Cassava (Manihot esculenta) defensins: Prospection, structural analysis and tissue-specific expression under biotic/abiotic stresses.

Defensins are a prominent family of antimicrobial peptides. They play sophisticated roles in the defense against pathogens in all living organisms, but few works address their expression under different conditions and plant tissues. The present work prospected defensins of Manihot esculenta Crantz, popularly known as cassava. Five defensin candidates (MeDefs) were retrieved from the genome sequences and characterized. Considering chromosome distribution, only MeDef1 and 2 occupy adjacent positions in the same chromosome arm. All 3D structures had antiparallel ß-sheets, an α-helix, and amphipathic residues distributed throughout the peptides with a predominance of cationic surface charge. MeDefs expression was validated by RT-qPCR, including two stress types (biotic: fungus Macrophomina pseudophaseolina, and abiotic: mechanical injury) and a combination of both stresses (fungus+injury) in three different tissues (root, stem, and leaf). For this purpose, ten reference genes (RGs) were tested, and three were chosen to characterize MeDef expression. MeDef3 was up-regulated at roots in all stress situations tested. MeDef1 and MeDef5 were induced in leaves under biotic and abiotic stresses, but not in both stress types simultaneously. Only MeDef2 was down-regulated in the stem tissue also with biotic/abiotic combined stresses. These results indicate that although defensins are known to be responsive to pathogen infection, they may act as preformed defense or, still, have tissue or stress specificities. Aspects of their structure, stability and evolution are also discussed.

Inhibition of defensin A and cecropin A responses to dengue virus 1 infection in Aedes aegypti. / Inhibición de las respuestas de defensina A y cecropina A contra la infección del virus dengue 1 en Aedes aegypti

INTRODUCTION: It is essential to determine the interactions between viruses and mosquitoes to diminish dengue viral transmission. These interactions constitute a very complex system of highly regulated pathways known as the innate immune system of the mosquito, which produces antimicrobial peptides that act as effector molecules against bacterial and fungal infections. There is less information about such effects on virus infections. OBJECTIVE: To determine the expression of two antimicrobial peptide genes, defensin A and cecropin A, in Aedes aegypti mosquitoes infected with DENV-1. MATERIALS AND METHODS: We used the F1 generation of mosquitoes orally infected with DENV-1 and real-time PCR analysis to determine whether the defensin A and cecropin A genes played a role in controlling DENV-1 replication in Ae. aegypti. As a reference, we conducted similar experiments with the bacteria Escherichia coli. RESULTS: Basal levels of defensin A and cecropin A mRNA were expressed in uninfected mosquitoes at different times post-blood feeding. The infected mosquitoes experienced reduced expression of these mRNA by at least eightfold when compared to uninfected control mosquitoes at all times post-infection. In contrast with the behavior of DENV-1, results showed that bacterial infection produced up-regulation of defensin and cecropin genes; however, the induction of transcripts occurred at later times (15 days). CONCLUSION: DENV-1 virus inhibited the expression of defensin A and cecropin A genes in a wild Ae. aegypti population from Venezuela.

Introducción. Es esencial determinar las interacciones entre los virus y los mosquitos para disminuir la transmisión viral. Estas interacciones constituyen un sistema muy complejo y muy regulado conocido como sistema inmunitario innato del mosquito, el cual produce péptidos antimicrobianos, moléculas efectoras que funcionan contra las infecciones bacterianas y fúngicas; se tiene poca información de su acción sobre los virus. Objetivo. Determinar la expresión de dos genes AMP (defensina A y cecropina A) en mosquitos Aedes aegypti infectados con el virus DENV-1. Materiales y métodos. Se infectaron oralmente mosquitos de generación F1 con DENV-1 y mediante el análisis con PCR en tiempo real se determinó el potencial papel de los genes defensina A y cecropina A en el control de la replicación del DENV-1 en Ae. aegypti. Como referencia, se infectaron mosquitos con Escherichia coli. Resultados: Los mosquitos no infectados expresaron niveles basales de los ARNm de los genes defensina A y cecropina A en diversos momentos después de la alimentación. Los mosquitos infectados experimentaron una reducción, por lo menos, de ocho veces en la expresión de estos ARNm con respecto a los mosquitos de control en todo el periodo posterior a la alimentación. En contraste con el comportamiento del virus DENV-1, los resultados mostraron que la infección bacteriana produjo una regulación positiva de los genes defensina y cecropina; sin embargo, la inducción de los transcritos ocurrió tardíamente (15 días). Conclusión. El virus DENV-1 inhibió la expresión de los genes defensina A y cecropina A en una población silvestre de Ae. aegypti en Venezuela.

