Biomedical subjects

H Alizadeh

Publications and source records attributed to H Alizadeh.

At least 19 recordsLinked to original sources

PubMed1998

Mannose induces the release of cytopathic factors from Acanthamoeba castellanii.

Acanthamoeba keratitis is a chronic inflammatory disease of the cornea which is highly resistant to many antimicrobial agents. The pathogenic mechanisms of this disease are poorly understood. However, it is believed that the initial phases in the pathogenesis of Acanthamoeba keratitis involve parasite binding and lysis of the corneal epithelium. These processes were examined in vitro, using Acanthamoeba castellanii trophozoites. Parasites readily adhered to Chinese hamster corneal epithelial cells in vitro; however, parasite binding was strongly inhibited by mannose but not by lactose. Although mannose prevented trophozoite binding, it did not affect cytolysis of corneal epithelial cells. Moreover, mannose treatment induced trophozoites to release cytolytic factors that lysed corneal epithelial cells in vitro. These factors were uniquely induced by mannose because supernatants collected from either untreated trophozoites or trophozoites treated with other sugars failed to lyse corneal cells. The soluble factors were size fractionated in centrifugal concentrators and found to be > or = 100 kDa. Treatment of the supernatants with the serine protease inhibitor phenylmethylsulfonyl fluoride inhibited most, but not all, of the cytopathic activity. These data suggest that the binding of Acanthamoeba to mannosylated proteins on the corneal epithelium may exacerbate the pathogenic cascade by initiating the release of cytolytic factors.

Acanthamoeba↗

PubMed1998

Impact of oral immunization with Acanthamoeba antigens on parasite adhesion and corneal infection.

PURPOSE: To determine whether oral immunization mitigates ongoing Acanthamoeba castellanii corneal infections in pigs. METHODS: Pigs were orally immunized with aqueous Acanthamoeba antigen mixed with cholera toxin (Ac-CT) or with saline, before or after ocular infection with A. castellanii. Mucosal secretions (i.e., tears and enteric wash) were tested for Acanthamoeba-specific IgA by enzyme-linked immunosorbent assay. Enteric washes were used as a source of IgA in assays measuring the binding of trophozoites to Chinese hamster corneal epithelial (CHCE) cells. RESULTS: Pigs immunized with Ac-CT before ocular challenge with A. castellanii had significant anti-Acanthamoeba IgA antibody titers in their tears and enteric washes and were protected against ocular infection. Enteric washes from orally immunized pigs inhibited trophozoite binding to CHCE cells in vitro by more than 75%. By contrast, pigs immunized after corneal infections had been established displayed keratitis of the same severity and duration as that in control pigs. However, 80% of the orally immunized animals were resistant to rechallenge with Acanthamoeba-laden contact lenses, whereas none of the control animals was resistant. CONCLUSIONS: Oral immunization with Ac-CT protects against Acanthamoeba keratitis when administered before corneal challenge. However, delaying oral immunization until after corneal disease is established fails to mitigate keratitis. The appearance of parasite-specific tear IgA correlates with protection and may act by preventing the parasite's binding to the corneal epithelium.

Acanthamoeba↗

PubMed1998

Role of mucosal IgA in the resistance to Acanthamoeba keratitis.

PURPOSE: To determine whether oral immunization with Acanthamoeba castellanii antigens elicits mucosal antibodies of the IgA isotype and whether mucosal antibodies affect parasite adhesion to the corneal epithelium. METHODS: Chinese hamsters were immunized with 100 microg aqueous Acanthamoeba antigen mixed with cholera toxin (Ac-CT) and subsequently challenged with parasite-laden contact lenses that were applied to abraded corneal surfaces. Tears and stool samples were examined for the presence of Acanthamoeba-specific IgA antibodies by enzyme-linked immunosorbent assay (ELISA). The effect of mucosal antibody on trophozoite binding to corneal epithelium and viability of trophozoites was examined in vitro. RESULTS: Hamsters immunized orally with Ac-CT showed significantly lower infection rates than did control groups (21.4% versus 72.6%). ELISA analysis of mucosal specimens showed the presence of parasite-specific IgA in stool samples and tears from hamsters orally immunized with Ac-CT, but not in control animals. In vitro assays showed that anti-Acanthamoeba IgA did not affect parasite viability. However, mucosal anti-Acanthamoeba IgA profoundly inhibited (>75%) the binding of parasites to corneal epithelial cells in vitro. CONCLUSIONS: Oral immunization with Ac-CT induces the production of parasite-specific IgA in mucosal secretions and prevents corneal infection. Mucosal antibody does not affect the viability of Acanthamoeba trophozoites but seems to prevent infection by inhibiting parasite binding to the corneal epithelium.

