Patients with severe infections caused by Pythium insidiosum may not respond to systemic antifungal agents. Administration of a vaccine can lead to an immune response that can help to control the infection. The efficacy of a vaccine was first demonstrated in animals with pythiosis.


Pythium insidiosum is a fungus-like organism related to diatoms and algae. It is a eukaryocyte and classified as an oomycete (Kingdom Stramenophila, phylum Oomycota).


Severe pythiosis (arteritis, disseminated disease) usually trigger a Th2 immune response which is nonprotective. This features IL-4, IL-5, neutralizing antibodies, IgE and eosinophils.


Vaccine administration causes a shift to a Th1 immune response which is protective. This features IL-2, gamma-interferon, IgG and activated macrophages.


Antigens used for the vaccine range from crude culture extracts to more purified products.


Requirements for successful immunotherapy:

(1) A patient with a functioning immune system.

(2) An antigenic dose that does not trigger an excessive inflammatory response. The dose is usually determined by inoculating small amounts of various dilutions of the vaccine.

(3) Resources for resuscitating the patient if an anaphylactic reaction occurs.


A patient with a functioning immune system who receives an appropriate vaccine dose will develop an inflammatory reaction at the site of the vaccination.


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