Expression and Purification of the VpDef Defensin in Escherichia coli using the Small Metal-Binding Proteins CusF3H+ and SmbP.

BACKGROUND: The heterologous production of antimicrobial peptides in bacterial models can produce insoluble proteins due to the lack of proper folding. Fusion proteins have been used to increase the expression and solubility of these types of proteins with varying degrees of success. OBJECTIVES: Here, we demonstrate the use of the small metal-binding proteins CusF3H+ (9.9kDa) and SmbP (9.9kDa) as fusion partners for the soluble expression of the bioactive antimicrobial peptide VpDef(6.9 kDa) in Escherichia coli. METHODS: The recombinant VpDef (rVpDef) peptide was expressed as a translational fusion with CusF3H+ and SmbP in Escherichia coli SHuffle under different small-scale culture conditions. The best conditions were applied to 1-liter cultures, with subsequent purification of the recombinant protein through IMAC chromatography. The recombinant protein was digested using enterokinase to liberate the peptide from the fusion protein, and a second IMAC chromatography step removed the fusion protein. The purified peptide was tested against two Gram-positive and two Gram-negative bacteria. RESULTS: The use either of CusF3H+ or of SmbP results in recombinant proteins that are found in the soluble fraction of the bacterial lysate; these recombinant proteins are easily purified through IMAC chromatography, and rVpDef is readily separated following enterokinase treatment. The purified rVpDef peptide exhibits antimicrobial properties against both Gram-positive and Gram-negative. CONCLUSION: Use of the fusion proteins CusF3H+ and SmbP results in production of a soluble recombinant protein containing the antimicrobial peptide rVpDef that is correctly folded and that retains its antimicrobial properties once purified.

Aminoglycosides can be a better choice over macrolides in COVID-19 regimen: Plausible mechanism for repurposing strategy.

In the current COVID-19 pandemic, prioritizing the immunity enhancers is equally important to anti-virals. Defensins are the forgotten molecules that enhance the innate immunity against various microbes. Although macrolides like azithromycin and clarithromycin etc., have been reported to act against respiratory infections but they lack the ability of immunity enhancement through defensins. The aminoglycosides were proved to have defensin mediated antiviral activity, that could enhance the immunity. So, Consideration of aminoglycosides can be a double edge sword viz., against respiratory infection as well as Immunity enhancer (along with anti-virals) for COVID-19 regimen.

Inducible expression of defensins and cathelicidins by nutrients and associated regulatory mechanisms.

Host defense peptides (HDPs) are crucial components of the body's first line of defense that protect organisms from infections and mediate immune responses. Defensins and cathelicidins are the two most important families of HDPs in mammals. In this review, we summarize the nutrients that are involved in inducible expression of endogenous defensins and cathelicidins. In addition, the mitogen-activated protein kinases (MAPK), nuclear factor kappa B (NF-κB) and histone deacetylase (HDAC) signaling pathways that play vital roles in the induction of defensin and cathelicidin expression are highlighted. Endogenous defensins and cathelicidins induced by nutrients may be potential alternatives to antibiotic treatments against infection and diseases. This review mainly focuses on the inducible expression and regulatory mechanisms of defensins and cathelicidins in multiple species by different nutrients and the potential applications of defensin- and cathelicidin-inducing nutrients.

Actinomyces Produces Defensin-Like Bacteriocins (Actifensins) with a Highly Degenerate Structure and Broad Antimicrobial Activity.

We identified a strain of Actinomyces ruminicola which produces a potent bacteriocin with activity against a broad range of Gram-positive bacteria, many of which are pathogenic to animals and humans. The bacteriocin was purified and found to have a mass of 4,091 ± 1 Da with a sequence of GFGCNLITSNPYQCSNHCKSVGYRGGYCKLRTVCTCY containing three disulfide bridges. Surprisingly, near relatives of actifensin were found to be a series of related eukaryotic defensins displaying greater than 50% identity to the bacteriocin. A pangenomic screen further revealed that production of actifensin-related bacteriocins is a common trait within the genus, with 47 being encoded in 161 genomes. Furthermore, these bacteriocins displayed a remarkable level of diversity with a mean amino acid identity of only 52% between strains/species. This level of redundancy suggests that this new class of bacteriocins may provide a very broad structural basis on which to deliver and design new broad-spectrum antimicrobials for treatment of animal and human infections.IMPORTANCE Bacteriocins (ribosomally produced antimicrobial peptides) are potential alternatives to current antimicrobials given the global challenge of antimicrobial resistance. We identified a novel bacteriocin from Actinomyces ruminicola with no previously characterized antimicrobial activity. Using publicly available genomic data, we found a highly conserved yet divergent family of previously unidentified homologous peptide sequences within the genus Actinomyces with striking similarity to eukaryotic defensins. These actifensins may provide a potent line of antimicrobial defense/offense, and the machinery to produce them could be used for the design of new antimicrobials given the degeneracy that exists naturally in their structure.