Acanthamoeba↗

PubMed1997

Inhibition of metastasis of intraocular melanomas by adenovirus-mediated gene transfer of plasminogen activator inhibitor type 1 (PAI-1) in an athymic mouse model.

Uveal melanoma is the most common intraocular malignancy in adults and results in the death of 50% of the patients. Plasminogen activators (PA) are believed to facilitate tumor metastasis by promoting invasion of tissue barriers. The present study explored the possibility of preventing the metastasis of intraocular melanomas by disrupting plasminogen activator function through gene transfer. A replication-deficient adenovirus vector was used for the in vivo transfer of plasminogen activator inhibitor type 1 (PAI-1) cDNA. Intraocular injection of an adenovirus vector (AdCMV-PAI-1) expressing plasminogen activator inhibitor-1 resulted in: (1) the transduction of more than 95% of human and murine uveal melanoma cells in the eyes of nude mice; (2) a 50% reduction in the number of animals developing liver metastases; and (3) a 78% reduction in the metastatic tumor burden in animals that eventually developed metastases. In other experiments intravenous injections of AdCMV-PAI-1 resulted in transduction of normal liver cells and culminated in a sharp reduction in the incidence of metastases and a significant prolongation of host survival. The results support the feasibility of disruption of PA function through gene transfer as a therapeutic strategy for preventing metastases and prolonging host survival.

Adenoviruses, Human↗

PubMed1997

Systemic immune response to Acanthamoeba keratitis in the Chinese hamster.

Recrudescence is a common and troubling feature of Acanthamoeba keratitis and suggests that corneal infection with this organism fails to stimulate the systemic immune apparatus. The present study examined the cell-mediated and humoral immune responses to Acanthamoeba keratitis in the Chinese hamster. Corneal infection with A. castellanii failed to induce either delayed-type hypersensitivity (DTH) or serum IgG antibody against parasite antigens. The failure to induce cell-mediated and humoral immunity did not result in anergy or tolerance since subsequent intramuscular (i.m.) immunization with parasite antigens elicited robust DTH and IgG antibody responses. The inability of corneal infections to induce primary cell-mediated immune responses was due to the absence of resident antigen-presenting cells in the central cornea because induction of Langerhans cell (LC) migration into the central cornea prior to infection with Acanthamoeba promoted the development of parasite-specific DTH. Although the presence of resident LC did not promote the development of a primary humoral immune response, subsequent i.m. immunization elicited heightened parasite-specific IgG antibody production which was indicative of an anamnestic response. Collectively, the results indicate that in the absence of resident antigen-presenting cells, corneal infection with Acanthamoeba fails to stimulate primary cell-mediated or humoral immunity. Induction of peripheral LC into the central corneal epithelium promotes the development of parasite-specific DTH, but does not exacerbate corneal disease.

Acanthamoeba↗

PubMed1997

In vitro amoebicidal activity of propamidine and pentamidine isethionate against Acanthamoeba species and toxicity to corneal tissues.

Effective chemotherapy for Acanthamoeba keratitis has been hampered because of the marked resistance of the parasites to a variety of antimicrobial agents. In view of the fact that topical Brolene (propamidine isethionate) and neosporin are currently considered to be the medical treatment of choice in Europe, we sought to determine whether pentamidine may be equally effective, because the drug is more readily available to ophthalmologists in the United States. In this study, we compared the amoebicidal activity of the Brolene (commercial product), propamidine isethionate and pentamidine isethionate (Pentam) in vitro against three different species of Acanthamoeba, and the drugs' corresponding biocompatibility with rabbit corneal epithelial and endothelial cell cultures. The results indicated that there were significant species differences in drug sensitivity. Propamidine (> 1,000 micrograms/ml) was clearly less effective than pentamidine (> 125 micrograms/ml) against A. castellanii, although equivalent potency (> 250 micrograms/ml) was observed against A. polyphaga. On the other hand, propamidine (> 31.25 micrograms/ml) was slightly more effective than pentamidine (> 62.5 micrograms/ml) against A. hatchetti. Both drugs were also relatively nontoxic after short-term contact with cell cultures, even though the highest concentration of pentamidine caused low-grade injury to the superficial epithelium and reversible membrane damage to the endothelium. Steady-state levels of propamidine at effective amoebicidal concentrations, however, were much more toxic than pentamidine, which indicated that the drug has a much lower therapeutic index. Our data suggest that pentamidine may be an effective therapeutic option because of its potency and low toxicity.

