Optimization of lymphocyte proliferation assay for cells with high spontaneous proliferation in vitro: CD4+ T cell proliferation in bovine leukemia virus infected animals with persistent lymphocytosis

Lymphocyte proliferation and apoptosis of lymphocyte subpopulations in bovine leukemia virus-infected dairy cows with high and low proviral load

Bovine leukemia virus (BLV) is one of the most important virus in dairy cattle. The infection behavior follows what we call the iceberg phenomenon: 60% of infected animals do not show clinical signs; 30% develop persistent lymphocytosis (PL); and the remaining 10%, die due to lymphosarcoma. BLV transmission depends on infected cell exchange and thus, proviral load is determinant. Understanding the mechanisms by which cattle governs the control of viral dissemination will be desirable for designing effective therapeutic or preventive strategies for BLV. The development of high proviral load (HPL) or low proviral load (LPL) might be associated to genetic factors and humoral immune responses, however cellular responses are not fully described. It is known that BLV affects cellular homeostasis: proliferation and apoptosis. It is also known that the BLV tropism is directed towards B lymphocytes, and that lymphocytotic animals have elevated amounts of these cells. Usually, when an animal is infected by BLV, the B markers that increase are CD21, CD5 and CD11b. This increase could be related to the modulation of apoptosis in these cells. This is the first work in which animals infected with BLV are classified according to their proviral load and the subpopulations of B and T lymphocytes are evaluated in terms of their percentage in peripheral blood and its stage of apoptosis and viability. PBMCs from HPL animals proliferated more than LPL and non-infected animals. CD11b⁺/CD5⁺ lymphocytes in LPL animals presented greater early and late apoptosis than HPL animals and cells of HPL animals had increased viability than LPL animals. Our results confirm that BLV alters the mechanism of apoptosis and proliferation of infected cells.

Antitumor activity of daphnodorins from Daphne genkwa roots

Daphne genkwa root has been traditionally used as an effective remedy to treat various tumors. However, the active constituents for its antitumor potency have not been well documented. During the screening for antitumor constituents, it was found that daphnodorins were responsible for the inhibition of tumor growth and metastasis. In this study, six daphnodorins including daphnodorins B (1), G (2), H (3), H-3''-methylether (4), H-3-methylether (5) and G-3''-methylether (6) were investigated for the protection against LLC-induced reduction of lymphoid organs and peripheral lymphocytes, and for the activities against tumor growth and metastasis. The six daphnodorins showed selective cytotoxicity to a number of tumor cell lines. Treatment of LLC-bearing mice with daphnodorin B and/or daphnodorin complex evidently protected peripheral lymphocytes from tumor-induced reduction, increased lymphocyte proliferation potential and inhibited tumor progression and metastasis at doses of 40 and 80 mg/kg. These results indicated that daphnodorin B or daphnodorin complex inhibited tumor growth and metastasis by protecting host immunocyte viability and proliferation potential, and selectively inhibiting tumor cell proliferation.

Total flavonoids of Daphne genkwa root significantly inhibit the growth and metastasis of Lewis lung carcinoma in C57BL6 mice

Daphne genkwa root has been traditionally used as an effective remedy to treat various tumors. However, the active constituents for its antitumor potency have not been well documented. During the screening for antitumor constituents, it was found that the total flavonoids of D. genkwa root (TFDR) were responsible for the inhibition of tumor growth and metastasis. In this study, TFDR was investigated for its chemical composition and activities against tumor growth and metastasis. HPLC indicates that daphnodorin B, containing 42.79% of the total, represents the predominant constituent in TFDR. Treatment of LLC-bearing mice with TFDR evidently protected peripheral lymphocytes from tumor-induced reduction, and increased lymphocyte proliferation potential and cytolytic activity of NK, and inhibited tumor progression and metastasis either 7 days before, or simultaneous with, or 7 days after LLC transplantation. TFDR also suggested higher cytotoxicity to a number of tumor cell lines than that to normal human kidney cell K293. TFDR also induced an enhancement on peripheral release of TNF-alpha at doses between 25 and 75 mg/kg. These results indicated that TFDR inhibited tumor growth and metastasis by protecting host immunocyte viability and its proliferation potential, and selectively inhibiting tumor cell proliferation, and improving cytolytic activity of NK cells, and enhancing TNF release in LLC-bearing mice. Daphnodorin B and its analogues in TFDR are the active constituents in the roots of D. genkwa, contributing to the inhibition of tumor growth and metastasis.

Oral administration of exopolysaccharide from Aphanothece halophytica (Chroococcales) significantly inhibits influenza virus (H1N1)-induced pneumonia in mice

The halophilous cyanobacterium Aphanothece halophytica releases large sums of single type sulfated exopolysaccharide in late logarithmic growth phase in culture. This polysaccharide contained sulfate up to 34.46% of the total moieties in the molecular. As a sulfated polysaccharide that can be biosynthesized in large quantities, however, its antiviral activity has not yet been reported. In this study, we examined effects of exopolysaccharide from A. halophytica Fremy (EPAH) on influenza virus A FM (H1N1) (FM1)-induced pneumonia and reduction in immunocompetence in mice. Previous and simultaneous treatment of EPAH at a dose of 60 mg/kg significantly inhibited pneumonia in FM1-infected mice by 30.4% and 26.7%, respectively. In post-treatment, EPAH displayed its most effective inhibition at a dose of 80 mg/kg with the inhibition rate at 18.69%. Simultaneous treatment of FM1-infected mice with EPAH showed effective improvement on reduction of lymphocyte number with its most effective dose at 60 mg/kg. FM1-infected mice simultaneously received EPAH at a dose of 40 mg/kg also acquired obvious enhancement on release of IL-2 on day 15, and those received EPAH at a dose of 60 mg/kg showed similar enhancement on day 10. Simultaneous treatment with EPAH indicated remarkable recovery or improvement of FM1-induced reduction of IL-1beta level and phagocytic capacity of RES. Simultaneous treatment with EPAH significantly resumed the cytolytic activity of natural killer cells in FM1-infected or CP treated mice at doses of 40 and 60 mg/kg. These results suggested that EPAH is an effective agent against FM1. The mechanisms of its action might be mediated, at least in part, by modulating the host immune system and the interaction positive charges in EPAH and negative charges FM1.

