The epidemiology of Leishmania mexicana is the study of the distribution and determinants of the infection caused by this parasite, one of the agents of cutaneous leishmaniasis (CL) in the Americas. Leishmania mexicana is endemic in Mexico and Central America, where the bite of infected sandflies of the genus Lutzomyia transmits it. The parasite can cause different clinical forms of CL, such as localized cutaneous leishmaniasis (LCL), diffuse cutaneous leishmaniasis (DCL), and mucocutaneous leishmaniasis (MCL).
The epidemiology of Leishmania mexicana is influenced by several factors, such as the diversity and distribution of the sandfly vectors, the availability and susceptibility of the animal reservoirs, the genetic variability and virulence of the parasite strains, and the environmental and social conditions that affect the exposure and immunity of the human hosts. Some of the main aspects of the epidemiology of Leishmania mexicana are:
● The sandfly vectors: The primary vector of Leishmania mexicana in Mexico is Lutzomyia olmeca olmeca, which is found in tropical rainforests and prefers biting humans. Other potential vectors are Lutzomyia cruciata, Lutzomyia shannoni, Lutzomyia ovallesi, and Lutzomyia panamensis, which have different ecological niches and feeding habits. The vector density and activity vary according to the season, altitude, temperature, humidity, and vegetation.
● The animal reservoirs: The main animal reservoirs of Leishmania mexicana are rodents of the genera Ototylomys, Peromyscus, Neotoma, Sigmodon, and Oryzomys, which are widely distributed in Mexico and Central America. Other possible reservoirs are marsupials, carnivores, bats, and domestic animals such as dogs and cats. The reservoirs maintain the parasite cycle in nature and serve as sources of infection for the sandflies and humans.
● The parasite strains: Leishmania mexicana is a complex that includes several strains or subspecies with different biological and molecular characteristics. Some of these strains are Leishmania mexicana mexicana, Leishmania mexicana amazonensis, Leishmania mexicana pifanoi, Leishmania mexicana garnhami, and Leishmania mexicana Aristides. The strains’ geographic distribution, vector specificity, reservoir preference, pathogenicity, and drug susceptibility can vary.
● The human hosts: The human hosts of Leishmania mexicana are people who live or work in areas where the parasite is endemic or travel to these areas for tourism or other reasons. The risk of infection depends on the frequency and duration of exposure to the sandfly bites, the type and location of the skin lesions, the immune status of the host, and the availability and access to diagnosis and treatment. The infection can cause different clinical forms of CL, such as LCL, DCL, or MCL.
The epidemiology of Leishmania mexicana is essential for understanding CL’s transmission dynamics and control strategies in Mexico and Central America. It also provides insights into the evolution and adaptation of the parasite to different hosts and environments.
Kingdom: Eukaryota
Phylum: Euglenozoa
Class: Kinetoplastea
Order: Trypanosomatida
Genus: Leishmania
Species: L. Mexicana
Leishmania mexicana structure:
Classification: Protozoan parasite in the Trypanosomatida order, characterized by a single flagellum, kinetoplast, and subpellicular microtubules.
Life Cycle: Two main stages – promastigote (in sandfly gut) with long flagellum and anterior kinetoplast, and amastigote (in macrophages) with short flagellum and posterior kinetoplast.
Surface Molecules: Important for host/vector interactions, including GIPLs, GSLs, and LPG with complex sugar structures.
Enzymes: Key enzymes like arginase, GPDH, and ICP are involved in metabolism, survival, and pathogenesis.
Nuclear Structure: Unique nucleus with nucleoplasm and peripheral chromatin, organized into mini-chromosomes attached to the nuclear envelope by NUP-1.
The antigenic type of Leishmania mexicana is determined by its surface glycoconjugates’ structure and composition, mainly glycoinositol phospholipids (GIPLs) and glycosphingolipids (GSLs). GIPLs are complex molecules that consist of a glycan core attached to a phosphatidylinositol anchor, which is embedded in the parasite membrane. GSLs are like GIPLs but have a ceramide anchor instead of a phosphatidylinositol one. GIPLs and GSLs can vary in their sugar residues, linkages, and modifications, affecting their antigenic properties and interactions with host cells.
