Improved formulation of a recombinant ricin A-chain vaccine increases its stability and effective antigenicity

Ricin is a potent toxin associated with bioterrorism for which no vaccine or specific countermeasures are currently available. A stable, non-toxic and immunogenic recombinant ricin A-chain vaccine (RTA 1-33/44-198) has been developed by protein engineering. We identified optimal formulation conditions for this vaccine under which it remained stable and potent in storage for up to 18 months, and resisted multiple rounds of freeze-thawing without stabilizing co-solvents. Reformulation from phosphate buffer to succinate buffer increased adherence of the protein to aluminum hydroxide adjuvant from 15 to 91%, with a concomitant increase of nearly threefold in effective antigenicity in a mouse model. Using Fourier-transform infrared spectroscopy, we examined the secondary structure of the protein while it was adhered to aluminum hydroxide. Adjuvant adsorption produced only a small apparent change in secondary structure, while significantly stabilizing the protein to thermal denaturation. The vaccine therefore may be safely stored in the presence of adjuvant. Our results suggest that optimization of adherence of a protein antigen to aluminum adjuvant can be a useful route to increasing both stability and effectiveness, and support a role for a "depot effect" of adjuvant.

Protection by the heavy metal chelator N,N,N',N'-tetrakis (2-pyridylmethyl)ethylenediamine (TPEN) against the lethal action of botulinum neurotoxin A and B

The ability of N,N,N',N'-tetrakis (2-pyridylmethyl)-ethyenediamine (TPEN) to protect against botulinum neurotoxin (BoNT) A and B was examined in vivo in mice. To determine the protective efficacy of TPEN, mice were injected i.p. with TPEN as a single bolus or as multiple injections 30 min before and 0, 2, 4 and 6 hr following i.v. challenges with BoNT-A or -B. TPEN treatment did not alter the 24 hr lethality of BoNT but did produce a significant delay in the time to death. For a moderate dose of serotype A (20 LD50), five divided doses of TPEN prolonged the time to death from 7.8 +/- 0.4 hr to 9.9 +/- 0.5 hr. For serotype B, examined under comparable conditions, the prolongation of the time to death was from 6.1 +/- 0.2 hr to 9.4 +/- 0.6 hr. The range of TPEN doses that could be examined in vivo was limited by its acute toxicity. Although low doses of TPEN (< or = 10 mg/kg) were well tolerated, higher doses (> or = 30 mg/kg) led to ataxia, loss of coordination, convulsions and death in 20.3 min or less. In clonal NG108-15 cells, TPEN was found to produce cytotoxicity as revealed by increases in the secretion of the marker enzyme lactate dehydrogenase (LDH), and enhanced reactivity with the vital dye trypan blue. From LDH concentration-response data determined 24 hr after addition of TPEN, the threshold concentration for observing cytotoxicity was 10 microM and the IC50 was 19.8 microM. At the highest TPEN concentration tested (100 microM), cytotoxicity was detected 8 hr after TPEN addition and increased in severity over a 3 day period. The cytotoxicity in NG108-15 cells appears to be distinct from the rapid-onset toxicity observed in whole animals. These results suggest that TPEN may be of potential benefit in delaying the lethal actions of BoNT-A and -B, but its use is limited by its initial and delayed toxicity. Since the therapeutic and toxic actions of TPEN are both related to zinc chelation, the use of TPEN would need to be restricted to low doses as part of a combination therapy.

Penetration of [3H]T-2 mycotoxin through abraded and intact skin and methods to decontaminate [3H]T-2 mycotoxin from abrasions

Penetration of 50 muCi of [3H]T-2 mycotoxin through abraded and intact skin was studied in anesthetized rats sacrificed at 5, 15, 30, 45, 60 and 90 min post-exposure. The greatest penetration was through abraded skin (49 +/- 7%) at 90 min post-exposure, whereas penetration through intact skin (2 +/- 3%) was substantially less (P less than 0.0015). Methods to decontaminate [3H]T-2 mycotoxin from abraded skin over time were studied. Treatment of [3H]T-2 contaminated abrasions by applying Trau + Medic dressing, applying Charcoal Cloth-Anti-bacterial Field Dressing (Charcoal Dressing), or swabbing with povidone-iodine 30 min post-exposure removed 17-32% of the applied [3H]T-2. Immediate blotting with immediate removal of the dressings absorbed 103 +/- 4% (Trau + Medic) and 87 +/- 4% (Charcoal Dressing) of the applied [3H]T-2, while immediate blotting and leaving the dressing in place for 30 min removed 91 +/- 5% (Trau + Medic) and 76 +/- 3% (Charcoal Dressing). It appears that immediate blotting with either dressing followed by immediate removal before application of a clean dressing is an effective method for decontaminating [3H]T-2 from abrasions.

