Induction of Siglec-FhiCD101hi eosinophils in the lungs following murine hookworm Nippostrongylus brasiliensis infection.

Helminth-induced eosinophils accumulate around the parasite at the site of infection, or in parasite-damaged tissues well after the helminth has left the site. The role of helminth-elicited eosinophils in mediating parasite control is complex. While they may contribute to direct parasite-killing and tissue repair, their involvement in long-term immunopathogenesis is a concern. In allergic Siglec-FhiCD101hi, eosinophils are associated with pathology. Research has not shown if equivalent subpopulations of eosinophils are a feature of helminth infection. In this study, we demonstrate that lung migration of rodent hookworm Nippostrongylus brasiliensis (Nb) results in a long-term expansion of distinct Siglec-FhiCD101hi eosinophil subpopulations. Nb-elevated eosinophil populations in the bone marrow and circulation did not present this phenotype. Siglec-FhiCD101hi lung eosinophils exhibited an activated morphology including nuclei hyper-segmentation and cytoplasm degranulation. Recruitment of ST2+ ILC2s and not CD4+ T cells to the lungs was associated with the expansion of Siglec-FhiCD101hi eosinophils. This data identifies a morphologically distinct and persistent subset of Siglec-FhiCD101hi lung eosinophils induced following Nb infection. These eosinophils may contribute to long-term pathology following helminth infection.

Il4ra-independent vaginal eosinophil accumulation following helminth infection exacerbates epithelial ulcerative pathology of HSV-2 infection.

How helminths influence the pathogenesis of sexually transmitted viral infections is not comprehensively understood. Here, we show that an acute helminth infection (Nippostrongylus brasiliensis [Nb]) induced a type 2 immune profile in the female genital tract (FGT). This leads to heightened epithelial ulceration and pathology in subsequent herpes simplex virus (HSV)-2 infection. This was IL-5-dependent but IL-4 receptor alpha (Il4ra) independent, associated with increased FGT eosinophils, raised vaginal IL-33, and enhanced epithelial necrosis. Vaginal eosinophil accumulation was promoted by IL-33 induction following targeted vaginal epithelium damage from a papain challenge. Inhibition of IL-33 protected against Nb-exacerbated HSV-2 pathology. Eosinophil depletion reduced IL-33 release and HSV-2 ulceration in Nb-infected mice. These findings demonstrate that Nb-initiated FGT eosinophil recruitment promotes an eosinophil, IL-33, and IL-5 inflammatory circuit that enhances vaginal epithelial necrosis and pathology following HSV-2 infection. These findings identify a mechanistic framework as to how helminth infections can exacerbate viral-induced vaginal pathology.

Impact of Helminth Infections on Female Reproductive Health and Associated Diseases.

A growing body of knowledge exists on the influence of helminth infections on allergies and unrelated infections in the lung and gastrointestinal (GI) mucosa. However, the bystander effects of helminth infections on the female genital mucosa and reproductive health is understudied but important considering the high prevalence of helminth exposure and sexually transmitted infections in low- and middle-income countries (LMICs). In this review, we explore current knowledge about the direct and systemic effects of helminth infections on unrelated diseases. We summarize host disease-controlling immunity of important sexually transmitted infections and introduce the limited knowledge of how helminths infections directly cause pathology to female reproductive tract (FRT), alter susceptibility to sexually transmitted infections and reproduction. We also review work by others on type 2 immunity in the FRT and hypothesize how these insights may guide future work to help understand how helminths alter FRT health.

Surfactant Protein A Impairs Genital HPV16 Pseudovirus Infection by Innate Immune Cell Activation in A Murine Model.

Abstract: Infection by oncogenic human papillomavirus (HPV) is the principle cause of cervical cancer and other anogenital cancers. The majority of cervical cancer cases occur in low- and middle-income countries (LMIC). Prophylactic vaccines exist to combat HPV infection but accessibility to these in LMIC is limited. Alternative preventative measures against HPV infection are therefore also needed to control cervical cancer risk. HPV employs multiple mechanisms to evade the host immune response. Therefore, an approach to promote HPV recognition by the immune system can reduce infection. Surfactant proteins A and D (SP-A and SP-D) are highly effective innate opsonins of pathogens. Their function is primarily understood in the lung, but they are also expressed at other sites of the body, including the female reproductive tract (FRT). We hypothesized that raised levels of SP-A and/or SP-D may enhance immune recognition of HPV and reduce infection. Co-immunoprecipitation and flow cytometry experiments showed that purified human SP-A protein directly bound HPV16 pseudovirions (HPV16-PsVs), and the resulting HPV16-PsVs/SP-A complex enhanced uptake of HPV16-PsVs by RAW264.7 murine macrophages. In contrast, a recombinant fragment of human SP-D bound HPV16-PsVs weakly and had no effect on viral uptake. To assess if SP-A modulates HPV16-PsVs infection in vivo, a murine cervicovaginal challenge model was applied. Surprisingly, neither naïve nor C57BL/6 mice challenged with HPV16-PsVs expressed SP-A in the FRT. However, pre-incubation of HPV16-PsVs with purified human SP-A at a 1:10 (w/w) ratio significantly reduced the level of HPV16-PsV infection. When isolated cells from FRTs of naïve C57BL/6 mice were incubated with HPV16-PsVs and stained for selected innate immune cell populations by flow cytometry, significant increases in HPV16-PsVs uptake by eosinophils, neutrophils, monocytes, and macrophages were observed over time using SP-A-pre-adsorbed virions compared to control particles. This study is the first to describe a biochemical and functional association of HPV16 virions with the innate immune molecule SP-A. We show that SP-A impairs HPV16-PsVs infection and propose that SP-A is a potential candidate for use in topical microbicides which provide protection against new HPV infections.

