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N C Phillips

Publications and source records attributed to N C Phillips.

At least 37 records · Page 2Linked to original sources
PubMed1992

Enhanced antibody response to liposome-associated protein antigens: preferential stimulation of IgG2a/b production.

The effect of liposome encapsulation on the antibody response to bovine serum albumin (BSA), human carcinoembryonic antigen (CEA) and sheep IgG (sIgG) has been determined in the mouse. Dipalmitoylphosphatidylcholine/dimyristolylphosphatidylglycerol liposomes (10:1 molar ratio; 1 mumol) containing BSA, CEA or sIgG induced significant levels of IgG antibodies after one injection, and enhanced the proportion of IgG2a/2b to IgG1 on subsequent boost injection. The IgG antibody titre induced by liposomal antigen was 100-400-fold greater than immunization with antigen alone. Immunization with antigen and the water-soluble adjuvant N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP; 50 micrograms) resulted in antibody titres intermediate between free and liposomal antigen. MDP did not enhance the proportion of IgG2a/2b to IgG1. Incorporation of the lipid soluble MDP derivative MDP-glycerol dipalmitate (MDP-GDP; 10 micrograms) liposomes containing protein antigens resulted in higher titres and enhanced IgG2b isotype expression. Analysis of serum IgG antibody-isotype levels after immunization and boost with BSA/MDP showed that the half-life of IgG2a/2b and IgG3 was significantly less than that of IgG1. Liposomal encapsulation resulted in longer IgG2a/2b and IgG3 half-lives, especially when MDP-GDP was present in the liposome. These results demonstrate that, whereas MDP preferentially stimulates IgG1 antibodies, liposomes elicit high levels of IgG2a/2b isotypes with significantly longer serum half-lives.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1992

Impaired stimulation of anti-bovine serum albumin IgG antibodies by vaccine adjuvants in murine acquired immunodeficiency syndrome.

The effect of three adjuvants - alum, N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), and liposomes - on the IgG antibody isotype response to bovine serum albumin (BSA), was determined in normal and LP-BM5 retrovirus infected C57BL/6 mice. Alum and MDP induced comparable levels of IgG antibodies in normal mice (predominantly IgG1 (greater than 90%)), whereas liposomes induced IgG1 (60%), IgG2a/b (30%) and IgG3 (10%) antibodies. IgG antibody levels using liposomes as adjuvant were five-fold higher than those observed with alum or MDP. Immunization after LP-BM5 infection significantly reduced the effectiveness of alum and MDP, IgG antibody levels being reduced by 80 and 90% at 3 or 7 weeks respectively. The adjuvant activity of liposomes was reduced by 55 and 65% when immunization was started 3 or 7 weeks post LP-BM5 infection. Boosting of pre-immune mice with BSA and alum, MDP or liposomes 3 weeks after LP-BM5 infection showed that, while the magnitude of the antibody response and isotype distribution was not affected, the persistence of the response was severely diminished compared to control, non-infected mice. The reduced immunoadjuvant activity correlated with a reduction in the frequency of splenic Thy1.2+/CD4+ T cells. These results demonstrated that liposomes were more effective than alum or MDP in inducing IgG antibodies, and that immunoadjuvant activity for prophylactic or therapeutic immunization for all 3 adjuvants was significantly impaired by retroviral infections.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1991

Liposomal muramyl dipeptide therapy of experimental M5076 liver metastases in mice.

The effectiveness of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) or of liposomes containing a lipophilic MDP derivative, MDP-glyceroyldipalmitate MDP-GDP in inhibiting the growth of M5076 reticulum cell sarcoma liver metastases in C57BL/6 mice has been determined. MDP (100 micrograms) or liposomal MDP-GDP (2.5 mumol containing 1 microgram) were equally effective in inhibiting liver metastatic growth when given as a single treatment 3 days before tumor cell injection. Therapeutic treatment, initiated 3 days after tumor cell injection and continued for a period of 2 weeks, failed to inhibit metastatic growth. Activation of thioglycollate-elicited peritoneal macrophages or Kupffer cells in vitro with MDP or liposomal MDP-GDP resulted in the expression of tumoricidal activity against M5076 tumor cells. Adoptive cellular therapy with four injections of 2 x 10(6) macrophages was ineffective: activation of the macrophages with either MDP or liposomal MDP-GDP prior to injection was effective in inhibiting liver metastatic growth. Incorporation of the macrophage toxin dichlorodimethylene diphosphonate within liposomes containing MDP-GDP abolished the ability of such liposomes to induce macrophage or Kupffer cell tumoricidal activity in vitro as well as the antitumor activity when administered 3 days before tumor cell challenge.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1991

Immunogenicity of immunoliposomes.

