The mucosal immune system of fish: The evolution of tolerating commensals while fighting pathogens
TL;DR: An updated view on how teleost skin, gills and gut immune cells and molecules, function in response to pathogens and commensals is provided and some of the future avenues that the field of fish mucosal immunity may follow in the next years are highlighted.
About: This article is published in Fish & Shellfish Immunology.The article was published on 2013-12-01 and is currently open access. It has received 527 citations till now. The article focuses on the topics: Mucosal immunology.
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TL;DR: This review affirms the relevance of probiotics in the mucosal immunity of fish by revisiting and bridging the current knowledge on teleost mucosa-associated lymphoid tissues, mucosal microbiota and immunomodulation of mucosal surfaces by probiotics.
294 citations
TL;DR: New research tools and in vivo models are currently being developed in order to help reveal the great intricacy of teleost mucosal adaptive immunity and help improve mucosal vaccination protocols for use in aquaculture.
Abstract: Teleost fish possess an adaptive immune system associated with each of their mucosal body surfaces. Evidence obtained from mucosal vaccination and mucosal infection studies reveal that adaptive immune responses take place at the different mucosal surfaces of teleost. The main mucosa-associated lymphoid tissues (MALT) of teleosts are the gut-associated lymphoid tissue (GALT), skin-associated lymphoid tissue (SALT), the gill-associated lymphoid tissue (GIALT) and the recently discovered nasopharynx-associated lymphoid tissue (NALT). Teleost MALT includes diffuse B cells and T cells with specific phenotypes different from their systemic counterparts that have co-evolved to defend the microbe-rich mucosal environment. Both B and T cells respond to mucosal infection or vaccination. Specific antibody responses can be measured in the gills, gut and skin mucosal secretions of teleost fish following mucosal infection or vaccination. Rainbow trout studies have shown that IgT antibodies and IgT+ B cells are the predominant B cell subset in all MALT and respond in a compartmentalized manner to mucosal infection. Our current knowledge on adaptive immunity in teleosts is limited compared to the mammalian literature. New research tools and in vivo models are currently being developed in order to help reveal the great intricacy of teleost mucosal adaptive immunity and help improve mucosal vaccination protocols for use in aquaculture.
290 citations
TL;DR: This review focuses upon the last 15 years of studies addressing the assessment of: (1) plant, herb and algae extracts; and (2) PAMPs, upon non-specific immune parameters of activation and immunostimulant diet efficacy.
249 citations
TL;DR: New information of TLRs in aquatic animals and their structural and functional relationship with warm-blooded animals is described and vaccines against many critical diseases of aquatic animals may be made more effective by supplementing TLR activators which will stimulate dendritic cells.
247 citations
TL;DR: Results indicate that LAB may vary in their immunological effects depending on the species and hosts, which includes their impacts on finfish aquaculture, possible routes for treatment and their interaction with fish immune responses.
Abstract: Fish intestinal mucosal surfaces comprise of a complex and dynamic community of microorganisms, which play important roles within the gastrointestinal (GI) tract. Of the bacteria colonising the GI tract, lactic acid bacteria (LAB), are generally considered as favourable bacteria due to their abilities to stimulating host GI development, digestive function, maintaining mucosal tolerance, stimulating immune response and provide protection towards bacterial pathogens. In early finfish studies culture-dependent methods were used to enumerate bacterial population levels within the GI tract; members of Lactobacillus, Lactococcus, Leuconostoc, Enterococcus, Streptococcus and Carnobacterium genera were isolated. However, due to limitations by using culture media, techniques such as denaturing gradient gel electrophoresis (DGGE), temporal temperature gradient electrophoresis (TTGE), 16S rRNA clone libraries, and MiSeq sequencing of 16S rRNA genes have been used during the last decade. These investigations have revealed the presence of Lactobacillus, Lactococcus, Leuconostoc, Enterococcus, Streptococcus, Carnobacterium, Weissella and Pediococcus as indigenous species. In the GI tract of warm water fish species, members of the genera Lactobacillus, Lactococcus, Leuconostoc, Enterococcus, Weissella and Pediococcus have commonly been identified, however, Carnobacterium are rarely identified. Numerous strains of LAB isolated from finfish are capable of producing antibacterial substances against different potential fish pathogenic bacteria as well as human pathogens. In addition, many LAB have the ability to inhibit growth of closely related bacteria including strains of carnobacteria, lactobacilli, lactococci, leuconostoc and pediococci. LAB are revealed be the most promising bacterial genera as probiotic in aquaculture. During the decade increasing number of research attempts are performed on evaluation of probiotic properties of different genus and species of LAB. Except limited contradictory reports, most of administered strains showed beneficial effects on growth performance, reproductive performance, immune responses and disease resistance of finfish. This eventually led to industrial scale up and introduction LAB-based commercial probiotics. Pathogenic LAB such as members of the genera Streptococcus, Enterococcus, Lactobacillus, Carnobacterium and Lactococcus have been detected from ascites, kidney, liver, heart and spleen of several finfish species. These pathogenic bacteria will be addressed in present review which includes their impacts on finfish aquaculture, possible routes for treatment.
