Metformin and risk of hematological cancers in patients with diabetes: a systematic review and meta-analysis

FUNDING

No external funding.

A systematic review with meta-analysis of the relation of aflatoxin B1 to growth impairment in infants/children

BACKGROUND

Aflatoxins are regarded as the most potent genotoxic and carcinogenic type of mycotoxins. This meta-analysis was performed to investigate a the relation of aflatoxin B1 (AFB1) to growth measurements of infants/children, including wasting, underweight, stunting, as well as weight-for-age (WAZ), height-for-age (HAZ), and weight-for-height (WHZ) z-scores.

METHODS

Electronic databases of PubMed, Web of Science, and Scopus were searched to identify related publications. Effect sizes for associations were pooled using the random effects analysis. Subgroup analysis by study design, method used to assess AFB1, and adjustment for covariateswas performed to detect possible sources of heterogeneity.

RESULTS

Pooled analysis of available data showed that AFB1 exposure was negatively associated growth z-scores, including WHZ (β = -0.02, 95%CI = -0.07 to 0.03), with WAZ (β = -0.18, 95%CI = -0.33 to -0.02), and HAZ (β = -0.17, 95%CI = -0.30 to -0.03) in infants/children. There was a remarkable heterogeneity among studies on WAZ and HAZ (P ≤ 0.001). In prospective cohort studies, AFB1 exposure was found to be significantly associated with the elevated risk of underweight (OR = 1.20, 95%CI = 1.03 to 1.40) and stunting (OR = 1.21, 95%CI = 1.11 to 1.33).

CONCLUSIONS

This meta-analysis highlighted the importance of AFB1 exposure as a potential risk factor for growth impairment in infants/children.

Campylobacter jejuni and Campylobacter coli in cecum contents of chickens of slaughter age: A microbiological surveillance

The presence of foodborne pathogens is a major concern for the food industry and increase in antibiotic resistance adds to the seriousness of this issue. Epidemiological studies have shown that there is little or no information from Iran on the prevalence of Campylobacter spp. in chickens of slaughter age. The aim of this study was to determine the prevalence, antibacterial susceptibility and type of Campylobacter species isolated from the cecum of chickens bred in Saqqez city, Kurdistan, western Iran. Campylobacter was isolated and identified by culture and molecular methods. Antibiotic susceptibility of Campylobacter species was performed by disk agar diffusion test and agar dilution methods. The bacterial isolates were typed by repetitive element sequence based polymerase chain reaction (rep-PCR) method. Fifty-five percent of the farms were found to be contaminated with Campylobacter spp. Gene amplification assay confirmed 67 isolates with Campylobacter spp., of which 57 (85.1%) were identified as C. jejuni and 10 (14.9%) as C. coli. Resistance to tetracycline was the most common finding (70.6%), followed by ciprofloxacin (63.7%) and amoxicillin (27.5%). All isolates retained their susceptibility towards gentamicin and meropenem. Results of MIC₅₀ and MIC₉₀ confirmed high resistance towards tetracycline and ciprofloxacin. Repetitive element sequence based-polymerase chain reaction (rep-PCR) placed C. jejuni in six profiles, while C. coli could not be separated as diverse clones. The present study focused on obtaining data regarding prevalence, antibiotic susceptibilities, genetic diversity at regular intervals and maintain and improve hygiene. The results of this study showed substantial genetic diversity of C. jejuni in chickens from western Iran.

A newly emerged focus of zoonotic cutaneous leishmaniasis in South-western Iran

Leishmaniasis is rising in many countries, including Iran, due to climate change, refugee crises, urbanization and etc. The aim of this study was to explore the epidemiology, extent and identity of Leishmania species in a newly emerged focus in Abdanan County, Ilam Province, South-western Iran. This study was performed as a descriptive cross-sectional study by a systematic house-to-house approach. The Leishmania species was identified by RFLP-PCR and sequencing. Altogether, 46799 individuals consisting of 22907 (48.9) female and 23892 (51.1%) male were interviewed and physically examined for the presence of skin lesions. Overall, the incidence rate was 0.34% (n = 160). All age groups were affected and the incidence rate was the highest in <10 years of age group (0.49%) and the lowest in >50 years old individuals (0.15%), although there was no significant difference regarding the sex and age. The majority of patients had one lesion (47.5%) on hands (56%) and most of the cases occurred in Abdanan city (%54) in summer. Based on the RFLP-PCR analysis, all the Leishmania isolates were L. major of single genotype. A newly emerged focus of zoonotic CL caused by L. major occurred in South-western of Iran. Multiple risk factors created this epidemic area. Further studies on the vector and reservoir are crucial needed to provide evidences to select the prophylactic and therapeutic measures for future control strategies.

