Editing Clostridium perfringens (section)

== Virulence ==
Membrane-damaging enzymes, pore-forming toxins, intracellular toxins, and hydrolytic enzymes are the functional categories into which ''C. perfringens''<nowiki/>' virulence factors may be divided. These virulence factor-encoding genes can be found on chromosomes and large plasmids.<ref name="Revitt-Mills-20152"/>

=== Carbohydrate-active enzymes ===
The human gastrointestinal tract is lined with [[Gastrointestinal wall|intestinal mucosa]] that secrete [[mucus]] and act as a defense mechanism against pathogens, toxins, and harmful substances. Mucus is made up of [[mucin]]s containing several [[O-linked glycosylation|O-linked glycan]] [[glycoprotein]]s that recognizes and forms a barrier around microbes, preventing them from attaching to endothelial cells and infecting them.<ref>{{Cite journal |last1=Ba |first1=Xuli |last2=Jin |first2=Youshun |last3=Ning |first3=Xuan |last4=Gao |first4=Yidan |last5=Li |first5=Wei |last6=Li |first6=Yunhui |last7=Wang |first7=Yihan |last8=Zhou |first8=Jizhang |date=2024-08-07 |title=Clostridium perfringens in the Intestine: Innocent Bystander or Serious Threat? |journal=Microorganisms |language=en |volume=12 |issue=8 |pages=1610 |doi=10.3390/microorganisms12081610 |issn=2076-2607 |pmc=11356505 |pmid=39203452 |doi-access=free}}</ref><ref name=":022">{{Cite journal |last1=Low |first1=Kristin E |last2=Smith |first2=Steven P |last3=Abbott |first3=D Wade |last4=Boraston |first4=Alisdair B |date=2020-05-30 |title=The glycoconjugate-degrading enzymes of ''Clostridium perfringens'': Tailored catalysts for breaching the intestinal mucus barrier |url=https://academic.oup.com/glycob/article/31/6/681/5848600 |journal=Glycobiology |volume=31 |issue=6 |pages=681–690 |doi=10.1093/glycob/cwaa050 |issn=1460-2423 |pmid=32472136|url-access=subscription }}</ref> ''C. perfringens'' can secrete different [[CAZy|carbohydrate-active enzymes]] (CAZymes) that aid in degrading mucins and other O-glycans within the intestinal mucosa. These enzymes include: Sialidases, Hexosaminidases, Galactosidases, and Fucosidases belonging to various [[glycoside hydrolase families]].<ref name=":022" />

==== Sialidase ====
[[Neuraminidase|Sialidases]], also called neuraminidases, function to breakdown mucin by [[Hydrolysis|hydrolyzing]] the terminal sialic acid residues located within the protein through the process of [[Desilylation|desialylation]]. ''C. perfringens'' has three sialidases belonging to [[Glycoside hydrolase family 33|glycoside hydrolase family 33 (GH33)]]: NanH, NanI, and NanJ. All strains of ''C. perfringens'' encode for at least one of these enzymes.<ref name=":022" /><ref>{{Cite journal |last1=Medley |first1=Brendon J. |last2=Low |first2=Kristin E. |last3=Irungu |first3=Jackline D. W. |last4=Kipchumba |first4=Linus |last5=Daneshgar |first5=Parandis |last6=Liu |first6=Lin |last7=Garber |first7=Jolene M. |last8=Klassen |first8=Leeann |last9=Inglis |first9=G. Douglas |last10=Boons |first10=Geert-Jan |last11=Zandberg |first11=Wesley F. |last12=Abbott |first12=D. Wade |last13=Boraston |first13=Alisdair B. |date=2024-10-01 |title=A "terminal" case of glycan catabolism: Structural and enzymatic characterization of the sialidases of Clostridium perfringens |journal=Journal of Biological Chemistry |volume=300 |issue=10 |pages=107750 |doi=10.1016/j.jbc.2024.107750 |doi-access=free |pmid=39251137 |pmc=11525138 |bibcode=2024JBiCh.300j7750M |issn=0021-9258}}</ref>

''C. perfringens'' can secrete NanI and NanJ through secretion signal [[peptide]]s located on each protein. Research suggests that NanH operates in the cytoplasm of ''C. perfringens'', as it does not contain a secretion signal peptide. NanH contains only a catalytic domain, whereas NanI and NanJ contain a [[catalytic domain]] and additional [[carbohydrate-binding module]]s (CBMs) to aid in catalytic activity. Located on their N-terminals, NanI contains CBM40, whereas NanJ contains both CBM40 and CBM32. Based on studies analyzing the three-dimensional structure of NanI, its [[active site]] has a pocket-like orientation that aids in the removal of sialic acid residues from sialomucins in the intestinal mucosa.<ref name=":022" />

