Involvement of β-defensin 130 (DEFB130) in the macrophage microbicidal mechanisms for killing Plasmodium falciparum

Human Defensin 5 Inhibits Plasmodium yoelii Development in Anopheles stephensi by Promoting Innate Immune Response

Malaria poses a serious threat to human health. Existing vector-based interventions have shortcomings, such as environmental pollution, strong resistance to chemical insecticides, and the slow effects of biological insecticides. Therefore, the need to develop novel strategies for controlling malaria, such as reducing mosquito vector competence, is escalating. Human defensin 5 (HD5) has broad-spectrum antimicrobial activity. To determine its effect on Plasmodium development in mosquitoes, HD5 was injected into Anopheles stephensi at various time points. The infection density of Plasmodium yoelii in An. stephensi was substantially reduced by HD5 treatment administered 24 h prior to infection or 6, 12, or 24 h post-infection (hpi). We found that HD5 treatment upregulated the expression of the innate immune effectors TEP1, MyD88, and Rel1 at 24 and 72 hpi. Furthermore, the RNA interference of MyD88, a key upstream molecule in the Toll signaling pathway, decreased the HD5-induced resistance of mosquitoes against Plasmodium infection. These results suggest that HD5 microinjection inhibits the development of malaria parasites in An. stephensi by activating the Toll signaling pathway.

Cross-continental admixture in the Kho population from northwest Pakistan

Northern Pakistan is home to many diverse ethnicities and languages. The region acted as a prime corridor for ancient invasions and population migrations between Western Eurasia and South Asia. Kho, one of the major ethnic groups living in this region, resides in the remote and isolated mountainous region in the Chitral Valley of the Hindu Kush Mountain range. They are culturally and linguistically distinct from the rest of the Pakistani population groups and their genetic ancestry is still unknown. In this study, we generated genome-wide genotype data of ~1 M loci (Illumina WeGene array) for 116 unrelated Kho individuals and carried out comprehensive analyses in the context of worldwide extant and ancient anatomically modern human populations across Eurasia. The results inferred that the Kho can trace a large proportion of their ancestry to the population who migrated south from the Southern Siberian steppes during the second millennium BCE ~110 generations ago. An additional wave of gene flow from a population carrying East Asian ancestry was also identified in the Kho that occurred ~60 generations ago and may possibly be linked to the expansion of the Tibetan Empire during 7th to 9th centuries CE (current era) in the northwestern regions of the Indian sub-continent. We identified several candidate regions suggestive of positive selection in the Kho, that included genes mainly involved in pigmentation, immune responses, muscular development, DNA repair, and tumor suppression.

Recombinant human β-defensin130 inhibited the growth of foodborne bacteria through membrane disruption and exerted anti-inflammatory activity

Foodborne pathogens causing food poisoning and infections are detrimental to human health, and the abuse of antibiotics induced severe antibiotic resistance in past decades. Thus, it is urgent to develop new antimicrobial agents. In the current study, human β-defensin 130 (hBD130), which is an antimicrobial peptide identified in human macrophages in 2017, was initially produced in Pichia pastoris. The purified hBD130 demonstrated broad bactericidal spectrum against foodborne pathogens through a membrane disruption, with concentrations ranging from 10 to 45 μg/mL. Moreover, hBD130 showed a low hemolytic effect and nearly no cytotoxicity to mammalian cells with a dosage of 400 μg/mL. In addition, the secretion amounts and mRNA levels of NO, IL-6, IL-1β, and TNF-α in LPS-induced mouse macrophage were significantly decreased with 1 mg/mL of hBD130. Taken together, these results showed that hBD130 is a promising antimicrobial agent to treat foodborne bacterial infections and inflammation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01087-y.

