Marina Sosa

Immunotherapy with natural interleukins and/or thymosin α1 potently augments T-lymphocyte responses of hydrocortisone-treated aged mice

Cytokines and thymic hormones are thought to play critical roles in the regulation of T-lymphocyte development and function. In an effort to determine the effectiveness of such agents in an immunotherapeutic strategy, we employed aged mice in a hydrocortisone treatment model to generate an immunodeficient state and to study its reconstitution. Mice were given five daily injections of a natural cytokine mixture (NCM), recombinant interleukins (rIL-1, rIL-2) or their combination, thymosin alpha 1 or fraction 5 (T alpha 1, TF5), or the combinations of NCM plus T alpha 1 and of NCM plus TF5. Spleen and thymus weights were obtained and the cellular responses to stimulation in vitro with NCM, IL-1, IL-2 and mitogens (PHA and Con A) were assayed. Both NCM and T alpha 1 in vivo treatment augmented thymocyte and splenocyte in vitro responses to both interleukins and mitogens. Neither treatments with equivalent doses of rIL-1, rIL-2 nor their combination, nor TF5 achieved similar results. Of all the treatments, only NCM plus T alpha 1 augmented spleen weight; none augmented thymus weight. Surface marker analyses of T-lymphocytes and subsets indicate that treatment of mice with NCM plus T alpha 1 increased spleen T-cell numbers of both CD4 and CD8 positive cells significantly. These data indicate that NCM and T alpha 1 alone and in combination may be therapeutically useful to restore T-lymphocyte number or function in secondary immunodeficiency.

Mixed interleukins and thymosin fraction V synergistically induce T lymphocyte development in hydrocortisone-treated aged mice

Analysis of the role of interleukins in T cell ontogeny in vitro indicates that the regulation of T cell development involves interleukins (ILs) as well as thymic hormones (THs). In order to assess their respective roles in T lymphocyte development in vivo, chemically thymectomized mice were treated with ILs and THs. After 2 days of hydrocortisone treatment, aged mice showed acute thymic involution (weight was less than 30% of control) and reduced spleen size (less than 80% of control) with progressive recovery to 8 days. After 2 days of hydrocortisone treatment, adult mice were injected for 5 days with mixed buffy coat interleukins (BC-IL; 50 units IL2 equivalence), purified IL2 (50 units), rIL1 beta (4 ng), and thymosin fraction V (TF5; 100 micrograms). The animals were sacrificed and spleens and thymuses were analyzed for weight, cellularity, T cell number, subsets, and function as determined by proliferative responses to concanavalin A and ILs. BC-IL treatment increased the recovery of spleen and thymus weights and cellularity with corresponding augmentation of number and function of T lymphocytes; neither IL1 or IL2 or their combination had this effect. TF5 had no effect alone but strongly potentiated the effect of BC-IL on T lymphocyte function. These data indicate that BC-IL in combination with thymic peptides potently promotes T lymphocyte development. The combination may be therapeutically relevant for immunorestoration.

Methyl inosine monophosphate: a potential immunotherapeutic for early human immunodeficiency virus (HIV) infection.

MIMP is a new thymomimetic purine under development for immunorestorative therapy. Lymphocytes were obtained from eight patients with acquired immunodeficiency disease (AIDS), eight with symptomatic pre-AIDS (ARC), and 22 normal controls and were stimulated in vitro with phytohemagglutinin (PHA). AIDS patients (mean CD4 counts of 40) showed PHA responses less than 10% of control while ARC patients (mean CD4 counts of 544) showed responses approximately 50% of the control responses. MIMP (0.1, 1, 10 and 100 micrograms/ml) progressively augmented the PHA responses in all these groups. The augmentation of the responses of the leukocytes of AIDS patients while statistically significant was minimal. The augmentation of the responses of ARC patients was significant and their maximal responses approached control levels. The effect of 1 micrograms/ml MIMP was comparable with that observed with indomethacin (10(-6) M) and interleukin-2 (IL2 - 4 units/ml) and was additive with each of these stimulants. In a parallel manner, MIMP restored the suppression of control lymphocytes induced by the immunosuppressive 17 amino acid fragment of the P41 peptide of HIV. In vivo experiments showed that MIMP significantly delayed death in a murine FLV AIDS model at a dose of 1 mg/kg by the oral or parenteral route. MIMP is under preclinical development for early HIV disease to forestall progression to AIDS by attenuating virus-induced immunosuppression.

The Case for Synergy of Thymic Hormones and Interleukins in Immune Reconstitution

The regulation of T cell development can be viewed as a process requiring the thymus and influenced by endocrine and interleukin-type hormonal influences. Thymic hormones are produced by thymic epithelial cells and regulate the differentiation and function of pre and post-thymic T cells but they do not alone induce intrathymic maturation. Interleukins I and II are produced by activated leukocytes (macrophages and T lymphocytes) and, in addition to regulating mature T cell proliferation, promote in a synergistic manner the proliferation and differentiation of pre T cells (prothymocytes and intrathymic precursors) and of immature thymocytes. Thymic epithelial cells produce thymic hormones and IL1, IL6 and GM-CSF which will, with IL2, promote the responses of immature and mature T lymphocytes. Mixed interleukins, but not thymosin fraction V, promote the development of T cells in neonatal mice and their renewal in aged hydrocortisone-treated mice. Combination treatment with mixed interleukins and thymosin fraction V are synergistic in restoring T cell number and function in secondary T cell immunodeficiency associated with aged hydrocortisone-treated mice.