Multilamellar immunoliposomes were prepared from dipalmitoylphosphatidylcholine (DPPC), cholesterol (CH), sphingomyelin (SPH) and biotinylated dipalmitoylphosphatidylethanolamine (PEB) in the molar ratio of 1:1:1:0.1 with surface linked avidin-biotinylated sheep (anti-mouse IgG) IgG (AV-sIgGB) or GK1.5 monoclonal rat (antimouse L3T4 antigen) IgG (AV-GK1.5B). The ability of these immunoliposomes to induce antibody responses against AV, sIgG or GK1.5 was determined. GK1.5B and sIgGB elicited a low-level antibody response (5-10 microgram/ml serum) after i.v. immunization and boosting. Liposomes (1 mumol) containing GK1.5B or sIgGB were more effective than free GK1.5B or sIgGB in eliciting antibodies (20-30 and 100-120 micrograms/ml serum, respectively). Liposomal AV mixed with either sIgG or GK1.5 gave antibody levels comparable to immunization with free GK1.5B or sIgGB. Liposomes with surface AV-sIgGB or AV-GK1.5B elicited antibodies against AV and high levels against GK1.5 or sIgG. Immunoliposomes possessing surface AV-sIgGB or AV-GK1.5B were eliminated from the circulation of normal mice relatively slowly (T1/2 15.5 and 30 min): in contrast, liposomal AV-sIgGB or AV-GK1.5B was rapidly eliminated from the circulation of immunized mice (T1/2 4.5 and 4.0 min). These results demonstrate that liposomes with surface IgG (immunoliposomes) are immunogenic, and that repeated administration elicits anti-IgG antibodies that result in a significant reduction in blood circulation residence times.

Animals↗
PubMed1991

The effect of a high-fat diet on murine macrophage activity.

The phagocytic, oxygen free radical generating and cytotoxic activities of macrophages from C57BL/6J mice fed either a normal or an atherogenic high-fat diet have been investigated. Phagocytosis of aggregated low density lipoprotein (LDL) was only slightly inhibited by the high-fat diet although phorbol myristate acetate (PMA)-induced hydrogen peroxide (H2O2) and superoxide anion (O2-) production was significantly reduced. Activation of tumoricidal activity against L929 target cells by lipopolysaccharide (LPS) or lymphocyte-derived macrophage-activating factor (MAF), but not N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), was also significantly reduced in macrophages from mice fed the high-fat diet. These results indicate that an atherogenic diet is capable of significantly affecting the responsiveness of macrophages to a number of stimulatory agents which act via specific membrane receptors.

Animals↗
PubMed1991

Liposomal encapsulation of 3'-azido-3'-deoxythymidine (AZT) results in decreased bone marrow toxicity and enhanced activity against murine AIDS-induced immunosuppression.

The effect of liposome encapsulation on the bone marrow toxicity and antiviral activity of AZT in C57BL/6 mice was determined. Liposomal encapsulation of AZT enhanced localization in the liver, spleen, and lung, and reduced localization in bone marrow. AZT administered i.v. (0.08-50 mg/kg/day) had significant bone marrow toxicity (30-50% reduction in cellularity) after five injections, maximum toxicity occurring at greater than or equal to 2 mg/kg/day. Parallel reductions in the number of erythrocytes and leukocytes were observed. AZT encapsulated in liposomes had no bone marrow toxicity at doses of 0.08-10 mg/kg/day, and erythrocyte and leukocyte numbers remained normal. Infection of C57BL/6 mice with LP-BM5 murine leukemia virus suppressed T- and B-cell mitogenic responses. Treatment of LP-BM5 retrovirus-infected mice with 2 mg/kg AZT three times weekly partially protected the mitogenic response at 4 but not at 7 weeks postinfection. Treatment with liposomal AZT resulted in normal T- and B-cell mitogenic responses at both 4 and 7 weeks postinfection.

