The Pathogenesis and Virulence of the Major Enterovirus Pathogens Associated with Severe Clinical Manifestations: A Comprehensive Review

Enteroviruses (EVs), particularly those within the species Enterovirus A and B, represent a significant global public health burden, especially in infants and young children. While often causing self-limiting hand, foot, and mouth disease (HFMD), certain serotypes can lead to severe neurological and cardiopulmonary complications. This comprehensive review focuses on the major pathogenic serotypes, including enterovirus A71 (EV-A71), coxsackievirus A16 (CV-A16), coxsackievirus A6 (CV-A6), coxsackievirus B3 (CV-B3), and enterovirus D68 (EV-D68). We began by reconstructing a phylogenetic tree based on VP1 protein sequences, elucidating the genetic relationships and evolutionary patterns among these serotypes, which underpin their diverse antigenicity and epidemiology. Building upon this genetic foundation, the review then provides a detailed synthesis of their distinct pathogenesis, highlighting the five-phase clinical progression from exanthematous phase to convalescence, and their unique tropisms for target organs such as the central nervous system and heart. Progressing to the molecular mechanisms, a critical component of this work is a systematic summary of the specific host receptors that mediate viral entry, including SCARB2 for EV-A71 and CV-A16, sialic acid and ICAM-5 for EV-D68, and CAR/CD55 for CV-B3, explaining the mechanistic basis for their tissue specificity and pathogenicity. Finally, to translate these insights into clinical applications, we critically evaluate the current landscape of vaccine development, noting the high efficacy (~90%) of inactivated EV-A71 vaccines in Asia and the significant global success of poliovirus vaccines, while also addressing the stark lack of cross-protective or licensed vaccines for other prevalent serotypes like CV-A16, CV-A6, and EV-D68. The review concludes that the high genetic diversity and serotype-specific immunity of enteroviruses pose a major challenge, necessitating a concerted shift towards the development of broad-spectrum vaccines and therapeutics informed by an integrated understanding of viral evolution, receptor usage, and pathogenesis.