Leishmania mexicana has four significant types of GIPLs, which differ in their glycan core structures: iM2, iM3, iM4, and EPiM3. The most abundant and immunodominant GIPL is EPiM3, which has an ethanolamine phosphate group attached to the terminal mannose residue. EPiM3 is located at the parasite cell surface, the flagellar pocket, and lysosomal membranes. It is involved in the attachment and invasion of macrophages, the modulation of phagolysosomal fusion, and the protection against lysosomal enzymes.
Leishmania mexicana also acquires a GSL from its host macrophages, identical to the Forssman antigen of mammalian cells. The Forssman antigen is a pentasaccharide with a GalNAcβ1-3GalNAcβ1-4Galβ1-4GlcNAcβ1-3Gal sequence linked to a ceramide anchor. It is not synthesized by the parasite but transferred from the macrophage membrane to the parasite surface by an unknown mechanism. The Forssman antigen may help the parasite to evade the host’s immune response by mimicking a self-antigen.
The antigenic variation of Leishmania mexicana is a dynamic process that involves changes in the expression and structure of GIPLs and GSLs in response to environmental stimuli and host immune pressure. The parasite can alter its antigenic type by switching between different GIPLs or acquiring different GSLs from different host cells. It allows the parasite to adapt to different host niches and escape from immune recognition and elimination.
Cutaneous leishmaniasis typically manifests as skin lesions and ulcers and is transmitted to humans through the bite of infected sandfly vectors. Here’s an overview of the pathogenesis of Leishmania mexicana:
Transmission: The life cycle of Leishmania mexicana involves two main hosts: the sandfly vector and a mammalian host, including humans. When an infected female sandfly bites a mammal to obtain a blood meal, it injects promastigote forms of the parasite into the host’s skin.
Invasion of Macrophages: Once injected into the host’s skin, the promastigotes are phagocytosed by macrophages, a type of immune cell. Within the macrophages, the promastigotes transform into amastigote forms, which are the intracellular stage of the parasite.
Intracellular Survival: Leishmania mexicana amastigotes evade the host immune system and replicate within the phagolysosomes of macrophages. This intracellular survival allows the parasite to avoid detection by the immune system and persist in the host.
Immune Response: As the parasite replicates within macrophages, it triggers an immune response. Infected individuals may develop local inflammation, which can result in the development of skin sores and ulcers. The severity of the immune response can vary among individuals, and some may be asymptomatic carriers.
Dissemination: In some cases, Leishmania mexicana can disseminate to other body parts, leading to more severe forms of the disease. It can occur through the bloodstream or lymphatic system.
Healing or Chronic Infection: The outcome of Leishmania mexicana infection can vary. Sometimes, the infection may spontaneously resolve, and the skin lesions heal. However, in other cases, the infection can become chronic if the immune system is compromised, leading to persistent skin lesions and potential complications.
The host defenses against Leishmania mexicana involve both innate and adaptive immune responses. The first line of defense is inherent immunity, and it involves phagocytic cells’ pattern recognition receptors (PRRs) recognizing the parasite, like macrophages and neutrophils, which then try to eliminate the parasite via generating reactive nitrogen and oxygen species (ROS & RNS) in an oxidative burst. However, Leishmania mexicana has developed strategies to resist or evade this mechanism.
Producing antioxidant enzymes like catalase, superoxide dismutase (SOD), and trypanothione reductase, which scavenge ROS and RNS and protect the parasite from oxidative damage.
Modulating the expression and activity of host PRRs like NOD-like receptors, C-type lectin receptors, and Toll-like receptors (CLRs), which can activate or inhibit the oxidative burst depending on the parasite strain and stage.
Adaptive immune response fights Leishmania mexicana through T and B cells, producing cytokines and antibodies. Response type depends on parasite strain, host genetics, and infection details. Generally, the Th1 response (IFN-γ, TNF-α) is protective, while the Th2 response (IL-4, IL-10) is detrimental. Exceptions exist.
Inducing regulatory T cells (Tregs), a subset of T cells that suppress the activation and function of other T cells and macrophages by producing IL-10 and TGF-β. Leishmania mexicana can stimulate Treg differentiation by expressing surface glycoconjugates that bind to host CLRs or acquiring host glycosphingolipids that mimic self-antigens.
