Schistosoma mansoni infection alters the host pre-vaccination environment resulting in blunted Hepatitis B vaccination immune responses

Schistosomiasis is a disease caused by parasitic flatworms of the Schistosoma spp., and is increasingly recognized to alter the immune system, and the potential to respond to vaccines. The impact of endemic infections on protective immunity is critical to inform vaccination strategies globally. We assessed the influence of Schistosoma mansoni worm burden on multiple host vaccine-related immune parameters in a Ugandan fishing cohort (n = 75) given three doses of a Hepatitis B (HepB) vaccine at baseline and multiple timepoints post-vaccination. We observed distinct differences in immune responses in instances of higher worm burden, compared to low worm burden or non-infected. Concentrations of pre-vaccination serum schistosome-specific circulating anodic antigen (CAA), linked to worm burden, showed a significant bimodal distribution associated with HepB titers, which was lower in individuals with higher CAA values at month 7 post-vaccination (M7). Comparative chemokine/cytokine responses revealed significant upregulation of CCL19, CXCL9 and CCL17 known to be involved in T cell activation and recruitment, in higher CAA individuals, and CCL17 correlated negatively with HepB titers at month 12 post-vaccination. We show that HepB-specific CD4+ T cell memory responses correlated positively with HepB titers at M7. We further established that those participants with high CAA had significantly lower frequencies of circulating T follicular helper (cTfh) subpopulations pre- and post-vaccination, but higher regulatory T cells (Tregs) post-vaccination, suggesting changes in the immune microenvironment in high CAA could favor Treg recruitment and activation. Additionally, we found that changes in the levels of innate-related cytokines/chemokines CXCL10, IL-1β, and CCL26, involved in driving T helper responses, were associated with increasing CAA concentration. This study provides further insight on pre-vaccination host responses to Schistosoma worm burden which will support our understanding of vaccine responses altered by pathogenic host immune mechanisms and memory function and explain abrogated vaccine responses in communities with endemic infections.

Schistosoma mansoni infection alters the host pre-vaccination environment resulting in blunted Hepatitis B vaccination immune responses

The impact of endemic infections on protective immunity is critical to inform vaccination strategies. In this study, we assessed the influence of Schistosoma mansoni infection on host responses in a Ugandan fishing cohort given a Hepatitis B (HepB) vaccine. Concentrations of schistosome-specific circulating anodic antigen (CAA) pre-vaccination showed a significant bimodal distribution associated with HepB titers, which were lower in individuals with high CAA. We established that participants with high CAA had significantly lower frequencies of circulating T follicular helper (cTfh) subpopulations pre- and post-vaccination and higher regulatory T cells (Tregs) post-vaccination. Polarization towards higher frequencies of Tregs: cTfh cells can be mediated by changes in the cytokine environment favoring Treg differentiation. In fact, we observed higher levels of CCL17 and soluble IL-2R pre-vaccination (important for Treg recruitment and development), in individuals with high CAA that negatively associated with HepB titers. Additionally, alterations in pre-vaccination monocyte function correlated with HepB titers, and changes in innate-related cytokines/chemokine production were associated with increasing CAA concentration. We report, that by influencing the immune landscape, schistosomiasis has the potential to modulate immune responses to HepB vaccination. These findings highlight multiple Schistosoma -related immune associations that could explain abrogated vaccine responses in communities with endemic infections.

Author Summary

Schistosomiasis drives host immune responses for optimal pathogen survival, potentially altering host responses to vaccine-related antigen. Chronic schistosomiasis and co-infection with hepatotropic viruses are common in countries where schistosomiasis is endemic. We explored the impact of Schistosoma mansoni ( S. mansoni ) infection on Hepatitis B (HepB) vaccination of individuals from a fishing community in Uganda. We demonstrate that high schistosome-specific antigen (circulating anodic antigen, CAA) concentration pre-vaccination, is associated with lower HepB antibody titers post-vaccination. We show higher pre-vaccination levels of cellular and soluble factors in instances of high CAA that are negatively associated with HepB antibody titers post-vaccination, which coincided with lower frequencies of circulating T follicular helper cell populations (cTfh), proliferating antibody secreting cells (ASCs), and higher frequencies of regulatory T cells (Tregs). We also show that monocyte function is important in HepB vaccine responses, and that high CAA is associated with alterations in the early innate cytokine/chemokine microenvironment. Our findings suggest that in individuals with high CAA and likely high worm burden, schistosomiasis creates and sustains an environment that is polarized against optimal host immune responses to the vaccine, which puts many endemic communities at risk for infection against HepB and other diseases that are preventable by vaccines.

