Vaccination of humans against cutaneous leishmaniasis: cellular and humoral immune responses

Interventions for American cutaneous and mucocutaneous leishmaniasis

BACKGROUND

On the American continent, cutaneous and mucocutaneous leishmaniasis (CL and MCL) are diseases associated with infection by several species of Leishmania parasites. Pentavalent antimonials remain the first-choice treatment. There are alternative interventions, but reviewing their effectiveness and safety is important as availability is limited. This is an update of a Cochrane Review first published in 2009.

OBJECTIVES

To assess the effects of interventions for all immuno-competent people who have American cutaneous and mucocutaneous leishmaniasis (ACML).

SEARCH METHODS

We updated our database searches of the Cochrane Skin Group Specialised Register, CENTRAL, MEDLINE, Embase, LILACS and CINAHL to August 2019. We searched five trials registers.

SELECTION CRITERIA

Randomised controlled trials (RCTs) assessing either single or combination treatments for ACML in immuno-competent people, diagnosed by clinical presentation and Leishmania infection confirmed by smear, culture, histology, or polymerase chain reaction on a biopsy specimen. The comparators were either no treatment, placebo only, or another active compound.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Our key outcomes were the percentage of participants 'cured' at least three months after the end of treatment, adverse effects, and recurrence. We used GRADE to assess evidence certainty for each outcome.

MAIN RESULTS

We included 75 studies (37 were new), totalling 6533 randomised participants with ATL. The studies were mainly conducted in Central and South America at regional hospitals, local healthcare clinics, and research centres. More male participants were included (mean age: roughly 28.9 years (SD: 7.0)). The most common confirmed species were L. braziliensis, L. panamensis, and L. mexicana. The most assessed interventions and comparators were non-antimonial systemics (particularly oral miltefosine) and antimonials (particularly meglumine antimoniate (MA), which was also a common intervention), respectively. Three studies included moderate-to-severe cases of mucosal leishmaniasis but none included cases with diffuse cutaneous or disseminated CL, considered the severe cutaneous form. Lesions were mainly ulcerative and located in the extremities and limbs. The follow-up (FU) period ranged from 28 days to 7 years. All studies had high or unclear risk of bias in at least one domain (especially performance bias). None of the studies reported the degree of functional or aesthetic impairment, scarring, or quality of life. Compared to placebo, at one-year FU, intramuscular (IM) MA given for 20 days to treat L. braziliensis and L. panamensis infections in ACML may increase the likelihood of complete cure (risk ratio (RR) 4.23, 95% confidence interval (CI) 0.84 to 21.38; 2 RCTs, 157 participants; moderate-certainty evidence), but may also make little to no difference, since the 95% CI includes the possibility of both increased and reduced healing (cure rates), and IMMA probably increases severe adverse effects such as myalgias and arthralgias (RR 1.51, 95% CI 1.17 to 1.96; 1 RCT, 134 participants; moderate-certainty evidence). IMMA may make little to no difference to the recurrence risk, but the 95% CI includes the possibility of both increased and reduced risk (RR 1.79, 95% CI 0.17 to 19.26; 1 RCT, 127 participants; low-certainty evidence). Compared to placebo, at six-month FU, oral miltefosine given for 28 days to treat L. mexicana, L. panamensis and L. braziliensis infections in American cutaneous leishmaniasis (ACL) probably improves the likelihood of complete cure (RR 2.25, 95% CI 1.42 to 3.38), and probably increases nausea rates (RR 3.96, 95% CI 1.49 to 10.48) and vomiting (RR 6.92, 95% CI 2.68 to 17.86) (moderate-certainty evidence). Oral miltefosine may make little to no difference to the recurrence risk (RR 2.97, 95% CI 0.37 to 23.89; low-certainty evidence), but the 95% CI includes the possibility of both increased and reduced risk (all based on 1 RCT, 133 participants). Compared to IMMA, at 6 to 12 months FU, oral miltefosine given for 28 days to treat L. braziliensis, L. panamensis, L. guyanensis and L. amazonensis infections in ACML may make little to no difference to the likelihood of complete cure (RR 1.05, 95% CI 0.90 to 1.23; 7 RCTs, 676 participants; low-certainty evidence). Based on moderate-certainty evidence (3 RCTs, 464 participants), miltefosine probably increases nausea rates (RR 2.45, 95% CI 1.72 to 3.49) and vomiting (RR 4.76, 95% CI 1.82 to 12.46) compared to IMMA. Recurrence risk was not reported. For the rest of the key comparisons, recurrence risk was not reported, and risk of adverse events could not be estimated. Compared to IMMA, at 6 to 12 months FU, oral azithromycin given for 20 to 28 days to treat L. braziliensis infections in ACML probably reduces the likelihood of complete cure (RR 0.51, 95% CI 0.34 to 0.76; 2 RCTs, 93 participants; moderate-certainty evidence). Compared to intravenous MA (IVMA) and placebo, at 12 month FU, adding topical imiquimod to IVMA, given for 20 days to treat L. braziliensis, L. guyanensis and L. peruviana infections in ACL probably makes little to no difference to the likelihood of complete cure (RR 1.30, 95% CI 0.95 to 1.80; 1 RCT, 80 participants; moderate-certainty evidence). Compared to MA, at 6 months FU, one session of local thermotherapy to treat L. panamensis and L. braziliensis infections in ACL reduces the likelihood of complete cure (RR 0.80, 95% CI 0.68 to 0.95; 1 RCT, 292 participants; high-certainty evidence). Compared to IMMA and placebo, at 26 weeks FU, adding oral pentoxifylline to IMMA to treat CL (species not stated) probably makes little to no difference to the likelihood of complete cure (RR 0.86, 95% CI 0.63 to 1.18; 1 RCT, 70 participants; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

Evidence certainty was mostly moderate or low, due to methodological shortcomings, which precluded conclusive results. Overall, both IMMA and oral miltefosine probably result in an increase in cure rates, and nausea and vomiting are probably more common with miltefosine than with IMMA. Future trials should investigate interventions for mucosal leishmaniasis and evaluate recurrence rates of cutaneous leishmaniasis and its progression to mucosal disease.