Modulating antibody production can have different effects on the infection depending on the isotype, specificity, and concentration of antibodies. Leishmania mexicana can induce IgG1 antibodies that bind to FcγRIII receptors on macrophages and inhibit their oxidative burst. Alternatively, it can induce IgG2 antibodies that bind to FcγRI receptors on macrophages and enhance their oxidative burst.
Altering antigen presentation is the process by which macrophages present parasite antigens to T cells via major histocompatibility complex (MHC) molecules. Leishmania mexicana can downregulate or upregulate MHC expression on macrophages depending on whether it wants to avoid or stimulate T cell recognition.
Leishmania mexicana is a parasite that causes cutaneous leishmaniasis, a skin infection resulting in ulcers, nodules, or diffuse lesions. The parasite is transmitted to animal sandflies found in Mexico and Central America by being bitten by an infected animal. The symptoms of Leishmania mexicana infection depend on the type and location of the skin lesion, the immune response of the host, and the species of Leishmania involved. Some common clinical manifestations are:
Localized cutaneous leishmaniasis (LCL): This is the most common form of the disease, which develops as an ulcer with raised borders at the site of the sandfly bite. The ulcer may heal spontaneously or persist for months or years. It may be located mainly in the ear (39.8% of cases) or other exposed parts of the body.
Diffuse cutaneous leishmaniasis (DCL): This is a rare and severe form of the disease, which occurs when the parasite spreads throughout the skin and causes multiple nodules or plaques that do not ulcerate. This form is associated with a poor immune response and ineffective treatment. It may affect any body part, mainly the face, arms, and legs.
The diagnosis of Leishmania mexicana, the parasite that causes cutaneous leishmaniasis in Mexico and Central America, can be done by various methods, such as:
Physical Exam: The doctor checks for skin issues and organ enlargement.
Microscopic Exam: Samples are examined under a microscope for amastigotes, the parasite form.
Molecular Methods: Techniques like PCR and DNA analysis identify the parasite.
Culture: Parasite isolation and identification in a lab is time-consuming and needs expertise.
The control of Leishmania mexicana infection can be achieved by different strategies, such as:
Preventing transmission: Use insect repellents, bed nets, and protective clothing to avoid sandfly bites.
Treating infection: Administer antiparasitic drugs like pentavalent antimonials or liposomal amphotericin B based on infection type and severity.
Enhancing immune response: Boost Th1-type immune response with compounds like garlic extract to aid in resistance and healing of the infection.
Leishmania mexicana – an overview | ScienceDirect Topics
(PDF) Leishmania (Leishmania) mexicana Infection in Wild Rodents from an Emergent Focus of Cutaneous Leishmaniasis in Yucatan, Mexico (researchgate.net)
The epidemiology of Leishmania mexicana is the study of the distribution and determinants of the infection caused by this parasite, one of the agents of cutaneous leishmaniasis (CL) in the Americas. Leishmania mexicana is endemic in Mexico and Central America, where the bite of infected sandflies of the genus Lutzomyia transmits it. The parasite can cause different clinical forms of CL, such as localized cutaneous leishmaniasis (LCL), diffuse cutaneous leishmaniasis (DCL), and mucocutaneous leishmaniasis (MCL).
The epidemiology of Leishmania mexicana is influenced by several factors, such as the diversity and distribution of the sandfly vectors, the availability and susceptibility of the animal reservoirs, the genetic variability and virulence of the parasite strains, and the environmental and social conditions that affect the exposure and immunity of the human hosts. Some of the main aspects of the epidemiology of Leishmania mexicana are:
● The sandfly vectors: The primary vector of Leishmania mexicana in Mexico is Lutzomyia olmeca olmeca, which is found in tropical rainforests and prefers biting humans. Other potential vectors are Lutzomyia cruciata, Lutzomyia shannoni, Lutzomyia ovallesi, and Lutzomyia panamensis, which have different ecological niches and feeding habits. The vector density and activity vary according to the season, altitude, temperature, humidity, and vegetation.
