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

Effect of Local Administration of Meglumine Antimoniate and Polyhexamethylene Biguanide Alone or in Combination with a Toll-like Receptor 4 Agonist for the Treatment of Papular Dermatitis due to Leishmania infantum in Dogs

Papular dermatitis is a cutaneous manifestation of canine Leishmania infantum infection associated with mild disease. Although it is a typical presentation, nowadays, there is still no established treatment. This study evaluated the safety and clinical efficacy of local meglumine antimoniate, locally administered polyhexamethylene biguanide (PHMB) alone or PHMB in combination with a Toll-like receptor 4 agonist (TLR4a) for the treatment of papular dermatitis due to L. infantum and assessed parasitological and immunological markers in this disease. Twenty-eight dogs with papular dermatitis were divided randomly into four different groups; three of them were considered treatment groups: PHMB (n = 5), PHMB + TLR4a (n = 4), and meglumine antimoniate (n = 10)), and the remaining were considered the placebo group (n = 9), which was further subdivided into two sub-groups: diluent (n = 5) and TLR4a (n = 4). Dogs were treated locally every 12 h for four weeks. Compared to placebo, local administration of PHMB (alone or with TLR4a) showed a higher tendency towards resolution of papular dermatitis due to L. infantum infection at day 15 (χ² = 5.78; df = 2, p = 0.06) and day 30 (χ² = 4.; df = 2, p = 0.12), while local meglumine antimoniate administration demonstrated the fastest clinical resolution after 15 (χ² = 12.58; df = 2, p = 0.002) and 30 days post-treatment (χ² = 9.47; df = 2, p = 0.009). Meglumine antimoniate showed a higher tendency towards resolution at day 30 when compared with PHMB (alone or with TLR4a) (χ² = 4.74; df = 2, p = 0.09). In conclusion, the local administration of meglumine antimoniate appears to be safe and clinically efficient for the treatment of canine papular dermatitis due to L. infantum infection.

Seroprevalence of canine leishmaniosis in asymptomatic dogs in Kosovo

Canine leishmaniosis (CanL) is a neglected zoonotic disease caused by Leishmania spp. Leishmania infantum is the species responsible for the zoonotic form of the disease where dogs are reservoir hosts. This study aimed to determine the seroprevalence of CanL in asymptomatic dogs in Kosovo. Blood samples were collected from 285 dogs in all seven regions in Kosovo (35-50 samples per region) from summer 2021 to spring 2022. Sera were tested using enzyme-linked immunosorbent assay (ELISA), and the presence of anti-Leishmania IgG was confirmed by an indirect fluorescent antibody test (IFAT). The true overall seroprevalence of CanL of asymptomatic dogs in Kosovo with ELISA was 4.21% (95% CI: 2.42-7.21) while with IFAT was 3.51% (95% CI: 1.92-6.34). The highest rates were found in the Prishtina region to be 8.0% (4/50) by ELISA and 6.0% (3/50) by IFAT, and in the Mitrovica region, the prevalence was 0% (0/40). There were no significant differences among the different regions, gender, age, health status, and breed. These findings highlight the presence of CanL in most regions of Kosovo and underline the veterinary relevance of clinically asymptomatic dogs infected with Leishmania.

Humoral Responses and Ex Vivo IFN-γ Production after Canine Whole Blood Stimulation with Leishmania infantum Antigen or KMP11 Recombinant Protein

The effect of Leishmania infantum soluble antigen (LSA) and recombinant Kinetoplastid Membrane Protein 11 (rKMP11) on the induction of ex vivo specific IFN-γ (n = 69) and antibody responses (n = 108) was determined in dogs. All dogs were tested for serological response to both antigens and divided into Group 1: healthy (Asturias, Spain, n = 26), Group 2: sick (n = 46), Group 3: healthy Ibizan hounds (Mallorca, Spain, n = 22) and Group 4: healthy (Bari, Italy, n = 14). Antibody levels were higher for LSA when compared to rKMP11 (p = 0.001). Ibizan hounds were all seronegative to rKMP11 and 18% were low seropositive to LSA. Sick dogs presented higher antibody response to both antigens compared to the rest of the groups (p < 0.0001). All groups showed higher IFN-γ levels after LSA compared to rKMP11 responses (p < 0.05). The highest response to LSA was found in Ibizan hounds (p < 0.05). IFN-γ to LSA and rKMP11 stimulation was observed in 34% and in 2.8% of the sick dogs, respectively. Here, we demonstrated that anti-rKMP11 antibodies are mainly present in dogs with moderate to severe disease. Furthermore, cellular immune response measured by specific ex vivo IFN-γ production was more intense to LSA than stimulated to rKMP11.

