A Leishmaniasis vaccine is a vaccine which would prevent

leishmaniasis Leishmaniasis is a wide array of clinical manifestations caused by parasites of the trypanosome genus ''Leishmania''. It is generally spread through the bite of phlebotomine sandflies, ''Phlebotomus'' and ''Lutzomyia'', and occurs most freq ...

. As of 2017, no vaccine for humans was available. Currently some effective leishmaniasis vaccines for dogs exist. The parasite which causes leishmaniasis is ''

Leishmania ''Leishmania'' is a parasitic protozoan, a single-celled organism of the genus '' Leishmania'' that are responsible for the disease leishmaniasis. They are spread by sandflies of the genus ''Phlebotomus'' in the Old World, and of the genus '' ...

'', which is a Trypanosomatida. The disease spreads from sandflies. Animals such as dogs can be a vector for having the parasite, spreading it to sandflies, and from sandflies to humans. A vaccination strategy to control or eliminate Leishmaniasis might include developing a vaccine for humans and other vaccines for animals. Scientists wish for a vaccine and there is vaccine research. There is also consideration that public health practices can control or eliminate leishmaniasis without a vaccine.

Leishmanization

People who recover from leishmaniasis gain immunity from reinfection. "Leishmanization" is the practice of

inoculation Inoculation is the act of implanting a pathogen or other microorganism. It may refer to methods of artificially inducing immunity against various infectious diseases, or it may be used to describe the spreading of disease, as in "self-inoculati ...

with live ''Leishmania'' to induce mild cutaneous leishmaniasis (CL) to prevent future dangerous infection. Some

Bedouin The Bedouin, Beduin, or Bedu (; , singular ) are nomadic Arab tribes who have historically inhabited the desert regions in the Arabian Peninsula, North Africa, the Levant, and Mesopotamia. The Bedouin originated in the Syrian Desert and A ...

and Kurdish cultures practiced leishmanization as traditional medicine. There are historic accounts and decades of medical research describing the efficacy of this. Traditional knowledge about leishmanization has informed the development of a leishmaniasis vaccine.

Vaccine development

A 2015 paper claimed that the development and use of a vaccine would be the best way to eliminate leishmaniasis from South Asia. Attempts to create a vaccine with live, inactivated or attenuated ''

'' have failed. Attempts to create a peptide, DNA, or protein vaccine have shown efficacy in animal vaccine models but not effective in humans. There are a series of challenges with explanations in molecular biology which explain the difficulty of vaccine development. Vaccine development is difficult because the parasites live in humans, sandflies, and other animals, so a vaccine in humans alone would not eliminate the protozoan in insects and animals. There is a challenge in interpreting the data in animal models to apply to humans. Another challenge is effectively transferring knowledge from laboratory settings to field practice. There is also a basic lack of scientific understanding of how an antiparasitic vaccine should generate and maintain immunological memory during parasitic infection. The development of a vaccine using

CRISPR-Cas9 Cas9 (CRISPR associated protein 9, formerly called Cas5, Csn1, or Csx12) is a 160 kilodalton protein which plays a vital role in the immunological defense of certain bacteria against DNA viruses and plasmids, and is heavily utilized in geneti ...

technology was published in 2020 which showed that inoculation with a live attenuated Leishmania major strain induces durable protection, analagous to leishmanization. Anothe gene deletion mutant was created in a Leishmania mexicana strain in 2022, showing complete inhibition of the typical cutaneous lesions in mouse models thanks to a diminished induction of the Th2 cytokines.

Clinical trials

As of 2016 there are several vaccines in development and three have gone to clinical trials. One clinical trial in Brazil used an inactivated vaccine for human immunotherapy. Another in Uzbekistan used an attenuated vaccine for human immunotherapy. Another in Brazil was

vaccination of dogs Vaccination of dogs is the practice of animal vaccination applied to dogs. Programs in this field have contributed both to the health of dogs and to the public health. In countries where routine rabies vaccination of dogs is practiced, for examp ...

to prevent those animals from spreading the disease. The dog vaccines are successful in providing immunity. In 2008, a vaccine for dogs was launched in Brazil, which is known as LeishTech, a recombinant protein based vaccine. In 2011 CaniLeish, a vaccine made with antigens from ''L. infantum'', was licensed in Europe. Efforts are on ongoing to develop further vaccines for dogs with one second generation vaccine up for approval in Brazil as of 2017.

History

In the early 1900s scientists learned how to culture the parasite, and work in the 1940s led by Saul Adler led to the practice of leishmanization being widespread in Israel and Russia until the 1980s, when large-scale clinical trials showed that the practice led to long-term skin lesions, exacerbation of psoriasis, and immunosuppression in some people. During the Iran–Iraq War over 2 million people in Iran were vaccinated this way. As of 2006 such vaccines were still licensed and used in Uzbekistan. Clinical trials with killed parasites had conflicting results in the 1940s, and work on such vaccines did not resume until the 1970s, when there were promising small clinical trials, and which continued with extensive clinical trials in Ecuador, Brazil, in Iran, through the 1990s. Preclinical work with genetically modified live attenuated parasite vaccines was conducted in the 1990s and 2000s, as did work with synthetic peptides, recombinant proteins, glycoproteins and

glycolipid Glycolipids are lipids with a carbohydrate attached by a glycosidic (covalent) bond. Their role is to maintain the stability of the cell membrane and to facilitate cellular recognition, which is crucial to the immune response and in the connec ...

s from leishmania species, and naked DNA. As of 2016, none of these second-generation vaccine candidates had reached the market, and few had been tested in clinical trials.

References

{{reflist, 3 Leishmaniasis Vaccines Animal vaccines