Vaccine development against the blood-stage malaria parasite is aimed at reducing the pathology of the disease. We constructed a recombinant Mycobacterium bovis bacille Calmette Guerin (rBCG) expressing the 19 kDa C-terminus of Plasmodium falciparum merozoite surface protein-1 (MSP-1(19)) to evaluate its protective ability against merozoite invasion of red blood cells in vitro. A mutated version of MSP-1(19), previously shown to induce the production of inhibitory but not blocking antibodies, was cloned into a suitable shuttle plasmid and transformed into BCG Japan (designated rBCG016). A native version of the molecule was also cloned into BCG (rBCG026). Recombinant BCG expressing the mutated version of MSP-1(19) (rBCG016) elicited enhanced specific immune response against the epitope in BALB/c mice as compared to rBCG expressing the native version of the epitope (rBCG026). Sera from rBCG016-immunized mice contained significant levels of specific IgG, especially of the IgG2a subclass, against MSP-1(19) as determined by enzyme-linked immunosorbent assay. The sera was reactive with fixed P. falciparum merozoites as demonstrated by indirect immunofluorescence assay (IFA) and inhibited merozoite invasion of erythrocytes in vitro. Furthermore, lymphocytes from rBCG016-immunized mice demonstrated higher proliferative response against the MSP-1(19) antigen as compared to those of rBCG026- and BCG-immunized animals. rBCG expressing the mutated version of MSP-1(19) of P. falciparum induced enhanced humoral and cellular responses against the parasites paving the way for the rational use of rBCG as a blood-stage malaria vaccine candidate.
Phosphatidylinositol 4-phosphate 5-kinase (PIP5K) may play an important role in host-cell invasion by the Eimeria species, protozoan parasites which can cause severe intestinal disease in livestock. Here, we report the structural organization of the PIP5K gene in Eimeria maxima (Weybridge strain). Two E. maxima BAC clones carrying the E. maxima PIP5K (EmPIP5K) coding sequences were selected for shotgun sequencing, yielding a 9.1-kb genomic segment. The EmPIP5K coding region was initially identified using in silico gene-prediction approaches and subsequently confirmed by mapping rapid amplification of cDNA ends and RT-PCR-generated cDNA sequence to its genomic segment. The putative EmPIP5K gene was located at position 710-8036 nt on the complimentary strand and comprised of 23 exons. Alignment of the 1147 amino acid sequence with previously annotated PIP5K proteins from other Apicomplexa species detected three conserved motifs encompassing the kinase core domain, which has been shown by previous protein deletion studies to be necessary for PIP5K protein function. Phylogenetic analysis provided further evidence that the putative EmPIP5K protein is orthologous to that of other Apicomplexa. Subsequent comparative gene structure characterization revealed events of intron loss/gain throughout the evolution of the apicomplexan PIP5K gene. Further scrutiny of the genomic structure revealed a possible trend towards "intron gain" between two of the motif regions. Our findings offer preliminary insights into the structural variations that have occurred during the evolution of the PIP5K locus and may aid in understanding the functional role of this gene in the cellular biology of apicomplexan parasites.
Cosmopolitan scuttle fly, Megaselia scalaris (Loew) (Diptera: Phoridae) is one of the commonest forensic species recorded colonizing human corpse indoors and in concealed environment. The occurrence of this species in such environments provides a higher evidential value to assist estimation of postmortem interval (PMI) compared to other forensically important dipterans. However, developmental and size data of M. scalaris are still lacking and they are derived from a limited range of thermal values. The objective of this study is to develop the growth model of M. scalaris by emphasizing the size range of larvae and puparia at different constant temperatures. This species was reared in six replicates at eight varying constant temperatures ranging from 23 to 36 °C and cow's liver was provided as food source. Larvae and puparia were sampled at set time intervals and measured by their length and weight. Because interpretation of forensic entomological evidence is subject to application of different techniques, development of M. scalaris is expressed herein by using developmental table, length/morphological stage diagrams and linear/nonlinear estimation methods. From the findings, it is very important to highlight that sexual dimorphism of M. scalaris during post feeding larva and pupa stage could be observed based on size and developmental periods. Mean length and weight ratios of male to female puparia are approximately 0.8 and 0.3-0.5, respectively, indicating sexual dimorphism of this species. Developmental period in female are 4.0-11.4 h (post feeding larval stage), 3.7-24.0 h (pupal stage), and 3.0-20.1 h (total developmental period) longer in male. Due to this dimorphism, PMI estimation using M. scalaris post feeding larva or puparium specimens must be carried out carefully by to avoid inaccuracy and misinterpretation.