Animals↗
PubMed1990

Clinical evaluation of liposomal tumor antigen vaccines in patients with stage-III melanoma.

In this study, we report the results of an active-specific immunotherapy phase I study using autologous tumor-associated antigens (TAA) incorporated within liposomal carriers in patients with metastatic malignant melanoma. A group of 13 patients were entered into the study and given subcutaneous (s.c.) injections of liposome-TAA preparations at 2- to 4-week intervals. Clinical and laboratory monitoring did not reveal any short- or long-term systemic or local toxicity. Three patients had a complete response, and two patients had a partial response (50% or greater size reduction in one or more tumor sites). The remaining eight patients showed no response with disease progression. Two of these eight patients are still undergoing treatment. The TAA preparations stimulated peripheral blood lymphocyte proliferation (PBL) in vitro in those patients exhibiting a clinical response: no such responses were observed in the nonresponder patients. NK cell activity did not correlate with PBL proliferation or clinical response status, whereas PBL cytostatic activity against heterologous melanoma tumor cells correlated with clinical responsiveness. This form of immunotherapy appears to be a safe and feasible candidate for a much larger phase I/II study.

Adult↗
PubMed1990

Immunoliposome targeting to CD4+ cells in human blood.

Liposomes were prepared from phospholipid formulations recognized or ignored by cells of the reticuloendothelial system (RES+ve or RES-ve, respectively). The ability of these liposomes to interact with CD4+ve cells in purified leukocyte fractions or in whole blood has been determined. RES+ve liposomes bound to monocytes in purified leukocyte fractions or in whole blood, but did not bind to lymphocytes. RES-ve liposomes did not bind to either monocytes or lymphocytes. The attachment of an anti-Leu3A (CD4) monoclonal antibody to the outer surface of RES-ve liposomes resulted in their interaction with both monocytes and lymphocytes. The binding was blocked by prior incubation of the leukocytes with free anti-Leu3A antibody. RES+ve liposomes were rapidly eliminated from the circulation of mice after intravenous injection, whereas RES-ve liposomes remained in the circulation for prolonged periods of time (half-life much greater than 5 h), even after incubation with the opsinizing acute-phase reactant, C-reactive protein. These results suggest that RES-ve liposomes possessing surface-bound anti-Leu3A may provide a means of targeting antiviral agents to those cells at risk from HIV infection.

Animals↗
PubMed1989

Induction of colony-stimulating activity in mice by injection of liposomes containing lipophilic muramyl peptide derivatives.

Colony-stimulating factor (CSF) activity induction by lipophilic derivatives of three muramyl peptides, glyceryl dipalmitate-MDP derivatives, was studied in vivo and in vitro and compared to the activity of the same compounds incorporated within freeze-dried liposomes. Two lipophilic derivatives (MDP-GDP and MDPGBe-GDP) were able to induce CSF activity in vivo and in vitro. The incorporation of these compounds within appropriately designed liposomes composed of distearoylphosphatidylcholine and phosphatidylserine (DSPC/PS) increased their ability to induce CSF activity in vivo but completely abrogated their ability to induce CSF activity in vitro. Furthermore, the phospholipid composition of liposomes influenced the efficacy of glycopeptide liposomal incorporation. Thus, the serum CSF-inducing effect of MDP-GDP was considerably enhanced by incorporation of this compound within liposomes composed of DSPC/PS at a molar ratio 7:0.3 but was not modified if the DSPC/PS molar ratio was 7:3. The lipophilic derivative of MDP (D-D), MDP (D-D)-GDP, was unable to induce CSF activity in vivo or in vitro but surprisingly became active in vivo after entrapment within DSPC/PS liposomes (molar ratio 7:0.3). Our results show that appropriate liposomes may be suitable carriers to deliver CSF activity-inducing agents to macrophages in vivo.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1989

Inhibition of experimental liver tumor growth in mice by liposomes containing a lipophilic muramyl dipeptide derivative.