Gut Microbiota and IL-17A: Physiological and Pathological Responses.

IL-17A is a cytokine which is produced by several immune and non-immune cells. The cytokine plays dual roles from protection from microbes and protection from pro-inflammatory based diseases to induction of the pro-inflammatory based diseases. The main mechanisms which lead to the controversial roles of IL-17A are yet to be clarified. Gut microbiota (GM) are the resident probiotic bacteria in the gastrointestinal tracts which have been introduced as a plausible regulator of IL-17A production and functions. This review article describes the recent information regarding the roles played by GM in determination of IL-17A functions outcome.

G.I. pros: Antimicrobial defense in the gastrointestinal tract.

The gastrointestinal tract is a complex environment in which the host immune system interacts with a diverse array of microorganisms, both symbiotic and pathogenic. As such, mobilizing a rapid and appropriate antimicrobial response depending on the nature of each stimulus is crucial for maintaining the balance between homeostasis and inflammation in the gut. Here we focus on the mechanisms by which intestinal antimicrobial peptides regulate microbial communities during dysbiosis and infection. We also discuss classes of bacterial peptides that contribute to reducing enteric pathogen outgrowth. This review aims to provide a comprehensive overview on the interplay of diverse antimicrobial responses with enteric pathogens and the gut microbiota.

Protective effect of inactivated blastoconidia in keratinocytes and human reconstituted epithelium against C. albicans infection.

Candida albicans is commensal yeast that colonizes skin and mucosa; however, it can become an opportunist pathogen by changing from blastoconidia (commensal form) into hypha (pathogenic form). Each form activates a different cytokines response in epithelial cells. Little is known about the commensal role of C. albicans in the innate immunity. This work studied whether stimulation with C. albicans blastoconidia induces protection in keratinocytes and/or in a reconstituted human epithelium (RHE) infected with C. albicans. For this, inactivated C. albicans blastoconidia was used to stimulate keratinocytes and RHE prior to infection with C. albicans. Blastoconidia induced different cytokine expression profiles; in the case of RHE it decreased interleukin (IL)-1ß and IL-10 and increased IL-8, tumor necrosis factor α (TNF-α), and interferon γ (IFN-γ). A significant increase in the expression of human ß-defensins (HBD) 2 and HBD3 was observed in blastoconidia stimulated keratinocytes and RHE, associated with impaired growth and viability of C. albicans. Additionally, blastoconidia stimulation decreased the expression of virulence factors in C. albicans that are associated with filamentation (EFG1, CPH1 and NRG1), adhesion (ALS5), and invasion (SAP2). Blastoconidia stimulated RHE was significantly less damaged by C. albicans invasion. These results show that the commensal form of C. albicans would exert a protective effect against self-infection.

Expression and production of recombinant scorpine as a potassium channel blocker protein in Escherichia coli.

Scorpine is a cationic protein from the venom of Pandinus imperator, belonging to potassium channel blocker family, which has been shown to have antibacterial, antiviral, and antiplasmodia activities. In the present study, a pET-44a vector containing scorpine synthetic gene with T7 Promoter (pET 44a-His6-Nus-His6-tev-scorpine) was transferred into Escherichia coli Rosetta-gami B (DE3) for soluble expression of the protein in the cytoplasm and its overproduction. After confirming recombinant scorpine peptide expression using SDS-PAGE and Western blot, augmentation of production was performed during two stages. At first, effects of three parameters including carbon source concentration of medium, temperature, and induction time were investigated in terrific broth (TB) medium. Afterward, the overexpression was performed by response surface methodology in TB + glucose. Under the optimized conditions, the highest production of 3.5 g/L in the TB + glucose medium (7.5 g/L glucose, induction at OD600 = 3.5 and 25 °C) was increased to 4.1 g/L in TB medium (2.5 g/L glycerol, induction at OD600 = 0.7 and 25 °C). Then, in order to increase the amount of protein production, effects of carbon concentration in the fermenter under the primary optimized condition was investigated. The amount of produced recombinant protein increased from 0.12 to 2.1 g/L.H. The results were similar to previous studies on optimizing and increasing the production of recombinant protein and in particular recombinant scorpine.