Blastocystis hominis is one of the most common intestinal protozoan parasites in humans, and reports have shown that blastocystosis is coupled with intestinal disorders. In the past, researchers have developed an in vitro model using B. hominis culture filtrates to investigate its ability in triggering inflammatory cytokine responses and transcription factors in human colonic epithelial cells. Studies have also correlated the inflammation by parasitic infection with cancer. The present study provides evidence of the parasite facilitating cancer cell growth through observing the cytopathic effect, cellular immunomodulation, and apoptotic responses of B. hominis, especially in malignancy. Here we investigated the effect of solubilized antigen from B. hominis on cell viability, using peripheral blood mononuclear cells (PBMCs) and human colorectal carcinoma cells (HCT116). The gene expressions of cytokines namely interleukin 6 (IL-6), IL-8, tumor necrosis factor alpha, interferon gamma, nuclear factor kappa light-chain enhancer of activated B cells (a gene transcription factor), and proapoptotic genes namely protein 53 and cathepsin B were also studied. Results exhibited favor the fact that antigen from B. hominis, at a certain concentration, could facilitate the growth of HCT116 while having the ability to downregulate immune cell responses (PBMCs). Therefore, there is a vital need to screen colorectal cancer patients for B. hominis infection as it possesses the ability to enhance the tumor growth.
The fact whether Blastocystis hominis can invade has always been in question. Apart from a few sporadic studies such as that done on gnotobiotic guinea pigs which showed surface invasion and mucosal inflammation of the host's intestine caused by B. hominis infection, no real documentation of invasion has been proven. Studies have shown that hyaluronidase is secreted during the penetration into the host's skin and gut by nematode parasites. Hyaluronidase activity in protozoa namely Entamoeba histolytica has also been described previously. This study attempts to determine hyaluronidase in urine samples of B. hominis-infected rats. The presence of hyaluronidase in urine provides an indirect evidence of invasion by B. hominis into colonic epithelium causing the degradation of extracellular matrix proteins namely hyaluronic acid (HA). HA is depolymerized by hyaluronidase which may be used by organisms to invade one another. In this study, the levels of urinary hyaluronidase of Sprague-Dawley rats infected with B. hominis were monitored for 30 days. Hyaluronidase levels in the infected rats were significantly higher on days 28 and 30 compared to the day before inoculation (P < 0.01 and P < 0.05, respectively). During this stage, parasitic burden in infected stools was also at a high level. Proinflammatory cytokines, interleukin-6 and interleukin-8, were also significantly higher (P < 0.05) in the serum of infected rats. The study demonstrates that since no other pathogen was present and that amoeboid forms of the parasites have been shown to exist previously, the elevated levels of hyaluronidase in this preliminary finding suggests that the organism is capable of having invasion or penetration activity in the hosts' intestine.
Nine 50-l surface water samples from a Malaysian recreational lake were examined microscopically using an immunomagnetisable separation-immunofluorescent method. No Cryptosporidium oocysts were detected, but 77.8% of samples contained low numbers of Giardia cysts (range, 0.17-1.1 cysts/l), which were genetically characterised by SSU rRNA gene sequencing. Genotype analyses indicated the presence of Giardia duodenalis assemblage A suggesting potential risk to public health. The present study represents the first contribution to our knowledge of G. duodenalis assemblages in Malaysian recreational water.
Blastocystis from infected stools of a person who showed chronic symptoms of abdominal discomfort and diarrhea were examined over a 6-month period, using transmission electron microscopy, for the ultrastructural changes from vacuolar to cystic stage. The study confirms the irregular shedding phenomenon of the organism previously reported, and for the first time, records sequential changes in encystation in stools collected over a time period. The study also confirms the existence of a precystic stage which has an immature cell wall consisting of a layer of a homogenous electron-dense mass surrounding the cell which acts as a intermediatory stage between the vacuolar and cystic stage.