The ability of liposomes containing a synthetic lipophilic muramyl dipeptide derivative, N-acetylmuramyl-L-alanyl-D-isoglutamyl-sn-glycerol dipalmitate (MDP-GDP), to inhibit the growth of experimental B16-F1 melanoma liver metastases in syngeneic C57BL/6 mice has been determined. Multiple i.v. injections of distearoylphosphatidylcholine:dimyristoylphosphatidylglycerol liposomes (1 mumol, 10:1 molar ratio) containing 0.1 to 1 microgram of MDP-GDP given at 3- to 4-day intervals after seeding the livers with tumor cells resulted in a significant inhibition of the number of experimental B16 liver metastases. Control liposomes or free MDP (100 micrograms) failed to affect the number of experimental metastases. A single prophylactic injection of liposomes containing MDP-GDP was equally effective in eliciting a reduction in the number of experimental liver metastases. The ability of liposomal MDP-GDP to inhibit the growth of liver metastases correlated with its ability to induce Kupffer cell tumoricidal activity against the tumor cell targets; activation of C57BL/6 Kupffer cell activity in vitro was most effective with liposomal MDP-GDP, followed by liposomal MDP and free MDP. Only liposomal MDP-GDP and liposomal MDP were able to induce Kupffer cell tumoricidal activity in situ, free MDP being inactive. Liposomal muramyl dipeptide therapy using lipophilic derivatives would appear to be an effective treatment for hepatic metastases derived from primary tumors.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1989

Kupffer cells and liver metastasis. Optimization and limitation of activation of tumoricidal activity.

Kupffer cells, tissue-fixed macrophages located in the sinusoids of the liver, represent the highest concentration of mononuclear phagocytes in the body. Their ability to act as scavengers of particulate material in the blood has given rise to speculation that they play a role in controlling hepatic metastases derived from blood-borne tumor cells. Circumstantial evidence for such a role has been obtained from animal studies where Kupffer cell function has been compromised or inhibited, and from anecdotal clinical observations. Current evidence suggests that Kupffer cells are capable of nonspecifically eliminating some circulating tumor cells from the circulation via phagocytosis. This surveillance mechanism would appear to be limited in capacity, and subject to a number of external factors. Recent studies have demonstrated that Kupffer cells can be activated to a tumoricidal state via the administration of biological response modifiers such as gamma interferon or muramyl peptides. The localization of liposomes within Kupffer cells after systemic administration has provided a considerable stimulus for the efficient targeting of macrophage-activating compounds to these cells. Such therapeutic intervention, while capable of inducing Kupffer cell tumoricidal activity in situ and inhibiting tumor growth, is limited with respect to the location of the tumor cells (sinusoidal versus parenchymal) and to the size of the metastatic nodule. Therapeutic intervention using liposomes containing macrophage-activating agents may only be of benefit in patients with minimal tumor load who are at risk for hepatic metastases, rather than those patients who already have clinically detectable liver tumors.

Animals↗
PubMed1989

Inhibition of murine hepatic tumor growth by liposomes containing a lipophilic muramyl dipeptide.

We have investigated the ability of liposomes containing a lipophilic muramyl dipeptide, N-acetylmuramyl-L-alanyl-D-isoglutamine glycerol dipalmitate (MDP-GDP) to activate Kupffer cell tumoricidal activity in situ and to inhibit the growth of experimental hepatic micrometastases of tumor cell line H-59, a liver-homing variant of the Lewis lung carcinoma. Liposomes prepared from distearoylphosphatidylcholine/dimyristoylphosphatidylglycerol (DSPC/DMPG) and containing MDP-GDP (1 mumol and 2 micrograms, respectively) were efficiently taken up by the liver after i.v. administration. A single i.v. injection of DSPC/DMPG liposomes containing MDP-GDP was capable of inducing Kupffer cell tumoricidal activity against H-59 tumor cells as measured in vitro. Control liposomes or 100 micrograms free MDP were ineffective in inducing Kupffer cell tumoricidal activity in situ. Two treatment regimens were evaluated in vivo: firstly, C57BL/6 mice were injected with tumor cell line H-59 and subsequently treated with multiple injections of liposomal MDP-GDP. Secondly, treatment with liposomal MDP-GDP was initiated prior to tumor cell injection and continued after tumor cell injection. The ability of liposomes containing MDP-GDP to reduce the number of hepatic micrometastases using the first protocol was related to the tumor cell inoculum, significant inhibition being observed at lower liver tumor burdens (less than 25 tumor nodules). Pretreatment of the mice prior to tumor cell challenge followed by treatment afterwards greatly enhanced the efficacy of liposomal MDP-GDP and brought about a highly significant inhibition of the growth of experimental metastases even at high liver tumor burdens (greater than 50 nodules).