Common Variants of Vitamin D Receptor Gene Polymorphisms and Susceptibility to Coronary Artery Disease: A Systematic Review and Meta-Analysis

BACKGROUND AND AIMS

ApaI, FokI, TaqI, and BsmI polymorphisms in the vitamin D receptor (VDR) gene have been reported to be associated with the risk of coronary artery disease (CAD), although the results of previous studies have been inconsistent. The aim of this study was to explore whether these polymorphisms play a role in the genetic susceptibility to CAD.

METHODS

A comprehensive search of Medline and Embase databases was conducted for studies evaluating the association between the VDR polymorphisms and CAD risk. Odds ratios with 95% confidence intervals were calculated to assess the strength of association in the dominant model, recessive model, allelic model, and genotypes contrast.

RESULTS

Nine studies involving a total of 5,259 cases and 1,981 controls were finally included in this meta-analysis. Overall, no significant associations were found between ApaI, FokI, TaqI, and BsmI polymorphisms and the risk of CAD in any of the genetic models (all p ˃ 0.05). Moreover, a subgroup analysis by ethnicity did not reveal a significant relationship between any of the examined polymorphisms and CAD risk in Caucasians and East-Asians for any model (all p ˃ 0.05).

CONCLUSION

Current evidence suggests that the ApaI, FokI, TaqI, and BsmI polymorphisms of the VDR gene might not be associated with genetic susceptibility to CAD. Further well-designed studies with large sample sizes are needed to confirm our results.

Psychomotor delay, a possible rare presentation of moyamoya disease

Moyamoya disease is a rare, chronic cerebrovascular occlusive disease of unknown etiology. It is characterized by progressive stenosis of the arteries of the circle of Willis leading to ischemic strokes in young people and cerebral hemorrhage, which is more frequent in adults. Secondarily, an abnormal network of fine collateral vessels arises at the base of the brain. The term moyamoya refers to the angiographic appearance of the cerebral vasculature. We present such a disease in an 18-month-old Iranian girl with global developmental delay, which is a very rare presentation of moyamoya disease. She was diagnosed by magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA).

An eigenstrain-based model for residual stress arising from transient local surface heating

We present a model for approximating residual stresses arising from thermally induced plasticity and apply it to a simple two-dimensional (plane strain) test problem of transient heating. The model uses stress fields derived from simple eigenstrains to perturb an initially elastic-only solution in a way that mimics plastic flow. The plane strain condition of the test problem gives rise to plastic strains in the out-of-plane direction, owing to constraints on thermal expansion. However, the model is able to cope with the challenges this poses and also encapsulates the time-dependent nature of the problem. We show that the model agrees well with finite-element simulations under moderate strength heat sources provided that appropriate plastic flow rules are used. There exists sufficient generality in the model to allow its extension to more realistic scenarios.

Oral immunization with Acanthamoeba castellanii mannose-binding protein ameliorates amoebic keratitis

Acanthamoeba castellanii mannose-binding protein (MBP) mediates adhesion of the amoebae to corneal epithelial cells, a key first step in the pathogenesis of Acanthamoeba keratitis (AK), a devastating corneal infection. In the present study, we demonstrate that oral immunization with recombinant MBP ameliorates AK in a hamster animal model and that this protection is associated with the presence of elevated levels of anti-MBP immunoglobulin A in the tear fluid of the immunized animals.

Radiofrequency and laser ablation of spinal lesions

Radiofrequency current and laser energy can be delivered locally through electrode-needle or optical fiber inserted in the tissue and allows local ablation of tissues, up to a volume of 4 to 5 cm in diameter with one application or vaporizes tissue. Tumor ablation guided with medical imaging proved a high local efficacy over 90% for tumors less than 25 mm in the liver, lung, and kidney. The spinal applications of the thermal energy of RF and laser are reported in this paper. First, the tumor ablation is reviewed with malignant and benign tumors. In malignant tumors, radiofrequency is very efficient in local tumor control and in pain management. The second part of this paper is devoted to disk diseases where laser and RF techniques increase their applications. The technique, indications and results of these techniques are reported and illustrated.