Skin Lesions in Feline Leishmaniosis: A Systematic Review

Feline leishmaniosis (FeL) is increasingly reported throughout the world and skin lesions predominate in the clinical picture. There are, however, few evidence-based data on cutaneous feline leishmaniosis and directions are strongly needed for a better management of the disease. In this study, we systematically reviewed what is currently known about the clinical dermatological presentation of FeL through analysis of the literature and, further, by adding unpublished cases managed by Italian veterinary dermatologists. Sixty-six feline cases of cutaneous leishmaniosis published in 33 articles between 1990 and 2020 met the inclusion criteria and were analyzed. Six unpublished cases of cutaneous FeL managed by Italian dermatologists were also reviewed. The majority of cases were reported from South America, followed by Europe and North America. Nodules were the most frequently reported clinical signs and the presence of Leishmania in lesioned skin was assessed mainly by cytology. A total of six Leishmania species have been identified as being responsible for skin lesions. Coinfections by FIV or FeLV were reported in 12.1% and 9.1% of the cases, respectively. Clinical data including treatment have been analyzed and discussed to provide directives for proper management of the disease for which cats may also serve as domestic reservoirs for human infections.

Toll-Like Receptors 2, 4, and 7, Interferon-Gamma, Interleukin 10, and Programmed Death Ligand 1 Transcripts in Leishmanin Skin Test-Positive Reactions of Ibizan Hound Dogs

The leishmanin skin test (LST) is an in vivo technique commonly used to evaluate the Leishmania-specific cellular immune response in dogs. However, information regarding the local immune response in LST-positive reactions is scarce. We examined the pattern of toll-like receptor 2 (TLR2), TLR4, TLR7, interleukin- (IL-) 10, interferon gamma (IFN-γ), and (program death ligand) PD-L1 gene expression in LST-positive reactions and paired normal-looking skin of nine infected Ibizan hound dogs. Healthy skin from ten seronegative dogs from a nonendemic area was analysed as a negative control. Immune gene expressions were examined by quantitative PCR (qPCR) analysis. LST-positive reactions presented significant upregulation of TLR2, TLR4, IL-10, IFN-γ, and PD-L1 and downregulation of TLR7 when compared with healthy skin of seronegative control dogs from a nonendemic area. All transcripts but TLR7 were significantly higher in LST-positive reaction than in paired normal-looking skin of Ibizan hound. The expression profile of immune genes in LST-positive reactions was similar to that previously observed in clinically lesioned skin of mildly diseased dogs with papular dermatitis due to Leishmania infantum infection. This data provide additional support for the important role of TLRs in canine leishmaniosis.

Toll-like receptors 2, 4 and 7, interferon-gamma and interleukin 10, and programmed death ligand 1 transcripts in skin from dogs of different clinical stages of leishmaniosis

Background

Canine leishmaniosis (CanL) caused by Leishmania infantum can have several dermatological manifestations. The type of immune response elicited against the parasite appears to be at the basis for such clinical variability. Much of the work in CanL has focused on adaptive immune response and there are scarce data on the importance of the innate immune responses. Moreover, few studies have evaluated the immunological response in the cutaneous lesions in dogs naturally infected with L. infantum and with different degrees of disease severity, and no study has compared clinically-lesioned with normal-looking skin.

