Farrokh Modabber

Autoclaved Leishmania major vaccine for prevention of visceral leishmaniasis: a randomised, double-blind, BCG-controlled trial in Sudan

BACKGROUND Visceral leishmaniasis is a major cause of morbidity and mortality in the Sudan. Drug treatment is expensive, and drug resistance is becoming increasingly common. Safe, effective, and cheap vaccines are needed. We report the results of a vaccine trial against human visceral leishmaniasis. METHODS We undertook a double-blind randomised trial to test the safety and efficacy of an autoclaved Leishmania major (ALM) promastigote vaccine (1 mg per dose). Of 5093 volunteers screened, 2306 had negative leishmanin skin tests and reciprocal titres of less than 6400 in the direct agglutination test. They were randomly assigned two doses of ALM mixed with BCG or BCG alone. Volunteers were followed up for 2 years. The primary endpoint was clinical visceral leishmaniasis or post-kala-azar dermal leishmaniasis. Analyses were by intention to treat. FINDINGS Side-effects were confined to the injection site. The cumulative frequency of visceral leishmaniasis at 2 years did not differ significantly between the group assigned ALM plus BCG and that assigned BCG alone (133/1155 [11.5%] vs 141/1151 [12.3%], p=0.6). The vaccine efficacy was 6% (95% CI -18 to 25). The proportion of individuals showing leishmanin skin conversion was significantly higher in the ALM plus BCG group than in the BCG alone group throughout follow-up (303 [30%] vs 72 [7%] at 42 days). Individuals whose leishmanin test converted after vaccination (induration > or =5 mm) had a significantly lower frequency of visceral leishmaniasis than non-responders (27/375 [7.2%] vs 210/1660 [12.7%], p=0.003). INTERPRETATION We found no evidence that two doses of ALM plus BCG offered significant protective immunity against visceral leishmaniasis compared with BCG alone. Leishmanin skin conversion with an induration of 5 mm or more in either group was associated with protection from the disease.

Randomised vaccine trial of single dose of killed Leishmania major plus BCG against anthroponotic cutaneous leishmaniasis in Bam, Iran.

BACKGROUND A vaccine consisting of a single dose of whole-cell autoclave-killed Leishmania major (ALM) mixed with BCG was assessed in comparison with BCG alone against anthroponotic (human to human transmission) cutaneous leishmaniasis in a randomised double-blind trial in Bam, Iran. METHODS 3637 schoolchildren, aged 6-15 years, with no history of cutaneous leishmaniasis and no response to a leishmanin skin test, were randomly assigned to receive 1 mg ALM mixed with BCG (n = 1839), or BCG alone (n = 1798). Safety of the vaccine and the incidence of confirmed cases of cutaneous leishmaniasis were followed up for 2 years. FINDINGS Side-effects were those usually associated with BCG vaccination, but tended to persist longer in the ALM + BCG group. After exclusion of four cases occurring within 80 days of vaccination (one in the ALM + BCG group and three in the BCG group), the 2-year incidence of cutaneous leishmaniasis did not differ significantly between vaccine and BCG groups: 2.8% vs 3.3%, respectively (total cases 112). A sex-stratified analysis showed that in boys the vaccine conferred a protective efficacy of 18% and 78% for the first and second years, respectively--a crude 2-year overall protection of 55% (95% CI 19-75%, p < 0.01). In the first 9 months after vaccination, there was a non-significant excess of cases in the ALM + BCG group (25 vs 16), whereas the incidence of cutaneous leishmaniasis thereafter was significantly reduced in the ALM + BCG group (27 vs 44, p < 0.05). INTERPRETATION A single dose of ALM + BCG was safe and more immunogenic than BCG alone, as measured by leishmanin skin test. The exact reason for the apparent protective effect of the vaccine in boys is unknown, and may be a chance finding. However, since boys are more exposed to the infection, which is indicated by higher disease prevalence in boys in this study population, the preferential protective effect in boys may have resulted from a greater booster effect produced by repeated exposure to infected sandflies. Booster injections or alternative adjuvants should be tried to improve the potential efficacy of this vaccine.

First generation leishmaniasis vaccines : A review of field efficacy trials

First generation candidate vaccines against leishmaniasis, prepared using inactivated whole parasites as their main ingredient, were considered as promising because of their relative ease of production and low cost. These vaccines have been the subject of many investigations over several decades and are the only leishmaniasis vaccine candidates which have undergone phase 3 clinical trial evaluation. Although the studies demonstrated the safety of the vaccines and several studies showed reasonable immunogenicity and some indication of protection, an efficacious prophylactic vaccine is yet to be identified. Despite this overall failure, these trials contributed significantly to increasing knowledge on human leishmaniasis immunology. To provide a collective view, this review discusses the methods and findings of field efficacy trials of first generation leishmaniasis vaccine clinical trials conducted in the Old and New Worlds.

