Avid Bioservices Inc (CDMO)

[jazzbeerman]

exposed PS as the fundamental immunosuppression signal, and PS-blocking as immunomodulatory therapy-



the below from a US patent application for therapeutic annexin V. It's out of Martin Herrmann's team, PS & autoimmunity giants, (who have recently started a company called Responsif in Germany, hoping to develop this tech). This is an excellent read to understand the role of PS in normal cell turnover, cancer, viral and parasitic infections, as well as the implications (now proven in the clinic by Peregrine's mab) of blocking PS.



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United States Patent Application 20040096467
Kind Code A1
Kalden, Joachim Robert ; et al. May 20, 2004

Drug, in particular for modulating the immunological response for the control of viruses, tumors, bacteria and parasites


http://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsea....





excerpts

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BACKGROUND OF THE INVENTION

[0003] Phosphatidylserine-dependent phagocytosis

[0004] Phosphatidylserine is a negatively charged phospholipid which is located in the inner layer of the plasma membrane in all cells. Occasionally, however, a phosphatidylserine molecule translocates to the outer layer of the plasma membrane. In living healthy cells, phosphatidylserine which has reached the outer layer is immediately transported back enzymatically to the inner layer of the plasma membrane. In contrast, the phosphatidylserine remains in the outer cell membrane layer in aged and in Plasmodium falciparum-infected erythrocytes, in sickle cells, post-inflammatory granulocytes and in apoptotic cells. If a certain degree of phosphatidylserine exposure is reached, phagocytes bind to these cells, which still maintain the integrity of their plasma membranes, via the phosphatidylserine receptor. If the phosphatidylserine density reaches a certain threshold value, the cells which are committed to die are very rapidly phagocytozed. In this process, no release of the cell contents to the surrounding tissue and therefore no activation of the immune system occurs. For this reason, this phagocytosis pathway, which depends on the recognition of phosphatidylserine on the surface of a dying cell, is called non-inflammatory.

[0005] The role of phosphatidylserine-dependent phagocytosis in Malaria-infections

[0006] In the course of physiological tissue turn-over, when cells which have grown old are removed, e.g. erythrocytes and apoptotic cells, such as post-inflammatory granulocytes, a specific immunosuppression is essential, since in these cases a pro-inflammatory phagocytosis would result in autoimmune phenomena. The non-inflammatory phagocytosis of Plasmodium falciparum-infected erythrocytes, however, is responsible, inter alia, for the extremely poor immune response and difficulties in the immunization against malaria. No measure described to date or prophylaxis against malaria considers the circumstance in which Plasmodium falciparum-infected erythrocytes are taken up into phagocytes by phosphatidylserine-dependent phagocytosis. Medicaments which affect this phagocytosis pathway are presently unknown.

[0007] The role of phosphatidylserine-dependent phagocytosis in viral infections

[0008] The role of the phosphatidylserine-dependent phagocytosis pathway is similar in viral infections. Viruses which are taken up into phagocytes through the phagocytosis of virus-infected apoptotic cells can thus escape immunosurveillance. The uptake of HIV in monocytes, for example, which takes place without triggering of the "respiratory burst", is responsible for the penetration of the HIV into the long-lived monocyte pool, which is early and unnoticed by the immune system. This infection of the monocytes/macrophages, which is presently not understood, is held causally responsible for the persistence of HIV and thus for the formation of the AIDS syndrome. Although the route of infection of monocytes/macrophages with HIV is presently still not clearly identified in molecular terms, an involvement of phosphatidylserine and the phosphatidylserine receptor is probable because of the non-inflammatory phagocytosis. It was for example possible to show, that retrovirus genomes from apoptotic cell debris can be taken up into cells and cause an infection of these cells. Since HIV can survive for a very long time in monocytes, and is possibly spontaneously released even years after the infection, the human immune system cannot completely eliminate the HIV from the body. Since the HIV damages the immune system somewhat on each release by destroying the CD 4-positive cells, the full degree of the AIDS syndrome can thus take several years to develop. Similar problems also exist in the elimination of other viruses persisting or replicating in phagocytes.

