Clinical Improvement of Disseminated Acanthamoeba Infection in a Patient with Advanced HIV Using a Non-Miltefosine-Based Treatment Regimen in a Low-Resource Setting

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.

The role of apoptosis and oxidative stress in the pathophysiology of Acanthamoeba spp. infection in the kidneys of hosts with different immunological status

BACKGROUND

Acanthamoeba spp. are opportunistic pathogens that cause inflammation, mostly in the brain, lungs and cornea. Recent reports indicate kidney dysfunction in hosts with systemic acanthamoebiasis. The aim of the study was to analyze the gene expression and protein concentration of NADPH oxidase 2 and 4 (NOX2 and NOX4, respectively) and nuclear erythroid 2-related factor (Nrf2) in the kidneys of hosts with systemic acanthamoebiasis. We also aimed to determine the protein and gene expressions of Bcl2, Bax, caspases 3 and 9.

METHODS

 Mice were divided into four groups based on their immunological status and Acanthamoeba sp. infection: A, immunocompetent Acanthamoeba sp.-infected mice; AS, immunosuppressed Acanthamoeba sp.- infected mice; C, immunocompetent uninfected mice; CS, immunosuppressed uninfected mice. NOX2, NOX4 and Nrf2 were analyzed by quantitative reverse transcription PCR (qRT-PCR) and ELISA methods, while pro-apoptotic and anti-apoptotic proteins (Bax and Bcl-2, respectively), Cas9, Cas3 were analyzed by qRT-PCR and western blot methods.  RESULTS: Increased gene expression and/or protein concentration of NOX2 and NOX4 were found in both immunocompetent and immunosuppressed mice infected with Acanthamoeba sp. (groups A and AS, respectively). Gene expression and/or protein concentration of Nrf2 were higher in group A than in control animals. Compared to control mice, in the AS group the expression of the Nrf2 gene was upregulated while the concentration of Nrf2 protein was decreased. Additionally in A group, higher gene and protein expression of Bcl-2, and lower gene as well as protein expression of Bax, caspases 3 and 9 were noted. In contrast, the AS group showed lower gene and protein expression of Bcl-2, and higher gene as well as protein expression of Bax, caspases 3 and 9.

CONCLUSIONS

This study is the first to address the mechanisms occurring in the kidneys of hosts infected with Acanthamoeba sp. The contact of Acanthamoeba sp. with the host cell surface and/or the oxidative burst caused by elevated levels of NOXs lead to an antioxidant response enhanced by the Nrf2 pathway. Acanthamoeba sp. have various strategies concerning apoptosis. In immunocompetent hosts, amoebae inhibit the apoptosis of kidney cells, and in immunosuppressed hosts, they lead to increased apoptosis by the intrinsic pathway and thus to a more severe course of the disease.

Extracellular Vesicles Secreted by Acanthamoeba culbertsoni Have COX and Proteolytic Activity and Induce Hemolysis

Several species of Acanthamoeba genus are potential pathogens and etiological agents of several diseases. The pathogenic mechanisms carried out by these amoebae in different target tissues have been documented, evidencing the relevant role of contact-dependent mechanisms. With the purpose of describing the pathogenic processes carried out by these protozoans more precisely, we considered it important to determine the emission of extracellular vesicles (EVs) as part of the contact-independent pathogenicity mechanisms of A. culbertsoni, a highly pathogenic strain. Through transmission electronic microscopy (TEM) and nanoparticle tracking analysis (NTA), EVs were characterized. EVs showed lipid membrane and a size between 60 and 855 nm. The secretion of large vesicles was corroborated by confocal and TEM microscopy. The SDS-PAGE of EVs showed proteins of 45 to 200 kDa. Antigenic recognition was determined by Western Blot, and the internalization of EVs by trophozoites was observed through Dil-labeled EVs. In addition, some EVs biological characteristics were determined, such as proteolytic, hemolytic and COX activity. Furthermore, we highlighted the presence of leishmanolysin in trophozites and EVs. These results suggest that EVs are part of a contact-independent mechanism, which, together with contact-dependent ones, allow for a better understanding of the pathogenicity carried out by Acanthamoeba culbertsoni.

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.