A randomised, double-blind, controlled trial of a killed L. major vaccine plus BCG against zoonotic cutaneous leishmaniasis in Iran

Safety and efficacy of killed (autoclaved) L. major promastigotes, ALM, mixed with BCG against zoonotic cutaneous leishmaniasis was tested in healthy volunteers (n = 2453) in a randomized double blind trial vs. BCG as control. Side-effects were similar in both groups but tended to be slightly more frequent and prolonged in the ALM + BCG group. Leishmanin skin test conversion (induration > or =5 mm) was significantly greater in the ALM + BCG than in the BCG group (36.2% vs. 7.9% on day-80 and 33% vs. 19%, after 1 year, respectively). Cumulative incidence rates for 2 years, were similar in both groups (18.0% vs. 18.5%). However, LST responders on day 80 (> or =5 mm) had a significantly lower incidence (35%) of CL during the first year than non-responders. A single dose of ALM + BCG is not sufficiently immunogenic to provide a measurable response when compared to BCG alone. A single dose of this vaccine has been shown to be safe with no evidence of an exacerbating response following natural infection; hence, multiple doses or other adjuvants should be considered to increase its immunogenicity.

Alum-precipitated autoclaved Leishmania major plus bacille Calmette-Guérrin, a candidate vaccine for visceral leishmaniasis: safety, skin-delayed type hypersensitivity response and dose finding in healthy volunteers

In a previous efficacy study, autoclaved Leishmania major (ALM) + bacille Calmette-Guérrin (BCG) vaccine was shown to be safe, but not superior to BCG alone, in protecting against visceral leishmaniasis. From June 1999 to June 2000, we studied the safety and immunogenicity of different doses of alum-precipitated ALM + BCG vaccine mixture administered intradermally to evaluate whether the addition of alum improved the immunogenicity of ALM. Twenty-four healthy adult volunteers were recruited and sequentially allocated to receive either 10 microg, 100 microg, 200 microg, or 400 microg of leishmanial protein in the alum-precipitated ALM + BCG vaccine mixture. Side effects were minimal for all doses and confined to the site of injection. All volunteers in the 10 microg, 100 microg, and 400 microg groups had a leishmanin skin test (LST) reaction of > or = 5 mm by day 42 and this response was maintained when tested after 90 d. Only 1 volunteer out of 5 in the 200 microg group had a LST reaction of > or = 5 mm by day 42 and the reasons for the different LST responses in this group are unclear. This is the first time that an alum adjuvant with ALM has been in used in humans and the vaccine mixture was safe and induced a strong delayed type hypersensitivity (DTH) reaction in the study volunteers. On the basis of this study we suggest that 100 1 microg of leishmanial protein in the vaccine mixture is a suitable dose for future efficacy studies, as it induced the strongest DTH reaction following vaccination.

Efficacy of Sodium Stibogluconate Alone and in Combination with Allopurinol for Treatment of Mucocutaneous Leishmaniasis

A randomized, open, controlled clinical trial was designed to evaluate the efficacy, tolerance, and safety of sodium stibogluconate plus allopurinol and sodium stibogluconate alone as treatment of patients with mucocutaneous leishmaniasis. In phase 1 of the study, all 22 patients with severe disease had improvement of their lesions, but only two had clinical cure (both of these patients received sodium stibogluconate alone). In phase 2, which included 59 patients with moderate disease, the cure rate among sodium stibogluconate recipients was 75% (21 of 28) compared with 63.6% (14 of 22) among the sodium stibogluconate plus allopurinol recipients. The rates of clinical adverse events were similar among both groups. Thrombocytopenia was more frequent in the sodium stibogluconate plus allopurinol recipients, but the difference was not statistically significant. Eight patients (two sodium stibogluconate recipients and six sodium stibogluconate plus allopurinol recipients) withdrew from the study because of severe thrombocytopenia. In this study, the addition of allopurinol to sodium stibogluconate provided no clinical benefit as treatment of mucocutaneous leishmaniasis.

