Serological Responses to Target Streptococcus pyogenes Vaccine Antigens in Patients With Proven Invasive β-Hemolytic Streptococcal Infections.

This article focuses on the immune responses to candidate vaccine antigens in adults with invasive β-hemolytic streptococcal (iBHS) infections caused by Lancefield group A (Streptococcus pyogenes; Strep A), group C/G (Streptococcus dysgalactiae subspecies equisimilis; SDSE), and group B (Streptococcus agalactiae; GBS). In a prospective observational study of 33 patients, robust antibody responses to six Strep A vaccine candidate antigens were observed in those with invasive Strep A infection, while significant cross-reactive responses to streptococcal C5a peptidase (ScpA) were also detected in patients with invasive SDSE and GBS infections. These findings suggest potential cross-species protection that could inform vaccine development targeting multiple Lancefield groups. The study highlights the importance of further research into immunological correlates of protection and the possibility that vaccines including ScpA or homologous antigens might prevent invasive infections across these streptococcal groups.