This represents the first study to determine the genetic diversity of Blastocystis sp. among cancer and HIV/AIDS patients. Forty Blastocystis sp. isolates obtained from 20 cancer and 20 HIV/AIDS patients were genotyped by PCR using seven pairs of known sequenced-tagged site primers. Out of the 40 isolates, 38 were identified as one of the known genotypes and two isolates were negative with all the STS primers. Blastocystis sp. subtype 3 which is reported to be associated with disease was found to be predominant among the study subjects.
This article is a review of the latest information on the prevalence of G. lamblia in South Asia, South East Asia and Far East, characterizing the current endemic situation within these regions. Around 33 published papers from 2002-2007 were collected on G. lamblia. The included countries were Nepal, Bangladesh, India, Cambodia, Vietnam, Malaysia, Philippines, Indonesia, Thailand, Republic of Korea, and China. Only five published papers were discarded because data was extracted before 2002-2007 or they are not included within our regions, emphasizing more on G. lamblia in animals, or performed at extensive molecular level. The prevalence of G. lamblia varied markedly between studies illustrating higher levels in the urban than in the rural areas, more among poor communities, slightly higher in males than in females with age range of 2-5-year-old children, and among university students, old-aged people, HIV-positive patients, and gastric carcinoma patients. Though G. lamblia is not a life-threatening parasite, nevertheless, it is still considered as the most common water-borne diarrhea-causing disease. It is important to understand the etiology, frequency, and consequences of acute diarrhea in children. Routine surveillance such as bi-annual follow-up treatments, treating G. duodenalis cysts and other protozoa oocysts detected in ground water sources, and continuous health education are the most preventive measures.
Despite frequent reports on the presence of Blastocystis hominis in human intestinal tract, its pathogenicity remains a matter of intense debate. These discrepancies may be due to the varying pathogenic potential or virulence of the isolates studied. The present study represents the first to investigate both phenotypic and genotypic characteristics of B. hominis obtained from symptomatic and asymptomatic individuals. Symptomatic isolates had a significantly greater size range and lower growth rate in Jones' medium than asymptomatic isolates. The parasite cells of symptomatic isolates exhibited rougher surface topography and greater binding affinity to Canavalia ensiformis (ConA) and Helix pomatia (HPA). The present study also identifies further phenotypic characteristics, which aided in differentiating the pathogenic forms from the non-pathogenic forms of B. hominis. Blastocystis subtype 3 was found to be correlated well with the disease.
This work investigated the anti-amoebic activity of two samarium (Sm) complexes, the acyclic complex [bis(picrato)(pentaethylene glycol)samarium(III)] picrate-referred to as [Sm(Pic)2(EO5)](Pic)-and the cyclic complex [bis(picrato)(18-crown-6)samarium(III)] picrate-referred to as [Sm(Pic)2(18C6)](Pic). Both Sm complexes caused morphological transformation of the protozoa Acanthamoeba from its native trophozoite form carrying a spine-like structure called acanthopodia, to round-shaped cells with loss of the acanthopodia structure, a trademark response to environmental stress. Further investigation, however, revealed that the two forms of the Sm complexes exerted unique cytotoxicity characteristics. Firstly, the IC50 of the acyclic complex (0.7 μg/mL) was ~ 10-fold lower than IC50 of the cyclic Sm complex (6.5 μg/mL). Secondly, treatment of the Acanthamoeba with the acyclic complex caused apoptosis of the treated cells, while the treatment with the cyclic complex caused necrosis evident by the leakage of the cell membrane. Both treatments induced DNA damage in Acanthamoeba. Finally, a molecular docking simulation revealed the potential capability of the acyclic complex to form hydrogen bonds with profilin-a membrane protein present in eukaryotes, including Acanthamoeba, that plays important roles in the formation and degradation of actin cytoskeleton. Not found for the cyclic complex, such potential interactions could be the underlying reason, at least in part, for the much higher cytotoxicity of the acyclic complex and also possibly, for the observed differences in the cytotoxicity traits. Nonetheless, with IC50 values of