Resistance of Acanthamoeba castellanii cysts to physical, chemical, and radiological conditions

Resistance of Acanthamoeba castellanii cysts to disinfection agents, antimicrobial agents, heat, freeze-thawing, ultraviolet radiation (UV), gamma irradiation, and cellulase were evaluated in vitro. Following exposure to different agents, the cysts were removed and cultured for A. castellanii trophozoites for 3-14 days. Solutions containing 20% isopropyl alcohol or 10% formalin effectively killed A. castellanii cysts. Hydrogen peroxide (3%, AOSept Disinfectant) effectively killed A. castellanii cysts after 4 hr of exposure. Polyhexamethylene biguanide (0.02%), clotrimazole (0.1%), or propamidine isethionate (Brolene) were effective in killing A. castellanii cysts in vitro. Acanthamoeba castellanii cysts were resistant to both 250 K rads of gamma irradiation and 800 mJ/cm2 of UV irradiation. Excystment of trophozoites was accelerated after exposure to 10, 100, and, 1,000 units of cellulase. These results suggest that A. castellanii cysts benefit by enhanced survival because of their resistance to very harsh environmental conditions.

Angiostatin produced by certain primary uveal melanoma cell lines impedes the development of liver metastases

OBJECTIVES

To evaluate the ability of human uveal melanomas to produce angiostatin in vitro and the effect of angiostatin on the development of liver metastases in vivo.

METHODS

Human uveal melanoma cell lines (OCM1, OCM3, MEL202, MEL285, 92-1, OM431, and OMM1) were assayed for their ability to produce angiostatin in vitro by an angiostatin bioassay and by Western blot analysis. The OCM3 and OMM1 tumor cells were inoculated either in the posterior or the anterior segment of nude mice. One group of mice in each experiment underwent enucleation and hepatic metastases were assayed by histopathologic and liver function analysis.

RESULTS

OCM1, OCM3, and 92-1 cell lines significantly inhibited bovine endothelial cell proliferation in vitro and generated 38-Kd angiostatin molecules. Enucleation of eyes containing OCM3 in the posterior segment resulted in a higher number of metastatic foci (26.5) in that group compared with the nonenucleated group of mice (11.17). After enucleation, elevated levels of serum aspartate transaminase and alanine aminotransferase were observed in mice bearing OCM3 in either anterior or posterior segments. The enucleation of eyes containing OMM1 (nonangiostatin-producing cells) had no significant effect on liver metastasis.

CONCLUSION

By removing a source of angiostatin, enucleation of melanoma-containing eyes may unwittingly exacerbate the metastatic potential of uveal melanomas.

CLINICAL RELEVANCE

In certain circumstances, enucleating a melanoma-containing eye may unwittingly exacerbate metastatic disease. The results also suggest that exogenous angiostatin may have potential therapeutic implications in the management of patients with primary intraocular melanomas.

Effect of steroids on Acanthamoeba cysts and trophozoites

PURPOSE

Topical steroids are frequently used to control corneal inflammation and uveitis or is administered after surgery, to prevent corneal graft rejection. This study was undertaken to determine whether steroids could affect the pathogenicity of Acanthamoeba castellanii.

METHODS

The effect of dexamethasone phosphate on excystment, proliferation, and encystment of trophozoites and cysts of A. castellanii was examined in vitro. Cytolysis capacity of steroid-treated Acanthamoeba was quantified by a spectrophotometric assay, and plasminogen activators were measured by a fibrinolysis assay. The influence of steroid treatment on corneal infection in a Chinese hamster model of Acanthamoeba keratitis was examined in vivo.

