Search

Spontaneous tumors are a major cause of death in cats. Treatment of human tumors has progressed dramatically in the past decade, partly due to the success of immunotherapies using immune checkpoint inhibitors, such as anti-programmed death 1 (PD-1) and anti-PD-ligand 1 (PD-L1) antibodies. However, little is known about the PD-1 pathway and its association with tumor disease in cats. This study investigated the applicability of anti-PD-1/PD-L1 therapy in feline tumors. We first determined the complete coding sequence of feline PD-L1 and PD-L2, and found that the deduced amino acid sequences of feline PD-L1/PD-L2 share high sequence identities (66–83%) with orthologs in other mammalian species. We prepared recombinant feline PD-1, PD-L1, and PD-L2 proteins and confirmed receptor–ligand binding between PD-1 and PD-L1/PD-L2 using flow cytometry. Next, we established an anti-feline PD-L1 monoclonal antibody (clone CL1Mab-7) to analyze the expression of PD-L1. Flow cytometry using CL1Mab-7 revealed the cell surface expression of PD-L1 in a feline macrophage (Fcwf-4) and five mammary adenocarcinoma cell lines (FKNp, FMCm, FYMp, FONp, and FONm), and showed that PD-L1 expression was upregulated by interferon-γ stimulation. Finally, immunohistochemistry using CL1Mab-7 also showed PD-L1 expression in feline squamous cell carcinoma (5/5, 100%), mammary adenocarcinoma (4/5, 80%), fibrosarcoma (5/5, 100%), and renal cell carcinoma (2/2, 100%) tissues. Our results strongly encourage further investigations of the PD-1/PD-L1 pathway as a potential therapeutic target for feline tumors. [ABSTRACT FROM AUTHOR]

Subacute and chronic infections with the intracellular protozoan parasite Toxoplasma gondii are associated with an increased risk of psychiatric diseases like schizophrenia. However, little is known about the mechanisms involved in T. gondii-induced neuronal disorders. Recently, we reported that Toll-like receptor 2 (TLR2) was required to initiate the innate immune response in cultured mouse brain cells. However, how TLR2 contributes to latent infection with T. gondii remains unclear. Therefore, we examined the role of TLR2 in brain pathology and behavior using wild-type (TLR2+/+) and TLR2-deficient (TLR2-/-) mice. The behavioral analyses showed that TLR2 deficiency increased the anxiety state of the uninfected and infected animals alike, and TLR2 deficiency showed no relationship with the infection. In the contextual and cued fear-conditioning tests, T. gondii infection decreased the mouse freezing reaction while TLR2 deficiency increased it, but there was no interaction between the two factors. Our histopathological analysis showed that the TLR2+/+ and TLR2-/- mice had similar brain lesions at 30 days post infection (dpi) with T. gondii. Higher numbers of parasites were detected in the brains of the TLR2-/- mice than in those from the TLR2+/+ mice at 30 dpi, but not at 7 and 14 dpi. No significant differences were observed in the proinflammatory gene expression levels in the TLR2+/+ and TLR2-/- mice. Therefore, it appears that TLR2 signaling in the brain might contribute to the control of parasite growth, but not to brain pathology or the impaired fear memory response induced by infection with T. gondii. [ABSTRACT FROM AUTHOR]

The apical complex of T oxoplasma gondii enables it to invade virtually all nucleated cells in warm-blooded animals, including humans, making it a parasite of global importance. Anti- T . gondii cellular defence mechanisms depend largely on interferon ( IFN)-γ production by immune cells. However, the molecular mechanism of IFN-β-mediated defence remains largely unclear. Here, mouse peritoneal macrophages and murine embryonic fibroblasts ( MEFs) primed with recombinant IFN-β and IFN-γ showed different pathways of activation. Treatment of these cells with IFN-β or IFN-γ inhibited T. gondii (type II PLK strain) growth. Priming macrophages with IFN-β had no effect on inflammatory cytokine expression, inducible nitric oxide synthase or indoleamine 2,3-dioxygenase, nor did it have an effect on their metabolites, nitric oxide and kynurenine respectively. In contrast, IFN-γ stimulation was characterized by classical macrophage activation and T . gondii elimination. IFN-β activation recruited the immunity-related GTPase M1 ( IRGM1) to the parasitophorous vacuole in the macrophages and MEFs. Anti-toxoplasma activities induced by IFN-β were significantly reduced after IRGM1 knockdown in murine macrophages and in IRGM1-deficient MEFs. Thus, this study unravels an alternative pathway of macrophage activation by IFN-β and provides a mechanistic explanation for the contribution of IRGM1 induced by IFN-β to the elimination of T . gondii. [ABSTRACT FROM AUTHOR]

