Presence of Leishmania braziliensis in blood samples from cured patients or at different stages of immunotherapy

Leishmania braziliensis is the cause for cutaneous leishmaniasis that afflicts thousands of people in South America. Patients suffering from this disease can get treatment, but after clinical treatment many patients show recurrent lesions a few years later. This is thought to happen because of reactivation of a persistent infection or reinfection. Reactivation of a persistent infection can occur by failure of the initial treatment or weak host immune response. Recurrent lesions could also be occurring because of L. braziliensis being a well adapting parasite that, unless a metabolic or an immunological imbalance occurs, can develop an equilibrium with its host. In order to test if leishmaniasis relapses are due to a persistent infection or because of L. braziliensis being adaptive, a study using blood PCR assays of patients who were in different stages of immunotherapy was conducted (Guevara et al. 1994).

Patients in this study were positively diagnosed for cutaneous leishmaniasis by microscopic observation of macrophages that contained L. braziliensis amastigotes in skin biopsies. Patients were at different stages of immunotherapy during the time of this experiment. Blood samples from each patient were extracted and centrifuged. The blood was then pipetted into an agrose PCR gel and electrophoresis was performed (Guevara et al. 1994).

            The results of this study showed that the presence of L. braziliensis found in cured patients is due either to a persistent infection or reinfection. The results support a persistent infection more, but reinfection could not be ruled out because patients still live in the same endemic area. An adaptive quality was ruled out because treatment is still effective in eliminating a large portion of the disease even after multiple treatments, so the parasite was not adapting to immunity against the treatment. In a previous work by Guevara et al. (1994), asymptomatic subjects were found harboring Leishmania DNA and the patients were immunoresponsive. These observations support the view that L. braziliensis is a difficult parasite to eliminate and that the infection is persistent (Guevara et al. 1994). 

This article relates to the study by Samuelson et al. (1991) “A Mouse Model of Leishmania braziliensis braziliensis Infection Produced by Coinjection with Sand Sly Saliva” because Samuelson et al. (1991) studied the transmission and intensity of Leishmania braziliensis infections while Guevara et al. (1994) studied the resilience and persistence of this infection. Both studies focused on specific aspects of L. braziliensis infections and are useful in studying this parasite’s ability to infect people and remain in the human body.

Citation

P. Guevara, E. Rojas, N. Gonzalez, J. Scorza, N. Anez, M. Valera, J. Ramirez, 1994, Presence of Leishmania braziliensis in blood samples from cured patients or at different stages of immunotherapy, Clinical and Diagnostic Laboratory Immunology, 1 (4): 385-389

-Kaitlin Smith

Immunological and Genetic Evidence for a Crucial Role of IL-10 in Cutaneous Lesions in Humans Infected with Leishmania braziliensis

Leishmania major is a parasite that is known for being the cause of cutaneous disease that can vary from mild skin ulcers to severe mucocutaneous disfiguration in mice. The severity of the disease depends on several factors, one being IFN-γ cytokines. IFN-γ cytokines are important in adaptive immunity against viral and intracellular bacterial infections. IFN-γ cytokines are produced as part of the innate immune response and directly inhibit viral replication. The cytokine, IL-10, is capable of inhibiting IFN-γ cytokines and are found often in cutaneous lesions caused by L. major. Nonhealing cutaneous lesions in mice infected with L. major have been found to be associated with low levels of IFN-γ and high levels of IL-10. Studies on leishmaniasis have been done frequently on mice, but few have been performed on cutaneous leishmaniasis in human patients and with different Leishmania species. Because of this, it is still unclear what the mechanisms are that contribute to some patients being resistant to this disease compared to patients who develop cutaneous lesions. In this study, Salhi et al. (2008) investigated the cytokines that play a role in Leishmania infections in human patients using Leishmania braziliensis.

