Exploring microbe-immune crosstalk: immunoglobulin coating of vaginal microbiota

Heleen Schuster MDa,b, Annelot Breedveld MScc, Andries Budding MD PhDa, Paul Savelkoul PhDa,d

aDepartment of Medical Microbiology and Infection Control, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands; bDepartment of Obstetrics and Gynecology, Amsterdam UMC, Univ of Amsterdam, Amsterdam, Netherlands; cDepartment of Molecular Cell Biology and Immunology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands; dDepartment of Medical Microbiology, Maastricht University Medical Centre, Maastricht, Netherlands

As knowledge on the role and composition of the vaginal microbiome is accumulating, more interest is directed to microbe:immune crosstalk. Local immunoglobulins (Igs) play an important role as mediator of mucosal immunity and homeostasis. In the vaginal mucosa, IgG is the dominating antibody, while at other mucosal surfaces IgA is most prevalent. In the gut, alterations in IgA coating of commensal bacteria are associated with inflammatory bowel disease and Clostridium difficile infection. Less is known about the role of local Igs in the female genital tract. We aim to provide insight in the IgA and IgG coating of vaginal bacteria using a combination of flow cytometry based techniques and microbiota profiling.

Vaginal swabs were collected from healthy volunteers. Fluorescence-Activated Cell Sorting (FACS) was used to sort micro-organisms according to IgA and IgG coating. The bacterial composition was analyzed with bacterial profiling technique IS-pro, using fragment variability of the 16S-2S rDNA intergenic spacer region.

Lactobacillus crispatus and L. iners dominated the vaginal microbiota of healthy volunteers and show large numbers of IgA and IgA/IgG coated Lactobacilli. Bacteria with only IgG on their surface were not detected. The proportions of Ig coated bacteria varied among individuals with similar microbial compositions.

Vaginal bacteria show varying amounts of IgA and IgA/IgG coating between different healthy volunteers. The high amount of Ig coated vaginal commensal bacteria demonstrate the importance of local Igs in the mucosal environment. Disturbances of the coating might lead to increased local inflammation and can possibly identify women at risk for diseases of the reproductive tract and adverse pregnancy outcomes. These promising results indicate a putative role of Igs in the maintenance of a healthy microbiome.