Methods

We determined and compared the transcription of toll like receptors (TLRs) 2, 4 and 7, interferon gamma (IFN-γ), interleukin (IL) 10 and programmed cell death protein ligand (PD-L) 1 by real-time PCR in paired clinically-lesioned and normal-looking skin from 25 diseased dogs (mild disease-stage I (n = 11) and moderate to severe disease-stages II and III (n = 14) as well as in normal-looking skin from healthy dogs (n = 10) from a non-endemic area. We also assessed the association between the transcripts in clinically-lesioned and normal-looking skin of dogs with leishmaniosis with clinicopathological, immunological and parasitological findings.

Results

Clinically-lesioned skin from mildly affected dogs was characterized by a significant upregulation of TLR2 (P < 0.0001) and IL-10 (P = 0.021) and downregulation of TLR7 (P = 0.004) when compared with more severely affected dogs. Normal-looking skin of mildly affected dogs was characterized by a significant lower expression of TLR7 (P = 0.003), IFN-γ (P < 0.0001) and PD-L1 (P = 0.001) when compared with more severely affected dogs. TLR2, TLR4, IL-10 and IFN-γ upregulation in clinically-lesioned skin was correlated with lower disease severity while TLR7 upregulation was correlated with markers of disease severity. Upregulation of TLR7, IL-10, IFN-γ and PD-L1 in normal-looking skin was correlated with disease severity.

Conclusions

This study demonstrated different expression profiles of immune genes in clinically-lesioned and normal-looking skin among mildly and more severely affected dogs. These immunological conditions might favor the maintenance and replication of the parasite in the skin of more severely affected dogs.

Leishmania species-dependent functional duality of toll-like receptor 2

Toll-like receptors (TLRs) are a subset of pattern recognition receptors (PRR) in innate immunity and act as a connecting link between innate and adaptive immune systems. During Leishmania infection, the activation of TLRs influences the pathogen-specific immune responses, which may play a decisive role in determining the outcome of infection, toward elimination or survival of the pathogen. Antigen-presenting cells (APCs) of the innate immune system such as macrophages, dendritic cells (DCs), neutrophils, natural killer (NK) cells, and NKT cells express TLR2, which plays a crucial role in the parasite recognition and elicitation of immune responses in Leishmania infection. Depending on the infecting Leishmania species, the TLR2 pathways may result in a host-protective or a disease-exacerbating response. While Leishmania major and Leishmania donovani infections trigger TLR2-related host-protective and non-protective immune responses, Leishmania mexicana and Leishmania infantum infections are reported to elicit TLR2-mediated host-protective responses and Leishmania amazonensis and Leishmania braziliensis infections are reported to evoke a disease-exacerbating response. These findings illustrate that TLR2-related effector functions are diverse and may be exerted in a species- or strain-dependent manner. TLR2 agonists or antagonists may have therapeutic potentials to trigger the desired immune response during leishmaniasis. In this review, we discuss the TLR2-related immune responses during leishmaniasis and highlight the novel insights into the possible role of TLR2-driven resistance or susceptibility to Leishmania.

Detection of Leishmania spp. Infection by Immunohistochemistry in Archived Biopsy Samples from Dogs with Colitis in an Area Endemic for Leishmaniosis

Previous studies have demonstrated the presence of Leishmania infantum amastigotes in the colonic mucosa of seropositive sick dogs. However, there are no studies that have investigated the presence of L. infantum infection in dogs diagnosed with inflammatory bowel disease (IBD). The aims of this study were: (1) to investigate retrospectively the presence of Leishmania spp. antigen by immunohistochemistry (IHC) in biopsy samples taken from the colon of dogs with IBD in an area endemic for leishmaniosis, and (2) to describe the main histopathological findings in these cases. Clinicopathological data and histopathological results were reviewed from 106 cases of canine colitis. IHC to detect Leishmania spp. antigen had been performed at the time of diagnosis in 13 cases and we performed IHC in 56 more cases. Five of the 69 cases (7.2%) were positive for Leishmania spp. antigen by IHC. Two positive biopsy samples had histiocytic inflammation and three had lymphoplasmacytic inflammation. The number of amastigotes was variable and independent of the type and grade of inflammatory infiltrate. The results suggest that Leishmania spp. infection is associated with chronic colitis in areas endemic for the infection. Therefore, Leishmania IHC should be used routinely as a diagnostic tool when evaluating colonic biopsy samples from dogs in endemic areas, to exclude or confirm an infection by this parasite in dogs with chronic colitis.