Antimicrobial peptide gene expression in Atlantic salmon (Salmo salar) seven days post-challenge with Neoparamoeba perurans

Amoebic gill disease in teleost fish is caused by the marine parasite Neoparamoeba perurans. To date, the role of antimicrobial peptides β-defensins and cathelicidins in this infection have not been explored. Using a high-throughput microfluidics quantitative polymerase chain reaction system (Biomark HD™ by Fluidigm), this study aimed to: firstly, to investigate organ-specific expression of antimicrobial peptide genes β-defensin-1, -3 and -4 and cathelicidin 2 in healthy Atlantic salmon; secondly, to compare the expression of these antimicrobial peptide genes in healthy versus asymptomatic Atlantic salmon seven days post-challenge with Neoparamoeba perurans. Results from this study indicate expression of the β-defensin and cathelicidin genes in the selected organs from healthy Atlantic salmon. Furthermore, a statistically significant upregulation of β-defensins -3 and -4 and cathelicidin 2 was detected in gill of parasite-challenged salmon. The upregulated cathelicidin and β-defensin genes in gill could indicate novel potential roles in innate immune responses to Neoparamoeba perurans.

Strategies for Antimicrobial Peptides Immobilization on Surfaces to Prevent Biofilm Growth on Biomedical Devices

Nosocomial and medical device-induced biofilm infections affect millions of lives and urgently require innovative preventive approaches. These pathologies have led to the development of numerous antimicrobial strategies, an emergent topic involving both natural and synthetic routes, among which some are currently under testing for clinical approval and use. Antimicrobial peptides (AMPs) are ideal candidates for this fight. Therefore, the strategies involving surface functionalization with AMPs to prevent bacterial attachment/biofilms formation have experienced a tremendous development over the last decade. In this review, we describe the different mechanisms of action by which AMPs prevent bacterial adhesion and/or biofilm formation to better address their potential as anti-infective agents. We additionally analyze AMP immobilization techniques on a variety of materials, with a focus on biomedical applications. Furthermore, we summarize the advances made to date regarding the immobilization strategies of AMPs on various surfaces and their ability to prevent the adhesion of various microorganisms. Progress toward the clinical approval of AMPs in antibiotherapy is also reviewed.

Factors influencing phagocytosis of malaria parasites: the story so far

There are seven known species of Plasmodium spp. that can infect humans. The human host can mount a complex network of immunological responses to fight infection and one of these immune functions is phagocytosis. Effective and timely phagocytosis of parasites, accompanied by the activation of a regulated inflammatory response, is beneficial for parasite clearance. Functional studies have identified specific opsonins, particularly antibodies and distinct phagocyte sub-populations that are associated with clinical protection against malaria. In addition, cellular and molecular studies have enhanced the understanding of the immunological pathways and outcomes following phagocytosis of malaria parasites. In this review, an integrated view of the factors that can affect phagocytosis of infected erythrocytes and parasite components, the immunological consequences and their association with clinical protection against Plasmodium spp. infection is provided. Several red blood cell disorders and co-infections, and drugs that can influence phagocytic capability during malaria are also discussed. It is hoped that an enhanced understanding of this immunological process can benefit the design of new therapeutics and vaccines to combat this infectious disease.

Use of gene expression studies to investigate the human immunological response to malaria infection

Background

Transcriptional profiling of the human immune response to malaria has been used to identify diagnostic markers, understand the pathogenicity of severe disease and dissect the mechanisms of naturally acquired immunity (NAI). However, interpreting this body of work is difficult given considerable variation in study design, definition of disease, patient selection and methodology employed. This work details a comprehensive review of gene expression profiling (GEP) of the human immune response to malaria to determine how this technology has been applied to date, instances where this has advanced understanding of NAI and the extent of variability in methodology between studies to allow informed comparison of data and interpretation of results.

Methods

Datasets from the gene expression omnibus (GEO) including the search terms; ‘plasmodium’ or ‘malaria’ or ‘sporozoite’ or ‘merozoite’ or ‘gametocyte’ and ‘Homo sapiens’ were identified and publications analysed. Datasets of gene expression changes in relation to malaria vaccines were excluded.