Cutaneous absorption and decontamination of [3H]T-2 toxin in the rat model

Cutaneous absorption and decontamination of [3H]T-2 mycotoxin using various treatment modalities incorporating water, detergent, sprays, and scrubbing of application sites were examined in the rat model at 5, 30, 60, and 1440 min (24 h) postexposure. Rats were killed immediately after treatment and radiolabeled T-2 remaining in full-thickness skin samples were determined. Absorption and decontamination were followed over time, and decontaminating treatment modalities were evaluated for efficacy. Less than 1% of the applied dose was absorbed in 5 min, and 50% was absorbed in 24 h. At 5 min, 99.5 +/- 0.05% of nonabsorbed (residual) [3H]T-2 was removed, and 58 +/- 5.2% of residual toxin was removed at 24 h with a 2.5% detergent/water spray. When treatment modalities were evaluated at 60 min, a 2.5% detergent/water scrub followed by a detergent/water spray produced optimal decontamination by removing 81 +/- 2.2% of residual toxin. All treatment modalities using detergent and/or water removed significant amounts of toxin (p less than or equal to .0001); a dry scrub was not efficacious. Treatment should be initiated as soon as possible after exposure for best results. However, the stratum corneum acts as a reservoir for the toxin, and decontamination should be carried out even if delayed several hours or days after exposure. Dermal absorption pharmacokinetics found in these studies are similar to those described for other low-molecular-weight compounds, and the decontamination results from T-2 toxin should be applicable to other, similar toxic substances.

Characterization of chemically tritiated microcystin-LR and its distribution in mice

Chemically tritiated microcystin-LR (spec. act. 194 mCi/mmol), purified to greater than 95% by C-18 reverse-phase high performance liquid chromatography, exhibited the same retention time and ultraviolet absorption profile as unlabeled toxin. Acid-hydrolyzed [3H]-toxin yielded tritiated glutamate and beta-methylasparate. Stability of the nonexchangeable [3H]-toxin in saline and urine was greater than 93% after 42 days stored at 22 degrees, 4 degrees or -20 degrees C. In blood, the breakdown of toxin was temperature- and time-dependent (63% at 22 degrees C, 28 days). Unlabeled toxin was stable for greater than 42 days stored at either 4 degrees or -20 degrees C in saline. The LD50 (mouse, i.p.) of [3H]-microcystin-LR and unlabeled toxin was the same [75 micrograms/kg (65-90) and 65 micrograms/kg (53-80), respectively]. From 3 to 90 min after i.p. injection of 70 micrograms/kg [3H]-microcystin-LR there was a slow absorption of toxin from the peritoneal cavity and efficient accumulation in liver. The elimination half-life of the plasma concentration curve was 29 min. Tritium distribution in tissue at death or 6 hr post injection was similar for all doses (13-101 micrograms/kg). At 101 micrograms/kg, liver contained 56 +/- 1%, intestine 7 +/- 1%, kidney 0.9 +/- 0.2% and carcass 10 +/- 1% of the injected dose. Heart, spleen, lung and skeletal muscle contained less than 1% of the radiolabel.

Induction of 33-kD and 60-kD Peroxidases during Ethylene-Induced Senescence of Cucumber Cotyledons

Ethylene enhanced the senescence of cucumber (Cucumis sativus L. cv ;Poinsett 76') cotyledons. The effect of 10 microliters per liter ethylene was inhibited by 1 millimolar silver thiosulfate, an inhibitor of ethylene action. An increase in proteins with molecular weights of 33 to 30 kilodaltons and lower molecular weights (25, 23, 20, 16, 12, and 10 kilodaltons) were observed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels after ethylene enhanced senescence. The measurement of DNase and RNase activity in gels indicated that these new proteins were not nucleases. Two proteins from ethylene-treated cotyledons were purified on the basis of their association with a red chromaphore and subsequently were identified as peroxidases. The molecular weights and isoelectric points (pI) of two of these peroxidases were 33 kilodaltons (cationic, pI = 8.9) and 60 kilodaltons (anionic, pI = 4.0). The observation that [(35)S]Na(2)SO(4) was incorporated into these proteins during ethylene-enhanced senescence suggests that these peroxidases represent newly synthesized proteins. Antibodies to the 33-kilodalton peroxidase precipitated two in vitro translation products from RNA isolated from ethylene-treated but not from control cucumber seedlings. This indicates that the increase in 33-kilodalton peroxidase activity represents de novo protein synthesis. Both forms of peroxidase degraded chlorophyll in vitro, which is consistent with the hypothesis that peroxidases have catabolic or scavenging functions in senescent tissues.