Safety and immunogenicity of a killed Leishmania (L.) amazonensis vaccine against cutaneous leishmaniasis in Colombia: a randomized controlled trial

The safety and immunogenicity of an intramuscular (i.m.) and intradermal (ID) formulation of autoclaved Leishmania (Leishmania) amazonensis vaccine was evaluated in 296 volunteers in a randomized, placebo-controlled, double-blind trial in Colombia. There were 4 vaccination groups: i.m. vaccine, i.m. placebo, ID vaccine, and ID placebo. The ID formulations were mixed with BCG as adjuvant at the time of injection. For each group, 3 vaccinations were given with a 20-day interval between injections, and adverse events were monitored at 20 min, and at 2, 7 and 21 days after each injection. BCG-induced adverse reactions resulted in cancellation of the third vaccine administration in the ID groups. Antibody titres did not differ significantly between the groups. Montenegro skin-test conversion was achieved by 86.4% and 90% of the i.m. vaccine group and by 25% and 5% of the i.m. placebo group 80 days and 1 year after vaccination, respectively. A significant increase in mean Leishmania-antigen lymphocyte proliferation indexes was observed after i.m. vaccine immunization, but not after i.m. placebo immunization, 80 days and 1 year after vaccination. Significant levels of IFN gamma but not IL-10 were observed 1 year after vaccination in the i.m. vaccine group compared to the i.m. placebo group. The good safety profile and evidence of Th1 immune reactions due to i.m. vaccination in this phase-I/II study suggest that a population-based phase-III efficacy trial of the i.m. vaccine should be initiated.

Dichotomy of protective cellular immune responses to human visceral leishmaniasis

Healing/protective responses in human visceral leishmaniasis (VL) are associated  with  stimulation/production  of  Th1  cytokines,  such  as  interferon IFN‐γ, and conversion in the leishmanin skin test (LST). Such responses were studied for 90 days in 44 adult healthy volunteers from VL non‐endemic areas, with no past history of VL/cutaneous leishmaniasis (CL) and LST non‐reactivity following injection with one of four doses of Alum‐precipitated autoclaved Leishmania major (Alum/ALM) ± bacille Calmette–Guérin (BCG), a VL candidate vaccine. The vaccine was well tolerated with minimal localized side‐effects and without an increase in antileishmanial antibodies or interleukin (IL)‐5. Five volunteers (5/44; 11·4%) had significant IFN‐γ production by peripheral blood mononuclear cells (PBMCs) in response to Leishmania antigens in their prevaccination samples (P = 0·001) but were LST non‐reactive. On day 45, more than half the volunteers (26/44; 59·0%) had significantly high LST indurations (mean 9·2 ± 2·7 mm) and high IFN‐γ levels (mean 1008 ± 395; median 1247 pg/ml). Five volunteers had significant L. donovani antigen‐induced IFN‐γ production (mean 873 ± 290; median 902; P = 0·001), but were non‐reactive in LST. An additional five volunteers (5/44; 11·4%) had low IFN‐γ levels (mean 110 ± 124 pg/ml; median 80) and were non‐reactive in LST (induration = 00 mm). The remaining eight volunteers had low IFN‐γ levels, but significant LST induration (mean 10 ± 2·9 mm; median 11). By day 90 the majority of volunteers (27/44; 61·4%) had significant LST induration (mean 10·8 ± 9·9 mm; P < 0·001), but low levels of L. donovani antigen‐induced IFN‐γ (mean 66·0 ± 62 pg/ml; P > 0.05). Eleven volunteers (11/44; 25%) had significantly high levels of IFN‐γ and LST induration, while five volunteers had low levels of IFN‐γ (<100 pg/ml) and no LST reactivity (00 mm). One volunteer was lost to follow‐up. In conclusion, it is hypothesized that cellular immune responses to human VL are dichotomatous, and that IFN‐γ production and the LST response are not in a causal relationship. Following vaccination and probably cure of VL infection, the IFN‐γ response declines with time while the LST response persists. LST is a simple test that can be used to assess candidate vaccine efficacy.

Immunological stimulation for the treatment of leishmaniasis: A modality worthy of serious consideration

Instead of relying on drugs to reduce the parasite burden of leishmaniasis, and waiting for the effector immune response to develop in time to control the parasites, immunotherapy in conjunction with chemotherapy can rapidly induce the effector immune response. With a safe and potent drug plus an affordable therapeutic vaccine (immunostimulant), which remains to be developed, a single visit by patients with visceral or cutaneous leishmaniasis might be sufficient to induce a quick and lasting recovery. Drug toxicity and the emergence of resistance could also be dramatically reduced compared with present long-term monotherapy. Immunotherapy could be an effective addition to chemotherapy for leishmaniasis.

Leishmaniasis recidivans among school children in Bam, South-east Iran, 1994–2006

Background  Leishmaniasis recidivans (LR) is a rare phenomenon in the world with high morbidity in children.