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.

Histological and Immunological Description of the Leishmanin Skin Test in Ibizan Hounds

The leishmanin skin test (LST), a delayed-type hypersensitivity (DTH) reaction to Leishmania infantum, can specifically identify dogs that have made a cell-mediated immune response to L. infantum infection. The Ibizan hound appears to be more resistant to L. infantum infection than other breeds of dog. The aim of this study was to describe the histological and immunohistochemical changes induced by the LST in Ibizan hounds living in an area highly endemic for leishmaniosis. The majority of dogs were apparently healthy, lacked serum antibody to L. infantum and blood parasitaemia, but had marked specific interferon gamma production after in-vitro blood stimulation with L. infantum. Leishmanin (3 × 10⁸ killed promastigotes of L. infantum/ml) was injected intradermally and biopsy samples were obtained from a positive reaction at 72 h from nine Ibizan hounds. A moderate to intense, perivascular to interstitial dermatitis and panniculitis characterized the inflammatory response at the injection site. In addition, three samples had diffuse inflammation in the deep dermis and panniculus. Oedema and necrosis were present in the deep dermis and panniculus. Congestion and haemorrhage were observed in five biopsies. T lymphocytes (CD3⁺) and large mononuclear cells (lysozyme^-) were the most prevalent cells. CD3⁺ cells were significantly more numerous than CD20⁺ B cells and lysozyme⁺ cells. B cells were sparsely distributed, especially in the deep dermis and panniculus. Rare neutrophils and macrophages (lysozyme⁺) were observed with few eosinophils. Toll-like receptor (TLR)-2 protein was expressed in large mononuclear cells mainly located in the superficial dermis. Leishmania immunohistochemistry was negative and quantitative polymerase chain reaction was positive in all cases. The intradermal injection of killed L. infantum promastigotes in Ibizan hounds causes similar histological and immunohistochemical findings to those described for human subjects and are indicative of a DTH response. Moreover, TLR2 protein is expressed in inflammatory cells similar to findings in clinically affected skin biopsy samples.

The inflammatory cytokine effect of Pam3CSK4 TLR2 agonist alone or in combination with Leishmania infantum antigen on ex-vivo whole blood from sick and resistant dogs

BACKGROUND

A wide spectrum of clinical manifestations and immune responses exist in canine L. infantum infection. Ibizan hounds are more "resistant" to disease than other dog breeds. Recognition of pathogen-associated molecule patterns by toll like receptors (TLRs) rapidly triggers a variety of anti-microbial immune responses through the induction of pro-inflammatory cytokines such as TNF-α and IL-6 which may play an important role in controlling Leishmania infection. The main objective of this study was to investigate and compare the effect of a TLR2 agonist (TLR2a) alone or in combination with L. infantum antigen (LSA) on ex vivo whole blood cytokine production from healthy seronegative IFN-γ non-producer dogs from an area of low in canine leishmaniosis endemicity (n = 11); sick seropositive dogs with low production of IFN-γ (n = 17) and healthy seronegative or low positive Ibizan hounds with a predominant IFN-γ production (n = 21) from a highly endemic area. Whole blood was stimulated with medium alone (Ø), LSA, concanavalin A, TLR2 (Pam3CSK4) receptor agonist (Ø + TLR2a) and TLR2a and LSA (LSA + TLR2a) for 48 h. Supernatants were harvested for measurement of canine TNF-α and IL-6 cytokines by ELISA.

