Nucleotide and Phenotypic Analyses of Quasispecies Detected in the Spike 1 Gene and its Encoded Protein following IBV Infection in Laying Hens.

The Spike (S) gene encodes the S

envelope glycoprotein and encoded by

the amino-terminus S1 gene, and the

carboxyl-terminus S2 gene (de Haan et

al., 2004). The S1 gene contains 3 hypervariable

regions (HVR) crucial for viral

infectivity, with high rates of

substitution and recombination due to

the RNA nature of the virus (Moreno et

al., 2017).

The “quasispecies”

concept, introduced by

Manfred Eigen in 1971,

characterizes how high

mutation rates in

viruses lead to a

diverse population of

closely related variants,

allowing the virus to

adapt and evolve

throughout the course

of an infection.