==== Hexosaminidase ====
The mucus layer consists of intestinal mucin glycans, glycolipids, and glycoproteins that contain [[hexosamines]], such as [[N-Acetylglucosamine|N-acetylglucosamine]] (GlcNAc) and [[N-Acetylgalactosamine|N-acetylgalactosamine]] (GalNAc). ''C. perfringens'' encodes for eight [[hexosaminidase]]s that break down hexosamines in the mucus. These hexosaminidases belong to four glycoside hydrolase families: GH36, GH84, GH89, and GH123.<ref name=":022" />

''C. perfringens'' encodes for AagA (''Cp''GH36A) and ''Cp''GH36B in [[Glycoside hydrolase family 36|glycoside hydrolase family 36 (GH36)]]: AagA removes GalNAc from O-glycans, and ''Cp''GH36B is expected to have a similar structure to AagA, but specificities on its function are unknown. NagH, NagI, NagJ, and NagK, belonging to glycoside hydrolase family 84 (GH84), cleave terminal GlcNAc residues using a substrate-assisted digestion mechanism. AgnC (''Cp''GH89), belonging to [[glycoside hydrolase family 89]] (GH89), both cleaves GlcNAc from the ends of mucin glycans and acts on gastric mucin. Belonging to glycoside hydrolase family 123 (GH123), ''Cp''Nga123 cleaves GalNAc, but research suggests that it only breaks down glycans taken up by ''C. perfringens'' due to the absence of a secretion signal peptide.<ref name=":022" />

==== Galactosidase ====
''C. perfringens'' has four [[galactosidases]] that belong to the [[glycoside hydrolase family 2|glycoside hydrolase family 2 (GH2)]]: ''Cp''GH2A, ''Cp''GH2B, ''Cp''GH2C, and ''Cp''GH2D. Research suggests that these enzymes are effective at breaking down core mucin glycan structures with the ability to bind [[galactose]] using CBM51. However, minimal research exists on the specific functioning of galactosidases in ''C. perfringens''.<ref name=":022" />

==== Fucosidase ====
[[Fucose]] monosaccharides are located on the terminal ends of core O-linked glycans. ''C. perfringens'' encodes for three fucosidases that belong to two glycoside hydrolase families: Afc1 and Afc2 in [[glycoside hydrolase family 29]] (GH29), and Afc3 in glycoside hydrolase family 95 (GH95). Afc3 contains a C-terminal CBM51 and is the only fucosidase that contains a carbohydrate-binding module in ''C. perfringens''. Fucosyl residues tend to cover the ends of glycans and protect them against enzymatic digestion, so research suggests that the ability of fucosidases to cleave complex and diverse fucosyl linkages is due to long-term adaptations in ''C. perfringens'' that persisted within close range of mucins.<ref name=":022" />