Acanthamoeba↗

PubMed1996

The role of macrophages in Acanthamoeba keratitis.

PURPOSE: Macrophages are thought to be the first line of defense in many infectious diseases and are present in high numbers in corneas with Acanthamoeba keratitis. Conjunctival macrophage depletion was performed in an animal model of Acanthamoeba infection to determine the importance of macrophages in this disease. METHODS: Selective elimination of macrophages was achieved by repeated subconjunctival injection of liposomes containing dichloromethylene diphosphonate in a Chinese hamster model of Acanthamoeba keratitis. RESULTS: Macrophage depletion affected the incidence, severity, and chronicity of keratitis. The incidence of infection in normal animals was approximately 60% but rose to 100% on day 4 in animals treated with liposomes containing dichloromethylene diphosphonate (C12MDP-LIP). Moreover, the clinical appearance of the keratitis in the C12MDP-LIP group was much more severe than in animals treated with liposomes containing phosphate-buffered saline at all time points. There was also a major change in the chronicity of keratitis, with an earlier onset and a prolonged and chronic course in the C12MDP-LIP treated hamsters. CONCLUSIONS: The profound exacerbation of Acanthamoeba keratitis in hamsters treated with C12MDP-LIP strongly suggests that macrophages play an important role in corneal infection with Acanthamoeba trophozoites, probably by acting as a first line of defense and eliminating significant numbers of Acanthamoeba trophozoites.

Acanthamoeba Keratitis↗

PubMed1995

Characterization of a plasminogen activator produced by Acanthamoeba castellanii.

Serine proteases play an important role in a diverse array of biological processes, including embryogenesis, metastasis, angiogenesis, thrombolysis and tissue invasion by certain parasites. The latter observation prompted us to explore the possibility that the tissue-invasive ocular parasite Acanthamoeba castellanii elaborates one or more serine proteases. Acanthamoeba sp. are pathogenic free-living amoebae that can produce an invasive, blinding inflammatory disease of the cornea, termed Acanthamoeba keratitis. The present study reports the preliminary purification and characterization of a novel plasminogen activator from an ocular isolate of A. castellanii. The parasite-derived enzyme has a molecular mass of approx. 40 kDa and produces a single band of lysis on fibrinogen-agarose zymographs. Activity of the enzyme is completely inhibited by treatment with diisopropylfluorophosphate, indicating that it is a serine protease. The parasite-derived serine protease is not inhibited by amiloride which is a strong inhibitor of urokinase-type plasminogen activator. Additionally, the enzyme is not inhibited by plasminogen activator inhibitor-1 which is the primary physiological inhibitor of both urokinase and tissue-type plasminogen activator. It does not cross-react with antibodies specific for human urokinase or tissue-type plasminogen activator. The parasite-derived enzyme activates plasminogen from several mammalian species, including human, cow and pig. Thus, it is possible that this parasite-derived serine protease contributes to the pathogenesis of Acanthamoeba keratitis.

Acanthamoeba↗

PubMed1995

Tissue-type plasminogen activator-induced invasion and metastasis of murine melanomas.

The role of tissue-type plasminogen activator (tPA) in the 'spontaneous' as well as 'experimental' metastasis of ocular melanomas in mice was evaluated by transfecting the D5.1G4 murine melanoma cell line that possesses low metastatic activity and low tPA activity with a full length cDNA encoding human tPA. For comparison, a highly metastatic melanoma cell line (Queen's) that constitutively expresses high tPA production, was transfected with a cDNA coding for human plasminogen activator inhibitor type 1 (PAI-1). Unlike non-transfected controls, transfected D5.1G4 melanoma cells expressed high levels of tPA and produced extensive pulmonary metastases following intravenous injection. By contrast, PAI-1 transfected Queen's melanoma cells expressed low tPA activity and displayed significantly reduced metastatic potential compared with nontransfected controls. Moreover, PAI-1 transfected Queen's melanoma cells did not metastasize from the eye while nontransfected parental cells produced extensive spontaneous metastases. Expression of tPA activity in transfected and nontransfected cell lines was completely blocked by an anti-tPA antibody. This antibody significantly inhibited the organ localization and frequency of lung metastases of both Queen's and tPA-transfected D5.1G4 melanomas. This study demonstrates that tPA is involved in the metastasis of murine intraocular melanomas.