RESULTS

Treatment of Acanthamoeba cysts with dexamethasone induced 4- to 10-fold increases in the number of trophozoites compared with untreated control cultures. Acceleration of trophozoite proliferation was observed when trophozoites were treated with dexamethasone. However, dexamethasone treatment did not affect encystment of Acanthamoeba trophozoites. Dexamethasone-treated trophozoites or cysts induced a significant cytopathic effect on corneal epithelial cells compared with untreated organisms. Supernatants collected from either dexamethasone-treated or untreated organisms failed to lyse corneal epithelial cells. Treatment of organisms with dexamethasone had no effect on production of plasminogen activators by Acanthamoeba trophozoites. Intramuscular injection of dexamethasone had a profound effect on the incidence, severity, and chronicity of keratitis. Keratitis in dexamethasone-treated hamsters was significantly more severe at all time points than in untreated animals (P < 0.05).

CONCLUSIONS

These findings indicate that exposure of Acanthamoeba trophozoites and cysts to dexamethasone increases the pathogenicity of the organisms. The results emphasize the importance of maintaining adequate amebicidal therapy if a topical steroid is used in the management of Acanthamoeba keratitis.

Role of fas ligand in uveal melanoma-induced liver damage

BACKGROUND

Uveal melanoma, the most common adult intraocular malignancy, metastasizes preferentially to the liver. Areas of cell death surrounding uveal melanoma metastases were observed in the livers of mice. We hypothesized that uveal melanoma cells might express Fas ligand (FasL), facilitating FasL-mediated apoptosis of Fas-expressing hepatocytes.

PURPOSE

To determine whether Fas ligand (FasL)-expressing human uveal melanoma cells induce apoptosis of human hepatocytes in vitro and in vivo.

METHODS

Human uveal melanoma cell lines were assayed for FasL expression by flow cytometry and immunohistology. A human hepatocyte cell line was assayed for Fas expression by flow cytometry. Apoptosis of hepatocytes was detected by annexin V staining in vitro, and terminal deoxynucleotidyl transferase nick end labeling (TUNEL) in vivo.

RESULTS

Human uveal melanoma cell lines expressed FasL, as determined by flow cytometry and immunohistology. Human hepatocytes were Fas-positive by flow cytometry. In vitro, annexin V staining revealed that human uveal melanoma cells induced apoptosis of human hepatocytes. TUNEL staining of liver metastases revealed apoptosis of murine hepatocytes in contact with metastatic human uveal melanoma cells.

CONCLUSION

FasL-induced apoptosis of hepatocytes in contact with FasL-positive human uveal melanoma cells may contribute to hepatic failure during metastatic disease.

Tear IgA and serum IgG antibodies against Acanthamoeba in patients with Acanthamoeba keratitis

PURPOSE

Exposure to Acanthamoebaspecies appears to be ubiquitous, as 50% to 100% of healthy human subjects display anti-Acanthamoebaantibodies. However, the presence of specific anti-Acanthamoebaantibodies in the serum and tears of patients has not been investigated. The prevalence of serum immunoglobulin G (IgG) and tear IgA against three species of Acanthamoebawas assessed in healthy subjects and patients with Acanthamoebakeratitis.

METHODS

The level of specific serum IgG and tear IgA against A. castellanii, A. astronyxis, and A. culbertsoniin the sera of 23 patients and 25 healthy subjects was tested by enzyme-linked immunosorbent assays. Total serum IgM, IgG, and IgA concentrations were measured by nephelometry. Acanthamoebakeratitis was diagnosed clinically and confirmed by in vivo confocal microscopy. In some patients, corneal biopsies were also performed and trophozoites were cultured on lawns of Escherichia colion non-nutrient agar.

RESULTS

All healthy subjects and patients with Acanthamoebakeratitis had detectable serum IgG antibodies against all Acanthamoebaantigens. However, patients with Acanthamoebakeratitis had significantly higher anti-AcanthamoebaIgG antibody titers than healthy subjects. In contrast, Acanthamoeba-specific tear IgA was significantly lower in patients with Acanthamoebakeratitis in comparison with healthy subjects. Total serum immunoglobulins did not differ significantly between healthy subjects and patients with Acanthamoebakeratitis.

CONCLUSIONS

The results suggest that a low level of anti-AcanthamoebaIgA antibody in the tears appears to be associated with Acanthamoebakeratitis.