Protective immunity using MPL-A and autoclaved Leishmania donovani as adjuvants along with a cocktail vaccine in murine model of visceral leishmaniasis

The current study is an extension of our previous study where we tested the protective efficacy of gp63 and Hsp70 against murine visceral leishmaniasis. The cocktail vaccine was combined with MPL-A and ALD adjuvants and the protection afforded by the three vaccines was compared. Inbred BALB/c mice were immunized twice at an interval of two weeks with the vaccine formulations. Two weeks after the booster, they were challenged with 10(7) promastigotes of Leishmania donovani and sacrificed on 30, 60 and 90 days post infection/challenge. The protective efficacy of vaccines was analyzed by assessment of the hepatic and splenic parasite burden and generation of cellular and humoral immune responses. The immunized animals revealed a significant reduction in parasite burden as compared to the infected controls. These animals also showed heightened DTH response, increased generation of IgG2a, IFN-γ and IL-2 by spleen cells. This was also accompanied by a decrease in the levels of IgG1 and IL-10. Mice immunized with gp63+Hsp70+MPL-A exhibited significantly greater protection in comparison to those immunized with gp63+Hsp70+ALD.

Leishmania sp. isolated from human cases of cutaneous leishmaniasis in Brazil characterized as Leishmania major-like

The identification and characterization of Leishmania are relevant to diagnosis, treatment, eco-epidemiology studies, prophylactic measures and control of the disease. Two strains of Leishmania (MHOM/BR/1971/BH49 and MHOM/BR/1971/BH121), isolated from human cutaneous leishmaniasis, were studied using biological and molecular characteristics, in comparison with WHO reference strains. These studies are important because both strains were incorporated in a vaccine against American cutaneous leishmaniasis, and one of these strains has been used to prepare specific and sensitive antigen for serodiagnosis of visceral leishmaniasis in Brazil. Studies were made on the growth rates of promastigotes in Grace's insect medium, infectivity to C57BL/6 and BALB/c mice, electrophoresic mobility patterns of isoenzymes, random amplification of polymorphic DNA (RAPD), simple sequence repeat-anchored PCR amplification (SSR-PCR) and DNA fingerprinting profiles, infectivity to murine macrophages and cellular immune response. Infections of mice and macrophages were significantly different among the strains studied. Attempts to infect mice with culture promastigotes were unsuccessful with BH121, but BH49 infected BALB/c and C57BL/6 mice. Isoenzyme electrophoretic mobility patterns, RAPD and SSR-PCR using DNA amplified by polymerase chain reaction (PCR) with nine arbitrary primers, as well as DNA fingerprinting studies with a biotin-labeled 33.15 fingerprinting probe showed similar profiles to those of the Leishmania major WHO reference strain.

Interventions for American cutaneous and mucocutaneous leishmaniasis

BACKGROUND

Pentavalent antimonial drugs are the most prescribed treatment for American cutaneous and mucocutaneous leishmaniasis. Other drugs have been used with varying success.

OBJECTIVES

To assess the effects of therapeutic interventions for American cutaneous and mucocutaneous leishmaniasis.

SEARCH STRATEGY

We searched the Cochrane Skin Group Specialised Register (January 2009), the Register of Controlled Clinical Trials in The Cochrane Library (Issue 1,2009), MEDLINE (2003 to January 2009), EMBASE (2005 to January 2009), LILACS (from inception to January 2009), CINAHL (1982-May 2007) and other databases.

SELECTION CRITERIA

Randomised controlled trials (RCTs) assessing treatments for American cutaneous and mucocutaneous leishmaniasis.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data.

MAIN RESULTS

We included 38 trials involving 2728 participants. Results are based on individual studies or limited pooled analyses. There was good evidence in:Leishmania braziliensis and L. panamensis infections:Intramuscular (IM) meglumine antimoniate (MA) was better than oral allopurinol for 28 days (1RCT n=127, RR 0.39; 95% CI 0.26, 0.58). Intravenous (IV)MA for 20-days was better than 3-day and 7-day IVMA plus 15% paromomycin plus 12% methylbenzethonium chloride (PR-MBCL) or 7-day IVMA (1RCT n= 150, RR 0.24; 95% CI 0.11, 0.50; RR 0.69; 95% CI 0.53, 0.90; RR 0.64; 95% CI 0.44, 0.92 respectively). Oral allopurinol plus antimonials was better than IV antimonials (2RCT n= 168, RR 1.90; 95% CI 1.40, 2.59; I(2)=0%).L. braziliensis infections:Oral pentoxifylline plus IV sodium stibogluconate (SSG) was better than IVSSG (1RCT n= 23, RR 1.66; 95% CI 1.03, 2.69); IVMA was better than IM aminosidine sulphate (1RCT n= 38, RR 0.05; 95% CI 0.00, 0.78) and better than IV pentamidine isethionate (1RCT n= 80, RR 0.45; 95% CI 0.29, 0.71). Intramuscular MA was better than Bacillus Calmette-Guérin (1RCT n= 93, RR 0.46; 95% CI 0.32, 0.65).L .panamensis infections:Oral allopurinol was better than IVMA (1RCT n= 58, RR 2.20; 95% CI 1.34, 3.60). Aminosidine sulphate at doses of 12 mg/kg/day and 18 mg/kg/day for 14 days were better than aminosidine sulphate 12 mg/kg/day for 7 days (1RCT n= 60, RR 0.23; 95% CI 0.07, 0.73; RR 0.23; 95% CI 0.07, 0.73 respectively). Oral ketoconazole for 28 days, oral miltefosine and topical PR-MBCL were better than placebo.

AUTHORS' CONCLUSIONS

Most trials have been designed and reported so poorly that they are inconclusive. There is a need for large well conducted studies that evaluate long-term effects of current therapies to improve quality and standardization of methods.