HcCUB-Lec, a newly identified C-type lectin that contains a distinct CUB domain and participates in the immune defense of the triangle sail mussel Hyriopsis cumingii.

As pattern recognition receptors (PRRs), C-type lectins (CTLs) play crucial roles in recognizing and eliminating pathogens in innate immunity. In this study, a novel CTL (HcCUB-Lec) was identified from the triangle sail mussel Hyriopsis cumingii. The full-length of HcCUB-Lec cDNA was 1558 bp with an open reading frame of 1281 bp that encodes a putative protein of 426 amino acid residues, including an N-terminal signal peptide, a complement Uegf Bmp1 (CUB) domain, a single carbohydrate recognition domain (CRD), and a transmembrane domain. Quantitative real-time PCR analysis revealed that HcCUB-Lec transcript was distributed in all examined tissues with the highest levels in hepatopancreas and was significantly upregulated in gills and hepatopancreas after immune challenge with Staphyloccocus aureus and Vibrio parahaemolyticus. When HcCUB-Lec was silenced by RNAi, the expression levels of three antimicrobial peptides, including whey acidic protein (HcWAP), defensin (HcDef), and lysozyme (HcLyso), were dramatically decreased in gills. The recombinant HcCUB-Lec and its individual CUB and CRD domains can bind with Gram-positive bacteria (S. aureus and Bacillus subtilis), Gram-negative bacteria (V. parahaemolyticus and Aeromonas hydrophila), and polysaccharides (lipopolysaccharide and peptidoglycan). Moreover, rHcCUB-Lec and its domains could also agglutinate S. aureus and V. parahaemolyticus in the presence of Ca2+ and can clear V. parahaemolyticus in H. cumingii. Results of this study suggest that HcCUB-Lec acts as an antimicrobial PRR that participates in the innate immune responses of H. cumingii.

Up-Regulation of Antimicrobial Peptides Gallerimycin and Galiomicin in Galleria mellonella Infected with Candida Yeasts Displaying Different Virulence Traits.

Galleria mellonella has been described as a cheap and an easy-to-reproduce model for the study of fungal infections. We hypothesized that yeasts with higher virulence potential decrease survival and significantly trigger an immune response in G. mellonella through the regulation of innate immunity-related genes encoding antimicrobial peptides (AMPs) such as gallerimycin and galiomicin. Candida albicans SC5314 and Candida dubliniensis CBS 7987, selected because of their different virulence potential, were used for a killing assay followed by the determination of gene expression using qPCR. In vivo results confirmed a significantly (p = 0.0321) lower pathogenicity for C. dubliniensis than for C. albicans. Accordingly, the induction of C. dubliniensis AMPs was lower at all the selected time points post-infection (1 h, 24 h, 48 h). Moreover, we observed an extremely high regulation of the galiomicin gene compared to the gallerimycin one, suggesting a different role of the tested AMPs in protecting G. mellonella from candidiasis.

Antifungal activity of synthetic cowpea defensin Cp-thionin II and its application in dough.

Plant defensins are small, cysteine-rich antimicrobial peptides of the immune system found in several organs during plant development. A synthetic peptide, KT43C, a linear analogue of the native Cp-thionin II found in cowpea seeds, was evaluated for its antifungal potential. It was found that KT43C displayed antifungal activity against Fusarium culmorum, Penicillium expansum and Aspergillus niger. Like native plant defensins, KT43C showed thermostability up to 100 °C and cation sensitivity. The synthetic peptide decreased the fungal growth without inducing morphogenic changes in the fungal hyphae. Non-inhibitory concentrations of the peptide induced permeabilization of the fungal membrane. In addition, high concentrations of KT43C induced the production of reactive oxygen species in the granulated cytoplasm. To investigate potential applications, the peptide was used as an additive in the preparation of dough which did not contain yeast. This peptide delayed the development of fungal growth in the dough by 2 days. Furthermore, KT43C did not induce red blood cell lysis up to a concentration of 200 µg.ml-1. These results highlight the potential for the use of synthetic antimicrobial defensins for shelf-life extension of food products.

Role of Cyclic di-GMP in the Bacterial Virulence and Evasion of the Plant Immunity.