The ornamental fish trade provides a pathway for the global translocation of aquatic parasites. We examined a total of 1020 fish imported from Singapore, Malaysia, Thailand, or Sri Lanka to Australia (including freshwater and marine fish species) for monogenean ectoparasites. Fish were received following veterinary certification that they showed no clinical signs of pests and diseases from the exporting country and visual inspection at Australian border control. Australian import conditions require mandatory treatment for goldfish with parasiticides (e.g. trichlorfon, formaldehyde, sodium chloride) for the presence of gill flukes (Dactylogyrus vastator Nybelin, 1924 and Dactylogyrus extensus Mueller and Van Cleave, 1932) prior to export. Over 950 individual parasites were detected in five imported fish species, representing 14 monogenean species. Seven Dactylogyrus spp. including D. vastator and three Gyrodactylus spp. infected goldfish, Carassius auratus Linnaeus, 1758, from Malaysia, Singapore, and Thailand. Dactylogyrus ostraviensis Řehulka, 1988, infected rosy barb, Pethia conchonius Hamilton, 1822, from Singapore, Sri Lanka, and Thailand while two Trianchoratus spp. infected three spot gourami, Trichopodus trichopterus Pallas, 1970 and pearl gourami Trichopodus leerii Bleeker, 1852, from Sri Lanka. Urocleidoides reticulatus Mizelle & Price, 1964, infected guppy, Poecilia reticulata Peters, 1859, from Sri Lanka. The discovery of D. vastator in goldfish, as well as 13 other monogenean species, shows that pre-export health requirements, which include chemical treatment of goldfish, and inspection of all ornamental fish species did not prevent infection by monogeneans. Inspection prior to exportation and at border control must account for the highly cryptic nature of monogenean parasites and consider alternatives to current pre-export conditions and visual inspection at border control.
Brain-eating amoebae (Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri) have gained increasing attention owing to their capacity to produce severe human and animal infections involving the brain. Early detection is a pre-requisite in successful prognosis. Here, we developed a nanoPCR assay for the rapid detection of brain-eating amoebae using various nanoparticles. Graphene oxide, copper and alumina nanoparticles used in this study were characterized using Raman spectroscopy measurements through excitation with a He-Ne laser, while powder X-ray diffraction patterns were taken on a PANanalytical, X'Pert HighScore diffractometer and the morphology of the materials was confirmed using high-resolution transmission electron microscopy (HRTEM). Using nanoparticle-assisted PCR, the results revealed that graphene oxide, copper oxide and alumina nanoparticles significantly enhanced PCR efficiency in the detection of pathogenic free-living amoebae using genus-specific probes. The optimal concentration of graphene oxide, copper oxide and alumina nanoparticles for Acanthamoeba spp. was determined at 0.4, 0.04 and 0.4 μg per mL respectively. For B. mandrillaris, the optimal concentration was determined at 0.4 μg per mL for graphene oxide, copper oxide and alumina nanoparticles, and for Naegleria, the optimal concentration was 0.04, 4.0 and 0.04 μg per mL respectively. Moreover, combinations of these nanoparticles proved to further enhance PCR efficiency. The addition of metal oxide nanoparticles leads to excellent surface effect, while thermal conductivity property of the nanoparticles enhances PCR productivity. These findings suggest that nanoPCR assay has tremendous potential in the clinical diagnosis of parasitic infections as well as for studying epidemiology and pathology and environmental monitoring of other microbes.
The Simulium rufibasis subgroup is one of three subgroups of the Simulium (Simulium) tuberosum species-group; it is characterized by a pair of clustered stout hairs on the ventral surface of female abdominal segment 7. A member of the S. rufibasis subgroup in Taiwan was investigated morphologically and genetically using the universal cytochrome c oxidase subunit I (COI) barcoding gene and polytene chromosomal banding pattern. The Taiwanese material is morphologically similar to S. rosliramlii Takaoka & Chen from Vietnam and represents the second species of the S. rufibasis subgroup known from Taiwan. It also represents a novel molecular lineage that is distinct from three other primary lineages identified as S. doipuiense, S. doipuiense/S. rufibasis, and S. weji previously reported from Thailand. The mitochondrial evidence for a distinct lineage in Taiwan is supported by chromosomal analysis, which revealed unique sex chromosomes. For nomenclatural stability, we associate the name S. arisanum Shiraki with the Taiwanese entity. Originally described from females from Taiwan, S. arisanum until now has remained an enigmatic species.