222 citations
References
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TL;DR: Using metabolic function analyses of identified genes, the human genome is compared with the average content of previously sequenced microbial genomes and humans are superorganisms whose metabolism represents an amalgamation of microbial and human attributes.
Abstract: The human intestinal microbiota is composed of 10(13) to 10(14) microorganisms whose collective genome ("microbiome") contains at least 100 times as many genes as our own genome. We analyzed approximately 78 million base pairs of unique DNA sequence and 2062 polymerase chain reaction-amplified 16S ribosomal DNA sequences obtained from the fecal DNAs of two healthy adults. Using metabolic function analyses of identified genes, we compared our human genome with the average content of previously sequenced microbial genomes. Our microbiome has significantly enriched metabolism of glycans, amino acids, and xenobiotics; methanogenesis; and 2-methyl-d-erythritol 4-phosphate pathway-mediated biosynthesis of vitamins and isoprenoids. Thus, humans are superorganisms whose metabolism represents an amalgamation of microbial and human attributes.
4,111 citations
TL;DR: It is indicated that host diet and phylogeny both influence bacterial diversity, which increases from carnivory to omnivory to herbivory; that bacterial communities codiversified with their hosts; and that the gut microbiota of humans living a modern life-style is typical of omnivorous primates.
Abstract: Mammals are metagenomic in that they are composed of not only their own gene complements but also those of all of their associated microbes. To understand the coevolution of the mammals and their indigenous microbial communities, we conducted a network-based analysis of bacterial 16S ribosomal RNA gene sequences from the fecal microbiota of humans and 59 other mammalian species living in two zoos and in the wild. The results indicate that host diet and phylogeny both influence bacterial diversity, which increases from carnivory to omnivory to herbivory; that bacterial communities codiversified with their hosts; and that the gut microbiota of humans living a modern life-style is typical of omnivorous primates.
3,072 citations
TL;DR: The gut microbiota has a beneficial role during normal homeostasis, modulating the host's immune system as well as influencing host development and physiology, including organ development and morphogenesis, and host metabolism.
Abstract: Establishing and maintaining beneficial interactions between the host and its associated microbiota are key requirements for host health. Although the gut microbiota has previously been studied in the context of inflammatory diseases, it has recently become clear that this microbial community has a beneficial role during normal homeostasis, modulating the host's immune system as well as influencing host development and physiology, including organ development and morphogenesis, and host metabolism. The underlying molecular mechanisms of host-microorganism interactions remain largely unknown, but recent studies have begun to identify the key signalling pathways of the cross-species homeostatic regulation between the gut microbiota and its host.
2,585 citations
TL;DR: This review describes the state of the art of probiotic research in the culture of fish, crustaceans, mollusks, and live food, with an evaluation of the results obtained so far.
Abstract: There is an urgent need in aquaculture to develop microbial control strategies, since disease outbreaks are recognized as important constraints to aquaculture production and trade and since the development of antibiotic resistance has become a matter of growing concern. One of the alternatives to antimicrobials in disease control could be the use of probiotic bacteria as microbial control agents. This review describes the state of the art of probiotic research in the culture of fish, crustaceans, mollusks, and live food, with an evaluation of the results obtained so far. A new definition of probiotics, also applicable to aquatic environments, is proposed, and a detailed description is given of their possible modes of action, i.e., production of compounds that are inhibitory toward pathogens, competition with harmful microorganisms for nutrients and energy, competition with deleterious species for adhesion sites, enhancement of the immune response of the animal, improvement of water quality, and interaction with phytoplankton. A rationale is proposed for the multistep and multidisciplinary process required for the development of effective and safe probiotics for commercial application in aquaculture. Finally, directions for further research are discussed.
2,072 citations
TL;DR: It is shown that, even though commensal bacteria are rapidly killed by macrophages, intestinal dendritic cells (DCs) can retain small numbers of live commensals for several days, which allows DCs to selectively induce IgA, which helps protect against mucosal penetration by Commensals.
Abstract: The enormous number of commensal bacteria in the lower intestine of vertebrates share abundant molecular patterns used for innate immune recognition of pathogenic bacteria. We show that, even though commensals are rapidly killed by macrophages, intestinal dendritic cells (DCs) can retain small numbers of live commensals for several days. This allows DCs to selectively induce IgA, which helps protect against mucosal penetration by commensals. The commensal-loaded DCs are restricted to the mucosal immune compartment by the mesenteric lymph nodes, which ensures that immune responses to commensal bacteria are induced locally, without potentially damaging systemic immune responses.
1,479 citations