis, defining how viruses evolve through constant adaptation to their hosts, and how rapid replication allows for real-time observation of evolutionary changes.

The Four Drivers of Evolution00:07:18

Discussion on the primary drivers of viral evolution: large progeny numbers, high mutation rates, quasi-species effects, and natural selection pressures.

Quasi-species and Mutation Rates00:12:32

Explanation of the quasi-species concept, noting that viral populations are dynamic clouds of related mutants rather than single-sequence entities, and the significance of the error threshold.

Genetic Bottlenecks and Müller's Ratchet00:26:37

Analysis of how genetic bottlenecks, such as plaque-to-plaque passage, cause fitness declines through the accumulation of mutations via Müller's ratchet, and how recombination helps rescue these populations.

Antigenic Drift and Shift00:37:16

Overview of influenza evolution via antigenic drift (accumulation of point mutations) and antigenic shift (reassortment of genome segments), which lead to new viral strains and pandemics.

Host-Virus Arms Races00:48:09

Examination of host-virus conflicts, specifically the Red Queen dynamics between host defense proteins like TRIM5alpha and viral counterparts, driven by positive selection.

Virulence and Historical Origins00:54:46

Discussion on the evolution of virulence using the myxoma virus in Australian rabbits as a case study, and techniques like molecular clocks and endogenous viral elements to date the origins of viruses.