Caseous necrosis in cutaneous leishmaniasis

Comparison of parasite load by qPCR and histopathological changes of inner and outer edge of ulcerated cutaneous lesions of cutaneous leishmaniasis

Background

Cutaneous leishmaniasis (CL) is an infectious vector-borne disease caused by protozoa of the Leishmania genus that affects humans and animals. The distribution of parasites in the lesion is not uniform, and there are divergences in the literature about the choice of the better sampling site for diagnosis–inner or outer edge of the ulcerated skin lesion. In this context, determining the region of the lesion with the highest parasite density and, consequently, the appropriate site for collecting samples can define the success of the laboratory diagnosis. Hence, this study aims to comparatively evaluate the parasite load by qPCR, quantification of amastigotes forms in the direct exam, and the histopathological profile on the inner and outer edges of ulcerated CL lesions.

Methods

Samples from ulcerated skin lesions from 39 patients with confirmed CL were examined. We performed scraping of the ulcer inner edge (base) and outer edge (raised border) and lesion biopsy for imprint and histopathological examination. Slides smears were stained by Giemsa and observed in optical microscopy, the material contained on the smears was used to determine parasite load by quantitative real-time PCR (qPCR) with primers directed to the Leishmania (Viannia) minicircle kinetoplast DNA. The histopathological exam was performed to evaluate cell profile, tissue alterations and semi-quantitative assessment of amastigote forms in inner and outer edges.

Principal findings

Parasite loads were higher on the inner edge compared to the outer edge of the lesions, either by qPCR technique (P<0.001) and histopathological examination (P< 0.003). There was no significant difference in the parasite load between the imprint and scraping on the outer edge (P = 1.0000).

Conclusion/Significance

The results suggest that clinical specimens from the inner edge of the ulcerated CL lesions are the most suitable for both molecular diagnosis and direct parasitological examination.

Caseating granulomas in cutaneous leishmaniasis

Background

Caseating granulomas are often associated with a mycobacterial infection (TB) and are thought to be exceedingly rare in cutaneous leishmaniasis (CL). However, no large series has accurately documented the incidence of caseating granulomas in CL.

Methods

A multiregional cohort consisting of 317 patients with CL [Syria (157), Pakistan (66), Lebanon (47), Saudi Arabia (43), Ethiopia (2) and Iran (2)] was reviewed. Clinical [age, sex, disease duration, lesion type and geographic and anatomic location] and microscopic data [presence of and type of granuloma, Ridley's parasitic index (PI) and pattern (RP)] were documented. Presence of microorganisms was evaluated using special stains (GMS, PAS, AFB and Gram) and polymerase chain reaction (PCR) for TB and CL. All cases included in this study were confirmed as CL by PCR followed by restriction fragment length polymorphism analysis for molecular speciation and were negative for other organisms by all other studies performed. Categorical and continuous factors were compared for granuloma types using Chi-square, t-test or Mann-Whitney test as appropriate.

Results

Granulomas were identified in 195 (61.5%) cases of CL and these were divided to 49 caseating (25.2%), 9 suppurative (4.6%) and 137 tuberculoid without necrosis (70.2%). Caseating and tuberculoid granuloma groups were significantly different in terms of the geographical source, with more cases harboring caseating granulomas in Saudi Arabia (p<0.0001). Histologically, both groups were also different in the distribution of their RP (p<0.0001) with a doubling RP3 in caseating granulomas (31% vs. 15%) as opposed to doubling of RP5 in tuberculoid granuloma group (38% vs. 19%). Time needed to achieve healing (RP5) was notably shorter in tuberculoid vs. caseating group (4.0 vs. 6.2 months). Parasitic Index, CL species and other considered variables did not differ for the granuloma type groups.

Conclusion

In our multiregional large cohort, a notable 18.2% of all CL cases harbored caseating granulomas therefore; CL should be considered part of the differential diagnosis for cases with caseating granulomas in endemic regions, especially considering that the regions included in our cohort are also endemic for TB. Of note, cases of CL with caseating granulomas also showed a slower healing process, with no association with specific species, which may be due to worse host immune response in such cases or to a more aggressive leishmania strains.