The hemostatic derangement produced by T-2 toxin in cynomolgus monkeys

T-2 toxin, a mycotoxin produced by several strains of the genus Fusarium, has been implicated as a cause of serious illness in both animals and man. Hemorrhage is a feature of the syndromes which have been described. An LD20 dose of T-2 was administered im to adult cynomolgus monkeys. This resulted in prolongation of prothrombin and activated partial thromboplastin times and a decrease in multiple coagulation factors. These changes were detected within hours of toxin administration, were maximal at 24 hr, and returned to normal over the next 3 days. Fibrin-fibrinogen degradation products were not detected at any time point. Repeated phlebotomy produced a significantly greater increase in platelet count in control monkeys, which could be taken as evidence for an effect of toxin on platelet kinetics. In treated animals, the hematocrit level declined by about 10%, but a similar decrease occurred in control animals. The white blood cell count increased 4 to 5 times over pretreatment values. Despite the changes in multiple laboratory parameters, treated monkeys did not exhibit clinical evidence of hemorrhage. In three animals which died as a result of toxicosis, necropsy revealed mild petechial hemorrhage involving the colon and heart, as well as necrosis of lymphoid tissues.

Fate and distribution of 3H-labeled T-2 mycotoxin in guinea pigs

T-2 toxin is a potent cytotoxic metabolite produced by the Fusarium species. The fate and distribution of 3H-labeled T-2 toxin were examined in male guinea pigs. Radioactivity was detected in all body tissues within 30 min after an im injection of an LD50 dose (1.04 mg/kg) of T-2 toxin. The plasma concentration of trichothecene molar equivalents versus time was multiphasic, with an initial absorption half-life equal to or less than 30 min. Bile contained a large amount of radioactivity which was identified as HT-2, 4-deacetylneosolaniol, 3'-hydroxy HT-2, 3'-hydroxy T-2 triol, and several more-polar unknowns. These T-2 metabolites are excreted from liver via bile into the intestine. Within 5 days, 75% of the total radioactivity was excreted in urine and feces at a ratio of 4 to 1. The appearance of radioactivity in the excreta was biphasic. Metabolic derivatives of T-2 excreted in urine were T-2 tetraol, 4-deacetylneosolaniol, 3'-hydroxy HT-2, and several unknowns. These studies showed a rapid appearance in and subsequent loss of radioactivity from tissues and body fluids. Only 0.01% of the total administered radioactivity was still detectable in tissues at 28 days. The distribution patterns and excretion rates suggest that liver and kidney are the principal organs of detoxication and excretion of T-2 toxin and its metabolites.

The hemostatic derangement produced by T-2 toxin in guinea pigs

T-2 toxin produced significant coagulation abnormalities when administered parenterally to Hartley strain guinea pigs. The animals developed depressed activity of all coagulation factors except fibrinogen. Platelet aggregation in whole blood was depressed in response to ADP and collagen. The animals also exhibited an initial rise followed by a fall in hematocrit level, leukocytosis, and a decrease in platelet count. These changes were detectable within hours of toxin administration, reached a maximum at 24 hr, and returned to normal over the next 2 days. Pretreatment of animals with vitamin K1 had no effect on the activity of coagulation factors. The activated partial thromboplastin time of dilutions of plasma from animals given T-2 toxin with plasma from control animals revealed a pattern which pointed to a deficiency of coagulation factors as the principal cause of prolonged clotting times in treated animals. The presence of a weak circulating anticoagulant could not be ruled out. The addition of T-2 to plasma and blood of normal animals in a concentration of 1 microgram/ml had no effect on clotting times or platelet aggregation.