Leishmania surface protein gp63 binds directly to human natural killer cells and inhibits proliferation

Natural killer (NK) cells contribute to immunity as the first line of defence in numerous infections by early cytokine secretion and cytotoxicity. In Leishmania infection, NK cells contribute with interferon-gamma and may assist in directing the immune response towards T helper type 1, which is essential for successful control of the parasites. Thus, NK cells may play an important role in both resistance and control of the infection. However, during Leishmania infection NK cells show signs of suppression. To explore the reason for this suppression, we exposed naive and interleukin (IL)-2 activated NK cells directly to promastigotes of Leishmania major in vitro. As a rapid consequence of contact between naive NK cells and promastigotes, expression of NK cell receptors show significant changes. We identify one of the major surface molecules of promastigotes, glycoprotein (gp) 63, as an important agent for these suppressive effects by using promastigotes of a gp63ko strain of L. major. Furthermore, proliferation of IL-2-activated purified NK cells is suppressed after exposure to the wild-type but not to gp63ko promastigotes. However, gp63ko L. major induced no NK cell proliferation when NK cells were co-cultured with peripheral blood mononuclear cells populations such as CD14(+) monocytes or T cells.

The influence of copper, selenium and zinc on the response to the Montenegro skin test in subjects vaccinated against American cutaneous leishmaniasis

We evaluated the relationship between the trace elements copper, zinc and selenium and the response to the Montenegro skin test (MST) in 172 volunteers vaccinated against American cutaneous leishmaniasis. The MST diameter was categorized as negative and in quartiles of positive response, constituting five groups. Trace element serum levels were analyzed by coupled plasma atomic emission spectrometry and hydride generation atomic absorption spectrometry, with study subjects classified into two groups depending on low or high levels of trace elements observed. MST-positive subjects had an MST diameter (mean+/-SD) of 10.35+/-4.64mm, with copper, selenium and zinc serum levels of 1433.7+/-665.7microg/l, 88.6+/-39microg/l and 999.2+/-366microg/l, respectively. The MST diameter was significantly different in the selenium groups only. The selenium levels also differed with the quartiles of the MST diameters of individuals testing positive (P<0.05). Our findings suggest that trace elements, particularly selenium, should be measured in future vaccine trials so that vaccine immunogenicity and response can be assessed and compared between different studies.

Successful vaccination against Leishmania chagasi infection in BALB/c mice with freeze-thawed Leishmania antigen and Corynebacterium parvum

This study evaluated the potential of a Leishmania antigen vaccine in protecting BALB/c mice against Leishmania chagasi. Mice received two subcutaneous doses of L. amazonensis vaccine with Corynebacterium parvum and subsequent boost was done without adjuvant. One week later, mice were challenged with L. chagasi. We observed that this vaccine caused a significant reduction in parasite load in liver and spleen and induced a high production of IFN-gamma and IL-4 by spleen cells from vaccinated mice in response to Leishmania antigen. Together, our data show that this vaccine is capable of inducing a Th1/Th2 response that is important to control parasite replication.

Leishmaniavaccines: progress and problems

Leishmaniaare protozoan parasites spread by a sandfly insect vector and causing a spectrum of diseases collectively known as leishmaniasis. The disease is a significant health problem in many parts of the world resulting in an estimated 12 million new cases each year. Current treatment is based on chemotherapy, which is difficult to administer, expensive and becoming ineffective due to the emergence of drug resistance. Leishmaniasis is considered one of a few parasitic diseases likely to be controllable by vaccination. The relatively uncomplicated leishmanial life cycle and the fact that recovery from infection renders the host resistant to subsequent infection indicate that a successful vaccine is feasible. Extensive evidence from studies in animal models indicates that solid protection can be achieved by immunisation with protein or DNA vaccines. However, to date no such vaccine is available despite substantial efforts by many laboratories. Advances in our understanding ofLeishmaniapathogenesis and generation of host protective immunity, together with the completedLeishmaniagenome sequence open new avenues for vaccine research. The major remaining challenges are the translation of data from animal models to human disease and the transition from the laboratory to the field. This review focuses on advances in anti-leishmania vaccine development over the recent years and examines current problems hampering vaccine development and implementation.

Immuno-biochemical evaluations of phenol and thimerosal as antigen preservatives in Montenegro skin test

Montenegro skin test (MST) represents the main complementary diagnostic test for tegumentary leishmaniases (TL) in endemic regions. Most antigen formulations used for the MST contain thimerosal as preservative. The Food and Drug Administration (FDA), however, recommended reducing or eliminating thimerosal from vaccines and other biological reagents and the Agência Nacional de Vigilância Sanitária (ANVISA) in Brazil, prohibited the use of mercurial compounds in immunobiologicals. In the search for an alternative stabilizer, phenol and thimerosal were tested as antigen preservatives in MST. Formulations were tested when fresh and after a 12-month storage at 4 degrees C in TL confirmed mice and human patients, and were evaluated for protein constitution by SDS-PAGE, Western blot and anti-gp63 ELISA. In mice, a decrease in the diagnostic effectiveness in merthiolate formulation was observed after a 12-month storage. SDS-PAGE, Western blot and anti-gp63 ELISA analyses showed a degradation of antigen proteins in both formulations after 12-month storage and that phenol-preserved antigen was quantitatively and qualitatively better than the merthiolate-preserved one. In patients, the average of induration diameter was larger in fresh antigens (p<0.05). However, storage time did not jeopardize their diagnostic capacity. No non-specific reactions produced by phenol or merthiolate were observed neither in humans nor in mice. Phenol could be a good alternative to replace the merthiolate in MST, and despite the proteolytic activity, antigens remain viable for at least 12 months.

