Viral, Bacterial and Fungal Infections in Patients with Recurrent Miscarriage – Joop S.E. Laven

 

One of the easiest microbiome to assess in human body is the vaginal microbiome or urogenital microbiome. Vaginal microbiome has less chances of contamination and has less diverse microbiome compared to other parts. Microbiome is defined with alpha and beta diversities; alpha diversity is about the diverse number of species and beta diversity is about the richness of those species. Community state types are the microbiome and environments which are different from each other in vagina and upper urogenital tract. There are five types of community state types, one of which is associated with poor outcomes in terms of recurrent miscarriage and reproductive performance. The microbiome composition also changes within the menstrual cycle, with a lot of diversity between different individuals. Causes of recurrent miscarriage are demographics, lifestyle, BMI, obesity, age, genetic, immunological, endocrine factors, etc. Women with miscarriage have much more often been treated in the past with antibiotics for genital tract infections, dysbiosis, and other kinds of infections, showing a link between vaginal microbiome and recurrent miscarriage. A study comparing women with normal pregnancy and no miscarriage vs women who miscarried showed different microbiome composition and alpha diversity in both groups. Women choosing abortion also had a different microbiome from those who miscarried. It is difficult to analyze uterus microbiome without contamination and studies done demonstrate it as a reflection of the vaginal microbiome. Another study showed Lactobacillus dominant cervico-vaginal microbiome in women who did not miscarry vs a more diverse microbiome lacking Lactobacillus dominance in women who miscarried. A study on uterine microbiota and menstrual cycle phase showed less richness and diversity in women with no miscarriage when they approach ovulation and a constant microbiome during the luteal phase, whereas women who miscarry do not attenuate their microbiome richness and diversity when they approach ovulation and still have a lot of alpha and beta diversity during luteal phase. When a study compared vaginal and uterine microbiome, it reflected a lot of diversity as well as similarity between the two, and women with recurrent miscarriage had a microbiome with higher concentration of Gardnerella vaginalis. A study looking at community state types showed type I, II, III and V more in women with viable pregnancy and type IV more dominant in women with complete and incomplete miscarriage. Another study on gut microbiome, metabolism and cytokines demonstrated different gut microbiome composition and different metabolome spectra (in terms of lipid metabolism, acetylcholine handling, etc.) in women with and without miscarriage. In summary, endometrial and vaginal microbiome with increased alpha diversity and decreased Lactobacillus dominance have shown association with recurrent miscarriage.

 

There are 1.5-2 kilos of bacterial and virome genome in human body. Studies on Herpes simplex, cytomegalovirus and Parvovirus have shown women with miscarriage more often positive for these antibodies, highlighting a positive relationship with these viruses and miscarriage. Certain Human Papillomaviruses have shown protective effect against recurrent miscarriage. The vaginal virome composition depends on community state type, history of bacterial vaginosis, and bacterium spectra. Looking at the immune regulation from the time of implantation and establishing a viable pregnancy, ratio of Th1 and Th2 (T-helper) cells from implantation phase changes to Th17 cells post implantation. A recent study looking at the CTLs (cytotoxic T lymphocytes) showed no difference in women with and without miscarriage. They further compared miscarriage with normal vs abnormal fetal keratotype, the number of T regulatory (Treg) cells, effector Treg cells were low and clonal Treg cells were much higher in miscarriage with abnormal fetal keratotype, indicating a causal relationship mediated through innate immune response. Women with lower concentration of peripheral natural killer cells always had issues with Gardnerella vaginalis and gram-negative anaerobes, indicating a relationship between microbiome composition and innate immune response.

 

In attempts to change the microbiome, a study used metformin, aspirin and combinations, and were able to bring a little bit of preferable change to the microbiome (Lactobacillus dominant). Attempts on transplanting a certain series of Lactobacillus showed temporary changes to the microbiome, however, without any changes on the outcomes. Male factors such as infertility have also shown to impact female microbiome. A recent study showed that community state type IV (type with poor outcome) is quite often changing into type I, II, III or V (types with good outcome), while the latter does not change much into type IV. Thus, wait and watch could also be a good option for these patients.

 

In summary, there might be a relationship between the innate immune system and microbiome. Virome needs to be assessed more often, and wait and watch is the only treatment option.

 

Dysbiosis and Reproduction – Henritte Svarre Nielsen

 

A healthy gut has more diverse microbiome, dysbiosis occurs when diversity decreases. Whereas in vagina, Lactobacillus is the only important bacteria, dysbiosis has less Lactobacillus and more pathogenic strains like Gardenerella vaginalis. However, there is lack of knowledge with dysbiosis due to lack of powered science, fast technological revolution making it difficult to compare studies, extreme cost of technology, and contamination in samples. Gut microbiome has influence on both available estrogen and progesterone. Studies on gut microbiome and PCOS (polycystic ovary syndrome) have shown difference in the gut microbiome of PCOS patients vs control. The study with largest number of participants comparing endometriosis patients with controls showed no difference in the gut microbiome of two groups. Another study on gut microbiome of healthy women showed no changes in the microbiome according to the menstrual cycle and there was no correlation to the use of hormonal or non-hormonal contraception. In conclusion, association of gut dysbiosis has been seen with PCOS as well as endometriosis, but the studies have been small, might have publication bias and causal mechanisms have not been studied.

 

A recent study on vaginal microbiome used daily sampling of vaginal microbiome throughout a full menstrual cycle and categorized women into four different categories with the dynamics. Constant dysbiotic throughout a menstrual cycle, dysbiotic only during menstruation, unstable dysbiosis throughout the cycle, and constant eubiotic. Several studies have demonstrated a correlation between dysbiosis and reproductive outcomes. One such study showed that women with dysbiosis had only 9% chance of achieving life birth after an IVF (in vitro fertilization) cycle compared to 35% in those without dysbiosis. It is possible to wait for an embryo transfer (ET) in a cycle where dysbiosis is absent. Study examining endometrial fluid and vaginal microbiome found no statistical difference in the bacterial content of the two, and a positive correlation between miscarriage and endometrial dysbiosis was noted. A larger study with 342 participants took samples of endometrial fluid and endometrial biopsies 80 days prior to ET in a stimulated cycle. Biomass was low in 38% of the cases, no significant difference was found between endometrial fluid and endometrial biopsies, and patients with lactobacillus dominance showed reproductive success. For reproductive tract dysbiosis, the options include waiting for spontaneous conversion, antibiotics, biotherapeutic Lactin V, and vaginal microbiome transplantation. Spontaneous conversion from dysbiosis to eubiosis occurs 30% times. Antibiotics can remove pathogens but not restore lactobacillus content, it has 60-70% success but has a higher recurrence rate. Vaginal microbiome test of a patient with a history of still births and miscarriage revealed her microbiome exclusively dominated by Gardnerella. A vaginal microbiome transplantation (VMT) with a donor microbiome consisting of almost exclusively Lactobacillus crispatus demonstrated symptom relief (smelly vaginal discharge, itching and pain) a week after the transplant and stayed stable for half a year. She was also treated with anticoagulation for antiphospholipid antibody syndrome. Later, she had a successful pregnancy and life birth. Testing showed that the patient had same Lactobacillus crispatus as donor, confirming donor engraftment.

 

In conclusion, gut microbiome is not well investigated in women’s health, reproductive tract dysbiosis is associated with poor reproductive outcome, successful dysbiosis treatment is yet to be found. A VMT done without antibiotics treatment showed symptom relief and donor engraftment. Further research is needed.

 

European Society of Human Reproduction and Embryology (ESHRE), 39th Annual Meeting, Copenhagen, Denmark, 25-28 June 2023







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