Therapeutic immunostimulating effects of plant mitogens exemplified by the L4 isolectin of PHA

Phytohemagglutinin-activated human T cells induce lethal graft-versus-host disease in cyclophosphamide and anti-CD122 conditioned NOD/SCID mice

Graft-versus-host disease (GVHD) is a common complication after allogeneic hematopoietic stem cell transplantation. Much of our knowledge regarding GVHD comes from experiments on the mouse hematopoietic system due to ethical and technical constraints. Thus, in vivo GVHD models of the human immune system are required. In this study, we report an effective and reliable protocol for xenogeneic GVHD (xeno-GVHD) model induction using NOD/SCID mice, in which mice underwent a conditioning regimen consisting of intraperitoneal injection of cyclophosphamide and anti-CD122, followed by transfusion of phytohemagglutinin-activated human peripheral blood mononuclear cells containing 1 × 10⁷ T cells, which has not been reported previously. The present model can be utilized to study human immune cell function in vivo and elucidate the mechanisms underlying the pathogenesis of human GVHD. In addition, this model system can help researchers to rapidly determine whether proposed therapeutic strategies for GVHD are efficient in vivo and will elucidate the underlying mechanisms of drugs and cells to be investigated. Furthermore, such a protocol will undoubtedly be very helpful to laboratories that have no available sources of irradiation.

Evaluation of bovine cutaneous delayed-type hypersensitivity (DTH) to various test antigens and a mitogen using several adjuvants

The Bacillus Calmette Guerin (BCG)-induced/purified protein derivative (PPD)-elicited tuberculin skin test is a reliable measure of cell-mediated immune response (CMIR), specifically delayed-type hypersensitivity (DTH); however, its use in livestock may confound diagnosis of Mycobacterium tuberculosis. Therefore, various alternative antigen/adjuvant combinations were evaluated as inducers of DTH that were compared to the BCG/PPD test system with the purpose of finding a skin DTH protocol that does not cross-react with the tuberculin test and allows identification of high and low CMIR responder phenotypes. Specifically, 30 non-lactating cows (five/treatment) were sensitized on day 0 with mycobacteria [BCG, M. tuberculosis or Mycobacterium phlei cell wall extract (MCWE)], and ovalbumin (OVA) emulsified in Freund's complete adjuvant (FCA), non-ulcerative Freund's adjuvant (NUFA), complete NUFA or MCWE. On day 21, cows were injected intradermally with various test antigens including PPD tuberculin, phlein, and OVA. Phosphate buffered saline was included as the negative control and the T-cell mitogen phytohemagglutinin (PHA) was also administered. Double skin-fold thickness was evaluated before and at 6, 24, and 48 h post-injection. Skin biopsies were taken at 24 and 48 h to assess oedema, necrosis, and inflammatory cell infiltration. BCG/PPD and M. phlei/phlein treatments when given with a Freund's adjuvant induced equivalent DTH with peak reactions at 24-48 h after antigen injection. Cows receiving NUFA had fewer injection site granulomas than FCA or CNUFA treatments. The change in skin thickness response to PHA peaked at 6 h. Only cows receiving mycobacteria in NUFA had skin response to OVA, which peaked 6-24 h post-injection. Only sites tested with PPD or phlein had significantly higher lymphocyte infiltration than control, whereas neutrophils were significantly higher at PHA test sites and eosinophils predominated at the PHA test sites. Macrophages were significantly more numerous at the PPD and/or phlein test sites in treatment groups that received killed mycobacteria in a Freund's adjuvant and/or with BCG, and at the PHA test sites in all treatment groups. It was concluded that the M. phlei/phlein system did induce DTH and was similar to the DTH induced by the BCG/PPD system when MCWE was administered with a Freund's adjuvant. Therefore, this protocol is suitable for detecting high/low CMIR responders in research herds. However, cross-reaction to PPD was evident following induction of DTH using M. phlei. Hence, this protocol does not alleviate the problem of artificial induction of DTH cross-reactivity and would not be suitable for commercial herds where tuberculin testing is required.

