antigenome

Antigenome is a term used in virology to describe the RNA strand that is complementary to a viral genome. It is produced during replication and serves as an intermediate template for synthesizing new genomes. The concept is most often discussed in the context of negative-sense RNA viruses, whose genomes must be copied into a positive-sense antigenome before generating additional copies of the genome.

During replication, the viral RNA-dependent RNA polymerase and associated proteins first copy the genome to yield the antigenome. The antigenome then serves as the template for producing progeny genomes. It is typically not packaged into virions and is not directly translated by host ribosomes; its primary function is to template replication rather than encode proteins.

In influenza A virus, for example, the negative-sense genomic RNA segments are copied into a positive-sense complementary RNA (cRNA), which acts as the antigenome and as the template for replication of new viral RNA. The antigenome is generally a transient molecule, present only within infected cells during replication cycles.

The term can also appear in broader discussions of viral replication for other negative-sense RNA viruses, where a positive-sense replicative intermediate is produced to amplify the genome. Overall, the antigenome is a non-infectious, intermediate RNA molecule that plays a central role in genome replication rather than in gene expression.