Leishmaniasis at the End of the Millennium

Leishmaniasis-HIV coinfection: current challenges

Leishmaniasis – human immunodeficiency virus (HIV) coinfection can manifest itself as tegumentary or visceral leishmaniasis. Almost 35 countries have reported autochthonous coinfections. Visceral leishmaniasis is more frequently described. However, usual and unusual manifestations of tegumentary leishmaniasis have been reported mainly in the Americas, but the real prevalence of Leishmania infection in HIV-infected patients is not clear. Regarding the clinical manifestations, there are some reports showing unusual manifestations in visceral leishmaniasis and tegumentary leishmaniasis in HIV-infected patients; yet, the usual manifestations are more frequent. Leishmaniasis diagnosis relies on clinical methods, but serological tests are used to diagnose visceral leishmaniasis despite them having a low sensitivity to tegumentary leishmaniasis. The search for the parasite is used to diagnose both visceral leishmaniasis and tegumentary leishmaniasis. Nevertheless, in HIV-infected patients, the sensitivity of serology is very low. Drugs available to treat leishmaniasis are more restricted and cause severe side effects. Furthermore, in HIV-infected patients, these side effects are more prominent and relapses and lethality are more recurrent. In this article, we discuss the current challenges of tegumentary leishmaniasis and visceral leishmaniasis–HIV infection, focusing mainly on the clinical manifestations, diagnosis, and treatment of leishmaniasis.

New challenges in the epidemiology and treatment of visceral leishmaniasis in periurban areas

Visceral leishmaniasis [VL] represents a major public health problem in many areas of the world. This review focuses on the impact of periurbanization on the epidemiology and treatment of VL, using Brazil as an example. VL continues to be mostly a disease of poverty with impact on families. However, the disease has expanded in Latin America, with foci reported as far south as Argentina. There is an increasing overlap of Leishmania infantum chagasi and HIV infections and other immunosuppressive conditions, resulting in VL emerging as an opportunistic infection. This new setting poses new challenges for VL disease control and patient management.

Proteomic approaches for discovery of new targets for vaccine and therapeutics against visceral leishmaniasis

Visceral leishmaniasis (VL) is the most devastating type caused by Leishmania donovani, Leishmania infantum, and Leishmania chagasi. The therapeutic mainstay is still based on the antiquated pentavalent antimonial against which resistance is now increasing. Unfortunately, due to the digenetic life cycle of parasite, there is significant antigenic diversity. There is an urgent need to develop novel drug/vaccine targets against VL for which the primary goal should be to identify and characterize the structural and functional proteins. Proteomics, being widely employed in the study of Leishmania seems to be a suitable strategy as the availability of annotated sequenced genome of Leishmania major has opened the door for dissection of both protein expression/regulation and function. Advances in clinical proteomic technologies have enable to enhance our mechanistic understanding of virulence/pathogenicity/host-pathogen interactions, drug resistance thereby defining novel therapeutic/vaccine targets. Expression proteomics exploits the differential expression of leishmanial proteins as biomarkers for application towards early diagnosis. Further using immunoproteomics efforts were also focused on evaluating responses to define parasite T-cell epitopes as vaccine/diagnostic targets. This review has highlighted some of the relevant developments in the rapidly emerging field of leishmanial proteomics and focus on its future applications in drug and vaccine discovery against VL.

Reduced pathology following infection with transgenic Leishmania major expressing murine CD40 ligand

Leishmanization is the inoculation of live Leishmania into the host to vaccinate against subsequent infections. This approach has been largely discontinued due to safety concerns. We have previously shown that combining CD40 ligand (CD40L) with Leishmania antigen preferentially induces a type 1 immune response and provides some protection to vaccinated mice (G. Chen, P. A. Darrah, and D. M. Mosser, Infect. Immun. 69:3255-3263, 2001). In the present study, we developed transgenic L. major organisms which express and secrete the extracellular portion of CD40L (L. major CD40LE). We hypothesized that these organisms would be less virulent but more immunogenic than wild-type organisms and therefore be more effective at leishmanization. Transgenic parasites expressing CD40L mRNA and protein were developed. BALB/c mice infected with these parasites developed significantly smaller lesions containing fewer parasites than animals infected with wild-type organisms. Infection of resistant C57BL/6 mice with low doses of transgenic parasites induced a significant amount of protection against subsequent high-dose infection with wild-type organisms. These results demonstrate that transgenic organisms expressing CD40L are less virulent than wild-type organisms while retaining full immunogenicity.

Photodynamic treatment of cutaneous leishmaniasis

Leishmaniasis is a widespread arthropod-borne protozoan zoonosis caused by more than 21 Leishmania species. Vectors are sandflies of different genera. The disease is classified into "Old World" versus "New World" leishmaniasis and further subclassified in cutaneous, mucocutaneous and visceral forms. Most therapeutic approaches are not evidence-based. We report a patient with facial cutaneous Leishmania tropica infection which proved to be resistant to various therapeutic regimes. Excellent results were achieved with photodynamic therapy.

The persistence, dissemination, and visceralization tendency of Leishmania major in Syrian hamsters

I monitored the persistence, dissemination, and the possible visceralization tendency of Leishmania major, the causative parasite of cutaneous leishmaniasis in North Africa and the Middle East in Syrian hamsters (Mesocricetus auratus). Hamsters were inoculated subcutaneously in the hind footpad, with 1 x 10(6)L. major metacyclic promastigotes and were sacrificed at months 1, 3, 6 and 10 post-infection (pi). Skin lesions, blood, spleens, livers and kidneys were screened by both Giemsa-stained smears and a polymerase chain reaction (PCR) for detection of L. major amastigotes. A few weeks pi, 61.7% of the inoculated hamsters developed a cutaneous lesion only at the inoculation site, while 38.3% of them developed non-self-healed lesions at sites distant from the inoculation site. PCR identified all the positive stained smears as well as false-negative ones, indicating that PCR was more sensitive than stained smears. The results confirmed the dissemination and persistence of L. major amastigotes in all tissues examined, except the kidneys, for a period extending to 10 months, only in those hamsters suffering from disseminated cutaneous lesions. Parasite DNA was detected in the bloods starting from the first month pi and starting from month 3 pi in the spleens and livers. Some, but not all, the animals with disseminated infections proved to be positive for parasite DNA in their organs. Persistence of the L. major amastigotes in the tissues differed from those of other species causing visceral diseases. These findings demonstrate a possible visceralization tendency for L. major previously recorded for L. tropica and L. mexicana.

Characterization of Leishmania chagasi DNA topoisomerase II: a potential chemotherapeutic target

DNA topoisomerase II (topo II), an enzyme essential for cellular replication, is an eminent target for antimicrobial therapy against Leishmania chagasi, the major cause of visceral leishmaniasis in Latin America. The complete L. chagasi (Lch) TOP2 gene, encoding L. chagasi topo II, was isolated from genomic DNA using the polymerase chain reaction. The LchTOP2 gene revealed an open reading frame (ORF) of 3,711 base pairs predicting a protein with 1,236 amino acids and an estimated molecular weight of 140 kDA. The L. chagasi topo II sequence had high identity with the L. donovani topo II (98.8%) and L. infantum topo II (98.7%), followed by Crithidia fasciculata topo II (84.4%), Trypanosoma cruzi topo II (67.6%) and Trypanosoma brucei topo II (66.6%). Lch topo II had low identity with the human homologs htopo II alpha (26.3%) and htopo II beta (26.4%). Differences between L. chagasi TOP2 and human TOP2 genes suggest that leishmanial topo II is a potential target for the development of new antileishmanial agents.