Transfer factor 1993: new frontiers

Herpes murine model as a biological assay to test dialyzable leukocyte extracts activity

Human dialyzable leukocyte extracts (DLEs) are heterogeneous mixtures of low-molecular-weight peptides that are released on disruption of peripheral blood leukocytes from healthy donors. DLEs improve clinical responses in infections, allergies, cancer, and immunodeficiencies. Transferon is a human DLE that has been registered as a hemoderivate by Mexican health authorities and commercialized nationally. To develop an animal model that could be used routinely as a quality control assay for Transferon, we standardized and validated a murine model of cutaneous HSV-1 infection. Using this model, we evaluated the activity of 27 Transferon batches. All batches improved the survival of HSV-1-infected mice, wherein average survival rose from 20.9% in control mice to 59.6% in Transferon-treated mice. The activity of Transferon correlated with increased serum levels of IFN-γ and reduced IL-6 and TNF-α concentrations. Our results demonstrate that (i) this mouse model of cutaneous herpes can be used to examine the activity of DLEs, such as Transferon; (ii) the assay can be used as a routine test for batch release; (iii) Transferon is produced with high homogeneity between batches; (iv) Transferon does not have direct virucidal, cytoprotective, or antireplicative effects; and (v) the protective effect of Transferon in vivo correlates with changes in serum cytokines.

Antiviral mode of action of bovine dialyzable leukocyte extract against human immunodeficiency virus type 1 infection

BACKGROUND

Bovine dialyzable leukocyte extract (bDLE) is derived from immune leukocytes obtained from bovine spleen. DLE has demonstrated to reduce transcription of Human Immunodeficiency Virus Type 1 (HIV-1) and inactivate the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway. Therefore, we decided to clarify the mode of antiviral action of bDLE on the inhibition of HIV-1 infection through a panel of antiviral assays.

RESULTS

The cytotoxicity, HIV-1 inhibition activity, residual infectivity of bDLE in HIV-1, time of addition experiments, fusion inhibition of bDLE for fusogenic cells and the duration of cell protection even after the removal of bDLE were all assessed in order to discover more about the mode of the antiviral action.HIV-1 infectivity was inhibited by bDLE at doses that were not cytotoxic for HeLa-CD4-LTR-β-gal cells. Pretreatment of HIV-1 with bDLE did not decrease the infectivity of these viral particles. Cell-based fusion assays helped to determine if bDLE could inhibit fusion of Env cells against CD4 cells by membrane fusion and this cell-based fusion was inhibited only when CD4 cells were treated with bDLE. Infection was inhibited in 80% compared with the positive (without EDL) at all viral life cycle stages in the time of addition experiments when bDLE was added at different time points. Finally, a cell-protection assay against HIV-1 infection by bDLE was performed after treating host cells with bDLE for 30 minutes and then removing them from treatment. From 0 to 7 hours after the bDLE was completely removed from the extracellular compartment, HIV-1 was then added to the host cells. The bDLE was found to protect the cells from HIV-1 infection, an effect that was retained for several hours.

CONCLUSIONS

bDLE acted as an antiviral compound and prevented host cell infection by HIV-1 at all viral life cycle stages. These cell protection effects lingered for hours after the bDLE was removed. Interestingly, bDLE inhibited fusion of fusogenic cells by acting only on CD4 cells. bDLE had no virucidal effect, but could retain its antiviral effect on target cells after it was removed from the extracellular compartment, protecting the cells from infection for hours.bDLE, which has no reported side effects or toxicity in clinical trials, should therefore be further studied to determine its potential use as a therapeutic agent in HIV-1 infection therapy, in combination with known antiretrovirals.

Transfer factors as immunotherapy and supplement of chemotherapy in experimental pulmonary tuberculosis

Problems of logistics, compliance and drug resistance point to an urgent need for immunotherapeutic strategies capable of shortening the current six month antibiotic regimens used to treat tuberculosis. One potential immunotherapeutic agent is transfer factors. Transfer factors (TF) are low molecular weight dialysable products from immune cells which transmit the ability to express delayed-type hypersensitivity (DTH) and cell mediated immunity from sensitized donors to nonimmune recipients. In this study we determined the efficiency of TF as immunotherapy to treat experimental tuberculosis. When BALB/c mice are infected via the trachea with Mycobacterium tuberculosis H37Rv there is an initial phase of partial resistance dominated by Th-1 type cytokines plus tumour necrosis factor-alpha (TNFalpha) and the inducible isoform of nitric oxide synthase (iNOS), followed by a phase of progressive disease characterized by increasing expression of IL-4, diminished expression of TNFalpha and iNOS, and low DTH. Animals in this late progressive phase of the disease (day 60) were treated with different doses of TF (one injection per week) obtained from spleen cells when the peak of immune protection in this animal model is reached (day 21), or with different doses of TF from peripheral leucocytes of PPD + healthy subjects. We show here that the treatment with murine or human TF restored the expression of Th-1 cytokines, TNFalpha and iNOS provoking inhibition of bacterial proliferation and significant increase of DTH and survival. This beneficial effect was dose dependent. Interestingly, murine TF in combination with conventional chemotherapy had a synergistic effect producing significant faster elimination of lung bacteria loads than chemotherapy alone.