Metabolic fate of S,S,S-tributyl phosphorotrithioate (DEF) in the lactating goat.

1. Metabolism of [1-14C] DEF (S,S,S-1-14C-tributyl phosphorotrithioate, 1) in the lactating goat has been investigated. A goat was dosed orally by capsule on 3 consecutive days at a rate of 0.82 mg/kg body weight/day based on 25 times the maximum DEF residue anticipated in animal feed. 2. Urine and milk were collected throughout the study. The goat was killed 21 h following the last treatment, and kidney, liver and composite samples of muscle and fat were collected. The radioactive residue levels (following the three doses) were 3.45 ppm in liver, 0.35 ppm in kidney, 0.19 ppm in fat, 0.06 ppm in muscle and 0.12 ppm in milk collected at the final 16 h and prior to killing. 3. Urinary metabolic profile indicated that DEF was efficiently metabolized to many metabolites. Tissue and milk extracts also indicated that DEF was extensively metabolized. 4. DEF comprised 31 and 5% of the total radioactive residue in fat and milk, respectively. The amount of DEF in liver, kidney and muscle represented < 1% of the total radioactive residue. 5. A major metabolite, 3-hydroxybutylmethyl sulphone (HBM sulphone, UP3), was found in tissue, milk and urine. The identification of this metabolite was accomplished by a combination of MS, nmr and comparison with an authentic standard. The glucuronide (UP1) and sulphate (UP2) conjugates of HBM sulphone were found in urine, and the sulphate conjugate was a major metabolite in kidney. 6. The hydrolytic products of DEF, S,S-dibutyl phosphorodithioate (Dibufos, U16) and S-butyl phosphorothiate (Bufos, U8), were identified as minor components in urine, comprising 5 and 4% of the total radioactive residue, respectively. Butyl mercaptan was not found, but mixed disulphides of butyl mercaptan with either glutathione (U10, 3%) or N-acetyl cysteine (U13, 2%) were found. 7. Direct evidence for the incorporation of DEF residue into natural constituents was also established. Fatty acids from milk and fat were isolated and shown to be radioactive.

Prevention of HIV-1 infection in chimpanzees by gp120 V3 domain-specific monoclonal antibody.

The acquired immunodeficiency syndrome (AIDS) is the late-stage clinical manifestation of long-term persistent infection with the human immunodeficiency virus type 1 (HIV-1). Immune responses directed against the virus and against virus-infected cells during the persistent infection fail to mediate resolution of the infection. As a result, a successful AIDS vaccine must elicit an immune state that will prevent the establishment of the persistent infection following introduction of the virus into the host. The third hypervariable (V3) domain of the HIV-1 gp120 envelope glycoprotein is a disulphide-linked closed loop of about 30 amino acids which binds and elicits anti-HIV-1 type-specific virus-neutralizing antibodies. The in vitro characteristics of anti-V3 domain antibody suggest that this antibody could by itself prevent HIV-1 infection in vivo, an idea supported by chimpanzee challenge studies in which protection against the HIV-1 persistent infection seemed to correlate with the presence of anti-V3 domain antibody. Here we directly demonstrate the protective efficacy of anti-V3 domain antibody in vivo and propose that this antibody is potentially useful as both a pre- and post-exposure prophylactic agent.

Prevention of HIV-1 IIIB infection in chimpanzees by CD4 immunoadhesin.

The first step in infection by the human immunodeficiency virus (HIV) is the specific binding of gp120, the envelope glycoprotein of HIV, to its cellular receptor, CD4. To inhibit this interaction, soluble CD4 analogues that compete for gp120 binding and block HIV infection in vitro have been developed. To determine whether these analogues can protect an uninfected individual from challenge with HIV, we used the chimpanzee model system of cell-free HIV infection. Chimpanzees are readily infected with the IIIB strain of HIV-1, becoming viraemic within about 4-6 weeks of challenge, although they do not develop the profound CD4+ T-cell depletion and immunodeficiency characteristic of HIV infection in humans. CD4 immunoadhesin (CD4-IgG), a chimaeric molecule consisting of the N-terminal two immunoglobulin-like regions of CD4 joined to the Fc region of human IgG1, was selected as the CD4 analogue for testing because it has a longer half-life than CD4, contributed by the IgG Fc portion of the molecule. In humans, this difference results in a 25-fold increased concentration of CD4-IgG in the blood compared with recombinant CD4. Here we report that pretreatment with CD4-IgG can prevent the infection of chimpanzees with HIV-1. The need for a preventative agent is particularly acute in perinatal HIV transmission. As recombinant CD4-IgG, like the parent IgG molecule, efficiently crosses the primate placenta, it may be possible to set up an immune state in a fetus before HIV transfer occurs, thus preventing infection.

Prevention of the hyperlipidemic serum or LDL-induced cellular cholesterol ester accumulation by 22-hydroxycholesterol and its analogue.

Incubation of monkey arterial smooth muscle cells with hyperlipidemic serum or low-density lipoproteins (LDL) produces intracellular cholesterol ester accumulation. Increased esterification of free cholesterol within the cell may account for this effect. To examine such a possibility, oxygenated sterols were used to block cholesterol esterification. The increased esterification of free cholesterol by smooth muscle cells and human skin fibroblasts, through their exposure to hyperlipidemic lipoproteins, was inhibited by 22-hydroxycholesterol and its analogue, SC-32561 (22-hydroxy-25-fluorocholesterol). The hyperlipidemic LDL-stimulated elevation in the cholesterol ester content of the smooth muscle cells was also prevented by these sterols. This reduction in cellular cholesterol ester did not coincide with an increase in free cholesterol. 22-Hydroxycholesterol also blocked the stimulation of the esterification of cholesterol due to 25-hydroxycholesterol. In the absence of lipoproteins, 22-hydroxycholesterol and SC-32561 had a minor effect on the incorporation of [14C]oleate into cholesterol esters, and efficiently reduced sterol synthesis in fibroblasts and smooth muscle cells. 22-Hydroxycholesterol and SC-32561 had the additional effect of lowering the number of cell-surface LDL receptors to a greater extent than did hyperlipidemic LDL. The presence of 22-hydroxycholesterol did not alter the interaction of normal LDL with the receptor. Oxygenated sterols recovered in the cell represented 4-21% of the total sterol content. The level of intracellular oxygenated sterols was significantly reduced by the presence of lipoproteins in the culture media. Due to the multiple effects of the oxysterols, they were not effective as tools in determining the contribution of acyl-coenzyme A:cholesterol acyltransferase enzyme activity to the intracellular pool of cholesterol esters. These results indicated that 22-hydroxycholesterol and SC-32561 effectively blocked the hyperlipidemic LDL-stimulated increase in smooth muscle cell cholesterol ester content by lowering cholesterol esterification, reducing cholesterol synthesis and down-regulating LDL cell-surface receptors.

Hypolipidemic activity of 5-aryl-3-methylvaleric acid derivatives.

Several 5-aryl-3-methylvaleric acid derivatives have been shown to be more potent hypolipidemic agents than the previously reported 5-(4-biphenylyl)-3-methylvaleric acid (1). The most active compound in this series was 5-(4-phenylsulfonylphenyl)-3-methylvaleric acid (10) which lowered serum cholesterol levels 45% and serum triglyceride levels 60% in normal rats. Significant lowering of the serum triglyceride levels was the predominant effect noted with most of the compounds tested.