Cutaneous leishmaniasis displays a wide spectrum of clinical and microscopic findings. The microscopic manifestations have been categorized into five groups. The type of granulomatous response defined in group V is usually tuberculoid in nature with exceedingly rare cases described with necrotizing granulomas in contrast to cutaneous infections with tuberculosis and other mycobacteria that are typically associated with necrotic granulomas. The old world countries endemic for cutaneous leishmania also happen to be endemic for other granulomatous diseases such as leprosy, tuberculosis and cutaneous mycoses. The most common diagnostic approach used in these countries is still microscopic examination despite the advances in molecular diagnostic techniques and culture methods. We document an 18.2% incidence of caseating granulomas in cutaneous leishmania. Hence, cutaneous leishmania should be part of the differential diagnosis for cases with caseating granulomas in endemic regions in addition to other causative infections.

American tegumentary leishmaniasis: correlations among immunological, histopathological and clinical parameters

BACKGROUND

American tegumentary leishmaniasis has an annual incidence of 1 to 1.5 million cases. In some cases, the patient's immune response can eliminate the parasite, and the lesion spontaneously resolves. However, when this does not occur, patients develop the disseminated form of the disease.

OBJECTIVE

To investigate the association between clinical, laboratory and pathological findings in cases of American tegumentary leishmaniasis.

METHODS

A retrospective study of the medical records of 47 patients with American cutaneous leishmaniasis. Clinical, laboratory and epidemiological data were collected, and semi-quantitative histopathological analyses were performed using the Spearman correlation coefficient (p <0.05).

RESULTS

Mean patient age was 40.5 years. A total of 29.7% individuals were female and 70.2% were male, and 40.4% of the patients were farmers. The ulcerative form was found in 53.2% of patients, of whom 59.6% had lesions in the limbs. The average time to diagnosis was 22.3 months. The following positive correlations were significant: age and duration of the disease, Montenegro reaction, degree of granulomatous transformation and epithelioid cell count; duration of disease, Montenegro reaction and number of lymphocytes; epithelial hyperplasia and edema, hemorrhaging, and epithelial aggression; number of plasmocytes and number of parasites. The main negative correlations found were as follows: age and serology; time and parasite load; epithelial hyperplasia and degree of granulomatous transformation.

CONCLUSION

The long duration of the disease could be explained by the fact that lesions were relatively asymptomatic, and therefore ignored by patients with low literacy levels. Individuals may have simply waited for spontaneous healing, which proved to be dependent on the activation of hypersensitivity mechanisms.

CD28 signaling in neutrophil induces T-cell chemotactic factor(s) modulating T-cell response

We previously reported that human peripheral blood neutrophils express CD28 and interact with macrophage B7 to generate CD28 signaling through PI-3 kinase. Here, we demonstrate that crosslinking of CD28 on neutrophils results in the release of IFN-gamma, which restricts amastigote growth and modulates CD4+ T cells cytokine secretion. CD28 crosslinking also induces a T-cell chemotactic factor (TCF) that induces chemotactic migration of CD4+ T cells. Based on our previous and the current set of data, we propose an operational model explaining how neutrophils are involved in Leishmania infection and how the reported effect of neutrophils on the control of infection is mediated by alteration of T-cell function.

Human neutrophil-expressed CD28 interacts with macrophage B7 to induce phosphatidylinositol 3-kinase-dependent IFN-gamma secretion and restriction of Leishmania growth

We previously showed that CD28 is expressed on human peripheral blood neutrophils and plays an important role in CXCR-1 expression and IL-8-induced neutrophil migration. In this work we demonstrate that Leishmania major infection of macrophages results in parasite dose-dependent IL-8 secretion in vitro and in IL-8-directed neutrophil migration, as blocked by both anti-IL-8 and anti-IL-8R Abs, toward the L. major-infected macrophages. In the neutrophil-macrophage cocultures, both CTLA4-Ig, a fusion protein that blocks CD28-CD80/CD86 interaction, and a neutralizing anti-IFN-gamma Ab inhibit the anti-leishmanial function of neutrophils, suggesting that the neutrophil-macrophage interaction via CD28-CD80/CD86 plays an important role in the IFN-gamma-dependent restriction of the parasite growth. Cross-linking of neutrophil-expressed CD28 by monoclonal anti-CD28 Ab or B7.1-Ig or B7.2-Ig results in phosphatidylinositol 3-kinase association with CD28 and in wortmannin-sensitive but cyclosporin A-resistant induction and secretion of IFN-gamma. Whereas the neutrophils secrete IFN-gamma with CD28 signal alone, the T cells do not secrete the cytokine in detectable amounts with the same signal. Thus, neutrophil-expressed CD28 modulates not only the granulocyte migration but also induction and secretion of IFN-gamma at the site of infection where it migrates from the circulation.