Animals↗

PubMed1995

In vitro characterization of Acanthamoeba castellanii cytopathic effect.

This study examined the mechanism of the cytopathic effect (CPE) of Acanthamoeba castellanii on human target cells. Pathogenic Acanthamoeba trophozoites were incubated with human ocular melanoma (OCM1) cells for 30 min, 1 hr, and 3 hr. The amoebae were treated with a calcium ionophore (A23187), phorbol myristate ester (PMA), calcium channel blocker (Bepridil), cytochalasin D, and L-leucyl-L-leucine methyl ester (leu-leu-OMe). Cytolysis was quantified using a spectrophotometric assay. Cocultures of amoeba and cells were also observed by transmission electron microscopy at 1, 2, and 3 hr. Results show that trophozoites formed pseudopodia that made intimate contact with the target cell membrane. Neither amebostomes nor phagocytosis was seen. The calcium ionophore A23187 increased the cytopathic effect of the trophozoites on the cultured OCM1. In contrast, cytochalasin D, Bepridil, and PMA reduced the cytopathic effect. Leu-leu-OMe did not result in killing of Acanthamoeba trophozoites. The results suggest that the cytopathic effect of Acanthamoeba trophozoites involves calcium channels and cytoskeletal elements. There was no evidence of trogocytosis or phagocytosis as sometimes occurs in cytolysis by other free-living amoeba. Although Acanthamoeba-mediated CPE in some ways resembles CPE produced by cytotoxic lymphocytes, the mechanisms are not identical.

Acanthamoeba↗

PubMed1995

Acanthamoeba keratitis.

The incidence of Acanthamoeba keratitis has decreased significantly, and it is no longer a reportable condition in the United States. Corneal abrasion and contact lenses play an important role in the development of Acanthamoeba keratitis. One of the most important features of the disease is severe pain, which is atypical for herpes simplex. The pathognomonic sign for Acanthamoeba is radial neuritis or inflammation around the corneal nerve caused by the parasites. The most important step in prevention of Acanthamoeba keratitis is effective education of patients about the care of contact lenses. A combination of Brolene and Neomycin is the best approach in treating Acanthamoeba keratitis. However, if treatment with these drugs fails, clotrimazole is recommended.

Acanthamoeba Keratitis↗

PubMed1995

Successful immunization against Acanthamoeba keratitis in a pig model.

The feasibility of inducing protective immunity to Acanthamoeba keratitis was tested in a pig model. Experiments were designed to determine if ocular infection with Acanthamoeba trophozoites would elicit protection against reinfection. Additional experiments examined whether injection of parasite antigens either intramuscularly, subconjunctivally, or by both routes would induce immunity. Therefore, four groups of animals were examined: (a) pigs that had resolved a primary corneal infection with Acanthamoeba; (b) pigs immunized intramuscularly; (c) pigs immunized subconjunctivally; and (d) pigs immunized intramuscularly and subconjunctivally. Animals were subsequently challenged with parasite-laden soft contact lenses and observed clinically for the appearance of Acanthamoeba keratitis. Acanthamoeba-specific serum antibody titers and blastogenic responses of peripheral blood lymphocytes were determined weekly. The results indicated that intramuscular injection of Acanthamoeba antigens failed to protect against ocular infection even though hosts developed high titers of IgG antibodies and displayed lymphocyte blastogenic responses to parasite antigens. Ocular infection alone failed to stimulate immunity in any of the animals. By contrast, 50% of the hosts immunized subconjunctivally were protected against corneal disease, and 100% of the animals immunized by a combination of intramuscular and subconjunctival administration of parasite antigens were completely protected against two separate ocular challenges with infectious parasites. Protection did not correlate with either IgG antibody titers or blastogenic potentials of peripheral blood lymphocytes. Interestingly, ocular infection alone failed to stimulate immunity to subsequent ocular challenge with infectious parasites. Thus, administration of parasite antigen via the subconjunctival route can protect against Acanthamoeba keratitis.

