Morphological Description of the Early Events during the Invasion of Acanthamoeba castellanii Trophozoites in a Murine Model of Skin Irradiated under UV-B Light

Toll-like receptors and inflammatory cytokines in the skin of Acanthamoeba spp. infected immunocompetent and immunosuppressed mice

Acanthamoeba spp. can cause opportunistic infections, such as cutaneous acanthamoebiasis (CA). Little is known about the role of TLRs and cytokines in the host skin during Acanthamoeba spp. infections. The study aimed to examine the gene and protein expression of TLR3, TLR7, IFN-γ, and IL-23 in the skin of mice experimentally infected with a clinical strain of Acanthamoeba spp. male BALB/c mice were assigned to four groups: group I (control group I) - with normal immunity (C, n = 5); group II (control group II) - with reduced immunity induced by methylprednisolone sodium succinate (MPS; CS, n = 5); group III - amoeba-infected hosts with normal immunity (A, n = 12); and group IV- amoeba-infected hosts with reduced immunity induced by MPS (AS, n = 12). The skin sections (2 cm × 2 cm) were collected from the animals at 8, 16, and 24 days post-infection (dpi). TLR3, TLR7, IFN-γ, and IL-23 gene and protein expressions were analyzed by quantitative real-time PCR and immunohistochemical staining. In the immunocompetent hosts, we noted higher expressions of TLR3 and IL-23 at all-time points, except 8th dpi when IL-23 gene expression was downregulated compared to the control group. The mRNA expressions of TLR7 and IFN-γ were higher at 16 and 24 dpi in the skin of immunocompetent Acanthamoeba spp.-infected hosts than in the uninfected mice. In the course of acanthamoebiasis in the mice with reduced immunity, we found significant upregulation of TLR3, IL-23, and TLR7 gene expressions only at the beginning of infection compared to the control group. A similar relationship was observed for IFN-γ at 8 and 16 dpi. The pathophysiology of Acanthamoeba infection in the skin is complex. The data presented in this paper add new insight, but they are not sufficient to explain the role of the studied receptors and cytokines. The clinical picture and mechanisms of host response appear to be influenced by the route of infection, immunological status and microorganisms carried within the parasites. CA remains a multifactorial phenomenon.

Staurosporine as a Potential Treatment for Acanthamoeba Keratitis Using Mouse Cornea as an Ex Vivo Model

Acanthamoeba is a ubiquitous genus of amoebae that can trigger a severe and progressive ocular disease known as Acanthamoeba Keratitis (AK). Furthermore, current treatment protocols are based on the combination of different compounds that are not fully effective. Therefore, an urgent need to find new compounds to treat Acanthamoeba infections is clear. In the present study, we evaluated staurosporine as a potential treatment for Acanthamoeba keratitis using mouse cornea as an ex vivo model, and a comparative proteomic analysis was conducted to elucidate a mechanism of action. The obtained results indicate that staurosporine altered the conformation of actin and tubulin in treated trophozoites of A. castellanii. In addition, proteomic analysis of treated trophozoites revealed that this molecule induced overexpression and a downregulation of proteins related to key functions for Acanthamoeba infection pathways. Additionally, the ex vivo assay used validated this model for the study of the pathogenesis and therapies of AK. Finally, staurosporine eliminated the entire amoebic population and prevented the adhesion and infection of amoebae to the epithelium of treated mouse corneas.

Acanthamoeba castellanii trophozoites that survive multipurpose solutions are able to adhere to cosmetic contact lenses, increasing the risk of infection

Amoebae of the genus Acanthamoeba are etiological agents of amoebic keratitis, for which up to now there is no treatment of choice and one of its main risk factors is the use of contact lenses, including cosmetic contact lenses. Recently there has been an increase in amoebic keratitis cases due to the use of cosmetic contact lenses. Therefore, having a solution for the care of lenses with an efficient disinfectant effect that prevents the adhesion of trophozoites to lenses becomes essential. This study was carried out to determine the effect of 8 multipurpose contact lenses care solutions on Acanthamoeba castellanii trophozoites viability, and the efficiency of two of them to prevent the trophozoites adherence onto two cosmetic contact lenses (Acuvue 2, approved by the US Food and Drug Administration, and Magic Eye CCL, not approved). After 3 h of interaction, only AO Sept Plus, OPTI FREE Replenish, Renu Plus, Bio True and Multiplus significantly reduced the number of viable trophozoites with respect to the control; at 6 h Renu Plus, and at 12 h Conta Soft Plus and Multiplus, maintained the inhibitory effect. Only Opti Free Pure Moist did not significantly reduce the number of viable trophozoites. Multiplus and Opti Free Pure Moist (selected for their greater and lesser antiamibic effect) significantly reduced trophozoite adherence to both lenses; however, Opti Free Pure Moist was more efficient, despite the fact that A. castellanii adhered similarly to both lenses. Our results show that in all the multipurpose solutions evaluated, hundreds of viable A. castellanii trophozoites remain after several hours of incubation. Therefore, storage of the lenses in their case with MPS maintains the potential risk of amoebic keratitis in, cosmetic contact lenses wearers. Moreover, the use of CCL, not approved by the FDA, can increase the risk factor for AK since its poor manufacture can favor the permanence of amoebae, in addition to being a risk for corneal integrity.

The Immunological Changes in the Skin of BALC/c Mice with Disseminated Acanthamoebiasis

Toll-like receptors (TLR) are involved in the recognition of numerous pathogens, including Acanthamoeba spp. Thanks to this, it is possible for immune cells to recognize microorganisms and trigger the body's innate immune response. The stimulation of TLRs also leads to the activation of specific immunity. The aim of the study was to determine the TLR2 and TLR4 gene expression in the skin of BALC/c mice infected with Acanthamoeba with AM22 strain isolated from a patient. Receptor expression was assessed by real-time polymerase chain reaction (qPCR) in the amoeba-infected host with normal (A) and reduced immunity (AS) as well as in the control host with normal immunity (C) and reduced immunity (CS). Statistical analysis of TLR2 gene expression in A and AS groups compared to C and CS groups, respectively, were statistically insignificant. In the A group, we found statistical upregulation of TLR4 gene expression at 8 dpi compared to the C group. While in AS group, TLR4 gene expression was at a similar level, such as in the CS group. Taking into account the host's immune status, the TLR4 gene expression was statistically higher in the skin of host from A group than in host from AS group at the beginning of the infection. Increased TLR4 gene expression in hosts with normal immunity infected with Acanthamoeba suggests the involvement of the studied receptor in the course of acanthamoebiasis. The above research results provide new data on the involvement of the studied receptor in the skin in the host's immune defense triggered during the Acanthamoeba infection.

Three encephalitis-causing amoebae and their distinct interactions with the host

Naegleria fowleri, Balamuthia mandrillaris, and Acanthamoeba spp. can cause devastating brain infections in humans which almost always result in death. The symptoms of the three infections overlap, but brain inflammation and the course of the disease differ, depending on the amoeba that is responsible. Understanding the differences between these amoebae can result in the development of strategies to prevent and treat these infections. Recently, numerous scientific advancements have been made in the understanding of pathogenicity mechanisms in general, and the basic biology, epidemiology, and the human immune response towards these amoebae in particular. In this review, we combine this knowledge and aim to identify which factors can explain the differences between the lethal brain infections caused by N. fowleri, B. mandrillaris, and Acanthamoeba spp.