● The animal reservoirs: The main animal reservoirs of Leishmania mexicana are rodents of the genera Ototylomys, Peromyscus, Neotoma, Sigmodon, and Oryzomys, which are widely distributed in Mexico and Central America. Other possible reservoirs are marsupials, carnivores, bats, and domestic animals such as dogs and cats. The reservoirs maintain the parasite cycle in nature and serve as sources of infection for the sandflies and humans.
● The parasite strains: Leishmania mexicana is a complex that includes several strains or subspecies with different biological and molecular characteristics. Some of these strains are Leishmania mexicana mexicana, Leishmania mexicana amazonensis, Leishmania mexicana pifanoi, Leishmania mexicana garnhami, and Leishmania mexicana Aristides. The strains’ geographic distribution, vector specificity, reservoir preference, pathogenicity, and drug susceptibility can vary.
● The human hosts: The human hosts of Leishmania mexicana are people who live or work in areas where the parasite is endemic or travel to these areas for tourism or other reasons. The risk of infection depends on the frequency and duration of exposure to the sandfly bites, the type and location of the skin lesions, the immune status of the host, and the availability and access to diagnosis and treatment. The infection can cause different clinical forms of CL, such as LCL, DCL, or MCL.
The epidemiology of Leishmania mexicana is essential for understanding CL’s transmission dynamics and control strategies in Mexico and Central America. It also provides insights into the evolution and adaptation of the parasite to different hosts and environments.
Kingdom: Eukaryota
Phylum: Euglenozoa
Class: Kinetoplastea
Order: Trypanosomatida
Genus: Leishmania
Species: L. Mexicana
Leishmania mexicana structure:
Classification: Protozoan parasite in the Trypanosomatida order, characterized by a single flagellum, kinetoplast, and subpellicular microtubules.
Life Cycle: Two main stages – promastigote (in sandfly gut) with long flagellum and anterior kinetoplast, and amastigote (in macrophages) with short flagellum and posterior kinetoplast.
Surface Molecules: Important for host/vector interactions, including GIPLs, GSLs, and LPG with complex sugar structures.
Enzymes: Key enzymes like arginase, GPDH, and ICP are involved in metabolism, survival, and pathogenesis.
Nuclear Structure: Unique nucleus with nucleoplasm and peripheral chromatin, organized into mini-chromosomes attached to the nuclear envelope by NUP-1.
The antigenic type of Leishmania mexicana is determined by its surface glycoconjugates’ structure and composition, mainly glycoinositol phospholipids (GIPLs) and glycosphingolipids (GSLs). GIPLs are complex molecules that consist of a glycan core attached to a phosphatidylinositol anchor, which is embedded in the parasite membrane. GSLs are like GIPLs but have a ceramide anchor instead of a phosphatidylinositol one. GIPLs and GSLs can vary in their sugar residues, linkages, and modifications, affecting their antigenic properties and interactions with host cells.
Leishmania mexicana has four significant types of GIPLs, which differ in their glycan core structures: iM2, iM3, iM4, and EPiM3. The most abundant and immunodominant GIPL is EPiM3, which has an ethanolamine phosphate group attached to the terminal mannose residue. EPiM3 is located at the parasite cell surface, the flagellar pocket, and lysosomal membranes. It is involved in the attachment and invasion of macrophages, the modulation of phagolysosomal fusion, and the protection against lysosomal enzymes.
Leishmania mexicana also acquires a GSL from its host macrophages, identical to the Forssman antigen of mammalian cells. The Forssman antigen is a pentasaccharide with a GalNAcβ1-3GalNAcβ1-4Galβ1-4GlcNAcβ1-3Gal sequence linked to a ceramide anchor. It is not synthesized by the parasite but transferred from the macrophage membrane to the parasite surface by an unknown mechanism. The Forssman antigen may help the parasite to evade the host’s immune response by mimicking a self-antigen.
The antigenic variation of Leishmania mexicana is a dynamic process that involves changes in the expression and structure of GIPLs and GSLs in response to environmental stimuli and host immune pressure. The parasite can alter its antigenic type by switching between different GIPLs or acquiring different GSLs from different host cells. It allows the parasite to adapt to different host niches and escape from immune recognition and elimination.
