Screening of a potential coxsackievirus B4 vaccine strain through analysis of biological features.

Coxsackievirus B4 (CVB4) is a major pathogen involved in hand, foot, and mouth disease as well as aseptic meningitis, and is associated with type 1 diabetes mellitus. Currently, no effective antiviral drugs or vaccines are available for CVB4 infections. Drawing on successful experience with inactivated vaccines for enterovirus 71 and poliovirus, we developed an inactivated CVB4 vaccine based on Vero cells. The highly pathogenic CVB4 virus strain 140/CHN/2019, isolated from Vero cells and classified as genotype D, reflecting the circulating strains in China. Through three cycles of plaque assays and successive passages, the clone strain KM140-G01 could adapt to Vero cells and grew to a titer exceeding 10⁷ CCID50/mL. The experimentally inactivated CVB4 vaccine, developed from KM140-G01, effectively elicited high levels of neutralizing antibodies in BALB/c mice, with titers ranging from Log2 7.2 to 11.0 and effectively neutralized various clinical isolates (> Log210). Maternal antibodies provided 100% protection against a lethal challenge with CVB4 isolates in lactating BALB/c mice. Therefore, the KM140-G01 strain in this study is a viable new candidate for the development of a coxsackievirus B4 vaccine. The CVB4-infected neonatal mouse model should substantially facilitate CVB4 vaccine evaluation.