Altered circulating levels of matrix metalloproteinases and inhibitors associated with elevated type 2 cytokines in lymphatic filarial disease

Association between the single-nucleotide polymorphism (rs1030868) variant in matrix metallopeptidase 2 gene and the development of lymphedema

Background

Understanding the genetic and molecular pathophysiology of lymphedema contributes to the identification of the complex interaction of genes associated with lymphedema and provides a key therapeutic opportunity to restore lymphatic function. This study aims to answer whether the single-nucleotide polymorphism (SNP) rs1030868 in the MMP-2 gene could be an associated variant in lymphedema development.

Methods

This study was carried out on 93 lymphedema cases (patients’ group) and 187 healthy individuals (control group). Genotyping of MMP-2 (rs1030868) was done following the protocol of Custom TaqMan® SNP Genotyping Assays. TaqMan™ Fast Advanced Master Mix (Cat# 4448892) was used.

Results

The risk alleles for MMP-2 SNP rs1030868 were A and G of lymphedema development. The GG genotype was associated with triple the risk of lymphedema (OR 3.2, 95% CI 1.2–6.5, p = 0.019), while the AA genotype was associated with 5.9 times the likelihood of lymphedema (OR 5.9, 95% CI 2.3–11.9, p < 0.001).

Conclusions

We concluded that the single-nucleotide polymorphisms of rs1030868 in the matrix metallopeptidase 2 gene (allele A and allele G) could be associated variants with the development of lymphedema.

Eosinophils in filarial infections: Inducers of protection or pathology?

Filariae are parasitic roundworms, which can cause debilitating diseases such as lymphatic filariasis and onchocerciasis. Lymphatic filariasis, also known as elephantiasis, and onchocerciasis, commonly referred to as river blindness, can lead to stigmatizing pathologies and present a socio-economic burden for affected people and their endemic countries. Filariae typically induce a type 2 immune response, which is characterized by cytokines, i.e., IL-4, IL-5 and IL-13 as well as type 2 immune cells including alternatively activated macrophages, innate lymphoid cells and Th2 cells. However, the hallmark characteristic of filarial infections is a profound eosinophilia. Eosinophils are innate immune cells and pivotal in controlling helminth infections in general and filarial infections in particular. By modulating the function of other leukocytes, eosinophils support and drive type 2 immune responses. Moreover, as primary effector cells, eosinophils can directly attack filariae through the release of granules containing toxic cationic proteins with or without extracellular DNA traps. At the same time, eosinophils can be a driving force for filarial pathology as observed during tropical pulmonary eosinophilia in lymphatic filariasis, in dermatitis in onchocerciasis patients as well as adverse events after treatment of onchocerciasis patients with diethylcarbamazine. This review summarizes the latest findings of the importance of eosinophil effector functions including the role of eosinophil-derived proteins in controlling filarial infections and their impact on filarial pathology analyzing both human and experimental animal studies.

Lymphatic filarial serum proteome profiling for identification and characterization of diagnostic biomarkers

Lymphatic Filariasis (LF) affects more than 863 million people in tropical and subtropical areas of the world, causing high morbidity and long illnesses leading to social exclusion and loss of wages. A combination of drugs Ivermectin, Diethylcarbamazine citrate and Albendazole is recommended by WHO to accelerate the Global Programme to Eliminate Lymphatic Filariasis (GPELF). To assess the outcome of GPELF, to re-evaluate and to formulate further strategies there is an imperative need for high quality diagnostic markers. This study was undertaken to identify Lymphatic Filarial biomarkers which can detect LF infections in asymptomatic cases and would also serve as indicators for differentiating among different clinical stages of the disease. A combination of Fourier-transform infrared spectroscopy (FT-IR), MMP zymography, SDS-PAGE, classical 2DE along with MALDI-TOF/MS was done to identify LF biomarkers from serum samples of different stages of LF patients. FT-IR spectroscopy coupled with univariate and multivariate analysis of LF serum samples, revealed significant differences in peak intensity at 3300, 2950, 1645, 1540 and 1448 cm^-1 (p<0.05). The proteomics analysis results showed that various proteins were differentially expressed (p<0.05), including C-reactive protein, α-1-antitrypsin, heterogeneous nuclear ribonucleoprotein D like, apolipoproteins A-I and A-IV in different LF clinical stages. Functional pathway analysis suggested the involvement of differentially expressed proteins in vital physiological pathways like acute phase response, hemostasis, complement and coagulation cascades. Furthermore, the differentiation between different stages of LF cases and biomarkers identified in this study clearly demonstrates the potential of the human serum profiling approach for LF detection. To our knowledge, this is the first report of comparative human serum profiling in different categories of LF patients.

