Immune Responses to Invasive Group B Streptococcal Disease in Adults.

Morven S Edwards,Erika Bartolini,Monica Fabbrini,Giada Buffi,Stefano Bonacci,Immaculada Margarit,Giovanna Tuscano,C Daniela Rinaudo,Marcia A Rench,Carol J Baker

doi:10.3201/eid2211.160914

Abstract

Immunization of nonpregnant adults could help prevent invasive group B Streptococcus (GBS) infections, but adult immune responses have not been investigated. We defined capsular polysaccharide (CPS) and pilus island (PI) surface antigen distribution and expression and immune responses to GBS infection in nonpregnant adults. Prospective surveillance from 7 hospitals in Houston, Texas, USA, identified 102 adults with GBS bacteremia; 43% had skin/soft tissue infection, 16% bacteremia without focus, and 12% osteomyelitis. CPS-specific IgG was determined by ELISA and pilus-specific IgG by multiplex immunoassay. CPS types were Ia (24.5%), Ib (12.7%), II (9.8%), III (16.7%), IV (13.7%), and V (12.7%); 9.8% were nontypeable by serologic methods. Pili, expressed by 89%, were most often PI-2a. CPS and pilus-specific IgG increased during convalescence among patients with strains expressing CPS or PI. All GBS expressed CPS or PI; 79% expressed both. Increased antibodies to CPS and PI during recovery suggests that GBS bacteremia in adults is potentially vaccine preventable.

Highlights

In the United States, group B Streptococcus (GBS) has emerged as a frequent cause of invasive infection in nonpregnant adults with underlying medical conditions
Participants and Setting We identified cases of GBS bacteremia by conducting prospective, laboratory-based surveillance from March 2012 through October 2014 at 4 Texas Medical Center hospitals (Houston, TX, USA) and 3 suburban affiliates of 1 Texas Medical Center hospital, all of which provided uniform diagnostic evaluations and medical care
As a group, nonpregnant adults demonstrated an immune response to major virulence antigens after invasive GBS infection

Summary

Introduction

In the United States, group B Streptococcus (GBS) has emerged as a frequent cause of invasive infection in nonpregnant adults with underlying medical conditions. The incidence of GBS disease among these patients increased from 3.6 cases/100,000 persons in 1990 to 7.3 cases/100,000 persons in 2007 (p65 years of age [2]. The Centers for Disease Control and Prevention Active Bacterial Core surveillance estimated that 28,000 cases of invasive GBS disease occurred in the United States during 2014 and that 25,900 (93%) cases occurred beyond infancy, primarily in nonpregnant adults [3]. Immunization of adults potentially could reduce the GBS disease burden in the United States, but data are needed regarding immune responses during convalescence from invasive disease [9]. We characterized CPS and PI genotypes and expression among isolates and explored immune responses to these surface antigens during convalescence from invasive infection in a cohort of nonpregnant adults

Methods

Results

Conclusion