Infections during pregnancy with pathogens such as helminths correlate with altered immune responses to common childhood immunizations. However, the molecular mechanisms that underlie this remain unknown. Using our murine model of maternal schistosomiasis, when immunized, males from infected mothers had a lower frequency of antigen-specific germinal center B cells and downregulation of transcripts downstream of BCR signaling compared to males from uninfected mothers. This is driven by a reduction in developing B cell populations within the bone marrow of pups from infected mothers. Males from infected mothers were impacted to a greater extent than their female littermate counterparts. We found this defect to be caused by aberrant expression of the long non-coding RNA Xist in males leading to dysregulated Igalpha expression on developing B cells. This, for the first time, links dysfunctional BCR signaling with Xist expression, while also proposing a detrimental function for Xist expression in males.

Il-4 has a critical role in organizing the peripheral lymph nodes in homeostasis and after vaccination. To further understand the molecular mechanisms and their impact in the immune response, we used single cell RNA-Seq of CD45+ cells in 4get and 4getIL4R−/− mice following tetanus/diphtheria immunization. We found that the lack of IL-4 signaling restrains the expression of key co-stimulatory and differentiation molecules CD83, CD86, and xbp1, while upregulating the jun/junb/fos pathways. These alterations result in reduced B cell proliferation and differentiation into plasma cells. Surprisingly, we found that in the absence of IL-4 signaling the ratio of dark to light zone residing germinal center shifts from the normal ratio to one dominated by the dark zone. The increase in Dark Zone germinal centers lead to an increase in the diversity of the repertoire in vaccinated 4getIL4R−/− mice as confirmed by VDJ-seq. We also observed that the upregulation of the transcription factor T-bet has the capacity of inducing a similar phenotype. Finally, even though the amount of memory B cells was increased in the absence of IL-4 signaling, we observed that these cells are not able to respond to a secondary challenge. These data suggest a pivotal role for IL-4 in governing B-cell differentiation and the development of optimal cellular and humoral immunity to vaccination. supported by grants from NIH R01 AI135045

Maternal helminth infections are a global public health concern that correlate with altered infant immune responses to childhood immunizations and infection. A mechanistic understanding of how maternal infection and inflammation alters the immune responses of offspring is lacking but is critical to decrease childhood morbidity and to understand the consequences of specific long-lived immunity defects. Using our model of maternal Schistosoma mansoni infection, we have shown that murine pups born to mothers chronically infected with Schistosoma mansoni have reduced responses to vaccinations, corresponding to what has been reported in humans. To determine the origin of this humoral immunity defect, we began investigating the plasticity and functionality of progenitors of lymphoid cells critical for a protective humoral response. We found an increase in the common lymphoid progenitors (CLPs) in the bone marrow of pups from Schistosome infected mothers, but a marked decrease in immature and transitional B cells in male mice, indicating sex-specific limitations during B cell maturation. Using single cell V(D)J sequencing, we found only male pups from infected mothers have a more restricted repertoire compared to male mice from uninfected mothers after immunization, leading to decreased antigen-specific B cells in the germinal center of the draining lymph node. We hypothesize that epigenetic regulation of key immune genes is the mechanistic root of long-lived defects in humoral immunity to foreign antigens during maternal Schistosomiasis. Supported by a grant from NIH (R01 AI135045)

Maternal helminth infections are a global public health concern that correlate with altered infant immune responses to childhood immunizations and infection. A mechanistic understanding of how maternal helminth infection alters the immune responses of offspring is critical to improve childhood vaccine regimens in endemic areas, decrease childhood morbidity, and to understand the consequences of specific defects in long-lived immunity. Our murine model of maternal Schistosoma mansoni infection demonstrated that pups born to mothers chronically infected with Schistosoma mansoni have reduced IL-4 production and B cell expansion. This defect continues following tetanus/diphtheria immunization, resulting in impaired immunity. To determine the origin of this humoral immunity defect, we began investigating lymphoid progenitors. We found an increase in the common lymphoid progenitors (CLPs) in the bone marrow of naïve mice from infected mothers. When immunized with a Tetanus/Diphtheria vaccination, there is a significant reduction in expansion of these progenitors in comparison to age matched controls from uninfected mothers coupled with a decrease in bone marrow B cells. RNA sequencing revealed a defect in stem cell pluripotency signaling pathway. Further analysis post-immunization shows a decrease in immature B cells in the bone marrow of pups from infected mothers, suggesting a more exclusive selection process or differential selective pressure, leading to lower B cell frequencies in the draining lymph node. We hypothesize that altered transcriptional regulation at the progenitor level caused by maternal Schistosomiasis is the mechanistic root of long-lived defects in humoral immunity to foreign antigens.

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