Helminth Coinfection Is Associated With Enhanced Plasma Levels of Matrix Metalloproteinases and Tissue Inhibitor of Metalloproteinases in Tuberculous Lymphadenitis

Matrix metalloproteinases (MMPs) are crucial for tissue remodeling and repair and are expressed in diverse infections, whereas tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors of MMPs. However, the interaction of MMPs and TIMPs in tuberculous lymphadenitis (TBL), an extra-pulmonary form of tuberculosis (EPTB) and helminth (Hel+) coinfection is not known. Therefore, this present study investigates the levels of circulating MMPs (1, 2, 3, 7, 8, 9, 12, 13) and TIMPs (1, 2, 3, 4) in TBL individuals with helminth (Strongyloides stercoralis [Ss], hereafter Hel+) coinfection and without helminth coinfection (hereafter, Hel-). In addition, we have also carried out the regression analysis and calculated the MMP/TIMP ratios between the two study groups. We describe that the circulating levels of MMPs (except MMP-8 and MMP-12) were elevated in TBL-Hel+ coinfected individuals compared to TBL-Hel- individuals. Similarly, the systemic levels of TIMPs (1, 2, 3, 4) were increased in TBL-Hel+ compared to TBL-Hel- groups indicating that it is a feature of helminth coinfection per se. Finally, our multivariate analysis data also revealed that the changes in MMPs and TIMPs were independent of age, sex, and culture status between TBL-Hel+ and TBL-Hel- individuals. We show that the MMP-2 ratio with all TIMPs were significantly associated with TBL-helminth coinfection. Thus, our results describe how helminth infection has a profound effect on the pathogenesis of TBL and that both MMPs and TIMPs could dampen the immunity against the TBL-Hel+ coinfected individuals.

Transcriptome-wide analysis of filarial extract-primed human monocytes reveal changes in LPS-induced PTX3 expression levels

Filarial nematodes modulate immune responses in their host to enable their survival and mediate protective effects against autoimmunity and allergies. In this study, we examined the immunomodulatory capacity of extracts from the human pathogenic filaria Brugia malayi (BmA) on human monocyte responses in a transcriptome-wide manner to identify associated pathways and diseases. As previous transcriptome studies often observed quiescent responses of innate cells to filariae, the potential of BmA to alter LPS driven responses was investigated by analyzing >47.000 transcripts of monocytes from healthy male volunteers stimulated with BmA, Escherichia coli LPS or a sequential stimulation of both. In comparison to ~2200 differentially expressed genes in LPS-only stimulated monocytes, only a limited number of differentially expressed genes were identified upon BmA priming before LPS re-stimulation with only PTX3↓ reaching statistical significance after correcting for multiple testing. Nominal significant differences were reached for metallothioneins↑, MMP9↑, CXCL5/ENA-78↑, CXCL6/GCP-2↑, TNFRSF21↓, and CCL20/MIP3α↓ and were confirmed by qPCR or ELISA. Flow cytometric analysis of activation markers revealed a reduced LPS-induced expression of HLA-DR and CD86 on BmA-primed monocytes as well as a reduced apoptosis of BmA-stimulated monocytes. While our experimental design does not allow a stringent extrapolation of our results to the development of filarial pathology, several genes that were identified in BmA-primed monocytes had previously been associated with filarial pathology, supporting the need for further research.