Plant pathogenic bacteria are responsible for the loss of hundreds of millions of dollars each year, impacting a wide range of economically relevant agricultural crops. The plant immune system detects conserved bacterial molecules and deploys an arsenal of effective defense measures at different levels; however, during compatible interactions, some pathogenic bacteria suppress and manipulate the host immunity and colonize and infect the plant host. Different bacteria employ similar strategies to circumvent plant innate immunity, while other tactics are specific to certain bacterial species. Recent studies have highlighted the secondary messenger c-di-GMP as a key molecule in the transmission of environmental cues in an intracellular regulatory network that controls virulence traits in many plant pathogenic bacteria. In this review, we focus on the recent knowledge of the molecular basis of c-di-GMP signaling mechanisms that promote or prevent the evasion of bacterial phytopathogens from the plant immune system. This review will highlight the considerable diversity of mechanisms evolved in plant-associated bacteria to elude plant immunity.

Dietary amino acid and vitamin complex protects honey bee from immunosuppression caused by Nosema ceranae.

Microsporidium Nosema ceranae is well known for exerting a negative impact on honey bee health, including down-regulation of immunoregulatory genes. Protein nutrition has been proven to have beneficial effects on bee immunity and other aspects of bee health. Bearing this in mind, the aim of our study was to evaluate the potential of a dietary amino acid and vitamin complex "BEEWELL AminoPlus" to protect honey bees from immunosuppression induced by N. ceranae. In a laboratory experiment bees were infected with N. ceranae and treated with supplement on first, third, sixth and ninth day after emergence. The expression of genes for immune-related peptides (abaecin, apidaecin, hymenoptaecin, defensin and vitellogenin) was compared between groups. The results revealed significantly lower (p<0.01 or p<0.001) numbers of Nosema spores in supplemented groups than in the control especially on day 12 post infection. With the exception of abacein, the expression levels of immune-related peptides were significantly suppressed (p<0.01 or p<0.001) in control group on the 12th day post infection, compared to bees that received the supplement. It was supposed that N. ceranae had a negative impact on bee immunity and that the tested amino acid and vitamin complex modified the expression of immune-related genes in honey bees compromised by infection, suggesting immune-stimulation that reflects in the increase in resistance to diseases and reduced bee mortality. The supplement exerted best efficacy when applied simultaneously with Nosema infection, which can help us to assume the most suitable period for its application in the hive.

Candida Infections and Human Defensins.

BACKGROUND: Candida species infections are an important worldwide health issue since they do not only affect immunocompromised patients but also healthy individuals. The host developed different mechanisms of protection against Candida infections; specifically the immune system and the innate immune response are the first line of defence. Defensis are a group of antimicrobial peptides, components of the innate immunity, produced at mucosal level and known to be active against bacteria, virus but also fungi. OBJECTIVES: The aim of the current work was to review all previous studies in literature that analysed defensins in the context of Candida spp. infections, in order to investigate and clarify the exact mechanisms of defensins anti-fungal action. METHODS: Several studies were identified from 1985 to 2017 (9 works form years 1985 to 1999, 44 works ranging from 2000 to 2009 and 35 from 2010 to 2017) searched in two electronic databases (PubMed and Google Scholar). The main key words used for the research were "Candida", "Defensins"," Innate immune system","fungi". RESULTS AND CONCLUSION: The findings of the reviewed studies highlight the pivotal role of defensins antimicrobial peptides in the immune response against Candida infections, since they are able to discriminate host cell from fungi: defensins are able to recognize the pathogens cell wall (different in composition from the human ones), and to disrupt it through membrane permeabilization. However, further research is needed to explain completely defensins' mechanisms of action to fight C. albicans (and other Candida spp.) infections, being the information fragmentary and only in part elucidated.

Antibacterial activity and phospholipid recognition of the recombinant defensin J1-1 from Capsicum genus.

The gene of the four disulfide-bridged defensin J1-1 from Capsicum was cloned into the expression vector pQE30 containing a 6His-tag as fusion protein. This construct was transfected into Origami strain of Escherichia coli and expressed after induction with isopropyl thiogalactoside (IPTG). The level of expression was 4 mg/L of culture medium, and the His-tagged recombinant defensin (HisXarJ1-1) was expressed exclusively into inclusion bodies. After solubilization, HisXarJ1-1 was purified by affinity and hydrophobic interaction chromatography. The reverse-phase HPLC profile of the HisXarJ1-1 product obtained from the affinity chromatography step showed single main peptide fraction of molecular masses of 7050.6 Da and after treatment with DTT a single fraction of 7, 042.6 Da corresponding to the reduced peptide was observed. An in vitro folding step of the HisXarJ1-1 generated a distinct profile of oxidized forms of the peptide this oxidized peptide was capable of binding phosphatidic acid in vitro. Possible dimer and oligomer of HisXarJ1-1 were visible in gel electrophoresis and immunodetected with anti-His antibodies. Pure recombinant defensin HisXarJ1-1 exhibited antibacterial activity against Pseudomonas aeruginosa.