Cutaneous leishmaniasis typically manifests as skin lesions and ulcers and is transmitted to humans through the bite of infected sandfly vectors. Here’s an overview of the pathogenesis of Leishmania mexicana:
Transmission: The life cycle of Leishmania mexicana involves two main hosts: the sandfly vector and a mammalian host, including humans. When an infected female sandfly bites a mammal to obtain a blood meal, it injects promastigote forms of the parasite into the host’s skin.
Invasion of Macrophages: Once injected into the host’s skin, the promastigotes are phagocytosed by macrophages, a type of immune cell. Within the macrophages, the promastigotes transform into amastigote forms, which are the intracellular stage of the parasite.
Intracellular Survival: Leishmania mexicana amastigotes evade the host immune system and replicate within the phagolysosomes of macrophages. This intracellular survival allows the parasite to avoid detection by the immune system and persist in the host.
Immune Response: As the parasite replicates within macrophages, it triggers an immune response. Infected individuals may develop local inflammation, which can result in the development of skin sores and ulcers. The severity of the immune response can vary among individuals, and some may be asymptomatic carriers.
Dissemination: In some cases, Leishmania mexicana can disseminate to other body parts, leading to more severe forms of the disease. It can occur through the bloodstream or lymphatic system.
Healing or Chronic Infection: The outcome of Leishmania mexicana infection can vary. Sometimes, the infection may spontaneously resolve, and the skin lesions heal. However, in other cases, the infection can become chronic if the immune system is compromised, leading to persistent skin lesions and potential complications.
The host defenses against Leishmania mexicana involve both innate and adaptive immune responses. The first line of defense is inherent immunity, and it involves phagocytic cells’ pattern recognition receptors (PRRs) recognizing the parasite, like macrophages and neutrophils, which then try to eliminate the parasite via generating reactive nitrogen and oxygen species (ROS & RNS) in an oxidative burst. However, Leishmania mexicana has developed strategies to resist or evade this mechanism.
Producing antioxidant enzymes like catalase, superoxide dismutase (SOD), and trypanothione reductase, which scavenge ROS and RNS and protect the parasite from oxidative damage.
Modulating the expression and activity of host PRRs like NOD-like receptors, C-type lectin receptors, and Toll-like receptors (CLRs), which can activate or inhibit the oxidative burst depending on the parasite strain and stage.
Adaptive immune response fights Leishmania mexicana through T and B cells, producing cytokines and antibodies. Response type depends on parasite strain, host genetics, and infection details. Generally, the Th1 response (IFN-γ, TNF-α) is protective, while the Th2 response (IL-4, IL-10) is detrimental. Exceptions exist.
Inducing regulatory T cells (Tregs), a subset of T cells that suppress the activation and function of other T cells and macrophages by producing IL-10 and TGF-β. Leishmania mexicana can stimulate Treg differentiation by expressing surface glycoconjugates that bind to host CLRs or acquiring host glycosphingolipids that mimic self-antigens.
Modulating antibody production can have different effects on the infection depending on the isotype, specificity, and concentration of antibodies. Leishmania mexicana can induce IgG1 antibodies that bind to FcγRIII receptors on macrophages and inhibit their oxidative burst. Alternatively, it can induce IgG2 antibodies that bind to FcγRI receptors on macrophages and enhance their oxidative burst.
Altering antigen presentation is the process by which macrophages present parasite antigens to T cells via major histocompatibility complex (MHC) molecules. Leishmania mexicana can downregulate or upregulate MHC expression on macrophages depending on whether it wants to avoid or stimulate T cell recognition.
Leishmania mexicana is a parasite that causes cutaneous leishmaniasis, a skin infection resulting in ulcers, nodules, or diffuse lesions. The parasite is transmitted to animal sandflies found in Mexico and Central America by being bitten by an infected animal. The symptoms of Leishmania mexicana infection depend on the type and location of the skin lesion, the immune response of the host, and the species of Leishmania involved. Some common clinical manifestations are:
Localized cutaneous leishmaniasis (LCL): This is the most common form of the disease, which develops as an ulcer with raised borders at the site of the sandfly bite. The ulcer may heal spontaneously or persist for months or years. It may be located mainly in the ear (39.8% of cases) or other exposed parts of the body.