Recombinant Brugia malayi pepsin inhibitor (rBm33) exploits host signaling events to regulate inflammatory responses associated with lymphatic filarial infections

Prolonged existence of filarial parasites and their molecules within the host modulate the host immune system to instigate their survival and induce inflammatory responses that contribute to disease progression. Recombinant Brugia malayi pepsin inhibitor (rBm33) modulates the host immune responses by skewing towards Th1 responses characterized by secretion of inflammatory molecules such as TNF-α, IL-6, nitric oxide (NO). Here we also specified the molecular signaling events triggered by rBm33 in peripheral blood mononuclear cells (PBMCs) of filarial endemic normals (EN). rBm33 predominantly enhanced the levels of nitric oxide in cultured PBMCs but did not result in oxidative stress to the host cells. Further, rBm33 treatment of human PBMCs resulted in higher GSH/GSSG levels. MYD88 dependent activation was found to be associated with rBm33 specific inflammatory cytokine production. rBm33 triggered intracellular signaling events also involved JNK activation in host PBMCs. In addition, c-Fos and not NF-κB was identified as the transcription factor regulating the expression of inflammatory cytokines in rBm33 stimulated PBMCs. rBm33 marked its role in filarial pathology by altered levels of growth factors but did not have a significant impact on matrix metalloproteinases (MMPs), tissue inhibitors of matrix metalloproteinases (TIMPs) activity of host PBMCs. Thus, the study outlines the signaling network of rBm33 induced inflammatory responses within the host immune cells.

Future Research Priorities for Morbidity Control of Lymphedema

Background:

Innovation in the treatment of lower extremity lymphedema has received low priority from the governments and pharmaceutical industry. Advancing lymphedema is irreversible and initiates fibrosis in the dermis, reactive changes in the epidermis and subcutis. Most medical treatments offered for lymphedema are either too demanding with a less than satisfactory response or patients have low concordance due to complex schedules. A priority setting partnership (PSP) was established to decide on the future priorities in lymphedema research.

Methods:

A table of abstracts following a literature search was published in workshop website. Stake holders were requested to upload their priorities. Their questions were listed, randomized, and sent to lymphologists for ranking. High ranked ten research priorities, obtained through median score, were presented in final prioritization work shop attended by invited stake holders. A free medical camp was organized during workshop to understand patients’ priorities.

Results:

One hundred research priorities were selected from priorities uploaded to website. Ten priorities were short listed through a peer review process involving 12 lymphologists, for final discussion. They were related to simplification of integrative treatment for lymphedema, cellular changes in lymphedema and mechanisms of its reversal, eliminating bacterial entry lesions to reduce cellulitis episodes, exploring evidence for therapies in traditional medicine, improving patient concordance to compression therapy, epidemiology of lymphatic filariasis (LF), and economic benefit of integrative treatments of lymphedema.

Conclusion:

A robust research priority setting process, organized as described in James Lind Alliance guidebook, identified seven priority areas to achieve effective morbidity control of lymphedema including LF. All stake holders including Department of Health Research, Government of India, participated in the PSP.

Immunology of lymphatic filariasis

The immune responses to filarial parasites encompass a complex network of innate and adaptive cells whose interaction with the parasite underlies a spectrum of clinical manifestations. The predominant immunological feature of lymphatic filariasis is an antigen-specific Th2 response and an expansion of IL-10 producing CD4(+) T cells that is accompanied by a muted Th1 response. This antigen-specific T-cell hyporesponsiveness appears to be crucial for the maintenance of the sustained, long-standing infection often with high parasite densities. While the correlates of protective immunity to lymphatic filariasis are still incompletely understood, primarily due to the lack of suitable animal models to study susceptibility, it is clear that T cells and to a certain extent B cells are required for protective immunity. Host immune responses, especially CD4(+) T-cell responses clearly play a role in mediating pathological manifestations of LF, including lymphedema, hydrocele and elephantiasis. The main underlying defect in the development of clinical pathology appears to be a failure to induce T-cell hyporesponsiveness in the face of antigenic stimulation. Finally, another intriguing feature of filarial infections is their propensity to induce bystander effects on a variety of immune responses, including responses to vaccinations, allergens and to other infectious agents. The complexity of the immune response to filarial infection therefore provides an important gateway to understanding the regulation of immune responses to chronic infections, in general.

Coincident helminth infection modulates systemic inflammation and immune activation in active pulmonary tuberculosis

BACKGROUND

Helminth infections are known to modulate innate and adaptive immune responses in active and latent tuberculosis (TB). However, the role of helminth infections in modulating responses associated with inflammation and immune activation (reflecting disease activity and/or severity) in TB is not known.