Myd88-dependent in vivo maturation of splenic dendritic cells induced by Leishmania donovani and other Leishmania species

The usual agent of visceral leishmaniasis in the Old World is Leishmania donovani, which typically produces systemic diseases in humans and mice. L. donovani has developed efficient strategies to infect and persist in macrophages from spleen and liver. Dendritic cells (DC) are sentinels of the immune system. Following recognition of evolutionary conserved microbial products, DC undergo a maturation process and activate antigen-specific naïve T cells. In the present report we provide new insights into how DC detect Leishmania in vivo. We demonstrate that in both C57BL/6 and BALB/c mice, systemic injection of L. donovani induced the migration of splenic DC from marginal zones to T-cell areas. During migration, DC upregulated the expression of major histocompatibility complex II and costimulatory receptors (such as CD40, CD80, and CD86). Leishmania-induced maturation requires live parasites and is not restricted to L. donovani, as L. braziliensis, L. major, and L. mexicana induced a similar process. Using a green fluorescent protein-expressing parasite, we demonstrate that DC undergoing maturation in vivo display no parasite internalization. We also show that L. donovani-induced DC maturation was partially abolished in MyD88-deficient mice. Taken together, our data suggest that Leishmania-induced DC maturation results from direct recognition of Leishmania by DC, and not from DC infection, and that MyD88-dependent receptors are implicated in this process.

Immune response measured in human volunteers vaccinated with autoclaved Leishmania major vaccine mixed with low dose of BCG

The immune responses induced against Leishmania antigens in volunteers who were vaccinated in a double-blind, randomized field efficacy trial of a preparation of autoclaved Leishmania major (ALM) mixed with a low dose of Bacille Calmette-Guerin vaccine (BCG) who developed either a cutaneous leishmaniasis (CL) lesion due to exposure to infected sandfly bite(s) or did not develop a lesion during the course of the trial were studied and compared with those of non-vaccinated controls. Blood samples were also assayed from different groups including volunteers with history of CL and volunteers with previous positive or negative leishmanin skin test (LST) without a history of CL. The vaccinated volunteers had received a single dose of either ALM mixed with a low dose of BCG or the same dose of BCG alone. The LST and in vitro proliferative response (stimulation index, SI), interferon gamma (IFN-gamma) production and, in a few cases, interleukin (IL)-4 production of peripheral blood mononuclear cells to soluble Leishmania antigens were measured. The results indicated that volunteers who developed CL in the vaccine arm showed a slightly higher SI than cases who received BCG alone. Volunteers with history of CL and volunteers with positive LST demonstrated the strongest proliferation indices and IFN-gamma production. The data suggest that a single dose of ALM + BCG induces a weak Th1 response in vaccinated volunteers that is far lower than that in volunteers with prior subclinical infection or volunteers with history of CL, who are presumed to be immune.

Immunoregulatory activity of CpG oligonucleotides in humans and nonhuman primates

Oligodeoxynucleotides (ODN) containing CpG motifs mimic the ability of microbial DNA to activate the innate immune system. The resultant response limits the early spread of infectious organisms while promoting the development of adaptive immunity. CpG ODN show promise as vaccine adjuvants and in the treatment of asthma, allergy, infection, and cancer. Due to evolutionary divergence in CpG recognition between species, CpG ODN that are most active in rodents are poorly immunostimulatory in primates. Thus, evidence that CpG ODN have therapeutic activity in mice must be confirmed in primates. Two distinct types of CpG ODN were identified that stimulate primate PBMC. D-type ODN trigger plasmacytoid DC to secrete IFNalpha, monocytes to mature into functionally active DC, and NK cells to secrete IFNgamma. K-type ODN stimulate B cells and monocytes to proliferate and secrete IgM, IL-10, and/or IL-6. In vivo studies in nonhuman primates indicate that proinflammatory or humoral immune responses can be selectively facilitated by judicious use of these distinct types of ODN.

Interferon-gamma-inducing oral vaccination with Leishmania amazonensis antigens protects BALB/c and C57BL/6 mice against cutaneous leishmaniasis

The induction of oral tolerance against disease-inducing antigens has emerged as a feasible strategy to prevent immunopathologies. In this study, we investigated the effect of oral immunization with whole antigens of Leishmania amazonensis promastigotes (LaAg) on murine cutaneous leishmaniasis. We found that two oral doses with 100 microg LaAg rendered BALB/c and C57BL/6 mice more resistant against subsequent infection with L. amazonensis. The oral vaccine also partially protected BALB/c mice against Leishmania major infection. Unlike the oral route, hepatic immunization was without effect, indicating a requirement for antigen passage through the gut mucosa. Oral LaAg significantly impaired the capacity of infected BALB/c mice to mount a disease-associated hypersensitivity response, compatible with peripheral tolerization. Both IFN-gamma and IL-10, but not IL-4 were greatly elevated in the mesenteric lymph nodes whereas only IFN-gamma was increased in the peripheral lymph nodes, compatible with a TH1 cytokine response. Gamma delta TCR+ T cells may be an important component in antigenic sensitization of the gut mucosa since their depletion during oral immunization reverted protection. These results demonstrate for the first time the feasibility of using the oral route of immunization to induce protection against cutaneous leishmaniasis using a crude parasite antigen.

Identification and purification of immunogenic proteins from nonliving promastigote polyvalent Leishmania vaccine (Leishvacin )

Immunogenic proteins from nonliving promastigote polyvalent Leishmania vaccine against American tegumentary leishmaniasis (Leishvacin ), produced by Biobr s (Biochemistry of Brazil ), Montes Claros, State of Minas Gerais, Brazil, were identified and purified by polyacrylamide electrophoresis gel and electroelution. C57BL/10 mice were vaccinated with proteins with estimated molecular weights of 42, 46, 63, 66, 73, 87, 97, and 160kDa in three doses of 30 g of each protein at 15-day intervals combined with 250 microg of Corynebacterium parvum followed by a challenge infection with 10(5) infective promastigotes from Leishmania (Leishmania) amazonensis. The ability of these proteins to induce immune response and protection was analyzed. No statistical difference was observed in the level of IFN-gamma induced by proteins in vaccinated groups in comparison with control groups. Six months after challenge infection, protection levels of 28.57; 42.86; 57.14; 42.86; 42.86, 57.14; 42.86 and 57.14% were demonstrated for each purified protein.