=== Major toxins ===
There are five major toxins produced by ''Clostridium perfringens.'' Alpha, beta, epsilon and enterotoxin are toxins that increase a cells permeability which causes an ion imbalance while iota toxins destroy the cell's actin cytoskeleton.<ref name="Stiles-20132">{{Cite journal |last1=Stiles |first1=Bradley G. |last2=Barth |first2=Gillian |last3=Barth |first3=Holger |last4=Popoff |first4=Michel R. |date=2013-11-12 |title=Clostridium perfringens Epsilon Toxin: A Malevolent Molecule for Animals and Man? |journal=Toxins |volume=5 |issue=11 |pages=2138–2160 |doi=10.3390/toxins5112138 |issn=2072-6651 |pmc=3847718 |pmid=24284826 |doi-access=free}}</ref> On the basis of which major, "typing" toxins are produced, ''C. perfringens'' can be classified into seven "toxinotypes", A, B, C, D, E, F and G:<ref name="pmid351488122">{{cite journal |vauthors=Johnston MD, Whiteside TE, Allen ME, Kurtz DM |date=February 2022 |title=Toxigenic Profile of Clostridium perfringens Strains Isolated from Natural Ingredient Laboratory Animal Diets |url= |journal=Comparative Medicine |volume=72 |issue=1 |pages=50–58 |doi=10.30802/AALAS-CM-22-000013 |pmc=8915413 |pmid=35148812}}</ref>
{| class="wikitable"
|+Toxinotypes of ''C. perfringens''<ref name="pmid351488122" />{{rp|at=fig.1}}<ref>{{Cite journal |last1=Rood |first1=Julian I. |last2=Adams |first2=Vicki |last3=Lacey |first3=Jake |last4=Lyras |first4=Dena |last5=McClane |first5=Bruce A. |last6=Melville |first6=Stephen B. |last7=Moore |first7=Robert J. |last8=Popoff |first8=Michel R. |last9=Sarker |first9=Mahfuzur R. |last10=Songer |first10=J. Glenn |last11=Uzal |first11=Francisco A. |last12=Van Immerseel |first12=Filip |date=2018-10-01 |title=Expansion of the Clostridium perfringens toxin-based typing scheme |journal=Anaerobe |volume=53 |pages=5–10 |doi=10.1016/j.anaerobe.2018.04.011 |issn=1075-9964 |pmc=6195859 |pmid=29866424 |doi-access=free}}</ref>
! {{diagonal split header|Type|Toxin}} 
!Alpha
!Beta
!Epsilon
!Iota
!Enterotoxin
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!Notes
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! scope="row" |A
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! scope="row" |B
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! scope="row" |C
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! scope="row" |D
| {{yes|+}} || {{no|-}} || {{yes|+}} || {{no|-}} || {{partial|+/-}} || {{no|-}}
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! scope="row" |E
| {{yes|+}} || {{no|-}} || {{yes|+}} || {{partial|+/-}} || {{no|-}}
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! scope="row" |F
| {{yes|+}} || {{no|-}} || {{yes|+}} || {{no|-}}
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! scope="row" |G
| {{yes|+}} || {{no|-}} || {{yes|+}}
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==== Alpha toxin ====
Alpha toxin (CPA) is a zinc-containing phospholipase C, composed of two structural domains, which destroy a cell's membrane. Alpha toxins are produced by all five types of ''C. perfringens.'' This toxin is linked to [[gas gangrene]] of humans and animals. Most cases of gas gangrene has been related to a deep wound being contaminated by soil that harbors ''C. perfringens''.<ref name="Stiles-20132" /><ref>{{Cite journal |last1=Li |first1=Ming |last2=Li |first2=Ning |date=2021-06-16 |title=Clostridium perfringens bloodstream infection secondary to acute pancreatitis: A case report |journal=World Journal of Clinical Cases |volume=9 |issue=17 |pages=4357–4364 |doi=10.12998/wjcc.v9.i17.4357 |issn=2307-8960 |pmc=8173429 |pmid=34141801 |doi-access=free}}</ref>

==== Beta toxin ====
Beta toxins (CPB) are a protein that causes hemorrhagic [[Clostridial necrotizing enteritis|necrotizing enteritis]] and [[Enterotoxemia|enterotoxaemia]] in both animals (type B) and humans (type C) which leads to the infected individual's feces becoming bloody and their intestines necrotizing.<ref name="Stiles-20132" /> [[Protease|Proteolytic enzymes]], such as trypsin, can break down CPB, making them ineffective. Therefore, the presence of trypsin inhibitors in colostrum makes CPB especially deadly for mammal offspring.<ref>{{Cite journal |last1=Garcia |first1=J.P. |last2=Beingesser |first2=J. |last3=Fisher |first3=D.J. |last4=Sayeed |first4=S. |last5=McClane |first5=B.A. |last6=Posthaus |first6=H. |last7=Uzal |first7=F.A. |date=4 January 2012 |title=The effect of Clostridium perfringens type C strain CN3685 and its isogenic beta toxin null mutant in goats |journal=Veterinary Microbiology |language=en |volume=157 |issue=3–4 |pages=412–419 |doi=10.1016/j.vetmic.2012.01.005 |pmc=3348370 |pmid=22296994}}</ref>

==== Epsilon toxin ====
Epsilon toxin (ETX) is a protein produced by type B and type D strains of ''C. perfringens.'' This toxin is currently ranked the third most potent bacterial toxin known.<ref>{{Cite journal |last1=Alves |first1=Guilherme Guerra |last2=Machado de Ávila |first2=Ricardo Andrez |last3=Chávez-Olórtegui |first3=Carlos Delfin |last4=Lobato |first4=Francisco Carlos Faria |date=2014-12-01 |title=Clostridium perfringens epsilon toxin: The third most potent bacterial toxin known |url=https://www.sciencedirect.com/science/article/pii/S1075996414001309 |journal=Anaerobe |volume=30 |pages=102–107 |doi=10.1016/j.anaerobe.2014.08.016 |issn=1075-9964 |pmid=25234332|url-access=subscription }}</ref> ETX causes [[Enterotoxemia|enterotoxaemia]] in mainly goats and sheep, but cattle are sometime susceptible to it as well. An experiment using mice found that ETX had an LD50 of 50-110&nbsp;ng/kg.<ref>{{Cite journal |last1=Xin |first1=Wenwen |last2=Wang |first2=Jinglin |date=2019-09-01 |title=Clostridium perfringens epsilon toxin: Toxic effects and mechanisms of action |journal=Biosafety and Health |volume=1 |issue=2 |pages=71–75 |doi=10.1016/j.bsheal.2019.09.004 |issn=2590-0536 |s2cid=208690896 |doi-access=free}}</ref> The excessive production of ETX increases the permeability of the intestines. This causes severe edema in organs such as the brain and kidneys.<ref>{{Cite journal |last1=Geng |first1=Zhijun |last2=Kang |first2=Lin |last3=Huang |first3=Jing |last4=Gao |first4=Shan |last5=Wang |first5=Jing |last6=Yuan |first6=Yuan |last7=Li |first7=Yanwei |last8=Wang |first8=Jinglin |last9=Xin |first9=Wenwen |date=2021-07-30 |title=Epsilon toxin from Clostridium perfringens induces toxic effects on skin tissues and HaCaT and human epidermal keratinocytes |journal=Toxicon |volume=198 |pages=102–110 |bibcode=2021Txcn..198..102G |doi=10.1016/j.toxicon.2021.05.002 |issn=0041-0101 |pmid=33965432 |s2cid=234343237 |doi-access=free}}</ref>