Exacerbation of Acanthamoeba keratitis in animals treated with anti-macrophage inflammatory protein 2 or antineutrophil antibodies

Neutrophils are thought to be involved in many infectious diseases and have been found in high numbers in the corneas of patients with Acanthamoeba keratitis. Using a Chinese hamster model of keratitis, conjunctival neutrophil migration was manipulated to determine the importance of neutrophils in this disease. Inhibition of neutrophil recruitment was achieved by subconjunctival injection with an antibody against macrophage inflammatory protein 2 (MIP-2), a powerful chemotactic factor for neutrophils which is secreted by the cornea. In other experiments, neutrophils were depleted by intraperitoneal injection of anti-Chinese hamster neutrophil antibody. The inhibition of neutrophils to the cornea resulted in an earlier onset and more severe infection compared to controls. Anti-MIP-2 antibody treatment produced an almost 35% reduction of myeloperoxidase activity in the cornea 6 days postinfection, while levels of endogenous MIP-2 secretion increased significantly. Recruitment of neutrophils into the cornea via intrastromal injections of recombinant MIP-2 generated an initially intense inflammation that resulted in the rapid resolution of the corneal infection. The profound exacerbation of Acanthamoeba keratitis seen when neutrophil migration was inhibited, combined with the rapid clearing of the disease in the presence of increased neutrophils, strongly suggests that neutrophils play an important role in combating Acanthamoeba infections in the cornea.

[Treatment of chronic myeloid leukemia with interferon-alpha]

The authors have treated 38 patients with chronic phase chronic myeloid leukemia in their single center in the last five years. Conventional chemotherapy provided about 40-50% hematological response, interferon-alpha seems to be more effective, complete hematological remission occurred in 65%. Interphase cytogenetics and fluorescein in situ hybridisation technique was used to measure the cytogenetic response. They observed complete cytogenetic remission in two cases (8%), major response in 11 (39%), minor response in 4 (15%) and minimal response in 4 cases (15%). Interferon-alpha is an effective, well-tolerated medicine in the treatment of chronic myeloid leukemia.

The diagnosis and management of Acanthamoeba keratitis

PURPOSE

The purpose of this study was to evaluate the immunology, pathogenesis and therapy of Acanthamoeba keratitis.

METHODS

The recent development of an animal model of Acanthamoeba keratitis and its impact on the medical treatment and immunology of Acanthamoeba keratitis was reviewed.

RESULTS

After initial reports, Acanthamoeba infection of the cornea remained a rare disease until an association with contact lens wear was first recognized. Although the disease is closely associated with contact lens wear, it appeared that the contaminated solutions that were coming into contact with the lenses caused the disease. All types of contact lenses can be associated with development of Acanthamoeba keratitis. Therefore, the contact lens serves as a carrier of Acanthamoeba to the surface of the eye. The typical patient with Acanthamoeba keratitis is a young healthy individual who is either a contact lens wearer or has had significant exposure to water contaminated with Acanthamoeba. There are several risk factors such as corneal trauma, contaminated solution and contact lenses that have been reported to be associated with Acanthamoeba keratitis. In spite of significant improvement in the diagnosis of Acanthamoeba keratitis, progress in developing and utilizing effective antimicrobial agents for treating this disease have been disappointing. A growing body of evidence suggests that the mammalian immune system, if properly activated, is capable of preventing and controlling ocular infections.

CONCLUSIONS

In order to develop effective immunotherapeutic modalities, and to better understand the immune effector mechanisms that protect the cornea against Acanthamoeba infection, it is necessary to fully characterize and evaluate the immunobiology of Acanthamoeba keratitis.

Experimental transplantation of cultured human limbal and amniotic epithelial cells onto the corneal surface

PURPOSE

Tissue-cultured corneal epithelial transplantation is a novel procedure that uses tissue-cultured epithelial cells to restore severely damaged ocular surfaces. In this study, we used tissue-cultured human limbal and amniotic epithelial cells as donor cells to investigate the feasibility of this procedure for reestablishment of a damaged ocular surface in experimental conditions.

METHODS

Primary human limbal epithelial cultures were established from banked limbal tissue. Amniotic epithelial cells were isolated from serologically screened human placenta and maintained in a specialized nutrient medium. Suspended cells (5 x 10(5)/ml) were seeded onto the concave surface of collagen corneal shields and incubated at 37 degrees C for 2-3 days. These cell-covered shields were then placed on a denuded stromal surface in organ culture and on New Zealand albino rabbit ocular surfaces that had the native epithelium previously removed. Specimens were collected 24, 48, 72, and 96 h later from organ-cultured corneal buttons and recipient animals, processed, and evaluated histologically.