Diffuse cutaneous leishmaniasis (DCL): This is a rare and severe form of the disease, which occurs when the parasite spreads throughout the skin and causes multiple nodules or plaques that do not ulcerate. This form is associated with a poor immune response and ineffective treatment. It may affect any body part, mainly the face, arms, and legs.
The diagnosis of Leishmania mexicana, the parasite that causes cutaneous leishmaniasis in Mexico and Central America, can be done by various methods, such as:
Physical Exam: The doctor checks for skin issues and organ enlargement.
Microscopic Exam: Samples are examined under a microscope for amastigotes, the parasite form.
Molecular Methods: Techniques like PCR and DNA analysis identify the parasite.
Culture: Parasite isolation and identification in a lab is time-consuming and needs expertise.
The control of Leishmania mexicana infection can be achieved by different strategies, such as:
Preventing transmission: Use insect repellents, bed nets, and protective clothing to avoid sandfly bites.
Treating infection: Administer antiparasitic drugs like pentavalent antimonials or liposomal amphotericin B based on infection type and severity.
Enhancing immune response: Boost Th1-type immune response with compounds like garlic extract to aid in resistance and healing of the infection.
Leishmania mexicana – an overview | ScienceDirect Topics
(PDF) Leishmania (Leishmania) mexicana Infection in Wild Rodents from an Emergent Focus of Cutaneous Leishmaniasis in Yucatan, Mexico (researchgate.net)
The epidemiology of Leishmania mexicana is the study of the distribution and determinants of the infection caused by this parasite, one of the agents of cutaneous leishmaniasis (CL) in the Americas. Leishmania mexicana is endemic in Mexico and Central America, where the bite of infected sandflies of the genus Lutzomyia transmits it. The parasite can cause different clinical forms of CL, such as localized cutaneous leishmaniasis (LCL), diffuse cutaneous leishmaniasis (DCL), and mucocutaneous leishmaniasis (MCL).
The epidemiology of Leishmania mexicana is influenced by several factors, such as the diversity and distribution of the sandfly vectors, the availability and susceptibility of the animal reservoirs, the genetic variability and virulence of the parasite strains, and the environmental and social conditions that affect the exposure and immunity of the human hosts. Some of the main aspects of the epidemiology of Leishmania mexicana are:
● The sandfly vectors: The primary vector of Leishmania mexicana in Mexico is Lutzomyia olmeca olmeca, which is found in tropical rainforests and prefers biting humans. Other potential vectors are Lutzomyia cruciata, Lutzomyia shannoni, Lutzomyia ovallesi, and Lutzomyia panamensis, which have different ecological niches and feeding habits. The vector density and activity vary according to the season, altitude, temperature, humidity, and vegetation.
● The animal reservoirs: The main animal reservoirs of Leishmania mexicana are rodents of the genera Ototylomys, Peromyscus, Neotoma, Sigmodon, and Oryzomys, which are widely distributed in Mexico and Central America. Other possible reservoirs are marsupials, carnivores, bats, and domestic animals such as dogs and cats. The reservoirs maintain the parasite cycle in nature and serve as sources of infection for the sandflies and humans.
● The parasite strains: Leishmania mexicana is a complex that includes several strains or subspecies with different biological and molecular characteristics. Some of these strains are Leishmania mexicana mexicana, Leishmania mexicana amazonensis, Leishmania mexicana pifanoi, Leishmania mexicana garnhami, and Leishmania mexicana Aristides. The strains’ geographic distribution, vector specificity, reservoir preference, pathogenicity, and drug susceptibility can vary.
● The human hosts: The human hosts of Leishmania mexicana are people who live or work in areas where the parasite is endemic or travel to these areas for tourism or other reasons. The risk of infection depends on the frequency and duration of exposure to the sandfly bites, the type and location of the skin lesions, the immune status of the host, and the availability and access to diagnosis and treatment. The infection can cause different clinical forms of CL, such as LCL, DCL, or MCL.
The epidemiology of Leishmania mexicana is essential for understanding CL’s transmission dynamics and control strategies in Mexico and Central America. It also provides insights into the evolution and adaptation of the parasite to different hosts and environments.