RESULTS

A significant increase of TNF-α was found in the supernatants of stimulated blood from all groups (Ø + TLR2a and LSA + TLR2a) when compared with medium alone. A similar pattern was observed for IL-6. Interestingly, a significant increase of TNF-α production was only observed when stimulation with LSA + TLR2a was compared with TLR2a alone in Ibizan hounds. A significant increase of TNF-α production was observed with stimulation of LSA + TLR2a when compared with LSA in all groups. Significantly higher concentrations of TNF-α and IL-6 were detected in Ibizan hounds, especially for the Ø + TLR2a and LSA + TLR2a treatments compared with other groups.

CONCLUSIONS

This study demonstrated that TLR2a alone enhances the production of the inflammatory cytokines TNF-α and IL-6 in sick, "resistant" and healthy non-infected dogs. In addition, a combination of LSA+TLR2a promoted a synergistic pro-inflammatory effect with TNF-α in Ibizan hounds but not in seropositive sick dogs and seronegative healthy dogs. These findings might suggest the importance of Pam3CSK4 as a possible immunomodulator for CanL.

Histological and parasitological distinctive findings in clinically-lesioned and normal-looking skin of dogs with different clinical stages of leishmaniosis

Background

Normal-looking skin of dogs with leishmaniosis frequently shows microscopic lesions along with the presence of Leishmania amastigotes. However, histological lesions with or without detection of amastigotes might not occur in less severe clinical cases. In addition, comparative studies between paired clinically-lesioned and normal-looking skin samples from dogs with different disease severity are lacking. The objective of this study was to compare histological and parasitological findings by Leishmania immunohistochemistry (IHC) and quantitative PCR (qPCR) on paired clinically-lesioned and normal-looking skin biopsies from 25 dogs with different clinical stages of leishmaniosis, 11 with stage I-mild disease (papular dermatitis) and 14 with stage II-III (ulcerative or exfoliative dermatitis).

Results

The study demonstrated microscopic lesions in 14 out of 25 (56%) samples from normal-looking skin biopsies. In those samples, perivascular to interstitial dermatitis composed by macrophages with lymphocytes and plasma cells was observed mainly in the superficial and mid-dermis. The intensity of the dermatitis was mild to moderate and always less prominent than in the clinically-lesioned skin. In normal-looking skin samples, the presence of parasites was detected by histology, IHC and qPCR in 5/25 (20%), 8/25 (32%) and 18/25 (72%), respectively. Leishmania was encountered in 11/25 (44%), 23/25 (92%) and 25/25 (100%) of clinically-lesioned skin samples by histology, IHC and qPCR, respectively. Normal-looking skin from dogs with stage I-mild disease was less frequently inflamed (P = 0.0172). Furthermore, Leishmania was more easily demonstrated by histology (P = 0.0464), IHC (P = 0.0421) or qPCR (P = 0.0068) in normal-looking skin of dogs with stage II-III-moderate to severe disease. In addition, in the latter group, there was a significantly higher parasite load studied by means of qPCR than in dogs with less severe disease (P = 0.043). Clinically-lesioned skin from dogs with stage I disease was more frequently characterised by the nodular to diffuse pattern and granuloma formation (P = 0.0166) and by a lower parasite load studied by means of qPCR (P = 0.043) compared with more diseased dogs.

Conclusions

Normal-looking skin from dogs with stage I is less likely to present histological lesions as well as harbour the parasite when compared with dogs with moderate to severe leishmaniosis.

The effect of Lucilia sericata- and Sarconesiopsis magellanica-derived larval therapy on Leishmania panamensis

This study's main objective was to evaluate the action of larval therapy derived from Lucilia sericata and Sarconesiopsis magellanica (blowflies) regarding Leishmania panamensis using an in vivo model. Eighteen golden hamsters (Mesocricetus auratus) were used; they were divided into 6 groups. The first three groups consisted of 4 animals each; these, in turn, were internally distributed into subgroups consisting of 2 hamsters to be used separately in treatments derived from each blowfly species. Group 1 was used in treating leishmanial lesions with larval therapy (LT), whilst the other two groups were used for evaluating the used of larval excretions and secretions (ES) after the ulcers had formed (group 2) and before they appeared (group 3). The three remaining groups (4, 5 and 6), consisting of two animals, were used as controls in the experiments. Biopsies were taken for histopathological and molecular analysis before, during and after the treatments; biopsies and smears were taken for assessing parasite presence and bacterial co-infection. LT and larval ES proved effective in treating the ulcers caused by the parasite. There were no statistically significant differences between the blowfly species regarding the ulcer cicatrisation parameters. There were granulomas in samples taken from lesions at the end of the treatments. The antibacterial action of larval treatment regarding co-infection in lesions caused by the parasite was also verified. These results potentially validate effective LT treatment against cutaneous leishmaniasis aimed at using it with humans in the future.

