Group B Streptococcus vaccine development: present status and future considerations, with emphasis on perspectives for low and middle income countries

Globally, group B Streptococcus (GBS) remains the leading cause of sepsis and meningitis in young infants, with its greatest burden in the first 90 days of life. Intrapartum antibiotic prophylaxis (IAP) for women at risk of transmitting GBS to their newborns has been effective in reducing, but not eliminating, the young infant GBS disease burden in many high income countries. However, identification of women at risk and administration of IAP is very difficult in many low and middle income country (LMIC) settings, and is not possible for home deliveries. Immunization of pregnant women with a GBS vaccine represents an alternate pathway to protecting newborns from GBS disease, through the transplacental antibody transfer to the fetus in utero. This approach to prevent GBS disease in young infants is currently under development, and is approaching late stage clinical evaluation. This manuscript includes a review of the natural history of the disease, global disease burden estimates, diagnosis and existing control options in different settings, the biological rationale for a vaccine including previous supportive studies, analysis of current candidates in development, possible correlates of protection and current status of immunogenicity assays. Future potential vaccine development pathways to licensure and use in LMICs, trial design and implementation options are discussed, with the objective to provide a basis for reflection, rather than recommendations.

Comparison and characterization of immunoglobulin G subclasses among primate species

Little information is available on the immunoglobulin G (IgG) subclasses expressed in the sera of nonhuman primate species. To address this issue, we compared the IgG subclasses found in humans (IgG1, IgG2, IgG3, and IgG4) to those of nonhuman primates, such as baboons and macaques. Cross-reactive antihuman IgG subtype-specific reagents were identified and used to analyze purified IgG from sera by solid-phase enzyme-linked immunosorbent assay. Protein A-purified human IgG obtained from sera was composed of IgG1, IgG2, IgG3, and IgG4, whereas baboon and macaque IgG was composed of IgG1, IgG2, and IgG4. Protein G-purified human IgG was composed of IgG1, IgG2, IgG3, and IgG4, whereas baboon and macaque IgG was composed of IgG1, IgG2, and IgG4. To test the possibility that baboon and macaque IgG3 is actually present, but is outcompeted for binding to proteins A and G by the other more abundant IgG subclasses, we repurified the IgG from sera that did not bind either protein A or protein G. We found a baboon IgG3 population in the sera that did not bind protein A, but bound protein G. No IgG3 subtype was detectable in macaque sera. These data suggest that baboon sera, like human sera, contain four IgG subtypes, whereas macaque sera exhibit only three of the human subclass analogs. In addition, the IgG subtype-specific reagents were shown to be useful in determining the IgG subclass distribution following vaccination of baboons with hepatitis B surface antigen.