Kingdom: Eukaryota
Phylum: Euglenozoa
Class: Kinetoplastea
Order: Trypanosomatida
Genus: Leishmania
Species: L. Mexicana
Leishmania mexicana structure:
Classification: Protozoan parasite in the Trypanosomatida order, characterized by a single flagellum, kinetoplast, and subpellicular microtubules.
Life Cycle: Two main stages – promastigote (in sandfly gut) with long flagellum and anterior kinetoplast, and amastigote (in macrophages) with short flagellum and posterior kinetoplast.
Surface Molecules: Important for host/vector interactions, including GIPLs, GSLs, and LPG with complex sugar structures.
Enzymes: Key enzymes like arginase, GPDH, and ICP are involved in metabolism, survival, and pathogenesis.
Nuclear Structure: Unique nucleus with nucleoplasm and peripheral chromatin, organized into mini-chromosomes attached to the nuclear envelope by NUP-1.
The antigenic type of Leishmania mexicana is determined by its surface glycoconjugates’ structure and composition, mainly glycoinositol phospholipids (GIPLs) and glycosphingolipids (GSLs). GIPLs are complex molecules that consist of a glycan core attached to a phosphatidylinositol anchor, which is embedded in the parasite membrane. GSLs are like GIPLs but have a ceramide anchor instead of a phosphatidylinositol one. GIPLs and GSLs can vary in their sugar residues, linkages, and modifications, affecting their antigenic properties and interactions with host cells.
Leishmania mexicana has four significant types of GIPLs, which differ in their glycan core structures: iM2, iM3, iM4, and EPiM3. The most abundant and immunodominant GIPL is EPiM3, which has an ethanolamine phosphate group attached to the terminal mannose residue. EPiM3 is located at the parasite cell surface, the flagellar pocket, and lysosomal membranes. It is involved in the attachment and invasion of macrophages, the modulation of phagolysosomal fusion, and the protection against lysosomal enzymes.
Leishmania mexicana also acquires a GSL from its host macrophages, identical to the Forssman antigen of mammalian cells. The Forssman antigen is a pentasaccharide with a GalNAcβ1-3GalNAcβ1-4Galβ1-4GlcNAcβ1-3Gal sequence linked to a ceramide anchor. It is not synthesized by the parasite but transferred from the macrophage membrane to the parasite surface by an unknown mechanism. The Forssman antigen may help the parasite to evade the host’s immune response by mimicking a self-antigen.
The antigenic variation of Leishmania mexicana is a dynamic process that involves changes in the expression and structure of GIPLs and GSLs in response to environmental stimuli and host immune pressure. The parasite can alter its antigenic type by switching between different GIPLs or acquiring different GSLs from different host cells. It allows the parasite to adapt to different host niches and escape from immune recognition and elimination.
Cutaneous leishmaniasis typically manifests as skin lesions and ulcers and is transmitted to humans through the bite of infected sandfly vectors. Here’s an overview of the pathogenesis of Leishmania mexicana:
Transmission: The life cycle of Leishmania mexicana involves two main hosts: the sandfly vector and a mammalian host, including humans. When an infected female sandfly bites a mammal to obtain a blood meal, it injects promastigote forms of the parasite into the host’s skin.
Invasion of Macrophages: Once injected into the host’s skin, the promastigotes are phagocytosed by macrophages, a type of immune cell. Within the macrophages, the promastigotes transform into amastigote forms, which are the intracellular stage of the parasite.
Intracellular Survival: Leishmania mexicana amastigotes evade the host immune system and replicate within the phagolysosomes of macrophages. This intracellular survival allows the parasite to avoid detection by the immune system and persist in the host.
Immune Response: As the parasite replicates within macrophages, it triggers an immune response. Infected individuals may develop local inflammation, which can result in the development of skin sores and ulcers. The severity of the immune response can vary among individuals, and some may be asymptomatic carriers.
Dissemination: In some cases, Leishmania mexicana can disseminate to other body parts, leading to more severe forms of the disease. It can occur through the bloodstream or lymphatic system.
Healing or Chronic Infection: The outcome of Leishmania mexicana infection can vary. Sometimes, the infection may spontaneously resolve, and the skin lesions heal. However, in other cases, the infection can become chronic if the immune system is compromised, leading to persistent skin lesions and potential complications.