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.

Leishmania infantum-specific production of IFN-γ and IL-10 in stimulated blood from dogs with clinical leishmaniosis

BACKGROUND

There is limited information available on cytokine profiles in dogs with different degrees of disease severity due to natural infection of Leishmania infantum. The aim of this study was to investigate L. infantum-specific IFN-γ and IL-10 production in blood from dogs with leishmaniosis at diagnosis and correlate these findings with disease severity, humoral immune response and blood parasitemia.

METHODS

Sixty dogs were diagnosed based on physical examination, routine laboratory tests, L. infantum-specific antibody levels measured by quantitative ELISA and blood parasitemia by real-time PCR. Heparin whole blood was stimulated with L. infantum soluble antigen (LSA) and concanavalin A (ConA) and incubated for 5 days. IFN-γ and IL-10 concentrations were measured in supernatants with sandwich ELISAs.

RESULTS

The majority of dogs (n = 36) were classified as LeishVet stage II (moderate disease). The rest of the dogs were classified as stage I (n = 10), III (n = 10) and IV (n = 4). Dogs classified with stage I and IIa presented significantly higher (P = 0.02) LSA IFN-γ concentrations, lower (P <0.0001) antibody levels and a tendency for lower blood parasitemia (P = 0.1) than dogs classified with stages IIb, III or IV while no differences in ConA IFN-γ or IL-10 concentrations were observed among groups. Thirty-five dogs produced significantly higher LSA IFN-γ (mean ± SD: 2320 ± 3960 pg/ml) and ConA IFN-γ (mean ± SD: 7887 ± 7273 pg/ml) when compared with 25 dogs that did not produce detectable LSA IFN-γ but produced ConA IFN-γ (mean ± SD: 4917 ± 5233 pg/ml). IFN-γ producer dogs presented lower (mean ± SD: 5750 ± 14,082 ELISA units (EU), P = 0.001) antibody levels and blood parasitemia (mean ± SD:   5 ± 10 parasites/ml, P = 0.001) when compared with IFN-γ non-producers (mean ± SD: 19,638 ± 28,596 EU and 1100 ± 5112 parasites/ml), respectively. LSA IL-10 was not detectable in 34 dogs while 49 dogs secreted ConA IL-10 (mean ± SD of 90 ± 103 pg/ml). LSA IFN-γ concentration was negatively correlated with blood parasitemia and antibody levels and positively correlated with ConA IFN-γ and LSA IL-10 concentrations.

CONCLUSIONS

The results of this study demonstrate that sick dogs lacking L. infantum specific IFN-γ production in stimulated whole blood produce a strong humoral response, have a high blood parasitemia and severe clinical disease. IL-10 does not appear to be a marker of disease severity.

Early reduction of Leishmania infantum-specific antibodies and blood parasitemia during treatment in dogs with moderate or severe disease

BACKGROUND

Leishmania infantum-specific antibodies are used extensively for the diagnosis and monitoring of treatment in canine leishmaniosis. Different views have been described for the measurement of L. infantum antibody levels for the monitoring of anti-leishmanial treatment. In addition, molecular techniques using blood are frequently employed in the clinical setting. However, there are not enough studies to prove the usefulness of PCR in diagnosis, treatment monitoring and in assessing the prognosis of the disease. The objectives of this study were to evaluate L. infantum-specific antibodies and blood parasitemia at the time of diagnosis and during treatment and to correlate these with the dog's clinical status.