Curative Potential of Foremost Mitogen Applications

This paper is presented as a sequel to the Mitogen Information Summaries article, representing a condensation of salient features involved with facilitating the curative potential of the more important mitogen applications. Following is a resumé of the critical attributes of mitogen therapy relative to the management of malignant tumors: (1) An inherent capability to recognize and destroy mutated or damaged tissues without altering those that are normal; (2) The capacity to induce global immunostimulation by the nonspecific activation of CD4+/- and CD8+/- cells with balanced production of a variety of cytokines able to stimulate B cell, NK cell, and macrophage pathways, at the same time augmenting myeloproliferation; (3) The ability to afford protection and accelerated recovery from the immunosuppressive and myelosuppressive effects of tumors, infections, GvH reactions, and autoimmune states along with the surgery, irradiation, chemotherapeutic agents, antibiotics, and suppressive factors used in their management; (4) Berke's in vitro data from the lectin-dependent cellular cytotoxicity (LDCC) system showing that systemic administration of mitogens such as PHA-L4 should indeed prove destructive to virtually any type of malignancy, leaving normal tissues undamaged; and (5) The potential of these activities to reconstitute the immune competence so vital to lasting cures. The potential role of L4 immunotherapy for infections may be defined by the following criteria: those, including drug-resistant infections, not satisfactorily treatable otherwise; those in which a rapid response is essential; those that are subclinical, latent, recurrent, chronic, persistent, highly lethal, or opportunistic; those in patients with impaired immune responses; and most importantly, those that are not likely to be adversely affected by immunostimulation. Certain paths of administration such as the intralesional (for granulomas), intrapleural (for pleurisy, empyema), and intraperitoneal (for peritonitis) routes might be tested as supplements to intravenous administration in treating infections using dosages comparable to tumor therapy. Intradermal or dermal applications might be used alone for localized viral or fungal skin lesions. The comparative advantages of each mitogen are listed as follows: PHA-L4, longest experience and most complete, including use in humans; Fraction IV PHA, nonagglutinating, otherwise comparable to L4; PWM, nonagglutinating in the broad mitogenic range, high potency that reduces dosage requirements, noncommercial product preferable for experimental studies and for potential advancement to human use.

Mitogens for curative therapy of HIV-1 infections; an update

The curative objectives of administering mitogens in conjunction with HAART have been to initiate killer reactions against HIV-1, replenish CD4 cells, rejuvenate CD8 cells, stimulate effective immune reactions against malignancies, generate tolerated immune responses against conventional and opportunistic infections, resist treatment-evading tactics of HIV mutations, and reconstitute both immune and hematopoietic competences. With recent observations that these aims might be thwarted by sequestration of HIV-1 infection in memory cells residing in the circulation, lymph nodes, and spleen as well as in various other sites not readily accessible to eradication, stronger emphasis should be focused primarily on mitogen-induced blockage of HIV-1 entry into CD4 cells. Equally important would be the mitogen panactivation of any cells sequestering virions and proviruses, thereby forcing them out of the latent G0 phase and exposing them to destruction by HAART and the immune responses. While the currently best established mitogens for HIV-1 therapy, PHA-L4 and PWM, might be successfully applied independently or in tandem, other mitogens may be found suitable for evaluation.

Mitogen therapy for biological warfare/terrorist attacks and viral hemorrhagic fever control

Ken Alibek was for 17 years a leader in Biopreparat, the Soviet Union's top secret agency involved in developing and stockpiling the most lethal bacteria, viruses, and toxins in the history of mankind before he defected with his family to the United States in 1992. Very contrite when he discovered he had been misled to believe that his efforts had been essential to the survival of his homeland, Alibek has become active sounding an alarm about, among other things, thousands of unemployed Russian scientists who have been seeking survival by selling their destructive expertise to rouge states and bioterrorists. Working full time in devising protective measures that might help control the damaging effects of terrorist attacks, Alibek has placed strong emphasis on stimulating nonspecific immunities of victims mainly with interleukins and other cytokines. A more productive alternative would be giving mitogens such as PHA and PWM to reinforce vaccine and antibiotic actions, at the same time stimulating protective immune, myelopoietic, and lymphopoietic responses. A key objective would be to find an effective management for the dreaded viral hemorrhagic fevers. Using Ebola infection as an experimental model, Yang et al. have shown that PHA can block both the viral secretions that inhibit neutrophil immune responses and the viral transmembrane glycoprotein that facilitates damage of the human endothelial cells responsible for the lethal hemorrhagic manifestations. Normal serum glycoproteins have in the past been clearly shown to inhibit the functions of PHA, thereby increasing dosage requirements. Extrapolation of this interaction with serum glycoproteins suggests that PHA given intravenously in adequate dosage should readily be able to block the deleterious Ebola virus glycoprotein effects. Data in an extensive classification of the hemorrhagic fever viruses recently presented by Barry make it possible to predict that mitogen therapy should be effective for virtually all of the disorders included. Therapeutic trials should best start with intravenous administration of PHA since this is the mitogen about which most is known and the only one given to humans, although the nonagglutinating advantages of fraction i.v. of PHA should be evaluated as a replacement. Functioning in a different mode, PWM has the advantage of much greater potency, and can be given either intravenously or orally, since these appear to be equally effective routes of administration. The best means of properly integrating the use of these mitogens needs to be determined.