Primary culture of the region of the amebocyte-producing organ of the snail Biomphalaria glabrata, the intermediate host of Schistosoma mansoni

Abstract

Biomphalaria glabrata snails are major hosts for the digenetic trematoda Schistosoma mansoni, the causative agent of human schistosomiasis. The success or failure of the infection will be dependent on the mobilization of the molluskan internal defense system, where a major role will be played by circulating hemocytes produced by the APO (amebocyte-producing organ) Schistosomiasis is a parasitic infection caused by the digenetic trematode Schistosoma mansoni Sambom, 1907. The disease is prevalent in 54 countries and territories of Africa, the Caribbean, the Mediterranean, and South America. It is estimated that 130 million people are infected with this species of parasite (Chitsulo et al. 2000). Although several advances have been achieved in the control of the schistosomiasis morbidity, mainly due to the development of new low toxicity and highly effective drugs against the parasite, it is still an endemic disease, whose control and/or eradication is very difficult in the wide regions where it occurs. The affected patients become debilitated, thus impairing the socio-economic development of the affected countries. In Brazil, it is estimated that eight million people are infected, whereas thirty million are at high risk of infection, since they live in hyper endemic areas (Katz 1997 In the S. mansoni-Biomphalaria interaction, besides the stringent physiological and biochemical compatibility between host and parasite, the success or failure of the infection will be strongly determined by the efficacy of the internal defense system of the snail. When in contact with the infective agent, the endogenous defense mechanisms of the mollusk are immediately activated, mediated by circulating effectors cells (hemocytes) and by soluble factors which are present in the hemolymph. Among these factors, lectins with specific carbohydratebinding capacities play an important role by immobilizing foreign objects by agglutination, promoting phagocytes by the hemocytes or even acting as cytophilic receptors for non-self recognition (Van der Knaap & Loker 1990).The hemocytes of Biomphalaria are capable of phagocytosis, encapsulation and, finally, destruction of the infective agents. Both morphologically and functionally, these cells resemble cells of the vertebrate monocytemacrophage series (Jeong et al. 1983, Bezerra et al. 2003. Experimental evidence has been accumulated assigning the production and storage of hemocytes to the hematopoietic organ, a structure that is located on the wall of the pericardium and posterior epithelium of the mollusk mantle. That organ, also known as amebocyte-producing organ or APO, is composed of a small quantity of primary ameboblasts that rest on a loose reticulum, which is formed by extensions of smooth muscles and fibroblasts (Jeong et al. 1983). In a recent study, Sullivan et al. (2004) reported an increase in the frequency of cell mitosis in the APO of B. glabrata following the inoculation of miracidia or cercariae antigens of S. mansoni. The mitotic ratio was intensified in Biomphalaria strai...

Ultrastructural characterization of cells in primary cultures from different adult tissues of Biomphalaria tenagophila TAIM, a strain that is absolutely resistant to Schistosoma mansoni infection

“…Moreover, cells in culture from SK (Fig. 12) were undistinguishable from those obtained in APO culture [Barbosa et al, 2006b]. Taking into account the close anatomical position of the APO and the SK within the reno-pericardial region, and difficulties inherent to APO dissection [Souza and Andrade, 2006], we cannot discard the possibility of contamination of previous APO cultures with SK tissue.…”

“…The cultures were performed according to Barbosa et al (2006b) with the following modifications: snail tissues were sliced into 1 mm fragments and placed in 24-well culture plates (25820 -Corning, NY, USA) containing 300 l of culture medium per well. Two culture media with different osmolalities were tested: Hansen's with 140 and Schneider's with 320 mOsm, both at pH 7.2.…”

“…Snail cells have been cultured in different media and have been shown to be tolerant to wide ranges of osmolality [Bayne et al, 1975;Benex and Gantier, 1975;Benex and Jacobelli, 1980;Hansen, 1976;Iwanaga, 2002;Barbosa et al, 2006b]. Nevertheless, the Bge cell line was established under low osmolality conditions [Hansen, 1976].…”

“…Cells from primary APO-derived cultures from the Taim strain of B. tenagophila were able to eliminate S. mansoni sporocysts in vitro, whereas those from a susceptible strain reacted weakly against S. mansoni sporocysts and failed to recognize the parasite as non-self [Nacif-Pimenta et al, 2012]. Primary cell cultures from other Biomphalaria organs-such as kidney, heart, digestive gland and ovotestis-were previously obtained, but were examined by optical microscopy only, and have thus not been fully characterized, except for cell shape and substrate adherence [Bayne et al, 1975;Benex and Gantier, 1975;Benex and Jacobelli, 1980;Hansen, 1976;Iwanaga, 2002;Barbosa et al, 2006b]. A more comprehensive characterization of Biomphalaria sp.…”

“…In the present study, we characterized the ultra structure of cells from different tissues of B. tenagophila using the previously described primary tissue culturing approach [Nacif-Pimenta et al, 2012;Barbosa et al, 2006b]. The availability of those cells in culture discloses potential models to search for hemocytes or their precursors in those tissues, as well as for studies of host-parasite interactions.…”