METHODS

Thirty-seven dogs were diagnosed and followed-up during treatment (days 30, 180 and 365). The treatment protocol consisted of a combination of meglumine antimoniate for one month and allopurinol for at least one year. Leishmania infantum-specific antibodies and blood parasitemia were assessed by an end point sera dilution ELISA and by real-time PCR, respectively.

RESULTS

The majority of dogs were classified as LeishVet stage II (moderate disease) at the time of diagnosis (86 %) and the rest as stage III. Results showed variable levels of specific antibodies at the time of diagnosis [median ± interquartile range (IQR): 1372 ± 8803 ELISA units (EU)]. Twenty-three seropositive dogs (64 %) were detected as PCR-positive at the time of diagnosis. Interestingly, a rapid significant antibody level reduction was observed by day 30 of treatment (median ± IQR: 604 ± 2168 EU). A continuing significant decrease of specific antibodies was also found at days 180 (median ± IQR: 201 ± 676 EU) and 365 (median ± IQR: 133 ± 329 EU) in association with clinical improvement. A significant blood parasitemia reduction was also observed at all time points studied. Mean parasites/ml ± SD were 19.4 ± 79.1 on day 0, 2.2 ± 11.7 on day 30, 0.9 ± 2.9 on day 180, and 0.3 ± 0.7 on day 365.

CONCLUSIONS

This study reports a significant reduction of L. infantum antibodies measured by an end point sera dilution ELISA method after 30 days of treatment associated with clinical improvement. A low proportion of sick dogs with moderate disease were negative by blood real-time PCR at the time of diagnosis.

Insights on adaptive and innate immunity in canine leishmaniosis

Canine leishmaniosis (CanL) is caused by the parasite Leishmania infantum and is a systemic disease, which can present with variable clinical signs, and clinicopathological abnormalities. Clinical manifestations can range from subclinical infection to very severe systemic disease. Leishmaniosis is categorized as a neglected tropical disease and the complex immune responses associated with Leishmania species makes therapeutic treatments and vaccine development challenging for both dogs and humans. In this review, we summarize innate and adaptive immune responses associated with L. infantum infection in dogs, and we discuss the problems associated with the disease as well as potential solutions and the future direction of required research to help control the parasite.

Toll-like receptor 9 regulates melanogenesis through NF-κB activation

Toll-like receptors play essential roles in the modulation of melanogenesis, which has been implicated in the pathogenesis of hyper- or hypopigmentation-related diseases. However, little is currently known regarding the role of TLR9 in human melanocytes. TLR9 recognizes unmethylated cytosine-phosphate-guanine motif-containing oligodeoxynucleotides, and cytosine-phosphate-guanine ODN2006 acts as an hTLR9 agonist. The aim of the present study was to investigate the effect of cytosine-phosphate-guanine ODN2006 on melanogenesis in the human melanocyte cells. MTT assay and enzyme-linked immunosorbent assay indicated that ODN2006 stimulation (0, 1, 5, 10 µM) dose-dependently reduced cell viability and promoted the production of TNF-α, IL-6, and IL-8 in PIG1 melanocytes. The mRNA and protein levels of PMEL and TYRosinase were elevated at 6 h, and then decreased 24 h later, but were significantly augmented 72 h later following ODN2006 stimulation; whereas, TLR9 expressions were time-dependently increased in PIG1 melanocytes. Moreover, ultraviolet B irradiation combined with ODN2006 stimulation induced much more significant enhancement of PMEL, TYRosinase, and TLR9 mRNA and protein after three days in PIG1 melanocytes, and the similar results were obtained using the primary human melanocytes. The expression of TLR9 protein was down-regulated by TLR9 siRNA transfection. ODN2006 had an additive effect on ultraviolet B-induced melanogenesis and PMEL expression, as well as NF-κB activation, which could be blocked by TLR9 knockdown, the NF-κB specific inhibitor PDTC, or the TBK1 inhibitor BX795. Collectively, we concluded that TLR9 regulates melanogenesis through NF-κB activation, suggesting that TLR9 may play a role in microbial-induced melanogenesis.