Impact of SARS-CoV-2 Infection on Maternal Microbiota and Its Consequences for Offspring

The human microbiome, comprising trillions of microorganisms inhabiting various body sites, plays a crucial role in maintaining human health and well-being.

It has been established that a significant portion of the microbial community that colonizes a newborn originates from the mother [1,2,3,4,5,6,7].

This newly acquired microbiome has a profound impact on the immune programming of infants, with long-term consequences for their health. Disturbances in the infant’s microbiome have been associated with increased susceptibility to infections, chronic inflammatory diseases, and reduced vaccine efficacy [8,9,10,11,12,13,14,15].

Animal studies have demonstrated that microbial dysbiosis during early life can influence disease pathogenesis through alterations in immune system maturation [12,13,14].

While the interplay between the microbiome and the immune system continues throughout human life, recent research has revealed the complex relationship between the microbiome, systemic physiology, and various health conditions, including both acute and chronic diseases [16].

Consequently, the window of opportunity for microbiome inoculation in infants either establishes a healthy immune system or leads to increased susceptibility to immune-mediated diseases [17,18,19,20,21,22,23,24,25]. However, the impact of SARS-CoV-2 infections on the microbiotas of pregnant women and their offspring remains largely unexplored.

SARS-CoV-2 Infection in Pregnant Women

Previous studies have found that patients with severe symptoms of SARS-CoV-2 display a dysbiotic microbiome [26]. Pregnant women with SARS-CoV-2 infection are particularly vulnerable to experiencing severe symptoms, leading to an increased risk of maternal complications and adverse perinatal outcomes [27, 28]. Despite this, there is limited research investigating the microbiotas of pregnant women with SARS-CoV-2 infection.

To date, only two studies have characterized the microbiotas of pregnant women with SARS-CoV-2 infection. The first study, conducted in Spain, reported an increased abundance of Bacteroidales in the nasopharyngeal swabs of pregnant women with active SARS-CoV-2 infection compared to healthy controls [29].

In the second study, conducted in Mexico, differences in the gut microbiota of SARS-CoV-2-positive pregnant women and their infants were observed compared to pregnant women without evidence of SARS-CoV-2 viral particles in stool [30].

However, most of the pregnant women included in the latter study were negative for SARS-CoV-2 on nasopharyngeal swabs and asymptomatic at the time of sample collection, indicating past SARS-CoV-2 infection.

Microbiota Changes in Pregnant Women and Offspring

Apart from the gut microbiota, the vaginal and oral microbiotas of pregnant women are critical in seeding the infant’s gut microbiota if born vaginally [1, 3]. However, there is limited research on the impact of SARS-CoV-2 infection at different stages of pregnancy on the initial seed of the infant’s microbiota, including the vaginal and oral microbiotas of pregnant women.

Therefore, the objective of this study was to determine whether SARS-CoV-2 infection during pregnancy, either in early or late stages or at the time of delivery, results in microbiota changes that are passed on to the offspring.

The study found that SARS-CoV-2 infection during pregnancy, particularly in early pregnancy or active infection at the time of delivery, was associated with perturbations in the vaginal, gut, and oral microbiota of pregnant women compared to

pregnant women without SARS-CoV-2 infection. These perturbations in the maternal microbiota may have consequences for the establishment of the infant’s microbiome and subsequent health outcomes.

Vaginal Microbiota

The vaginal microbiota of pregnant women plays a crucial role in the colonization of the infant’s gut during birth. It is characterized by a predominance of Lactobacillus species, which provide a protective barrier against potential pathogens and help maintain a healthy microbial balance. However, SARS-CoV-2 infection during pregnancy has been associated with alterations in the vaginal microbiota composition.

Studies have shown that pregnant women with SARS-CoV-2 infection had a decreased abundance of Lactobacillus species in their vaginal microbiota compared to uninfected pregnant women [29]. This dysbiosis may impact the transmission of beneficial bacteria to the newborn during delivery, potentially influencing the infant’s gut microbiota composition and immune development.

Gut Microbiota

The gut microbiota plays a vital role in immune system development and overall health. Perturbations in the maternal gut microbiota can have long-lasting effects on the offspring’s health. Limited research has been conducted specifically on the impact of SARS-CoV-2 infection on the gut microbiota of pregnant women and their infants.

In a study conducted in Mexico, it was observed that the gut microbiota composition differed between SARS-CoV-2-positive pregnant women and their infants compared to SARS-CoV-2-negative pregnant women [30].

The study found a higher abundance of opportunistic pathogens, such as Klebsiella pneumoniae and Enterococcus faecium, in the gut microbiota of SARS-CoV-2-positive pregnant women and their infants. These findings suggest that maternal SARS-CoV-2 infection may lead to dysbiosis in the gut microbiota of both the mother and the infant.

Oral Microbiota

The oral microbiota also plays a significant role in the colonization of the infant’s gut microbiota, particularly through vertical transmission during breastfeeding. However, the impact of SARS-CoV-2 infection on the oral microbiota of pregnant women and its consequences for the offspring are not well-studied.

Future Directions

Further research is needed to better understand the impact of SARS-CoV-2 infection on the maternal microbiota and its consequences for offspring health. Longitudinal studies that follow pregnant women from early pregnancy through delivery and assess the microbiota at multiple body sites (vaginal, gut, oral) are necessary to elucidate the dynamics of microbial changes associated with SARS-CoV-2 infection.

Additionally, studies should explore the functional implications of microbiota alterations and their potential relationship with immune development and disease susceptibility in infants born to SARS-CoV-2-positive mothers. This research could help identify strategies to mitigate the negative effects of SARS-CoV-2 infection on the maternal microbiota and optimize infant health outcomes.

Conclusion

SARS-CoV-2 infection during pregnancy can impact the composition of the maternal microbiota, including the vaginal, gut, and oral microbiota. These alterations may have consequences for the establishment of the infant’s microbiome and subsequent health outcomes. Further research is needed to understand the functional implications of these microbial changes and develop interventions to support maternal and infant microbiota health in the context of SARS-CoV-2 infection.

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reference link : https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-023-01577-z#Sec23