The host defenses against Leishmania mexicana involve both innate and adaptive immune responses. The first line of defense is inherent immunity, and it involves phagocytic cells’ pattern recognition receptors (PRRs) recognizing the parasite, like macrophages and neutrophils, which then try to eliminate the parasite via generating reactive nitrogen and oxygen species (ROS & RNS) in an oxidative burst. However, Leishmania mexicana has developed strategies to resist or evade this mechanism.
Producing antioxidant enzymes like catalase, superoxide dismutase (SOD), and trypanothione reductase, which scavenge ROS and RNS and protect the parasite from oxidative damage.
Modulating the expression and activity of host PRRs like NOD-like receptors, C-type lectin receptors, and Toll-like receptors (CLRs), which can activate or inhibit the oxidative burst depending on the parasite strain and stage.
Adaptive immune response fights Leishmania mexicana through T and B cells, producing cytokines and antibodies. Response type depends on parasite strain, host genetics, and infection details. Generally, the Th1 response (IFN-γ, TNF-α) is protective, while the Th2 response (IL-4, IL-10) is detrimental. Exceptions exist.
Inducing regulatory T cells (Tregs), a subset of T cells that suppress the activation and function of other T cells and macrophages by producing IL-10 and TGF-β. Leishmania mexicana can stimulate Treg differentiation by expressing surface glycoconjugates that bind to host CLRs or acquiring host glycosphingolipids that mimic self-antigens.
Modulating antibody production can have different effects on the infection depending on the isotype, specificity, and concentration of antibodies. Leishmania mexicana can induce IgG1 antibodies that bind to FcγRIII receptors on macrophages and inhibit their oxidative burst. Alternatively, it can induce IgG2 antibodies that bind to FcγRI receptors on macrophages and enhance their oxidative burst.
Altering antigen presentation is the process by which macrophages present parasite antigens to T cells via major histocompatibility complex (MHC) molecules. Leishmania mexicana can downregulate or upregulate MHC expression on macrophages depending on whether it wants to avoid or stimulate T cell recognition.
Leishmania mexicana is a parasite that causes cutaneous leishmaniasis, a skin infection resulting in ulcers, nodules, or diffuse lesions. The parasite is transmitted to animal sandflies found in Mexico and Central America by being bitten by an infected animal. The symptoms of Leishmania mexicana infection depend on the type and location of the skin lesion, the immune response of the host, and the species of Leishmania involved. Some common clinical manifestations are:
Localized cutaneous leishmaniasis (LCL): This is the most common form of the disease, which develops as an ulcer with raised borders at the site of the sandfly bite. The ulcer may heal spontaneously or persist for months or years. It may be located mainly in the ear (39.8% of cases) or other exposed parts of the body.
Diffuse cutaneous leishmaniasis (DCL): This is a rare and severe form of the disease, which occurs when the parasite spreads throughout the skin and causes multiple nodules or plaques that do not ulcerate. This form is associated with a poor immune response and ineffective treatment. It may affect any body part, mainly the face, arms, and legs.
The diagnosis of Leishmania mexicana, the parasite that causes cutaneous leishmaniasis in Mexico and Central America, can be done by various methods, such as:
Physical Exam: The doctor checks for skin issues and organ enlargement.
Microscopic Exam: Samples are examined under a microscope for amastigotes, the parasite form.
Molecular Methods: Techniques like PCR and DNA analysis identify the parasite.
Culture: Parasite isolation and identification in a lab is time-consuming and needs expertise.
The control of Leishmania mexicana infection can be achieved by different strategies, such as:
Preventing transmission: Use insect repellents, bed nets, and protective clothing to avoid sandfly bites.
Treating infection: Administer antiparasitic drugs like pentavalent antimonials or liposomal amphotericin B based on infection type and severity.
Enhancing immune response: Boost Th1-type immune response with compounds like garlic extract to aid in resistance and healing of the infection.
Leishmania mexicana – an overview | ScienceDirect Topics
(PDF) Leishmania (Leishmania) mexicana Infection in Wild Rodents from an Emergent Focus of Cutaneous Leishmaniasis in Yucatan, Mexico (researchgate.net)
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