Adenosine deaminase-1 delineates human follicular helper T cell function and is altered with HIV

Follicular helper T cells (Tfh) play critical roles instructing, and initiating T-cell dependent antibody responses. The underlying mechanisms that enhance their function is therefore critical for vaccine development. Here we apply gene array analysis identifying adenosine deaminase (ADA) as a key molecule that delineates a human Tfh helper program in proliferating circulating Tfh (cTfh) cells and Germinal Centers Tfh (GC-Tfh). ADA-1 expression and enzymatic activity are increased in efficient cTfh2-17/GC-Tfh cells. Exogenous ADA-1 enhances less efficient cTfh1 and pro-follicular Tfh PD-1+ CXCR5+ cells to provide B cell help, while pharmacological inhibition of ADA-1 activity impedes cTfh2-17/GC-Tfh function and diminished antibody response. Mechanistically, ADA-1 controls the Tfh program by influencing IL6/IL-2 production, controlling CD26 extracellular expression and could balance signals through adenosine receptors. Interestingly, dysfunctional Tfh from HIV infected-individual fail to regulate the ADA pathway. Thus, ADA-1 regulates human Tfh and represents a potential target for development of vaccine strategy.

Adenosine DeAminase (ADA) as an adjuvant molecule for human HIV-1 vaccine

Follicular helper T cells (Tfh) play critical role in shaping, instructing, and initiating T-cell dependent antibody responses. Understanding the underlying mechanisms that enhance their function is therefore critical for vaccine development. Using a unique gene array analysis, we have identified adenosine deaminase (ADA), as a novel key molecule that drives Tfh helper program in proliferating Germinal Centers Tfh (GC Tfh) and circulatory Tfh (cTfh) cells following their interactions with B cells. In fact, our gene array analysis showed that CD26 and ADA were exclusively up-regulated within the less efficient cTfh1 (CD4+CD45RA−CXCR5+CXCR3+) and cTfh2-17 (CD4+CD45RA−CXCR5+CXCR3+CCR6+/−) subsets, respectively. ADA enzymatic activity is significantly higher, as well, in cTfh2-17 than in the less-efficient cTfh1 cells. Exogenous ADA enhances the ability of Tfh cells to provide B cell help while inhibition of ADA activity by specific inhibitors impeded Tfh function and blunted antibody response. Our results further demonstrated that enhancement of Tfh function by ADA pathway could be due to increase in IL-6 and decrease in IL-2 production in the co-culture, and maintenance of low extracellular expression of CD26. Moreover, blocking IL-2 in cTfh2-17 co-culture from virally suppressed HIV subjects (ST) showed a significant decrease of CD26 expression associated with a rescued helper capacity. Finally, in vivo use of recombinant ADA as an adjuvant in a DNA based HIV vaccine enhanced Tfh cells differentiation and enhanced anti-Env humoral response and isotype class-switch.

Thus, ADA activity fine-tunes Tfh helper program and deciphering how ADA regulate the function of Tfh subsets would benefit future vaccine adjuvant design.

Altered Memory Circulating T Follicular Helper-B Cell Interaction in Early Acute HIV Infection