Systemic Induction of the Defensin and Phytoalexin Pisatin Pathways in Pea (Pisum sativum) against Aphanomyces euteiches by Acetylated and Nonacetylated Oligogalacturonides.

Oligogalacturonides (OGs) are known for their powerful ability to stimulate the plant immune system but little is known about their mode of action in pea (Pisum sativum). In the present study, we investigated the elicitor activity of two fractions of OGs, with polymerization degrees (DPs) of 2-25, in pea against Aphanomyces euteiches. One fraction was nonacetylated (OGs - Ac) whereas the second one was 30% acetylated (OGs + Ac). OGs were applied by injecting the upper two rachises of the plants at three- and/or four-weeks-old. Five-week-old roots were inoculated with 105 zoospores of A. euteiches. The root infection level was determined at 7, 10 and 14 days after inoculation using the quantitative real-time polymerase chain reaction (qPCR). Results showed significant root infection reductions namely 58, 45 and 48% in the plants treated with 80 µg OGs + Ac and 59, 56 and 65% with 200 µg of OGs - Ac. Gene expression results showed the upregulation of genes involved in the antifungal defensins, lignans and the phytoalexin pisatin pathways and a priming effect in the basal defense, SA and ROS gene markers as a response to OGs. The reduction of the efficient dose in OGs + Ac is suggesting that acetylation is necessary for some specific responses. Our work provides the first evidence for the potential of OGs in the defense induction in pea against Aphanomyces root rot.

Heterologous Expression Systems for Plant Defensin Expression: Examples of Success and Pitfalls.

Defensins are a superfamily of antimicrobial peptides, present in vertebrates, invertebrates, fungi and plants, suggesting that they appeared prior to the divergence in eukaryotes. The destitution of toxicity to mammalian cells of plant defensins has led to a new research ground, i.e., their potential medical use against human infectious diseases. Isolating defensins from natural sources, like plant tissues, can be time-consuming, labor intensive and usually present low yields. Strategies for large-scale production of purified active defensins have been employed using heterologous expression systems (HES) for defensin production, usually based in E. coli system. Like any other technology, HES present limitations and drawbacks demanding a careful experimental design prior the system selection. This review is proposed to discuss some of the major concerns when choosing to heterologously express plant defensins, with special attention on bacterial expression systems.

Functions of Antimicrobial Peptides in Vertebrates.

OBJECTIVE: The aim of this review is to examine the multiple activities of antimicrobial peptides (AMPs) in vertebrates. CONTENT: The largest AMP families are the cathelicidins and defensins, but several peptides derived from bigger proteins have also been reported. Cathelicidins are characterized by a conserved Nterminal pro-region and a variable region that encodes the C-terminal mature peptide. The ß-defensins comprise a large family of AMPs that have diversified their functions, apparently without losing their antimicrobial activity. Cathelicidins and ß-defensins are present in all vertebrates studied so far; α- defensins are present in mammals, while θ-defensins are only present in some non-human primates. The AMPs are regulated by posttranslational modifications that mainly include proteolysis, amidation, ADP-ribosylation, glycosylation and phosphorylation. In addition to their antimicrobial effects, AMPs show activity against viral particles and interfere in different steps of virus replication. Moreover, AMPs may both promote and inhibit cancer growth: several vertebrate AMPs kill cancer cells, and some tumors grow in an environment wherein the expression of ß-defensins is reduced; however, human cathelicidin and some ß-defensins are overexpressed in several types of cancer and are correlated with tumor growth. AMPs are part of the complex network of cells and molecules that forms the vertebrate innate defense system and they induce adaptive responses. In addition, they participate in sperm maturation and male reproduction. CONCLUSION: AMPs are multifunctional peptides that participate in immune responses, wound healing, angiogenesis, toxin neutralization, iron metabolism, male reproduction, among other functions. However, AMPs may also contribute to excessive inflammation and tumorigenesis.