The very low LD50 of ETX has led to concern that it may be used as a bioweapon. It appeared on the [[select agent]] lists of the US CDC and USDA, until it was removed in 2012. There are no human vaccines for this toxin, but effective vaccines for animals exist.<ref name="MEDCOE2">{{cite book |last1=Stiles |first1=Bradley G. |url=https://medcoe.army.mil/borden-tb-medical-aspects-bio-war |title=Medical Aspects of Biological Warfare |last2=Barth |first2=Gillian |last3=Popoff |first3=Michel R. P |date=2018 |publisher=Health Readiness Center of Excellence (US Army) |isbn=9780160941597 |edition=2 |chapter=Clostridium Perfringens Epsilon Toxin}}</ref>

==== Iota toxin ====
Iota toxin (ITX) is a protein produced by type E strains of ''C. perfringens.'' Iota toxins are made up of two, unlinked proteins that form a multimeric complex on cells. Iota toxins prevent the formation of filamentous actin. This causes the destruction of the cells cytoskeleton which in turn leads to the death of the cell as it can no longer maintain homeostasis.<ref>{{Cite journal |last1=Sakurai |first1=Jun |last2=Nagahama |first2=Masahiro |last3=Oda |first3=Masataka |last4=Tsuge |first4=Hideaki |last5=Kobayashi |first5=Keiko |date=2009-12-23 |title=Clostridium perfringens Iota-Toxin: Structure and Function |journal=Toxins |volume=1 |issue=2 |pages=208–228 |doi=10.3390/toxins1020208 |issn=2072-6651 |pmc=3202787 |pmid=22069542 |doi-access=free}}</ref>

==== Enterotoxin ====
This toxin (CPE) causes food poisoning. It alters intracellular claudin tight junctions in gut epithelial cells. This pore-forming toxin also can bind to human ileal and colonic epithelium in vitro and necrotize it. Through the caspase-3 pathway, this toxin can cause apoptosis of affected cells. This toxin is linked to type F strains, but has also been found to be produced by certain types of C, D, and E strains.<ref>{{Cite journal |last1=Kiu |first1=Raymond |last2=Hall |first2=Lindsay J. |date=2018-12-01 |title=An update on the human and animal enteric pathogen Clostridium perfringens |journal=Emerging Microbes & Infections |language=en |volume=7 |issue=1 |page=141 |doi=10.1038/s41426-018-0144-8 |issn=2222-1751 |pmc=6079034 |pmid=30082713 |doi-access=free}}</ref>

=== Other toxins ===
TpeL is a toxin found in type B, C, and G<ref name="pmid340765062">{{cite journal |last1=Orrell |first1=KE |last2=Melnyk |first2=RA |date=18 August 2021 |title=Large Clostridial Toxins: Mechanisms and Roles in Disease. |journal=Microbiology and Molecular Biology Reviews |volume=85 |issue=3 |pages=e0006421 |doi=10.1128/MMBR.00064-21 |pmc=8483668 |pmid=34076506}}</ref> strains. It is in the same [[protein family]] as [[Clostridium difficile toxin A|''C. difficile'' toxin A]].<ref>{{cite journal |last1=Chen |first1=J |last2=McClane |first2=BA |date=June 2015 |title=Characterization of Clostridium perfringens TpeL toxin gene carriage, production, cytotoxic contributions, and trypsin sensitivity. |journal=Infection and Immunity |volume=83 |issue=6 |pages=2369–81 |doi=10.1128/IAI.03136-14 |pmc=4432761 |pmid=25824828}}</ref> It does not appear important in the pathogenesis of types B and C infections, but may contribute to virulence in type G strains. It glycosylates Rho and [[Ras GTPase]]s, disrupting host cell signaling.<ref name="pmid340765062" />