Blastocystis sp. is a gastrointestinal (GI) protozoan parasite reported to cause non-specific GI symptoms including diarrhea, flatulence, abdominal pain, and nausea. Complete eradication of Blastocystis sp. is rather challenging even with the drug of choice, i.e., metronidazole. Here, we report on two Blastocystis sp.-infected individuals, who presented increased parasite load and exacerbated symptoms upon treatment with the usual recommended dosage and regime of metronidazole. The two studies uniquely demonstrate for the first time a cyst count as high as fivefold more than the original cyst count before treatment and show an exacerbation of GI symptoms despite treatment. The study provides additional support in recognizing metronidazole resistance in Blastocystis sp. and its consequences towards the pathogenicity of the parasite.
Simulium dermatitis is an IgE-mediated skin reaction in animals and humans caused by the bites of black flies. Although Simulium nigrogilvum has been incriminated as the main human-biting black fly species in Thailand, information on its salivary allergens is lacking. Salivary gland extract of S. nigrogilvum females was subjected to sodium dodecylsulfate-polyacrylamide gel electrophoresis, and the separated components were applied onto nitrocellulose membranes for immunoblotting, which was performed by probing the protein blots with sera from 17 individuals who were allergic to the bites of S. nigrogilvum. IgE-reactive protein bands were characterized further by liquid chromatography-mass spectrometry (LC-MS/MS) analysis. Nine protein bands (79, 42, 32, 25, 24, 22, 15, 13, and 11 kDa) were recognized in the serum of the subjects. Four of the nine protein bands (32, 24, 15, and 11 kDa) showed IgE reactivity in all (100%) of the tested sera, and they were identified as salivary secreted antigen 5-related protein, salivary serine protease, erythema protein, and hypothetical secreted protein, respectively. Three other proteins, salivary serine protease (25 kDa), salivary D7 secreted protein (22 kDa), and hypothetical protein (13 kDa), reacted with > 50% of the sera. The relevance of the identified protein bands as allergens needs to be confirmed by using pure recombinant proteins, either in the in vivo skin prick test or in vitro detection of the specific IgE in the serum samples of allergic subjects. This will be useful for the rational design of component-resolved diagnosis and allergen immunotherapy for the allergy mediated by the bites of black flies.
The geographical distribution of tuberculosis (TB) overlaps with various parasitic infections. Uncovering the characteristics of coinfecting parasites that potentially affect the host susceptibility to TB is pertinent as it may provide input to current TB therapeutic and prophylactic measures. The present study was aimed at examining the types of parasitic infections in TB patients and healthy TB contacts (HC) in Orang Asli, Malaysian aborigines, who dwelled in the co-endemic areas. Stool and serum samples were collected from Orang Asli who fulfilled the selection criteria and provided written informed consents. Selected parasitic infections in the two study groups were determined by stool examination and commercial serum antibody immunoassays. The prevalence of parasitic infections in TB and HC participants were 100% (n = 82) and 94.6% (n = 55) respectively. The parasitic infections comprised toxocariasis, trichuriasis, amoebiasis, toxoplasmosis, hookworm infection, ascariasis, strongyloidiasis, and brugian filariasis, in decreasing order of prevalence. Overall, helminth or protozoa infection did not show any significant association with the study groups. However, when the species of the parasite was considered, individuals exposed to trichuriasis and toxoplasmosis showed significant odds reduction (odds ratio (OR) 0.338; 95% confidence interval (CI) 0.166, 0.688) and odds increment (OR 2.193; 95% CI 1.051, 4.576) to have active pulmonary TB, respectively. In conclusion, trichuriasis and toxoplasmosis may have distinct negative and positive associations respectively with the increase of host susceptibility to TB.
Eliminating the Plasmodium vivax malaria parasite infection remains challenging. One of the main problems is its capacity to form hypnozoites that potentially lead to recurrent infections. At present, primaquine is the only drug used for the management of hypnozoites. However, the effects of primaquine may differ from one individual to another. The aim of this work is to determine new measures to reduce P. vivax recurrence, through primaquine metabolism and host genetics. A genetic study of MAO-A, CYP2D6, CYP1A2 and CYP2C19 and their roles in primaquine metabolism was undertaken of healthy volunteers (n = 53). The elimination rate constant (Ke) and the metabolite-to-parent drug concentration ratio (Cm/Cp) were obtained to assess primaquine metabolism. Allelic and genotypic analysis showed that polymorphisms MAO-A (rs6323, 891G>T), CYP2D6 (rs1065852, 100C>T) and CYP2C19 (rs4244285, 19154G>A) significantly influenced primaquine metabolism. CYP1A2 (rs762551, -163C>A) did not influence primaquine metabolism. In haplotypic analysis, significant differences in Ke (p = 0.00) and Cm/Cp (p = 0.05) were observed between individuals with polymorphisms, GG-MAO-A (891G>T), CT-CYP2D6 (100C>T) and GG-CYP2C19 (19154G>A), and individuals with polymorphisms, TT-MAO-A (891G>T), TT-CYP2D6 (100C>T) and AA-CYP2C19 (19154G>A), as well as polymorphisms, GG-MAO-A (891G>T), TT-CYP2D6 (100C>T) and GA-CYP2C19 (19154G>A). Thus, individuals with CYP2D6 polymorphisms had slower primaquine metabolism activity. The potential significance of genetic roles in primaquine metabolism and exploration of these might help to further optimise the management of P. vivax infection.