The RV254 cohort of HIV-infected very early acute (4thG stage 1 and 2) (stage 1/2) and late acute (4thG stage 3) (stage 3) individuals was used to study T helper- B cell responses in acute HIV infection and the impact of early antiretroviral treatment (ART) on T and B cell function. To investigate this, the function of circulating T follicular helper cells (cTfh) from this cohort was examined, and cTfh and memory B cell populations were phenotyped. Impaired cTfh cell function was observed in individuals treated in stage 3 when compared to stage 1/2. The cTfh/B cell cocultures showed lower B cell survival and IgG secretion at stage 3 compared to stage 1/2. This coincided with lower IL-10 and increased RANTES and TNF-α suggesting a role for inflammation in altering cTfh and B cell responses. Elevated plasma viral load in stage 3 was found to correlate with decreased cTfh-mediated B cell IgG production indicating a role for increased viremia in cTfh impairment and dysfunctional humoral response. Phenotypic perturbations were also evident in the mature B cell compartment, most notably a decrease in resting memory B cells in stage 3 compared to stage 1/2, coinciding with higher viremia. Our coculture assay also suggested that intrinsic memory B cell defects could contribute to the impaired response despite at a lower level. Overall, cTfh-mediated B cell responses are significantly altered in stage 3 compared to stage 1/2, coinciding with increased inflammation and a reduction in memory B cells. These data suggest that early ART for acutely HIV infected individuals could prevent immune dysregulation while preserving cTfh function and B cell memory.

The HIV-specific T cell memory response diminishes rapidly even after the initiation of anti-retroviral treatment (ART), and there is no control of viral rebound if treatment is interrupted. Restoration or preservation of memory T cells or B cells with treatment, to allow for control of virus replication after ART is stopped, is therefore very important. CD4⁺ T cells, in particular T follicular helper (Tfh) cells, have a major role in mediating antiviral immunity by providing help to B cells, which is key to a strong and efficient anti-HIV antibody response. The unique RV254 cohort provided the best setting to analyze immune responses during very early acute HIV, as the study was able to enroll individuals that were infected for less than 2 weeks and initiated treatment approximately 1–2 days after recruitment. We aimed to study the capacity of memory circulating Tfh (cTfh) cells to promote B cell help in acute HIV infection, and found the interaction to be dysfunctional in the later stage compared to the very early stages, accompanied by increased levels of proinflammatory cytokines and a reduction in regulatory cytokines. High levels of plasma viremia correlated with low cTfh-mediated B cell antibody production in later stage acute individuals; and memory B cells were significantly decreased but could be restored with ART, compared to chronically infected individuals, who could not normalize this compartment compared to healthy individuals. Overall, we show that the cTfh- B cell interaction and B cell memory compartment is altered in late stage acute infection, mainly attributed to an increase in inflammation and skewing of the response away from helper to proinflammatory. Identifying individuals for treatment in the earliest stages of acute infection, prior to immune damage, could preserve cTfh function and the anti-HIV B cell response, therefore reducing the chances of viral rebound upon the cessation of ART.

Global analyses of monocyte subsets revealed age-related alternations after stimulation of pathogen recognition receptors

In the aging population, intricate interactions between the innate and adaptive immune response is not as effective compared to younger adults. Monocytes play an important role in defense against microbes and express an array of pattern recognition receptors (PRRs). We applied a comprehensive approach to evaluate the effects of a broad range of innate immune agonists (LPS, CLO97, and 5′pppRNA) on monocyte subsets isolated from healthy non-frail adults and old subjects. We analyzed transcriptome data and measured cytokine and chemokine, ROS, and NO production. Under ex vivo conditions, we observed a larger proportion of genes were specifically upregulated in the classical (CD14+CD16−) and non-classical (CD14dimCD16+) monocytes while the intermediate (CD14+CD16+) monocytes showed a smaller proportion of upregulated genes. Distinct genes observed across both age groups for CD16+ monocytes included: CX3CR1, IL21R, IFITM1/2/3, SIGLEC10, and SOD1; whereas CD16− monocytes expressed CCR1/2, SELL, CD64, CD93, CD36, and CD14. Analysis of the transcriptional profiles elicited by innate agonists revealed age-related alternations in functional pathways. After stimulation of RIGI with 5′pppRNA, we observed that classical monocytes isolated from adults uniquely expressed the RIGI MDA5 mediated induction of IFNα and IFNβ pathway, as well as the IFNα transcript, which corresponded to higher levels of IFNα production. In addition, agonists elicited higher levels of IFNγ from non-classical monocytes isolated from adults. Our findings represent a comprehensive analysis of the influence of human aging on PRRs signaling and have implications for strategies to enhance the immune response in the context of infection or immunization.