Detection and characterization of leishmania antigens from an American cutaneous leishmaniasis vaccine for diagnosis of visceral leishmaniasis

Antigens were isolated from vaccines against American Cutaneous Leishmaniasis (ACL) and their reactivity tested against nine different groups of human sera and two groups of dog sera. These antigens react specifically with human and dog visceral leishmaniasis sera when compared to sera from non-infected individuals. Sera from humans from endemic areas of ACL before, or one year after, vaccination, and ACL patients treated and cured by immunotherapy with polyvalent vaccine, did not display significant differences of reactivity to these antigens. In contrast, they displayed a significantly higher reactivity to the antigens when compared to sera from healthy humans from non-endemic areas. No sera reactivity was observed with patients carrying Chagas' disease or tuberculosis. These antigens are polysaccharides aggregates and present molecular masses ranging from 90 to over 200 KDa. These data suggest the use of these antigens for sero-diagnosis of human and canine visceral leishmaniasis.

Vaccination against cutaneous leishmaniasis: current status

The different cutaneous leishmaniases are distinct in their etiology, epidemiology, transmission, and geographical distribution. In most instances cutaneous leishmaniasis is limited to one or a few skin ulcers that develop at the site where the parasites were deposited during the bite of the sandfly vector. Lesions typically heal spontaneously after several months but some lesions can be large and follow a chronic, more severe course. Protective immunity is usually acquired following cutaneous infection with Leishmania spp., so prevention of disease through prophylactic immunization appears to be feasible. Since vaccination with live, virulent parasites is associated with an unacceptable rate of adverse events, attention has turned to the use of killed or attenuated parasite vaccines and defined subunit vaccines. Whole parasite vaccines have the advantage of delivering multiple antigenic epitopes that may be necessary for initiation of a broad-based immune response. Persistent or repeated immune-stimulation by parasite antigens and/or sustained expression of interleukin-12 appear to be critical elements in the development of durable immunity. A number of purified or recombinant antigens, when co-administered with a vaccine adjuvant, appear promising as vaccine candidates against cutaneous leishmaniasis. The sustained expression of recombinant Leishmania antigens by vaccination with DNA is an attractive approach because it mimics the persistent antigenic stimulation of subclinical infection. Effective vaccine-induced immunity must generate an antigen-specific memory T cell population that, upon exposure to the infecting parasite, rapidly produces a type 1 effector T cell response that leads to interferon-gamma-mediated activation of infected macrophages to kill the intracellular parasites. This parasite-directed recall response must be prompt and of sufficient magnitude to overcome the subversive effect that the intracellular infection has on macrophage effector function. It is unlikely that vaccination against cutaneous leishmaniasis would induce sterile immunity, but a small number of parasites are likely to persist subclinically.

The role of BCG in human immune responses induced by multiple injections of autoclaved Leishmania major as a candidate vaccine against leishmaniasis

To determine if BCG was required in booster injections for autoclaved Leishmania major (ALM) vaccine, 75 volunteers with no response to leishmanin were injected double-blind and randomly with either ALM+BCG or BCG alone for the first injection and boosted either with ALM+BCG, ALM or BCG alone for the second and third. Addition of BCG to the boosters significantly increased the frequency and the magnitude of leishmanin skin tests (LSTs); however, there was no difference in proliferative and IFN-gamma responses (a month and a year later). Three injections of BCG produced no observable adverse reaction; hence BCG could be used in booster injections to increase the protective potential of this candidate vaccine.

Saponins, IL12 and BCG adjuvant in the FML-vaccine formulation against murine visceral leishmaniasis

The FML antigen of Leishmania donovani, in combination with either Riedel de Haën (R), QuilA, QS21 saponins, IL12 or BCG, was used in vaccination of an outbred murine model against visceral leishmaniasis (VL). Significant and specific increases in anti-FML IgG and IgM responses were detected for all adjuvants, and in anti-FML IgG1, IgG2a and IgG2b and delayed type of hypersensitivity to L. donovani lysate (DTH), only for all saponins and IL12. The QS21-FML and QuilA-FML groups achieved the highest IgG2a response. QuilA-FML developed the strongest DTH and QS21-FML animals showed the highest serum IFN-gamma concentrations. The reduction of parasitic load in the liver in response to each FML-vaccine formulation was: 52% (P<0.025) for BCG-FML, 73% (P<0.005) for R-FML, 93% (P<0.005) for QuilA-FML and 79.2% (P<0.025) for QS21-FML treated animals, respectively. Protection was specific for R-FML and QS21-FML while the QuilA saponin treatment itself induced 69% of LDU reduction. The FML-saponin vaccines promote significant, specific and strong protective effects against murine visceral leishmaniasis. BCG-FML induced minor and non-specific protection while IL12-FML, although enhancing the specific antibody and IDR response, failed to reduce the parasitic load of infected animals.

Vaccination of C57BL/10 mice against cutaneous Leishmaniasis using killed promastigotes of different strains and species of Leishmania

Antigenic extracts from five Leishmania stocks were used to vaccinate C57BL/10 mice. The Leishvacin(R) and PH8 monovalent vaccine yielded the highest IFN-gamma levels in the supernatants of spleen cell culture from vaccinated animals. Each single strain immunized group showed evidence of protective immunity six months after the challenge with promastigotes of Leishmania (Leishmania) amazonensis. No differences were detected between the vaccinated groups. It can be concluded that vaccines composed of single Leishmania stocks can provide protection to C57BL/10 mice against L. (L.) amazonensis infection.

Immunochemotherapy for cutaneous leishmaniasis: a controlled trial using killed Leishmania (Leishmania) amazonensis vaccine plus antimonial

BACKGROUND

Leishmaniasis is endemic in 88 countries in the world, and 350 million individuals are at risk of acquiring the disease. Treatment for American cutaneous leishmaniasis (ACL) is long, expensive, and associated with important side-effects.