Pre-conception maternal helminth infection transfers via nursing long-lasting cellular immunity against helminths to offspring.

Maternal immune transfer is the most significant source of protection from early-life infection, but whether maternal transfer of immunity by nursing permanently alters offspring immunity is poorly understood. Here, we identify maternal immune imprinting of offspring nursed by mothers who had a pre-conception helminth infection. Nursing of pups by helminth-exposed mothers transferred protective cellular immunity to these offspring against helminth infection. Enhanced control of infection was not dependent on maternal antibody. Protection associated with systemic development of protective type 2 immunity in T helper 2 (TH2) impaired IL-4Rα-/- offspring. This maternally acquired immunity was maintained into maturity and required transfer (via nursing) to the offspring of maternally derived TH2-competent CD4 T cells. Our data therefore reveal that maternal exposure to a globally prevalent source of infection before pregnancy provides long-term nursing-acquired immune benefits to offspring mediated by maternally derived pathogen-experienced lymphocytes.

Helminth-induced IL-4 expands bystander memory CD8+ T cells for early control of viral infection.

Infection with parasitic helminths can imprint the immune system to modulate bystander inflammatory processes. Bystander or virtual memory CD8+ T cells (TVM) are non-conventional T cells displaying memory properties that can be generated through responsiveness to interleukin (IL)-4. However, it is not clear if helminth-induced type 2 immunity functionally affects the TVM compartment. Here, we show that helminths expand CD44hiCD62LhiCXCR3hiCD49dlo TVM cells through direct IL-4 signaling in CD8+ T cells. Importantly, helminth-mediated conditioning of TVM cells provided enhanced control of acute respiratory infection with the murid gammaherpesvirus 4 (MuHV-4). This enhanced control of MuHV-4 infection could further be explained by an increase in antigen-specific CD8+ T cell effector responses in the lung and was directly dependent on IL-4 signaling. These results demonstrate that IL-4 during helminth infection can non-specifically condition CD8+ T cells, leading to a subsequently raised antigen-specific CD8+ T cell activation that enhances control of viral infection.

Hookworm exposure decreases human papillomavirus uptake and cervical cancer cell migration through systemic regulation of epithelial-mesenchymal transition marker expression.

Persistent infection with human papillomavirus (HPV) is responsible for nearly all new cervical cancer cases worldwide. In low- and middle-income countries (LMIC), infection with helminths has been linked to increased HPV prevalence. As the incidence of cervical cancer rises in helminth endemic regions, it is critical to understand the interaction between exposure to helminths and the progression of cervical cancer. Here we make use of several cervical cancer cell lines to demonstrate that exposure to antigens from the hookworm N. brasiliensis significantly reduces cervical cancer cell migration and global expression of vimentin and N-cadherin. Importantly, N. brasiliensis antigen significantly reduced expression of cell-surface vimentin, while decreasing HPV type 16 (HPV16) pseudovirion internalization. In vivo infection with N. brasiliensis significantly reduced vimentin expression within the female genital tract, confirming the relevance of these in vitro findings. Together, these findings demonstrate that infection with the hookworm-like parasite N. brasiliensis can systemically alter genital tract mesenchymal markers in a way that may impair cervical cancer cell progression. These findings reveal a possible late-stage treatment for reducing cervical cancer progression using helminth antigens.

Surfactant Protein-D Is Essential for Immunity to Helminth Infection.

Pulmonary epithelial cell responses can enhance type 2 immunity and contribute to control of nematode infections. An important epithelial product is the collectin Surfactant Protein D (SP-D). We found that SP-D concentrations increased in the lung following Nippostrongylus brasiliensis infection; this increase was dependent on key components of the type 2 immune response. We carried out loss and gain of function studies of SP-D to establish if SP-D was required for optimal immunity to the parasite. N. brasiliensis infection of SP-D-/- mice resulted in profound impairment of host innate immunity and ability to resolve infection. Raising pulmonary SP-D levels prior to infection enhanced parasite expulsion and type 2 immune responses, including increased numbers of IL-13 producing type 2 innate lymphoid cells (ILC2), elevated expression of markers of alternative activation by alveolar macrophages (alvM) and increased production of the type 2 cytokines IL-4 and IL-13. Adoptive transfer of alvM from SP-D-treated parasite infected mice into naïve recipients enhanced immunity to N. brasiliensis. Protection was associated with selective binding by the SP-D carbohydrate recognition domain (CRD) to L4 parasites to enhance their killing by alvM. These findings are the first demonstration that the collectin SP-D is an essential component of host innate immunity to helminths.