Reversible Reprogramming of Circulating Memory T Follicular Helper Cell Function during Chronic HIV Infection

Despite the overwhelming benefits of antiretroviral therapy (ART) in curtailing viral load in HIV-infected individuals, ART does not fully restore cellular and humoral immunity. HIV-infected individuals under ART show reduced responses to vaccination and infections and are unable to mount an effective antiviral immune response upon ART cessation. Many factors contribute to these defects, including persistent inflammation, especially in lymphoid tissues, where T follicular helper (Tfh) cells instruct and help B cells launch an effective humoral immune response. In this study we investigated the phenotype and function of circulating memory Tfh cells as a surrogate of Tfh cells in lymph nodes and found significant impairment of this cell population in chronically HIV-infected individuals, leading to reduced B cell responses. We further show that these aberrant memory Tfh cells exhibit an IL-2-responsive gene signature and are more polarized toward a Th1 phenotype. Treatment of functional memory Tfh cells with IL-2 was able to recapitulate the detrimental reprogramming. Importantly, this defect was reversible, as interfering with the IL-2 signaling pathway helped reverse the abnormal differentiation and improved Ab responses. Thus, reversible reprogramming of memory Tfh cells in HIV-infected individuals could be used to enhance Ab responses. Altered microenvironmental conditions in lymphoid tissues leading to altered Tfh cell differentiation could provide one explanation for the poor responsiveness of HIV-infected individuals to new Ags. This explanation has important implications for the development of therapeutic interventions to enhance HIV- and vaccine-mediated Ab responses in patients under ART.

Clearance of virus infection from the CNS

Viruses that cause encephalomyelitis infect neurons and recovery from infection requires noncytolytic clearance of virus from the nervous system to avoid damaging these irreplaceable cells. Several murine model systems of virus infection have been used to identify clearance mechanisms. Quantitative analysis of Sindbis virus clearance over 6 months shows three phases: day 5-7, clearance of infectious virus, but continued presence of viral RNA; day 8-60, decreasing levels of viral RNA; day 60-180, maintenance of viral RNA at low levels. Antiviral antibody and interferon-γ have major roles in clearance with a likely role for IgM as well as IgG antibody. Long-term residence of virus-specific immune cells in the nervous system is necessary to prevent virus reactivation.

The kinetics of B-cell trafficking and long-term maintenance in the CNS induced by Sindbis virus infection (39.14)

Anti-viral antibodies are essential for both the clearance of Sindbis virus (SINV) and long-term suppression of reactivation in the CNS. To characterize the changing functional characteristics of B-cells and identify important determinants of B-cell trafficking and long-term maintenance, CNS tissue from SINV-infected mice was assessed at various times post-infection (pi) using flow cytometry and qRT-PCR. Plasmablasts (PBs) and memory B-cells (MBs) (CD19+CD38+CD138-IgM-IgD-) were 70% of the B-cell population for at least 6-mo pi, while plasma cells (CD19+/-CD38-CD138-) were less than 5% of the population. Staining for intracellular and surface IgG at day 26 pi detected 50% PBs and 60% MBs. A small population of CD19+CD38-CD138- cells was detected indicating possible germinal center (GC) B-cells in the brain. Further staining for GC marker GL-7 detected GL-7+ CD38+/- cells in the brain for at least 1-mo pi. mRNA levels of CXCL9/CXCL10 (trafficking), CCL19/CXCL13 (follicle formation), and BAFF (B-cell survival) peaked on days 5-7 pi. Levels gradually decreased and returned close to baseline by 6-mo pi except for BAFF that was maintained at a low level. The expression of CXCR3, CCR7, and BAFF receptor were detected on B-cells for at least 1-mo pi. These results suggest that PBs and MBs play a role in the long-term suppression of SINV replication and that the brain may provide a microenvironment for differentiation and survival of B-cells.

