Which laboratory technique is used for detecting poliovirus and assessing genetic relatedness in VDPVs?

• A. RT-PCR
• B. ELISA
• C. Gram stain
• D. VP1 sequencing

Answer: (D)

Sequencing the VP1 region provides direct genetic information that lets us quantify how far an isolate has diverged from the Sabin vaccine strains and how closely related different isolates are. The VP1 gene encodes the major capsid protein and accumulates mutations as the virus evolves, so its sequence is the most informative marker for genetic relatedness among poliovirus isolates. By comparing VP1 sequences from an isolate to reference Sabin strains and to other regional isolates, labs can determine if a virus is vaccine-derived and map transmission links—key steps in identifying and tracking VDPVs. RT-PCR can detect viral RNA, but it doesn’t yield the sequence needed to assess relatedness; ELISA detects viral antigens, and Gram stain is not applicable to viruses.