RESULTS

The cells grown on the collagen shield were spread uniformly and unpolarized after 48 h in culture. They were repolarized and tightly adhered to the recipient corneal stroma 24 h after transplantation, as demonstrated by formation of cell-substrate hemidesmosomes (HDs) and donor-specific antigen immunostaining. The donor cells were retained in six of 15 rabbits receiving limbal cells and four of 12 rabbits receiving amniotic cells for as long as 10 days after surgery.

CONCLUSION

Cultured human limbal and amniotic epithelial cells can be successfully transplanted onto a denuded corneal surface where they adhere tightly to underlying stroma by hemidesmosomes.

Inhibition of intraocular tumor growth by topical application of the angiostatic steroid anecortave acetate

PURPOSE

This study examined the effect of an angiostatic agent on the growth of a highly vascularized intraocular tumor.

METHODS

A murine uveal melanoma cell line (99E1) was transplanted intracamerally into athymic nude BALB/c mice. Mice were treated topically three times per day beginning on the day of tumor transplantation and continuing through day 28. Groups included (a) 1% anecortave acetate, (b) vehicle control, or (c) no treatment. Tumor growth was scored clinically according to the volume of anterior chamber occupied by tumor. Intraocular tumor weights were determined on days 10, 14, 21, and 28. The effect of the test agents on tumor cell proliferation was examined in vitro by [3H]thymidine incorporation.

RESULTS

Tumors grew progressively in untreated mice and mice treated with the vehicle; tumors filled the entire eye by day 20 and frequently perforated the globe by day 21. By contrast, tumors treated with anecortave acetate grew significantly slower (P < 0.025) and did not perforate the eye. On days 21 and 28 the net tumor weight of the AL-3789-treated animals was 40% to 30% of controls (P < 0.05). Tumor inhibition was presumably due to the angiostatic properties of anecortave acetate because the compound did not affect tumor cell proliferation in vitro.

CONCLUSIONS

The topical ocular administration of anecortave acetate restricted the growth of a highly vascularized angiogenic intraocular tumor.

Monoclonal IgA antibodies protect against Acanthamoeba keratitis

Acanthamoeba keratitis is a rare, yet sight-threatening corneal infection. Ocular infection does not appear to induce protective immunity as repeated corneal infections occur in both humans and experimental animals. However, we have recently demonstrated that activation of the common mucosal immune system by oral immunization with Acanthamoeba antigens protects both Chinese hamsters and pigs against ocular infection with A. castellanii. Protection correlates closely with the appearance of anti- Acanthamoeba antibodies in the tears. To test the hypothesis that oral immunization induces specific protective IgA antibodies, two monoclonal IgA antibodies specific for Acanthamoeba antigens were generated. Both antibodies detected epitopes on the surface of fixed Acanthamoeba trophozoites. When delivered intraperitoneally, one monoclonal antibody (14E4) was detected in stool and tear samples. This clone also protected naive animals against ocular challenge with Acanthamoeba trophozoites (43% infection rate compared to a 91% infection rate in animals receiving control IgA). In vitro functional studies showed that neither antibody induced encystment or directly killed Acanthamoeba trophozoites. However, both monoclonal anti- Acanthamoeba IgA antibodies produced a three-fold inhibition in the adherence of trophozoites to corneal epithelial cells in vitro. These data show that monoclonal anti- Acanthamoeba IgA antibodies can protect against Acanthamoeba keratitis and suggest that this occurs by inhibiting adhesion of the parasite to the corneal epithelium.

The pathogenesis of Acanthamoeba keratitis

Free-living amoebae of the genus Acanthamoeba produce a progressive, blinding infection of the corneal surface. The pathogenesis of Acanthamoeba keratitis involves parasite-mediated cytolysis and phagocytosis of corneal epithelial cells and induction of programmed cell death. Acanthamoeba spp. elaborate a variety of proteases which may facilitate cytolysis of the corneal epithelium, invasion of the extracellular matrix, and dissolution of the corneal stromal matrix.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 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.

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.

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.

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.

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.

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.