Dependence of stress resistance on a spore coat heteropolysaccharide in Dictyostelium

In Dictyostelium, sporulation occurs synchronously as prespore cells approach the apex of the aerial stalk during culmination. Each prespore cell becomes surrounded by its own coat comprised of a core of crystalline cellulose and a branched heteropolysaccharide sandwiched between heterogeneous cysteine-rich glycoproteins. The function of the heteropolysaccharide, which consists of galactose and N-acetylgalactosamine, is unknown. Two glycosyltransferase-like genes encoding multifunctional proteins, each with predicted features of a heteropolysaccharide synthase, were identified in the Dictyostelium discoideum genome. pgtB and pgtC transcripts were modestly upregulated during early development, and pgtB was further intensely upregulated at the time of heteropolysaccharide accumulation. Disruption of either gene reduced synthase-like activity and blocked heteropolysaccharide formation, based on loss of cytological labeling with a lectin and absence of component sugars after acid hydrolysis. Cell mixing experiments showed that heteropolysaccharide expression is spore cell autonomous, suggesting a physical association with other coat molecules during assembly. Mutant coats expressed reduced levels of crystalline cellulose based on chemical analysis after acid degradation, and cellulose was heterogeneously affected based on flow cytometry and electron microscopy. Mutant coats also contained elevated levels of selected coat proteins but not others and were sensitive to shear. Mutant spores were unusually susceptible to hypertonic collapse and damage by detergent or hypertonic stress. Thus, the heteropolysaccharide is essential for spore integrity, which can be explained by a role in the formation of crystalline cellulose and regulation of the protein content of the coat.

Role of SP65 in assembly of the Dictyostelium discoideum spore coat

Like the cyst walls of other protists, the spore coat of Dictyostelium discoideum is formed de novo to protect the enclosed dormant cell from stress. Spore coat assembly is initiated by exocytosis of protein and polysaccharide precursors at the cell surface, followed by the infusion of nascent cellulose fibrils, resulting in an asymmetrical trilaminar sandwich with cellulose filling the middle layer. A molecular complex consisting of cellulose and two proteins, SP85 and SP65, is associated with the inner and middle layers and is required for proper organization of distinct proteins in the outer layer. Here we show that, unlike SP85 and other protein precursors, which are stored in prespore vesicles, SP65 is, like cellulose, synthesized just in time. By tagging the SP65 locus with green fluorescent protein, we find that SP65 is delivered to the cell surface via largely distinct vesicles, suggesting that separate delivery of components of the cellulose-SP85-SP65 complex regulates its formation at the cell surface. In support of previous in vivo studies, recombinant SP65 and SP85 are shown to interact directly. In addition, truncation of SP65 causes a defect of the outer layer permeability barrier as seen previously for SP85 mutants. These observations suggest that assembly of the cellulose-SP85-SP65 triad at the cell surface is biosynthetically regulated both temporally and spatially and that the complex contributes an essential function to outer layer architecture and function.

Initiation of Mucin-type O-Glycosylation in Dictyostelium Is Homologous to the Corresponding Step in Animals and Is Important for Spore Coat Function

Like animal cells, many unicellular eukaryotes modify mucin-like domains of secretory proteins with multiple O-linked glycans. Unlike animal mucin-type glycans, those of some microbial eukaryotes are initiated by alpha-linked GlcNAc rather than alpha-GalNAc. Based on sequence similarity to a recently cloned soluble polypeptide hydroxyproline GlcNAc-transferase that modifies Skp1 in the cytoplasm of the social ameba Dictyostelium, we have identified an enzyme, polypeptide alpha-N-acetylglucosaminyltransferase (pp alpha-GlcNAc-T2), that attaches GlcNAc to numerous secretory proteins in this organism. Unlike the Skp1 GlcNAc-transferase, pp alpha-GlcNAc-T2 is predicted to be a type 2 transmembrane protein. A highly purified, soluble, recombinant fragment of pp alpha-GlcNAc-T2 efficiently transfers GlcNAc from UDP-GlcNAc to synthetic peptides corresponding to mucin-like domains in two proteins that traverse the secretory pathway. pp alpha-GlcNAc-T2 is required for addition of GlcNAc to peptides in cell extracts and to the proteins in vivo. Mass spectrometry and Edman degradation analyses show that pp alpha-GlcNAc-T2 attaches GlcNAc in alpha-linkage to the Thr residues of all the synthetic mucin repeats. pp alpha-GlcNAc-T2 is encoded by the previously described modB locus defined by chemical mutagenesis, based on sequence analysis and complementation studies. This finding establishes that the many phenotypes of modB mutants, including a permeability defect in the spore coat, can now be ascribed to defects in mucin-type O-glycosylation. A comparison of the sequences of pp alpha-GlcNAc-T2 and the animal pp alpha-GalNAc-transferases reveals an ancient common ancestry indicating that, despite the different N-acetylhexosamines involved, the enzymes share a common mechanism of action.