METHODS

In this double-blind, placebo-controlled study, we treated 102 patients with ACL using either a combination of a single-strain Leishmania amazonensis killed promastigote vaccine plus a half dose of meglumine antimoniate, or placebo plus the same half dose regimen of meglumine antimoniate, in 10-day series followed by 10-day intervals.

RESULTS

Of the 47 patients in the experimental arm, 47 (100%) were cured after four series of treatment, compared to four of 49 (8.2%) in the control group (P < 0.0001). Six patients were lost to follow-up.

CONCLUSIONS

The combination of a single-strain Leishmania (Leishmania) amazonensis killed promastigote vaccine with a half dose regimen of antimonial is highly effective for the treatment of ACL.

A randomized double-blind placebo-controlled trial to evaluate the immunogenicity of a candidate vaccine against American tegumentary leishmaniasis

This study was aimed at evaluating the immunogenicity of a vaccine composed of killed Leishmania amazonensis promastigotes using several different protocols in a randomized, double-blind and controlled trial design in order to select one of them for further efficacy trials. One hundred and fourteen leishmanin skin test (LST)-negative healthy volunteers were allocated into eight groups that received either two or three deep intramuscular injections of vaccine at doses of 180, 360 and 540 microg or similar injections of placebo. Cell-mediated immune responses were evaluated before and after vaccination by means of LST as well as proliferative responses and cytokine production in Leishmania antigen-stimulated peripheral blood mononuclear cell cultures. The majority of the subjects who actually received vaccine converted to positive LST (89.5%). On the other hand, none of the subjects who received placebo converted to positive LST. Proliferative responses and production of interferon-gamma and interleukin-2 were significantly higher after vaccination than before vaccination in all groups, including those that received placebo. The dose of 360 microg provided the highest LST conversion rate (100%), as well as the greatest increase in interferon-gamma and interleukin-2 production after vaccination.

Differences in gamma interferon production in vitro predict the pace of the in vivo response to Leishmania amazonensis in healthy volunteers

The initial encounter of Leishmania cells and cells from the immune system is fundamentally important in the outcome of infection and determines disease development or resistance. We evaluated the anti-Leishmania amazonensis response of naive volunteers by using an in vitro priming (IVP) system and comparing the responses following in vivo vaccination against the same parasite. In vitro stimulation allowed us to distinguish two groups of individuals, those who produced small amounts of gamma interferon (IFN-gamma) (n = 16) (low producers) and those who produced large amounts of this cytokine (n = 16) (high producers). IFN-gamma production was proportional to tumor necrosis factor alpha and interleukin 10 (IL-10) levels but did not correlate with IL-5 production. Volunteers who produced small amounts of IFN-gamma in vitro remained low producers 40 days after vaccination, whereas high producers exhibited increased IFN-gamma production. However, 6 months after vaccination, all individuals tested produced similarly high levels of IFN-gamma upon stimulation of their peripheral blood mononuclear cells with Leishmania promastigotes, indicating that low in vitro producers respond slowly in vivo to vaccination. In high IFN-gamma producers there was an increased frequency of activated CD8(+) T cells both in vitro and in vivo compared to the frequency in low producers, and such cells were positive for IFN-gamma as determined by intracellular staining. Such findings suggest that IVP responses can be used to predict the pace of postvaccination responses of test volunteers. Although all vaccinated individuals eventually have a potent anti-Leishmania cell-mediated immunity (CMI) response, a delay in mounting the CMI response may influence resistance against leishmaniasis.

[Evaluation of the sensitization power of Montenegro skin test]

The Montenegro skin test, used to diagnose cutaneous leishmaniasis, is now being considered to detect immunogenicity after vaccination. In this study, we evaluated the ability of this test to induce immune response and IFN-g production in subjects not previously exposed to Leishmania. The Montenegro skin test was performed using antigens of L. amazonensis produced by our laboratory (group I) or by FIOCRU-RJ (group II). At day 30, 33% of the subjects from group I and 42% from group II were positive, compared to 67% from group I and 50% from group II at day 90. IFN-y was detected in 56 % of subjects from group I and 17% from group II at day 30 (169+/-309 and 11+/-36pg/ml) and in 67% from group I and 58% from group II by day 360 (69+/-107 and 18+/-20pg/ml). These data demonstrate that the Montenegro skin test induces not only a delayed hypersensitivity reaction, but also IFN-y production.

Biochemical and biological characterization of the protective Leishmania pifanoi amastigote antigen P-8

The Leishmania pifanoi amastigote antigen P-8 has been previously shown to induce protective immunity in a murine model of cutaneous leishmaniasis (L. Soong, S. M. Duboise, P. Kima, and D. McMahon-Pratt, Infect. Immun. 63:3559-3566, 1995). As this antigen is of interest for further vaccine studies, the biochemical characterization of P-8 was undertaken. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western-blot analysis, and gel filtration chromatography revealed that P-8 antigen consisted of two proteoglycolipid complexes. The P-8 epitope is associated with the L. pifanoi amastigote-specific glycolipid components found in the two complexes. The P-8 complex 1 (P-8c1) consists of a 56-kDa serine metalloproteinase, apolipoprotein E (derived from fetal bovine serum), and amastigote-specific glycolipids. The P-8 complex 2 (P-8c2) consists of a 31-kDa cysteine proteinase associated with amastigote glycolipids. Biochemical analyses suggest that the P-8 antigenic glycolipids may be distinct from previously described Leishmania glycolipids (glycosylinositol-phospholipids and sphingoglycolipids). Protective immunity studies revealed that P-8c1 (serine metalloproteinase-glycolipid complex) confers comparable protection against infection as immunopurified P-8. The isolated P-8c2 (cysteine proteinase-glycolipid complex) does not provide significant protection, nor does stimulation with P-8c2 result in significant T-cell activation in P-8- or P-8c2-vaccinated mice. Consequently, the P-8c1 complex appears to be the immunodominant component of P-8.