Evaluation of type 1 immune response in naïve and vaccinated animals following challenge with Leptospira borgpetersenii serovar Hardjo: involvement of WC1(+) gammadelta and CD4 T cells

Organisms within the Hardjo serovar of Leptospira species are harbored in cattle throughout the world, causing abortion in pregnant animals as well as being shed in the urine, thereby providing sources of zoonotic infection for humans. We recently showed that sterile immunity in vaccinated cattle is associated with induction of a type 1 (Th1) cell-mediated immune response. Here naïve and previously vaccinated pregnant cattle were challenged with a virulent strain of serovar Hardjo and subsequently evaluated for expression of a type 1 immune response. Lymphocytes that responded in a recall response to antigen by undergoing blast transformation were evident in cultures of peripheral blood mononuclear cells (PBMC) from vaccinated cattle throughout the postchallenge test period while those from naïve cattle were evident at one time point only. Nevertheless, beginning at 2 weeks after challenge, gamma interferon (IFN-gamma) was measured in supernatants of antigen-stimulated PBMC cultures from nonvaccinated animals although the amount produced was always less than that in cultures of PBMC from vaccinated animals. IFN-gamma(+) cells were also evident in antigen-stimulated cultures of PBMC from vaccinated but not from nonvaccinated animals throughout the postchallenge period. The IFN-gamma(+) cells included CD4(+) and WC1(+) gammadelta T cells, and a similar proportion of these two subpopulations were found among the dividing cells in antigen-stimulated cultures as ascertained by carboxyfluorescein succinimidyl ester loading. Finally, while naïve and vaccinated animals had similar levels of antigen-specific immunoglobulin G1 (IgG1) following challenge, vaccinated animals had twofold-more IgG2. In conclusion, while infection may induce a type 1 response we suggest that it is too weak to prevent establishment of chronic infection.

Improving the in vitro antigen specific T cell proliferation assay: the use of interferon-alpha to elicit antigen specific stimulation and decrease bystander proliferation

The measurement of the proliferative response of primed T cells to an antigenic stimulus (lymphocyte transformation assay: LTT) is commonly used for determining T cell immune responsiveness. However, the ratio between the spontaneous and the antigen-triggered response (stimulation index) is frequently quite low (<3-5) making the interpretation difficult. We modified the assay by the addition of interferon-alpha and the use of fresh autologous serum instead of human AB pool serum. These measures significantly enhanced the stimulation index following stimulation with tetanus toxoid, Candida albicans and tick-borne encephalitis (TBE) viral antigen in studies of sensitized patients. There was no concomitant increase in false positive results. Kinetic studies showed a reduced nonspecific background proliferation of non-stimulated cultures particularly between days 4 and 6 of culture. Furthermore, the positive effect of interferon-alpha were confirmed in studies of patients with contact allergy to nickel and gold. We conclude that this modified form of proliferation assay significantly increases the signal to noise ratio which can be attained. This may be of particular value when looking at T cell responses in immunocompromised patients or in diagnostic attempts to detect very low frequencies of antigen-specific T cells.

Regulation of bovine leukemia virus tax and pol mRNA levels by interleukin-2 and -10

Recently, particular cytokines have been identified to affect progression of a variety of diseases and retrovirus infections. Previously, we demonstrated that interleukin-2 (IL-2), IL-12, and gamma interferon increased in peripheral blood mononuclear cells (PBMCs) from animals with early disease and decreased in PBMCs from animals with late disease stages of bovine leukemia virus (BLV) infection. In contrast, IL-10 increased with disease progression. To examine the effects of these cytokines on BLV expression, BLV tax and pol mRNA and p24 protein were quantified by competitive PCR and immunoblotting, respectively. IL-10 inhibited BLV tax and pol mRNA levels in BLV-infected PBMCs; however, the inhibitory effect of IL-10 was prevented in PBMCs depleted of monocytes and/or macrophages (monocyte/macrophages). To determine whether these factors were secreted or monocyte/macrophage associated, monocyte/macrophage-depleted PBMCs were cultured with isolated monocyte/macrophages in transwells where contact between monocyte/macrophages and nonadherent PBMCs was blocked. BLV tax and pol mRNA levels increased in transwell cultures similar to cultures containing nonseparated cells, and IL-10 addition inhibited the increase of BLV tax and pol mRNA. These results suggest that monocyte/macrophages secrete soluble factor(s) that increases BLV mRNA levels and that secretion of these soluble factor(s) could be inhibited by IL-10. In contrast, IL-2 increased BLV tax and pol mRNA and p24 protein production. Thus, IL-10 production by BLV-infected animals with late stage disease may serve to control BLV mRNA levels, while IL-2 may increase BLV mRNA in the early disease stage. To determine a correlation between cell proliferation and BLV expression, the effect of IL-2 and IL-10 on PBMC proliferation was tested. As anticipated, IL-2 stimulated while IL-10 suppressed antigen-specific PBMC proliferation. The present study, combined with our previous findings, suggests that increased IL-10 production in late disease stages suppresses BLV mRNA levels, while IL-2-activated immune responses stimulate BLV expression by BLV-infected B cells.