Acanthamoeba↗

PubMed1994

Capacity of simian virus 40 T antigen to induce self-tolerance but not immunological privilege in the anterior chamber of the eye.

Transgenic mice bearing the simian virus 40 (SV40) large T oncogene developed progressively growing intraocular tumors and displayed characteristics of immunological tolerance to SV40 T antigen. Transgenic mice failed to mount CTL responses to SV40 T antigen-bearing tumor cell lines derived from the transgenic intraocular tumors. Spleen cells from transgenic hosts were able to prevent the in vivo and in vitro generation of CTL responses by lymphocytes from normal syngeneic FVB/N mice. Adoptive transfer of spleen cells from tolerant transgenic donors temporarily inhibited the immunological rejection of SV40 T antigen-positive tumor cells transplanted to normal syngeneic FVB/N recipients. Thus, introduction of SV40 transforming sequences into the mouse germline induced tolerance to SV40 T antigen. However, in normal FVB/N mice, SV40 T antigen-bearing tumor cells failed to experience immune privilege in the anterior chamber and did not elicit systemic down-regulation of delayed-type hypersensitivity responses that characteristically occur when antigens are introduced into the anterior chamber. The results indicate that within the anterior chamber of the eye, SV40 T antigen-bearing cells are perceived by the host's immune system much differently than are other categories of antigen. Thus, SV40 T antigen effectively induces self-immunological tolerance when its gene is introduced into the host's germline but fails to experience immunological privilege in the anterior chamber of the eye in normal hosts.

Animals↗

PubMed1994

Antibody-dependent neutrophil-mediated killing of Acanthamoeba castellanii.

Neutrophils from naive rats lysed low numbers of Acanthamoeba castellanii in the presence of normal rat serum and significantly higher numbers of the parasite in the presence of serum from immunized rats. With normal rat serum, neutrophils from rats immunized with crude parasite extract or from naive rats killed similar percentages of A. castellanii. However, neutrophils from immunized rats killed a significantly greater percentage of parasites in the presence of serum from immunized rats than was seen with any other combination of serum and neutrophils. The addition of supernatant from cultures of concanavalin A-stimulated rat spleen cells to incubations of the parasite in the presence of neutrophils from naive or immunized rats and immune serum resulted in the highest levels of amoebolysis seen in this study. This study has shown that neutrophils from naive rats or from rats immunized with A. castellanii antigen display a very limited amoebolytic capability which is significantly augmented in the presence of serum from immunized rats and further boosted by the addition of supernatant from Con A-stimulated rat spleen cell cultures.

Acanthamoeba↗

PubMed1994

Apoptosis as a mechanism of cytolysis of tumor cells by a pathogenic free-living amoeba.

Previous studies have shown that trophozoites of the pathogenic free-living amoeba Acanthamoeba castellanii rapidly lysed a variety of tumor cells in vitro. Tumor cells undergoing parasite-mediated lysis displayed characteristic cell membrane blebbing reminiscent of apoptosis. The present investigation examined the role of apoptosis (programmed cell death) in Acanthamoeba-mediated tumor cell lysis. The results showed that more than 70% of tumor cell DNA was fragmented following exposure to Acanthamoeba cell extracts. By contrast, only 7% of untreated control cells underwent DNA fragmentation. DNA fragmentation increased significantly in a dose-dependent fashion following concentration of the parasite extract. Apoptosis was also confirmed by DNA ladder formation. Characteristic DNA ladders, consisting of multimers of approximately 180 to 200 bp, were produced by tumor cells exposed to Acanthamoeba cell extracts. The morphology of tumor cell lysis was examined by light and scanning electron microscopy. Tumor cells exposed to parasite extract displayed morphological features characteristic of apoptosis including cell shrinkage, cell membrane blebbing, formation of apoptotic bodies, and nuclear condensation. By contrast, similar effects were not found in tumor cells exposed to extract similarly prepared from normal mammalian cells (i.e., human keratocytes). The results suggest that at least one species of pathogenic free-living amoeba is able to lyse tumor cells by a process that culminates in apoptosis.

Acanthamoeba↗

PubMed1994

Rejection of intraocular tumors from transgenic mice by tumor-infiltrating lymphocytes.