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1989

Role of mononuclear phagocytes in elimination of Plasmodium chabaudi AS infection.

The role of mononuclear phagocytes in acquired immunity resulting in the intraerythrocytic destruction and elimination of malarial parasites was investigated in the murine model of infection with Plasmodium chabaudi AS. Mice were treated 1 day before or 6 days after infection with agents which either result in augmentation or activation of the non-specific, microbicidal effector function of mononuclear phagocytes or in depletion of cells of this lineage. To examine the effect of agents which activate mononuclear phagocytes. A/J mice, which are susceptible to P. chabaudi AS and exhibit fulminant parasitaemia and death within 10 days of intraperitoneal infection with 10(6) P-RBC, were treated intravenously with muramyl dipeptide (MDP) or liposome-encapsulated MDP-glycerol dipalmitate (MDP-GDP). Treatment administered 1 day before infection was ineffective. Treatment on day 6 post-infection with liposome-encapsulated MDP-GDP (1 microgram) resulted in a significant decrease in parasitaemia on day 8 and survival, while treatment with free MDP (100 micrograms) resulted only in a significant decrease in parasitaemia. To examine the effect of depletion of mononuclear phagocytes, C57BL/6 mice, which are resistant to P. chabaudi AS infection and eliminate the parasite by 4 weeks, were treated intravenously with 3 mg silica. Silica administered 1 day before or 6 days post-infection abrogated resistance resulting in a delay in elimination of the parasite and host mortality. Treatment on day 6 was more effective, with death by day 13 post-infection of 70% of the normally resistant C57BL/6 mice which exhibited fulminant parasitaemia levels. These results thus provide in-vivo evidence that mononuclear phagocytes play a critical role in the elimination of infection with the murine malaria species P. chabaudi AS. Furthermore, these results suggest that the time of administration of agents which alter mononuclear phagocyte function may be important in determining their effect on host antimalarial defences.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1989

The comparative effects of tumor necrosis factor on tumor cells growing anchorage dependently and independently.

Tumor necrosis factor (TNF) is a macrophage-derived cytokine that has been shown to exert differential cytotoxic and/or cytostatic effects on many human and animal tumor cells. In vitro assays of TNF effects have been performed mainly on cultured tumor cells growing as a monolayer. However, tumor cells may respond differently to the effects of growth factors depending on whether they grow in two-dimensional monolayer cultures or in three-dimensional colonies in soft agar. We have tested the effect of TNF on the anchorage-dependent (monolayer) and anchorage-independent (soft agar) growth of five rat, two mouse, and one human tumor cell lines. The results indicate that tumor cells may demonstrate different growth responses in these two culture conditions, and that some tumor cells that are resistant to the cytostatic effect of TNF in monolayer cultures may demonstrate significant sensitivity when growing in soft agar medium. One of the rat tumor cell lines unaffected by TNF in monolayer culture was actually stimulated in their colony growth in soft agar medium. The clonogenic techniques of cultivating human tumor cells in soft agar may be suitable for the screening of TNF-sensitive tumors for therapeutic consideration with this substance.

Agar↗
PubMed1988

Oral etoposide.

Etoposide, a semisynthetic derivative of podophyllotoxin, has been commercially available for intravenous use for a number of years, and has been used as part of first-line combination chemotherapy programs for small cell lung cancer (SCLC). It has also been used to treat testicular cancer, non-small cell lung cancer, and a variety of other malignancies. Etoposide for oral use has become commercially available and is approved for use in the treatment of SCLC. Although no clinical trials comparing intravenous and oral etoposide in SCLC have been reported, several pharmacokinetic studies have been described. These studies have demonstrated a mean bioavailability of 50 percent, with a wide range among patients. Other pharmacokinetic parameters are similar for both the intravenous and oral methods of administration. Based on these results, the recommended dose of oral etoposide is twice the intravenous dose. Oral etoposide has been demonstrated to be effective in the treatment of SCLC. It offers a reasonable and cost-effective outpatient alternative for this group of patients.

Administration, Oral↗