Immunochemotherapy in American cutaneous leishmaniasis: immunological aspects before and after treatment

In this study, we evaluated the immune response of patients suffering from cutaneous leishmaniasis treated with two distinct protocols. One group was treated with conventional chemotherapy using pentavalent antimonium salts and the other with immunochemotherapy where a vaccine against cutaneous leishmaniasis was combined with the antimonium salt. Our results show that, although no differences were observed in the necessary time for complete healing of the lesions between the two treatments, peripheral blood mononuclear cells from patients treated by chemotherapy showed smaller lymphoproliferative responses at the end of the treatment than those from patients in the immunochemotherapy group. Furthermore, IFN-gamma production was also different between the two groups. While cells from patients in the chemotherapy group produced more IFN-gamma at the end of treatment, a significant decrease in this cytokine production was associated with healing in the immunochemotherapy group. In addition, IL-10 production was also less intense in this latter group. Finally, an increase in CD8+ -IFN-gamma producing cells was detected in the chemotherapy group. Together these results point to an alternative treatment protocol where healing can be induced with a decreased production of a potentially toxic cytokine.

Vaccination against Leishmania major in a CBA mouse model of infection: role of adjuvants and mechanism of protection

Gp63 is a major surface protein of Leishmania promastigotes. Its protective efficacy has been tested in several experimental models using different mouse strains, gp63 forms, adjuvants and routes of immunization, giving rise to conflicting results. This investigation was designed to determine whether these discrepancies could be ascribed to differing experimental procedures, and to compare gp63-induced protection with that achieved using live promastigotes. Preliminary experiments demonstrated that gp63 was an extremely potent immunogen compared to a standard antigen (ovalbumin). Protection against Leishmania major infection afforded by gp63 inoculation was studied in CBA mice. Injection of gp63 in saline, or of CFA, BCG, and C. parvum without antigen, induced significant protection. When gp63 and adjuvants were combined, results differed depending on the site of vaccination relative to that of the challenge infection. Vaccination with gp63 plus adjuvants in the tail (i.e. close to the site of infection) led to a stronger reduction of lesion size than the basal level of protection elicited by adjuvants alone, except in the case of CFA. Surprisingly however, when the antigen was injected at a distance from the site of infection (immunization in the hind foot pads, infection in the rump), the protective effect of gp63 was decreased by the adjuvants. Finally, vaccination at either site using live parasites (radioattenuated or virulent promastigotes) resulted in most instances in better protection than achieved by any protocol using gp63 and adjuvants. While anti-gp63 T cells proliferated in vitro in response to L. major-infected bone marrow-derived macrophages, they were unable to activate macrophages for parasite killing. This is in contrast with lymphocytes from mice immunized with live parasites, which both proliferated and stimulated significant killing of the microorganisms within 48 h.

Protection of C57BL/10 mice by vaccination with association of purified proteins from Leishmania (Leishmania) amazonensis

In the past few years, induction of protective immunity to cutaneous leishmaniasis has been attempted by many researchers using a variety of antigenic preparations, such as living promastigotes or promastigote extracts, partially purified, or defined proteins. In this study, eleven proteins from Leishmania (Leishmania) amazonensis (LLa) with estimated molecular mass ranging from 97 to 13.5kDa were isolated by polyacrylamide gel electrophoresis and electro-elution. The proteins were associated as vaccine in different preparations with gp63 and BCG (Bacilli Calmette-Guérin). The antigenicity of these vaccines was measured by their ability to induce the production of IFN-gamma by lymphocyte from subjects vaccinated with Leishvacinregister mark or target. The immunogenicity was evaluated in vaccinated mice. C57BL/10 mice were vaccinated with three doses of each vaccine consisting of 30 microg of each protein at 15 days interval. One hundred microg of live BCG was only used in the first dose. Seven days after the last dose, they received a first challenge infection with 10(5) infective promastigotes and four months later, a second challenge was done. Two months after the second challenge, 42.86% of protection was obtained in the group of mice vaccinated with association of proteins of gp63+46+22kDa, gp63+13.5+25+42kDa, gp63+46+42kDa, gp63+66kDa, and gp63+97kDa; 57. 14% of protection was demonstrated with gp63+46+97+13.5kDa, gp63+46+97kDa, gp63+46+33kDa, and 71.43% protection for gp63 plus all proteins. The vaccine of gp63+46+40kDa that did not protect the mice, despite the good specific stimulation of lymphocytes (LSI = 7. 60) and 10.77UI/ml of IFN-gamma production. When crude extract of L. (L.) amazonensis was used with BCG a 57.14% of protection was found after the first challenge and 28.57% after the second, the same result was observed for gp63. The data obtained with the vaccines can suggest that the future vaccine probably have to contain, except the 40kDa, a cocktail of proteins that would protect mice against cutaneous leishmaniasis.

Leishmania pifanoi amastigote antigen P-4: epitopes involved in T-cell responsiveness in human cutaneous leishmaniasis

In experimental murine cutaneous leishmaniasis, the purified Leishmania pifanoi amastigote protein P-4 has been shown to induce significant protection against infection. Further, recent studies examining the response of peripheral blood mononuclear cells (PBMC) from Leishmania braziliensis-infected human patients have demonstrated that the P-4 protein selectively elicits a significant TH1-like response. Because a TH1-like response is associated with cure, epitope studies were conducted to further evaluate the human response to P-4. PBMC from confirmed cutaneous leishmaniasis patients infected with L. braziliensis in Rio de Janeiro, Brazil, an area where the disease is endemic, were examined for T-cell proliferation and/or cytokine production in response to whole-parasite homogenate, isolated P-4 protein, and/or P-4 peptides. Twenty of the 22 patients (91%) examined responded to the native P-4 protein by proliferation and/or gamma interferon (IFN-gamma) production. According to the proliferation data, PBMC from 14 patients (64%) were found to respond to the intact P-4 protein (stimulation index of >/=2.5). Fifty-seven percent of the P-4-responsive patients studied responded to at least one of the P-4 peptides; 11 individual peptides were found to elicit a proliferative response. Of 17 patients examined for cytokine production, no PBMC produced detectable interleukin-4 in response to P-4 protein or peptides. However, PBMC from 14 patients (82%) produced significant levels of IFN-gamma (>/=20 pg/ml) in response to native P-4 protein. Nineteen of the 23 peptides were found to elicit an IFN-gamma response from at least two patients. These data indicate that multiple epitopes spanning the entire P-4 molecule are responsible for the TH1-like immune response observed, indicating that the intact P-4 amastigote molecule, rather than selected peptides, may prove to be the most useful for leishmaniasis vaccine development.

