Which laboratory method identifies the poliovirus serotype by genetic region sequencing?

• A. RT-PCR for viral RNA
• B. Virus isolation in cell culture
• C. Serology to detect antibodies
• D. Sequencing of VP1 region to identify serotype and origin

Answer: (D)

Sequencing the VP1 region to identify serotype and origin relies on the fact that this part of the poliovirus genome encodes the major surface protein whose sequence varies in a serotype-specific way. By reading the VP1 genetic code, you can unambiguously tell which serotype is present (types 1, 2, or 3) and place the virus on a phylogenetic tree to infer its lineage and origin. This genetic region provides the most precise and actionable information for poliovirus characterization, which is crucial for surveillance, tracking transmission, and distinguishing wild-type from vaccine-derived or circulating strains.

RT-PCR detects viral RNA and can indicate presence or quantity, but serotype identification isn’t guaranteed unless primers are specifically designed for that purpose. Virus isolation in cell culture confirms infectious virus but doesn’t reveal serotype. Serology detects antibodies, which reflect host exposure rather than the virus’s genotype or lineage.