Research using the immune stimulant being developed by RibiImmunoChem Research Inc. has found that it can selectivelyaffect different cells of the immune system, and thereby mayprove useful in AIDS and in cancer.
The new research was conducted at the National Institute ofAllergy and Infectious Diseases and published in the Septemberissue of the journal Infection and Immunity.
The study shows that Ribi's monophosphoryl lipid A, aderivative of the powerful bacterial toxin that prompts theimmune system's overreaction in septic shock, dampensimmune suppression without stopping killer cells.
The finding confirms the idea that suppressor cells and killercells are distinct subsets of CD8 T cells, and opens the way tomanipulating each separately.
By selectively eliminating suppression, the immune system isprevented from shutting down, as it normally would followinga challenge. And lipid A leaves killer cells on the alert forinfected or tumorous cells.
The new study "supports part of our rationale of how lipid Aworks," Ribi spokesman Jeffrey McDowell told BioWorld.Continued action of the immune system would be desirable incancer.
The stimulant is part of the company's vaccine againstmelanoma, said McDowell.
Ribi's melanoma vaccine, delivered with an adjuvant thatincludes lipid A, is in Phase II testing, and the company plansto start Phase III trials in October. Lipid A itself is in PhaseI/II testing to determine its activity in preventing orameliorating septic shock.
Lipid A in the company's adjuvant is also included in othervaccines being tested by Ribi and by the company incollaboration with SmithKline Beecham and Biomira Inc. ofEdmonton, Alberta.
The Hamilton, Mont., company (NASDAQ:RIBI) is not directlypursuing the lead in AIDS. "An AIDS study would be prohibitivefor us," McDowell said. But "a third party" is using a model ofsuppressed immunity to investigate the potential of lipid A inthat condition, which is characterized by an imbalance ofsupressor, helper and killer T cells.
-- Roberta Friedman, Ph.D. Special to BioWorld
(c) 1997 American Health Consultants. All rights reserved.