Results

Twenty-three GEO datasets and 25 related publications were included in the final review. All datasets related to Plasmodium falciparum infection, except two that related to Plasmodium vivax infection. The majority of datasets included samples from individuals infected with malaria ‘naturally’ in the field (n = 13, 57%), however some related to controlled human malaria infection (CHMI) studies (n = 6, 26%), or cells stimulated with Plasmodium in vitro (n = 6, 26%). The majority of studies examined gene expression changes relating to the blood stage of the parasite. Significant heterogeneity between datasets was identified in terms of study design, sample type, platform used and method of analysis. Seven datasets specifically investigated transcriptional changes associated with NAI to malaria, with evidence supporting suppression of the innate pro-inflammatory response as an important mechanism for this in the majority of these studies. However, further interpretation of this body of work was limited by heterogeneity between studies and small sample sizes.

Conclusions

GEP in malaria is a potentially powerful tool, but to date studies have been hypothesis generating with small sample sizes and widely varying methodology. As CHMI studies are increasingly performed in endemic settings, there will be growing opportunity to use GEP to understand detailed time-course changes in host response and understand in greater detail the mechanisms of NAI.

β-Defensins: Farming the Microbiome for Homeostasis and Health

Diverse commensal populations are now regarded as key to physiological homeostasis and protection against disease. Although bacteria are the most abundant component of microbiomes, and the most intensively studied, the microbiome also consists of viral, fungal, archael, and protozoan communities, about which comparatively little is known. Host-defense peptides (HDPs), originally described as antimicrobial, now have renewed significance as curators of the pervasive microbial loads required to maintain homeostasis and manage microbiome diversity. Harnessing HDP biology to transition away from non-selective, antibiotic-mediated treatments for clearance of microbes is a new paradigm, particularly in veterinary medicine. One family of evolutionarily conserved HDPs, β-defensins which are produced in diverse combinations by epithelial and immune cell populations, are multifunctional cationic peptides which manage the cross-talk between host and microbes and maintain a healthy yet dynamic equilibrium across mucosal systems. They are therefore key gatekeepers to the oral, respiratory, reproductive and enteric tissues, preventing pathogen-associated inflammation and disease and maintaining physiological normality. Expansions in the number of genes encoding these natural antibiotics have been described in the genomes of some species, the functional significance of which has only recently being appreciated. β-defensin expression has been documented pre-birth and disruptions in their regulation may play a role in maladaptive neonatal immune programming, thereby contributing to subsequent disease susceptibility. Here we review recent evidence supporting a critical role for β-defensins as farmers of the pervasive and complex prokaryotic ecosystems that occupy all body surfaces and cavities. We also share some new perspectives on the role of β-defensins as sensors of homeostasis and the immune vanguard particularly at sites of immunological privilege where inflammation is attenuated.

Differential Gene Expression Profile of Human Neutrophils Cultured with Plasmodium falciparum-Parasitized Erythrocytes

Neutrophils (PMNs) are the most abundant cellular component of our innate immune system, where they play central roles in the pathogenesis of and resistance to a broad range of diseases. However, their roles in malarial infection remain poorly understood. Therefore, we examined the transcriptional gene profile of human PMNs in response to Plasmodium falciparum-parasitized erythrocytes (iRBCs) by using oligonucleotide microarrays. Results revealed that PMNs induced a broad and vigorous set of changes in gene expression in response to malarial parasites, represented by 118 upregulated and 216 downregulated genes. The transcriptional response was characterized by the upregulation of numerous genes encoding multiple surface receptors, proteins involved in signal transduction pathways, and defense response proteins. This response included a number of genes which are known to be involved in the pathogenesis of malaria and other inflammatory diseases. Gene enrichment analysis suggested that the biological pathways involved in the PMN responses to the iRBCs included insulin receptor, Jak-STAT signaling pathway, mitogen-activated protein kinase (MAPK), and interleukin and interferon-gamma (IFN-γ) signaling pathways. The current study provides fundamental knowledge on the molecular responses of neutrophils to malarial parasites, which may aid in the discovery of novel therapeutic interventions.