[0009] Other retroviruses and particularly the subgroup of the lentiviruses can especially be mentioned here. Some of these viruses (e.g. EIAV, Maedi Visna Virus, CAEV) persist in the phagocytes of hoofed animals and lead to autoimmune diseases. No previously described measure or prophylaxis against HIV infection or infection with other viruses surviving in phagocytes considers the circumstance in which apoptotic cells can be phagocytozed via the phosphatidylserine-dependent pathway. Medicaments which block or modify this phagocytosis pathway are presently unknown.

[0010] The role of phosphatidylserine-dependent phagocytosis in sickle cell anemia

[0011] The situation is different in patients with sickle cell anemia. Owing to the continuous and extremely rapid phagocytosis of autologous, genetically modified erythrocytes, anemia occurs in these patients, which can lead to death in severe cases if untreated. Here, the fact that the phosphatidylserine mediated phagocytosis proceeds in a non-inflammatory manner is less prominent than the fact that phosphatidylserine-exposing cells are eliminated in an extremely rapid and efficient way. Since there are no medicaments which block or modify this phagocytosis pathway, sickle cell anemia is presently treated with repeated blood transfusions.

[0012] The role of phosphatidylserine-dependent phagocytosis in erythrocyte stability

[0013] A problem similar to that in sickle cell anemia also occurs in the storage of erythrocytes for transfusion. Even under blood bank conditions, an increasing number of erythrocytes exposes phosphatidylserine on their surface during storage. After the transfusion, these erythrocytes are very rapidly cleared by phagocytes and thus are lost. Moreover, the transfusion of a substantial amount of aged erythrocytes exposing phosphatidylderine on their surfaces can be stressful to the recipient's organism. Since there are presently no medicaments or additives to conserved blood which prevent this phagocytosis, the storage of erythrocytes is strictly limited in terms of time.

[0014] The role of phosphatidylserine-dependent phagocytosis in cancer therapy

[0015] Tumor vaccines prepared of autologous apoptotic cancer cells, after injection are usually rapidly eliminated by macrophages via anti-inflammatory phagocytosis and therefore do not result in an efficient sensitization of the immune system to the tumor.

[0016] In the preparation of tumor vaccines, the tumor cells returned to the bodies of patients or experimental animals are irradiated in order to prevent the formation of metastases. Since under these circumstances apoptosis is induced in the tumor cells and these are then eliminated in a non-inflammatory manner via the phosphatidylserine-dependent phagocytosis pathway, only a relatively weak immune response usually occurs to the respective tumor. Since at present no substances are known which block or modify the phosphatidylserine-dependent phagocytosis pathway, classical immunization routes and adjuvants are currently used in order to increase the immune response to tumor cells.

[0017] Cancer vaccines pursue the strategy of a specific activation of the immune system to achieve the recognition and elimination of the tumor. One possibility is the use of whole tumor cells as vaccines since they display cancer-associated antigens as the immunological key to the destruction of the tumor they were derived from. An obstacle of these vaccinations is the weak immunogenicity of cancer cells alone, which could be overcome by the additional use of immunostimulatory or response modifying molecules. Annexin V is a monomeric protein ligand of anionic phospholipids and exhibits high affinity to membrane bound phosphatidylserine, which is translocated from the inner to the outer cell membrane layer in apoptotic cells. Apoptotic tumor cells do express phosphatidylserine and consequently might maintain an anti-inflammatory and non-immunogenic environment. Apoptotic tumor cells coated with chicken annexin V lack the phosphatidylserine signal on their surface which reduces the interaction with its receptor. In this case, phagocytosis occurs via different receptors, inducing macrophages to secrete pro-inflammatory mediators and dendritic cells to migrate and maturate, thus achieving a specific immune response against the tumor.


"[0030] Another possible mechanism is the assumption that proteins known to bind phosphatidylserine with high affinity, such as annexins, will be able to block the exposed phosphatidylserine to reduce its interaction with the PSR. Annexin V coating the surface of an apoptotic cell and thereby shielding the PSR most probably reduces the interaction of phosphatidylserine with its receptor. Several other cell surface or bridging molecules interacting with phosphatidylserine might also be impaired. The overall result would be the loss of the dominating PSR function, the stimulation of macrophages to create a pro-inflammatory environment and a signal for the full maturation of dendritic cells, their migration to lymph nodes, and immune stimulatory antigen presentation, resulting in the stimulation of a specific T cell response. "


etc.


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