Background Neospora caninum, a Toxoplasma gondii-like obligate intracellular parasite, causes abortion in cattle and neurological signs in canines. To understand neosporosis better, studies on host cell migration and host immune responses during the early phase of infection are important. Although the C-C chemokine receptor 5 (CCR5) plays a crucial role in immune cell migration, the role played by it in protective immunity against N. caninum is poorly understood. Methods CCR5-/- mice were used to investigate their sensitivity levels to N. caninum infection and their ability to activate immune cells against this parasite. Results Increased mortality and neurological impairment were observed in the N. caninum-infected CCR5-/- mice. In comparison with wild-type mice, CCR5-/- mice experienced poor migration of dendritic cells and natural killer T cells to the site of infection. Dendritic cells in an in vitro culture from CCR5-/- mice could not be activated upon infection with N. caninum. Furthermore, higher levels of IFN-γ and CCL5 expression, which are associated with brain tissue damage, were observed in the brain tissue of CCR5-/- mice during the acute phase of the infection, while there was no significant difference in the parasite load between the wild-type and CCR5-/- animals. Additionally, a primary microglia culture from CCR5-/- mice showed lower levels of IL-6 and IL-12 production against N. caninum parasites. Conclusions Our findings show that migration and activation of immune cells via CCR5 is required for controlling N. caninum parasites during the early phase of the infection. [ABSTRACT FROM AUTHOR]

Neospora caninum is a protozoan parasite that causes neurological disorders in dogs and cattle. It can cause nonsuppurative meningoencephalitis and a variety of neuronal symptoms are observed, particularly in dogs. However, the pathogenic mechanism, including the relationship between the parasite distribution and the clinical signs, is unclear. In this study, to understand the pathogenic mechanism of neosporosis, parasite distribution and lesions were assessed in the brain of mice infected with N. caninum (strain Nc-1). Host gene expression was also analyzed with RNA sequencing (RNA-Seq). The histopathological lesions in the frontal lobe and the medulla oblongata were significantly more severe in symptomatic mice than in asymptomatic mice, although no association between the severity of the lesions and parasite numbers was found. In infected mice, the expression of 772 mouse brain genes was upregulated. A GOstat analysis predicted that the upregulated genes were involved in the host immune response. Genes whose expression correlated positively and negatively with parasite numbers were involved in the host immune response, and neuronal morphogenesis and lipid metabolic processes, respectively. These results suggest that changes in the gene expression profile associated with neuronal functions as well as immune responses can contribute to the pathogenesis in N. caninum-infected animals. [ABSTRACT FROM AUTHOR]

Neospora caninum causes abortion and stillbirth in cattle. Identification of effective drugs against this parasite remains a challenge. Previous studies have suggested that disruption of abscisic acid (ABA)-mediated signaling in apicomplexan parasites such as Toxoplasma gondii offers a new drug target. In this study, the ABA inhibitor, fluridone (FLU), was evaluated for its action against N. caninum . Production of endogenous ABA within N. caninum was confirmed by ultra-performance liquid chromatography–tandem quadruple mass spectrometry. Subsequently, FLU treatment efficacy was assessed using in vitro . Results revealed that FLU inhibited the growth of N. caninum and T. gondii in vitro (IC 50 143.1 ± 43.96 μM and 330.6 ± 52.38 μM, respectively). However, FLU did not affect parasite replication at 24 h post-infection, but inhibited egress of N. caninum thereafter. To evaluate the effect of FLU in vivo , N. caninum -infected mice were treated with FLU for 15 days. FLU treatment appeared to ameliorate acute neosporosis induced by lethal parasite challenge. Together, our data shows that ABA might control egress in N. caninum . Therefore, FLU has potential as a candidate drug for the treatment of acute neosporosis. [ABSTRACT FROM AUTHOR]

Highlights: [•] We confirmed the immunogenicity of TgPF in mice after Toxoplasma gondii infection. [•] TgPF-OML administration increased the survival of mice after Toxoplasma gondii infection. [•] TgPF-OML administration reduced the parasite burden in mouse brains after infection. [•] Immunization with TgPF-OML induced TgPF-specific interferon-γ and IgG production. [Copyright &y& Elsevier]