History, Research, and Development  
  HOME:: LEISHMANIASIS:: LINKS AND REFERENCES ::
VACCINE: HISTORY :: RESEARCH ::CURRENT DEVELOPMENTS :: GLOBAL IMPLICATIONS ::
   

Clinical Trials

Leishmaniasis vaccine clinical trials have been conducted using various suspensions of Leishmania sp. components since 1937. First-generation vaccines have sought to examine the efficacy of vaccines derived from autoclaved Leishmania sp. promastigotes in the presence of various adjuvants and these trials have produced interesting and varied results depending largely on the dosage of the vaccine administered and the type of Leishmaniasis investigated. Important studies have been conducted internationally, particularly in regions with high prevalence of Leishmaniasis. Typically in these trials, a control group is administered a vaccine comprised solely of an adjuvant mixture or a placebo and an experimental group is administered a combination vaccine. To determine if an immune response has been triggered, the induration at the site of injection is measured via the Leishmanin Skin Test (LST) and a skin reaction of at least 5mm is indicative of a conversion of the test. All study participants are monitored for the duration of the trial and an observation is made about the percentage of the population that develops Leishmaniasis over the course of the study. In general study participants who have a conversion of the Leshmanin Skin Test are usually less likely to develop Leishmaniasis during the course of the study than those who do not convert the test, or those participants who are in the control group. As trials have been conducted on both healthy and immuno-compromised populations, interestingly enough in trials among patients already infected with Leishmaniasis some more effective vaccines have demonstrated immunotherapeutic as well as prophylactic properties and have promoted healing of persistent lesions. In general in human models efficacy ratings (in terms of preventing future infection) of various trials range from 0% - 75%, with Cutaneous Leishmaniasis vaccines having the highest efficacy ratings and Visceral Leishmaniasis vaccines having the lowest efficacy ratings. Animal models have produced similar results with respect to triggering an immune response, particularly in infected mice and non-human primates. Fortunately, few human trials have reported any severe adverse side-effects to potential vaccines, and thus future clinical trials aim to continue to measure the dose-response effects of various vaccines on humans.

From Mice to Men...

PHOTO CAPTION:
"Razi Institute, Teheran: Leishmaniasis vaccine production - A technician injects a mouse with leishmaniasis vaccine. Bottles from each batch produced are tested on animals and for quality."
-WHO/TDR/Crump
PHOTO CAPTION:
"Institute of Primate Research (IPR):
Feeding tubes containing infected sandflies applied to the forehead of anaesthetized vervet monkeys. The work is being carried out as part of a project to investigate the development of a vaccine (Old World) for leishmaniasis."
-WHO/TDR/Stone
PHOTO CAPTION:
"Leishmaniasis vaccine - Clinical trials:
Reaction of volunteer number 22 (14 days after vaccination)."
-WHO/TDR/Bahar