Endometrial receptivity and embryo implantation in carnivores-commonalities and differences with other mammalian species

Endometrial receptivity and embryo implantation processes are a major point of pregnancy failure in many mammalian species, including humans. Although reproductive biology in many carnivore species remains enigmatic, the few that have been studied so far are invaluable comparative models. The goals of this review are to (1) summarize current data on the mechanisms involved in uterine receptivity and embryo implantation in carnivores, including commonalities and differences with other mammalian species and (2) identify research priorities to better understand a key phenomenon in a critical group of mammals. Besides unique reproductive traits in some carnivores (induced vs. spontaneous ovulation in cats, ovulation at the germinal vesicle stage in dogs), preimplantation embryo development is comparable with other orders. However, the timing of implantation varies, especially in species having an embryonic diapause. Mechanisms involved in endometrial receptivity and decidualization still remain to be fully understood, but specific markers have already been identified. Importantly, the use of endogenous hormones to control the ovarian activity may impact endometrial receptivity and subsequent embryo implantation. Next, research efforts should take advantage of advanced technologies to further study embryo implantation in carnivores and to provide more relevant models to reproductive medicine or for the conservation of rare and endangered species.

Parasite Specific Antibody Levels, Interferon-γ and TLR2 and TLR4 Transcripts in Blood from Dogs with Different Clinical Stages of Leishmaniosis

Canine leishmaniosis has a wide range of disease severity from mild (stage I), to severe (stages II–III), or very severe disease (stage IV). The objective of the study was to evaluate and compare serum antibody levels, Leishmania infantum specific IFN-γ production and TLR2 and TLR4 transcripts in non-stimulated blood from dogs with different clinical stages at the time of diagnosis as well as blood parasitemia. Enzyme-Linked ImmunoSorbent Assay (ELISAs) were performed to determine serum antibody levels and IFN-γ production and quantitative polymerase chain reaction (qPCRs) in order to determine blood parasite load and TLR2 and TLR4 transcripts. Older dogs were significantly affected by more severe disease with higher antibody levels and blood parasitemia than dogs with mild disease. IFN-γ production was significantly higher in dogs with stage I disease when compared to dogs with more severe disease. Relative quantification of TLR2 in dogs with mild disease was similar to that of control dogs. On the other hand, TLR2 transcripts were significantly higher in dogs with severe disease as compared with that from control healthy dogs. No differences were found in TLR4 relative quantification between groups. This study demonstrates that dogs with different clinical stages of leishmaniosis present different levels of biological markers indicative of different immune responses.

TLR-2 and TLR-4 transcriptions in unstimulated blood from dogs with leishmaniosis due to Leishmania infantum at the time of diagnosis and during follow-up treatment

Innate immunity, in particular, the role of toll-like receptors (TLRs), has not been extensively studied in canine L. infantum infection. The main aim of this study was to determine the transcription of TLR2 and TLR4 in the blood of dogs with natural clinical leishmaniosis at the time of diagnosis and during treatment follow-up and subsequently correlate these findings with clinical, serological and parasitological data. Forty-six Leishmania-seropositive sick dogs with a high antibody level at the time of diagnosis were studied and compared with 34 healthy seronegative dogs. Twenty-two of these sick dogs were treated with meglumine antimoniate and allopurinol and followed-up at 30, 180 and 365days following the start of treatment. Clinical status was defined by a thorough physical examination, complete blood count, biochemistry profile, electrophoresis of serum proteins, and urinary protein/creatinine ratio (UPC). EDTA blood was stored in RNAlater^® solution before RNA extraction and cDNA production were performed. TLR2, TLR4 and three reference genes (HPRT-1, CG14980 and SDHA) were studied in each blood sample by real time PCR. The relative quantification of TLR2 was higher (mean 3.5) in sick dogs when compared with seronegative healthy dogs (mean 1.3; P=0.0001) while the relative quantification of TLR4 was similar in both groups. In addition, the relative quantification of TLR2 significantly decreased during follow-up at all time points compared with day 0 whereas no changes were observed with TLR4 transcription. A significant positive correlation was noted between TLR2 and UPC, total protein, beta and gamma globulins, specific L. infantum antibodies and blood parasite load while a negative correlation was observed with albumin, albumin/globulin ratio, hematocrit and hemoglobin. TLR4 transcript did not correlate with any parameter. These findings indicate an up-regulation of TLR2 transcription in unstimulated blood in naturally infected sick dogs as compared to healthy dogs suggesting active innate immune and proinflammatory responses. In addition, TLR2 transcription is reduced with clinical improvement during treatment. In contrast, TLR4 transcription appears to be similar among groups at the time of diagnosis with no changes during treatment follow-up suggesting a less important role for this TLR in clinical canine leishmaniosis.

Histopathological findings and detection of Toll-like receptor 2 in cutaneous lesions of canine leishmaniosis

A broad spectrum of clinical manifestations ranging from a chronic subclinical infection to a non-self-limiting illness has been described for canine leishmaniosis (CanL). This clinical variation is determined by a variable immune response, presumably genetically determined, against the infection. Although different types of adaptive immune response in dogs with CanL have been investigated in several studies, the mechanisms that underlie and determine this variability are still poorly understood. It is currently thought that innate immune response, and particularly the role of specific mediators of the innate immune system, such as toll-like receptors (TLRs), plays a central role in this polarization. However, there is limited data available concerning the role that TLRs play in canine Leishmania infantum infection. The objective of this descriptive study was to characterize and compare the inflammatory pattern, the Leishmania burden and expression of TLR2 in skin lesions derived from dogs with different clinical stages of leishmaniosis and cutaneous lesions. Routine histology, Leishmania and TLR2 immunohistochemistry assays were performed in 11 patients with papular dermatitis (stage I - mild disease) and 10 patients with other cutaneous lesions (stage II-III - moderate to severe disease). A significantly higher frequency of granuloma formation was demonstrated in skin samples of dogs with stage I when compared with dogs of stage II-III. Although not statistically significant, a trend for a lower parasite burden was observed for skin lesions of dogs with stage I when compared with dogs of stage II-III. A lower expression of TLR2 in skin biopsies from dogs with stage I was statistically significant compared with stage II-III. The results obtained in this study indicated an association with TLR2 in the pathogenesis of canine cutaneous leishmaniosis. Further studies are required to fully elucidate these findings.