The study was performed in a population living in two villages and farms located at the edge of a forest in Bahia. This region was chosen because it is endemic for cutaneous leishmaniasis caused by L. braziliensis. Patients were mainly farmers and were chosen if they were diagnosed with cutaneous leishmaniasis and responded to Glucantime treatments. Blood samples were taken from the 140 test subjects and the peripheral blood mononuclear cells (PBMCs) were isolated by centrifugation before the cytokine levels were measured (Salhi et al. 2008)

The results suggest cytokines play a key role in cutaneous leishmaniasis. In patients diagnosed with cutaneous leishmaniasis from Leishmania braziliensis, IFN-γ levels were very low while IL-10 levels were much higher when they had larger, slower healing lesions. This is an important study because if more studies are conducted on IL-10 and IFN-γ cytokines, a more efficient cure for cutaneous leishmaniasis could result from this. Using this same experiment for other species of Leishmania could give us a better insight as to how to prevent these lesions from forming.

 

            This article relates to the study by Samuelson et al. (1991) “A Mouse Model of Leishmania braziliensis braziliensis Infection Produced by Coinjection with Sand Sly Saliva” because Samuelson et al. (1991) studied how L. braziliensis is transmitted to humans while Salhi et al. (2008) studied the cutaneous lesions that occur from L. braziliensis. Both studies focus on the effects of getting cutaneous leishmaniasis and are useful in understanding how cases of cutaneous leishmaniasis can vary in different patients.

Citation

A. Salhi, V. Rodrigues, F. Santoro, H. Dessein, A. Romano, L. Roberto Castellano, M. Sertorio, S. Rafati, C. Chevillard, A. Prata, A. Alcais, L. Argiro, A. Dessein, 2008, Immunological and Genetic Evidence for a Crucial Role of IL-10 in Cutaneous Lesions in Humans Infected with Leishmania braziliensis, Journal of Immunology, 180: 6139-6148

-Kaitlin Smith

Moving on from the Intestine: New Species of Trematode Take up Residence in the Gall Bladder

            Tkach et al. (2012) add Opisthioglyphe sharmai to the growing list of parasitic species that have turtles as their hosts with their species description. The turtles were bought from professional trappers in Malaysia and were killed about a week later in order to necropsy them and search for internal parasites. A new species of trematode was identified in the gall bladder, which is a highly unusual location in the definitive host (Tkach et al., 2012). The specimens were then collected for close observation and identification.

            Many characteristics were noted such as the body length, width, various ratios of body parts, the size/shape/location of male and female reproductive organs and the differences between juvenile and adult specimens (Tkach et al., 2012). There were many features that indicated that O. sharmai was indeed a new species of trematode. Their cirrus sac extends farther posterior to the ventral sucker, when all other species of Opisthioglyphe have a cirrus sac that is anterior to the ventral sucker or partially overlaps it. Tkach et al. (2012) proceeded to mention specific details that differentiate O. sharmai from other species in the same genus. The definitive hosts of O. sharmai are Malayan box turtles, Cuora amboinensis, and black marsh turtles, Siebenrockiella crassicollis.

            Tkach et al. (2012) conclude their species identification by mentioning the differentiation that they believe exists between the new species (O. sharmai) and another species (Opisthioglyphe koisarensis) that supposedly also has a posteriorly extending cirrus sac. Tkach et al. (2012) consider the drawings and article that introduce O. koisarensis to be brief and incomplete, which questions the validity of truth of the article. The authors actually consider O. koisarensis to belong in Dolichosalcus because of the shown distribution of vitelline follicles are characteristic of Dolichosalcus and not of Opisthioglyphe  (Tkach et al., 2012). Future studies should be done to try to find O. koisarensis and compare it directly to O. sharmai in order to know for certain that they are separate species.

            The information that is introduced by Tkach et al. (2012) continues to expand on the already known parasites of turtles introduced by previous articles. Ogawa et al. (1997) introduced Balaenophilus as an ectoparasite of sea turtles, and Rigby et al. (2008) introduced two species of nematodes from Camallanus. All of these articles emphasize the importance of details and an analytical mind when comparing species to discover if there really is a new species discovered. In this case, Tkach et al. (2012) introduce the importance of continuously critiquing scientific knowledge. There was already a species with a posteriorly extending cirrus sac (O. koisarensis), but the authors looked at it and came to the conclusion that what was written wasn’t accurate. 