A morphological and molecular phylogenetic study of proteocephalid tapeworms of the genus Acanthotaenia von Linstow, 1903, parasites of monitors (Varanidae), was carried out. The type species, A. shipleyi von Linstow, 1903, which was originally described based on an immature specimen from Sri Lanka, is redescribed based on new material from the type host, Varanus salvator, in Sri Lanka, Malaysia, and Vietnam, and its neotype is designated. In addition, Acanthotaenia susanae n. sp. is described from Varanus nebulosus in Vietnam. The new species differs from congeners by the large size of the scolex, width of the rostellum and the number of testes. New molecular data (sequences of lsrDNA and cox1) revealed Acanthotaenia paraphyletic with the inclusion of Australotaenia bunthangi de Chambrier & Scholz, 2012, a parasite of Enhydris enhydris (Ophidia: Homalopsidae) in Cambodia. Molecular data confirm a wide distribution of A. shipleyi (isolates from Malaysia and Vietnam were almost identical) and indicate a strict host specificity (oioxeny) of individual species of the genus. Type specimens of four species made it possible to supplement their morphological descriptions. A survey of all species of Acanthotaenia recognised as valid is presented and the following taxonomic changes are proposed: Acanthotaenia pythonis Wahid, 1968 described from the green python, Morelia viridis, in a zoo, is transferred to Kapsulotaenia as Kapsulotaenia pythonis (Wahid, 1968) n. comb., because it possesses intrauterine eggs grouped in capsules. Acanthotaenia gracilis (Beddard, 1913) from Varanus varius in Australia is considered to be species inquirenda because its original descriptions did not contain sufficient data for adequate circumscription and differentiation from congeners and type material was not available. Generic diagnosis of Acanthotaenia is amended and a key to its seven species is provided.
Acanthamoeba castellanii belonging to the T4 genotype is an opportunistic pathogen which is associated with blinding eye keratitis and rare but fatal central nervous system infection. A. castellanii pose serious challenges in antimicrobial chemotherapy due to its ability to convert into resistant, hardy shell-protected cyst form that leads to infection recurrence. The fatty acid composition of A. castellanii trophozoites is known to be most abundant in oleic acid which chemically is an unsaturated cis-9-Octadecanoic acid and naturally found in animal and vegetable fats and oils. This study was designed to evaluate antiacanthamoebic effects of oleic acid against trophozoites, cysts as well as parasite-mediated host cell cytotoxicity. Moreover, oleic acid-conjugated silver nanoparticles (AgNPs) were also synthesized and tested against A. castellanii. Oleic acid-AgNPs were synthesized by chemical reduction method and characterized by ultraviolet-visible spectrophotometry, atomic force microscopy, dynamic light scattering analysis, and Fourier transform infrared spectroscopy. Viability, growth inhibition, encystation, and excystation assays were performed with 10 and 5 μM concentration of oleic acid alone and oleic acid-conjugated AgNPs. Bioassays revealed that oleic acid alone and oleic acid-conjugated AgNPs exhibited significant antiamoebic properties, whereas nanoparticle conjugation further enhanced the efficacy of oleic acid. Phenotype differentiation assays also showed significant inhibition of encystation and excystation at 5 μM. Furthermore, oleic acid and oleic acid-conjugated AgNPs also inhibited amoebae-mediated host cell cytotoxicity as determined by lactate dehydrogenase release. These findings for the first time suggest that oleic acid-conjugated AgNPs exhibit antiacanthamoebic activity that hold potential for therapeutic applications against A. castellanii.