We all know that vaccines for many important viral and bacterial diseases are produced successfully . while this is not occur in case of parasitic diseases . can my collegues tell me why?
One theoretical concept that might give us some answers in the future, is that lymphocytes evolved from protozoa. So, it's like asking them to attack their distant cousins. In the case of African trypanosomiasis lymphocytes actually help the parasite to enter the brain.
Intensive lesions have shown that helminths have the potential to inhibit specific immune cells, leading to weaker immune responses
Mechanisms of anti-parasitic immunity are quite different from antibacterial and antiviral ones with leading input of hypersensitivity responses.
T hank you dear Chumak Anatoli and i am agree with you about the difference in mechanism between anti- parasitic immunity and anti-bacterial and viral ones but i am guess the project for vaccines production against parasitic diseases need continues attempts and more immunological researches , best regards Jwad Ali
Not sure I have the correct answer. One aspect is the antigenic complexity of the parasite and the fact that natural protection mechanism are not fully understood. Malaria is a good example as so far not effective vaccines are available. It looks like that none is naturally protected by infection only those who have ethero or omozygosis conditions that modify the red cell metabolism (C/S/Beta/Alfa emoglobins, or Favism etc) do not allow the full Plasmodium cycle and are not ill. As for other parasites It may be well the same. To me understanding fully the mechanism of natural protection, if any does exist, is the prerequisit to develop an effective vaccine. In addition, it has to be technically feasible. And it may not be always the case. Hoping this is helpful.
I think ,is comeback to changing surface antigen of parasite. because, these able to produce different antigen and immune system can’t detected them.
Many reasons for that:
1-The parasites have many antigens.
2-Have many stages and morphology.
3-It moved and migrates in other organs.
4-It can surrounded itself as a cyst.
5-It can hiding from immunity in safe place as eye.
Thanks Dr. Jwad,
Some parasites have autoinfection phenomena, others have Retroinfectin phenomena that need more immunity actions.
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