Formation of the outer layer of the Dictyostelium spore coat depends on the inner-layer protein SP85/PsB

The Dictyostelium spore is surrounded by a 220 microm thick trilaminar coat that consists of inner and outer electron-dense layers surrounding a central region of cellulose microfibrils. In previous studies, a mutant strain (TL56) lacking three proteins associated with the outer layer exhibited increased permeability to macromolecular tracers, suggesting that this layer contributes to the coat permeability barrier. Electron microscopy now shows that the outer layer is incomplete in the coats of this mutant and consists of a residual regular array of punctate electron densities. The outer layer is also incomplete in a mutant lacking a cellulose-binding protein associated with the inner layer, and these coats are deficient in an outer-layer protein and another coat protein. To examine the mechanism by which this inner-layer protein, SP85, contributes to outer-layer formation, various domain fragments were overexpressed in forming spores. Most of these exert dominant negative effects similar to the deletion of outer-layer proteins, but one construct, consisting of a fusion of the N-terminal and Cys-rich C1 domain, induces a dense mat of novel filaments at the surface of the outer layer. Biochemical studies show that the C1 domain binds cellulose, and a combination of site-directed mutations that inhibits its cellulose-binding activity suppresses outer-layer filament induction. The results suggest that, in addition to a previously described early role in regulating cellulose synthesis, SP85 subsequently contributes a cross-bridging function between cellulose and other coat proteins to organize previously unrecognized structural elements in the outer layer of the coat.

Passive immunization with Neisseria meningitidis PorA specific immune sera reduces nasopharyngeal colonization of group B meningococcus in an infant rat nasal challenge model

To examine the protective efficacy of specific immune sera generated by meningococcal vaccine candidates against nasopharyngeal colonization, we developed an infant rat nasal colonization model for group B meningococcus. In this model, Sprague-Dawley infant rats were challenged intranasally in with host adapted, piliated Neisseria meningitidis group B strains H355 or H44/76 administered concurrently with iron dextran. Colonization was assessed by quantitative culture of nasal homogenates and expressed as log(10) colony forming units (c.f.u.) per nose. Three to five log(10) c.f.u. of N. meningitidis were routinely recovered from the nasal tissue up to 4 days post-challenge. Passive immunization (i.p.) of the infant rats with either PorA or whole cell antisera 24 h prior to homologous challenge resulted in a significant reduction of N. meningitidis colonization in the nasal tissues of these animals. These results demonstrate that this model can be utilized to evaluate the role of antibody to prevent the initial nasopharyngeal colonization by group B meningococcus.

Enhancing The Clinical Practicum Experience Through Journal Writing

Although journaling is commonplace, its usefulness or effectiveness has been rarely supported by empirical data or examples. The purpose of this article is to highlight integration of classroom and clinical learning, decision-making skills and level of skill acquisition in the Senior Practicum experiences through student journal entry exemplars. Critical thinking, observation and description, and empathy and release of feelings will be discussed.

Measurement of central venous oxygen saturation in patients with myocarial infarction

Central venous oxygen saturation (CVSO 2 ) was measured in 31 patients with myocardial infarction. CVSO 2 correlated well with the patients' clinical course. In those patients not in heart failure, mean ± sem for CVSO 2 was 70 ± 1%. When heart failure was present, CVSO 2 averaged 56 ± 1%. When both heart failure and shock were present, CVSO 2 averaged 43 ± 1%. In nine patients, serial determinations of arterial oxygen saturation and CVSO 2 were made. In 22 of 26 instances, either a fall in CVSO 2 was accompanied by an increase in the arteriovenous oxygen saturation difference or an increase in CVSO 2 was accompanied by a decrease in arteriovenous oxygen saturation difference. Serial measurements of CVSO 2 appear to be a useful method of monitoring changes in myocardial function in patients with myocardial infarction.