Immune responses induced by a Leishmania (Leishmania) amazonensis recombinant antigen in mice and lymphocytes from vaccinated subjects

In the search for Leishmania recombinant antigens that can be used as a vaccine against American Cutaneous Leishmaniasis, we identified a Leishmania (Leishmania) amazonensis recombinant protein of 33 kD (Larp33) which is recognized by antibodies and peripheral blood leukocytes (PBL) from subjects vaccinated with Leishvacin, Larp33 was expressed in Escherichia coli after cloning of a 2.2 kb Sau3 digested genomic fragment of L. (L.) amazonensis into the pDS56-6 His vector. Immunoblotting analysis indicated that Larp33 corresponds to an approximately 40-kD native protein expressed in promastigotes of L. (L.) amazonensis and L. (Viannia) braziliensis. Northern blots of total RNA also demonstrated that the gene coding for this protein is expressed in promastigotes of the major lineages of Leishmania causing American Cutaneous Leishmaniasis. Larp33 induced partial protection in susceptible mouse strains (BALB/c and C57BL/10) against L. (L.) amazonensis after vaccination using Bacille Calmette-Guerin (BCG) as adjuvant. In vitro stimulation of splenocytes from BALB/c protected mice with Larp33 elicited the secretion of IL-2 and IFN-gamma, suggesting that a Th1 cell-mediated protective response is associated with the resistance observed in these mice. As revealed by its immunogenic and antigenic properties, this novel recombinant antigen is a suitable candidate to compose a vaccine against cutaneous leishmaniasis.

Assessment of immunity induced in mice by glycoproteins derived from different strains and species of Leishmania

A comparative study was undertaken on the immunogenic properties of 63kDa glycoproteins obtained from five different strains/species of Leishmania and assessed in C57BL/10 mice. The humoral immune response was assessed by ELISA against the five different antigens of the immunized animals. The cellular immune response was derived from Leishmania. The response was found to be species-specific in all of determined by means of the cytokine profiles secreted by the spleen cells of immunized animals. The presence of gamma-IFN and IL-2, and the absence of IL-4 in the supernatants of cells stimulated by L. amazonensis antigen established that the cellular response is of Th1 type. The five glycoproteins tested were equally effective in protecting C57BL/10 mice against challenge by L. amazonensis. About 50% of the immunized animals were protected for six months.

Leishmania pifanoi amastigote antigens protect mice against cutaneous leishmaniasis

In the search for a leishmaniasis vaccine, extensive studies have been carried out with promastigote (insect stage) molecules. Information in this regard on amastigote (mammalian host stage) molecules is limited. To investigate host immune responses to Leishmania amastigote antigens, we purified three stage-specific antigens (A2, P4, and P8) from in vitro-cultivated amastigotes of Leishmania pifanoi by using immunoaffinity chromatography. We found that with Corynebacterium parvum as an adjuvant, three intraperitoneal injections of 5 micrograms of P4 or P8 antigen provided partial to complete protection of BALB/c mice challenged with 10(5) to 10(7) L. pifanoi promastigotes. These immunized mice developed significantly smaller or no lesions and exhibited a 39- to 1.6 x 10(5)-fold reduction of lesion parasite burden after 15 to 20 weeks of infection. In addition, P8 immunization resulted in complete protection against L. amazonensis infection of CBA/J mice and partial protection of BALB/c mice, suggesting that this antigen provided cross-species protection of mice with different H-2 haplotypes. At different stages during infection, vaccinated mice exhibited profound proliferative responses to parasite antigens and increased levels of gamma interferon production, suggesting that a Th1 cell-mediated immune response is associated with the resistance in these mice. Taken together, the data in this report indicate the vaccine potential of amastigote-derived antigens.

Effective immune protection of pigs against cysticercosis

A scolex protein antigen (SPA) was prepared from cysticerci of Taenia solium obtained from naturally infected pigs. Yorkshire pigs were vaccinated with SPA plus incomplete Freund's adjuvant (IFA) or with SPA plus Corynebacterium parvum (CP). Controls were given IFA plus phosphate-buffered saline (PBS) or CP plus PBS. All animals were given three subcutaneous injections at 20-day intervals. Ten days after the third injection, the pigs were fed with 10(4) viable eggs of T. solium. All pigs developed a delayed type hypersensitivity, and a transient eosinophilia after the first dose of vaccine. High titers of specific antibodies were detected in the sera of vaccinated animals and in infected controls. A protection level of 71.43% was recorded in animals vaccinated with SPA plus IFA and of 75.00% in those vaccinated with SPA plus CP.

Th1-like human T-cell clones recognizing Leishmania gp63 inhibit Leishmania major in human macrophages

The major surface protease of Leishmania major, gp63, has been suggested as a vaccine candidate for cutaneous leishmaniasis. In this study gp63 was purified from L. major promastigotes. A panel of human T-cell clones recognizing this protein were generated from individuals who had previously had self-healing cutaneous leishmaniasis. The T-cell clones expressed CD4, and the alpha chain of the T-cell antigen receptor. GP63 reactive T-cell clones activated by antigen or by immobilized anti-CD3 antibody released relative large amounts of interferon-gamma and no or little interleukin-4, thereby resembling Th1 cells. Autologous mononuclear cells and Epstein-Barr virus-transformed B cell lines were equally efficient in presenting the antigen to the T cells. The gp63 reactive T cells induced resistance to infection in cultured human macrophages by L. major. The data confirm that human CD4+ T cells recognizing gp63 can take part in the host defence against L. major infections.