Cytokine-based rapid process control of live virus production: MCP-1 as a cross-family biomarker in Vero cells.

Rapid determination of infectious virus titers is essential for efficient vaccine process development, yet conventional assays such as TCID50 and plaque assays require several days and limit throughput. Cytokine secretion represents a potential surrogate marker, enabling rapid detection of productive infection. Here, we evaluated cytokine secretion in Vero cells infected with live vaccine candidates from the Flaviviridae (Japanese encephalitis virus [JEV], yellow fever virus [YFV], Zika virus [ZIKV]) and Togaviridae (Chikungunya virus [CHIKV]) families. Cytokine profiling revealed consistent induction of MCP-1 across flavivirus infections, with RANTES detectable at lower intensity, while CHIKV infection suppressed cytokine release. MCP-1 secretion showed a strong quantitative correlation with infectious titers for JEV (R² = 0.86) and YFV (R² = 0.88), best described by logarithmic models at 18 and 24 h post infection. Additionally, MCP-1 dynamics reflected infection conditions, distinguishing medium and MOI effects in roller bottle production. These results establish MCP-1 as a rapid, cross-family biomarker of infectious virus replication and highlight its potential as a Process Analytical Technology (PAT) tool for automatable in-process monitoring and accelerated vaccine manufacturing.