Works Cited:

Ogawa, K., Matsuzaki K., Misaki H. 1997. A New Species of Balaenophilus (Copepoda: Harpacticoida), an Ectoparasite of a Sea Turtle in Japan. Zoological Science 14: 691-700.

Rigby, M. C., R. S. K. Sharma, R. F. Hechinger, T. R. Platt and J. C. Weaver. 2008. Two New Species of Camallanus (Nematoda: Camallanidae) from Freshwater Turtles in Queensland, Australia. The Journal of Parasitology 96 (4): 752-757.

Tkach, V.V., T.R., Platt and S.E. Greiman. 2012. A New Species of Opisthioglyphe (Trematoda: Telorchiidae) from Gall Bladder of Turtles in Malaysia. The Journal of Parasitology 98 (4): 863 – 868.

New Species of Camallanus in Freshwater Turtles

            Rigby et al. (2008) discovered two new species of nematodes within Camallanus and did an in depth examination to ensure that their discoveries were truly new species. The researchers examined the newly found species by looking at known characteristics, and measuring those specific features with a light microscope. They also utilized SEM as a technique to examine the buccal capsules in detail (Rigby et al., 2008).

            The first species that Rigby et al. (2008) discovered was Camallanus nithoggi, which infects the small intestines of their host Elseya latisternum (a freshwater turtle). C. nithoggi was determined to fall into Camallanus because of the characteristic smooth longitudinal ridges located on the two lateral buccal capsules. Named after a Norse god, C. nithoggi was described in great detail in order to differentiate it from other species of the same genus (Rigby et al., 2008). Rigby et al. (2008) mentioned the differences between sexes, the shape of buccal capsule, the excretory pore location, papillae arrangement, esophagus shape, and many other things that separate it from known species.  They focus primarily on buccal characteristics including the compososition of three parts, the number of ridges for each sex (four for males, five for females), the three peribuccal shields that exist and the species specific characteristic of buttressing on the buccal capsule.

            The second species discovered by Rigby et al. (2008) was Camallanus waelhreow, which was identified as a separate species of Camallanus using the same methodology for C. nithoggi. C. waelhreow is found in the small intestine of river turtles:  Emydura krefftii, Emydura macquarrii and Emydura macquarrii dharra (Rigby et al., 2008). I personally found it intriguing that this species name came from the Old English word for bloodthirsty, which is appropriate considering its diet of blood.

            Rigby et al (2008) focused the end of their species summation on the features of the buccal capsule that are visible because the use of SEM. The observed buccal capsule features had never been seen on another species before, which is interesting in itself. More interesting is that the buttressing on both of the new species is unique but has no function. Rigby et al. (2008) hypothesizes that these observed characteristics represent an intermediate step in the evolution of the posterior buccal capsule in species of Paracamallanus and Oncophora.

Rigby et al. (2008) focused a lot on the technical jargon of specific species identifiers that are very scientifically relevant but do not interest me very much. Despite that, Rigby et al. (2008) managed to emphasize the importance of the details in identifying a new species concisely. The mention of these species’ as an evolutionary stepping stone is also very interesting because discussion of evolution on a large scale is very common but rarely happens on the smaller level of parasitic organisms.

            Rigby et al. (2008) expanded upon my accumulated knowledge about parasites that infect turtles. Ogawa et al. (1997) introduced a new species Balaenophilus in their species description, but it was an ectoparasite and a copepod which is very different from a nematode species description. However, the similarities between the two articles as species descriptions were evident in terms of the great detail that was given.

Works Cited:

Ogawa, K., Matsuzaki K., Misaki H. 1997. A New Species of Balaenophilus (Copepoda: Harpacticoida), an Ectoparasite of a Sea Turtle in Japan. Zoological Science 14: 691-700.

Rigby, M. C., R. S. K. Sharma, R. F. Hechinger, T. R. Platt and J. C. Weaver. 2008. Two New Species of Camallanus (Nematoda: Camallanidae) from Freshwater Turtles in Queensland, Australia. The Journal of Parasitology 96 (4): 752-757.