METHODOLOGY

We measured markers of inflammation and immune activation in active pulmonary TB individuals (ATB) with co-incidental Strongyloides stercoralis (Ss) infection. These included systemic levels of acute phase proteins, matrix metalloproteinases and their endogenous inhibitors and immune activation markers. As a control, we measured the systemic levels of the same molecules in TB-uninfected individuals (NTB) with or without Ss infection.

PRINCIPAL FINDINGS

Our data confirm that ATB is associated with elevated levels of the various measured molecules when compared to those seen in NTB. Our data also reveal that co-incident Ss infection in ATB individuals is associated with significantly decreased circulating levels of acute phase proteins, matrix metalloproteinases, tissue inhibitors of matrix metalloproteinases as well as the systemic immune activation markers, sCD14 and sCD163. These changes are specific to ATB since they are absent in NTB individuals with Ss infection.

CONCLUSIONS

Our data therefore reveal a profound effect of Ss infection on the markers associated with TB disease activity and severity and indicate that co-incidental helminth infections might dampen the severity of TB disease.

Insights into the pathogenesis of disease in human lymphatic filariasis

Although two thirds of the 120 million people infected with lymph-dwelling filarial parasites have subclinical infections, ∼40 million have lymphedema and/or other pathologic manifestations including hydroceles (and other forms of urogenital disease), episodic adenolymphangitis, lymphedema, and (in its most severe form) elephantiasis. Adult filarial worms reside in the lymphatics and lymph nodes and induce lymphatic dilatation. Progressive lymphatic damage and pathology results primarily from the host inflammatory response to the parasites but also perhaps from the host inflammatory response to the parasite's Wolbachia endosymbiont and as a consequence of superimposed bacterial or fungal infections. This review will attempt to shed light on disease pathogenesis in lymphatic filariasis.

Genomics of Loa loa, a Wolbachia-free filarial parasite of humans

Loa loa, the African eyeworm, is a major filarial pathogen of humans. Unlike most filariae, Loa loa does not contain the obligate intracellular Wolbachia endosymbiont. We describe the 91.4 Mb genome of Loa loa, and the genome of the related filarial parasite Wuchereria bancrofti, and predict 14,907 Loa loa genes based on microfilarial RNA sequencing. By comparing these genomes to that of another filarial parasite, Brugia malayi, and to several other nematode genomes, we demonstrate synteny among filariae but not with non-parasitic nematodes. The Loa loa genome encodes many immunologically relevant genes, as well as protein kinases targeted by drugs currently approved for humans. Despite lacking Wolbachia, Loa loa shows no new metabolic synthesis or transport capabilities compared to other filariae. These results suggest that the role played by Wolbachia in filarial biology is more subtle than previously thought and reveal marked differences between parasitic and non-parasitic nematodes.

Immunopathogenesis of lymphatic filarial disease

Although two thirds of the 120 million people infected with lymph-dwelling filarial parasites have subclinical infections, ~40 million have lymphedema and/or other pathologic manifestations including hydroceles (and other forms of urogenital disease), episodic adenolymphangitis, tropical pulmonary eosinophilia, lymphedema, and (in its most severe form) elephantiasis. Adult filarial worms reside in the lymphatics and lymph nodes and induce changes that result in dilatation of lymphatics and thickening of the lymphatic vessel walls. Progressive lymphatic damage and pathology results from the summation of the effect of tissue alterations induced by both living and nonliving adult parasites, the host inflammatory response to the parasites and their secreted antigens, the host inflammatory response to the endosymbiont Wolbachia, and those seen as a consequence of secondary bacterial or fungal infections. Inflammatory damage induced by filarial parasites appears to be multifactorial, with endogenous parasite products, Wolbachia, and host immunity all playing important roles. This review will initially examine the prototypical immune responses engendered by the parasite and delineate the regulatory mechanisms elicited to prevent immune-mediated pathology. This will be followed by a discussion of the proposed mechanisms underlying pathogenesis, with the central theme being that pathogenesis is a two-step process-the first initiated by the parasite and host innate immune system and the second propagated mainly by the host's adaptive immune system and by other factors (including secondary infections).