The present study examined the role of tumor infiltrating lymphocytes (TIL) in the rejection of intraocular tumors from SV40 transgenic mice. Tumor cells from an intraocular tumor arising in an SV40 transgenic FVB/N mouse were transplanted into the eyes of syngeneic FVB/N mice and the TIL isolated. TIL were assessed for direct cytolytic activity in vitro. TIL were also transferred passively to immunosuppressed FVB/N mice to determine if they could mediate intraocular tumor rejection. The role of CD4+ and CD8+ T cells in intraocular tumor rejection was evaluated by depleting the respective cell populations in FVB/N hosts prior to intraocular tumor challenge. The results showed that intraocular tumors undergoing rejection in immunocompetent syngeneic hosts became infiltrated with T cells, with the CD8+ subset predominating at the time of rejection. By contrast, athymic nude mice did not reject the intraocular tumors nor did the tumors become infiltrated with TIL. TIL displayed direct, tumor-specific cytolytic activity immediately after isolation from the tumor-containing eyes. FVB/N hosts depleted of CD4+ T cells were unable to reject their intraocular tumors. In vivo depletion of CD8+ T cells delayed, but did not prevent tumor rejection. Adoptively transferred TIL mediated swift rejection of intraocular tumors in immunoincompetent recipients. Recipients of TIL, but not recipients of normal spleen cells, acquired significant tumor-specific CTL activity that was demonstrable in vitro. The results strongly suggest, but do not prove, that TIL mediate rejection of intraocular tumors from transgenic mice by direct cytolysis. Although CD4+ T cells are necessary for tumor rejection and are capable of direct cytolysis, the predominant effector cells are CD8+ CTL.

Animals↗

PubMed1994

Characterization of intraocular tumors arising in transgenic mice.

PURPOSE: To characterize intraocular tumors that arise by in situ transformation in the choroid-retinal pigment epithelium (RPE) in transgenic mice bearing the SV40 oncogene under the control of the mouse tyrosinase promoter. METHODS: Tumors from TySV40 transgenic mice were characterized in vivo and in vitro by immunohistology, compound microscopy, and electron microscopy. Tumor cell lines were established and characterized for growth and metastatic potential in the eyes of nude mice. RESULTS: On light microscopy, ocular tumors were predominantly epithelioid, although occasional clusters of spindle cells were also present. Transmission electron microscopy revealed the presence of numerous basal infoldings and abundant multilaminated basement membranes on the ocular tumors. Tumors stained with antibodies to melanoma-associated antigens, gangliosides GD2 and GD3, and the SV40 T antigen. Radiolabeled transgenic tumor cells preferentially localized in the liver after intravenous injection in normal mice. Intracamerally transplanted transgenic tumors metastasized from the eyes to the livers of nude mice. CONCLUSIONS: In TySV40 transgenic mice, intraocular tumors develop that arise at the choroid-RPE interface, and they display morphologic and ultrastructural features consistent with RPE carcinomas. However, the transgenic tumors express melanoma-associated antigens and a propensity to metastasize to the liver, two features characteristic of uveal melanomas. The TySV40 transgenic murine tumors represent potentially useful tools for investigations into the biology and metastasis of intraocular neoplasms.

Animals↗

PubMed1993

In vitro and in vivo tumoricidal properties of a pathogenic/free-living amoeba.

The chemotactic and tumoricidal properties of the pathogenic/free-living amoeba Acanthamoeba castellanii were examined in vivo and in vitro. A. castellanii trophozoites displayed strong positive chemotactic responses to human melanoma (OCM-1) and murine melanoma (D5.1G4) cells. Although the parasites typically invade and destroy the corneal epithelium and stroma, positive chemotactic responses were not detected against extracts of either of these corneal elements. In vitro studies revealed that viable parasites, as well as cell-free parasite lysates, produced swift and extensive cytolysis of a wide variety of tumor cells. The tumoricidal properties of A. castellanii were examined in vivo and revealed that injection of viable parasites or cell-free parasite lysates into progressively growing subcutaneous melanomas resulted in 83% and 53% reductions in the tumor masses compared with untreated controls. The feasibility of utilizing the tumoricidal properties of pathogenic/free-living amoebae and their cell-free products in the treatment of drug-resistant or radioresistant tumors warrants further investigation.

Acanthamoeba↗