A surgical procedure and tethering system for chronic blood sampling, infusion, and temperature monitoring in caged nonhuman primates

A jacket and tethering system was used to maintain chronic catheters in monkeys, which provided catheter access and manipulability without further restraint. Surgical placement of catheters and a temperature probe allowed for a common cutaneous exit and interface with the jacket and tether. Monkeys were fitted in a sterile leather or denim jacket which was attached to a sterilized flexible stainless steel cable. Through this conduit, an indwelling temperature probe, as well as catheters from the internal jugular and femoral veins, were attached to a swivel unit located on the upper portion of the cage. The internal jugular catheter was used for the continuous infusion of support solution. The catheter from the femoral vein was maintained with a heparin lock and used for serial blood sampling. Using this system, it was possible to obtain frequent blood samples and body temperature readings, and to administer a continuous intravenous infusion without chemical or excessive physical restraint. To date, 367 monkeys, 322 cynomolgus (Macaca fasicularis), 16 rhesus (Macaca mulatta), and 21 African green (Cercopithecus aethiops) have been studied using this procedure.

Lack of enhanced nocturnal growth hormone release in tethered cynomolgus monkeys

To determine spontaneous 24-h patterns of growth hormone (GH) plasma levels in unsedated and unrestrained nonhuman primates, a jacket and tethering system were used to study six cynomolgus monkeys. Hourly blood samples were collected, and body temperatures were recorded over 24-h periods. Measurements of GH were made on all samples. In one 24-h study cortisol levels were also measured as well to document a normal circadian rhythm. GH was released at mean intervals of 4.5 +/- 0.47 h (mean +/- SE) over the 24-h studies. There were no day-to-night differences in either the mean interval of GH release (day, 4.6 +/- 0.66 h; night, 4.4 +/- 0.51) or the mean GH values (day, 9.8 +/- 1.7 mU/l; night, 7.9 +/- 0.8). An apparent midday peak in GH in the 24-h studies followed feeding. As expected, body temperature was higher during the day than night, documenting a normal circadian rhythm. Plasma cortisol also showed a normal circadian variation with a low point midday and a progressive rise during the night in the one 24-h cycle in which it was measured. GH in unsedated, unrestrained cynomolgus monkeys was released in 4- to 5-h cycles both day and night without increased nighttime release. This contrasts sharply with the known nocturnal sleep release of GH seen in humans.

Diurnal response in endogenous amino acid oxidation of meal-fed rats

A model has been developed to measure the effects of dietary protein on daily fluctuations in the rate of endogenous amino acid oxidation in meal-fed and starved rats. In addition, N tau-methylhistidine and hydroxyproline were utilized to determine changes in the rate of degradation of myofibrillar and collagen proteins. In rats meal-fed a normal diet of 18% (w/w) casein, a diurnal response was observed in rate of oxidation of radioactive amino acids contained in endogenous labelled body protein, with a nadir 16--20 h and maximum 4--8 h after beginning the feeding. This observation in part may be related to alterations in flux of amino acids from non-hepatic tissues to site of oxidation in liver, as well as alterations in rates of amino acid oxidation after a protein meal. When meal-fed a 70% protein diet, the maximal rates of endogenous amino acid oxidation were significantly increased by 4--8 h after meal-feeding, with no change in fractional rates of degradation of myofibrillar- or collagen-protein breakdown. This could suggest increases in activities of enzymes involved in amino acid oxidation, in rats meal-fed 70% compared with 18% dietary protein. In contrast, meal-feeding of a protein-free diet muted the diurnal response in the rate of oxidation of endogenously labelled amino acids, which correlated with a decrease in the fractional rate of degradation of myofibrillar or collagen protein. Thus dietary protein is apparently responsible for the observed diurnal rhythm rhythms in the rate of amino acid oxidation, whereas carbohydrates tend to mute the response.

Glucose and alanine metabolism during bacterial infections in rats and rhesus monkeys

To investigate the effects of bacterial infection on glucose and alanine metabolism, a variety of studies were carried out in rat and monkey models. These included glucose turnover by a pulse-dose technique in infected rats; alanine and glucose production and utilization in control and septic monkeys; in vivo measurement of gluconeogenesis in rats, with and without an alanine load; the in vitro rate of glucose formation from various substrates by isolated liver perfusion and hepatic cells; and in vivo rates of oxidation of glucose labeled with 14C at the 1 or 6 carbon position. In rats, glucose turnover was markedly accelerated 24 hr after inoculation of either 10(4) or 10(7) Streptococcus pneumoniae. Glucose utilization and production were also accelerated during illness and early recovery from a pneumococcal infection in monkeys. The rates of gluconeogenesis as measured by either a pulse technique in rats or continuous infusion of labeled alanine in monkey were significantly elevated during pneumococcal septicemia. During the agonal stages (10(7) of the pneumococcal infection in rat, an alanine load resulted in a decreased rate of labeled glucose production and an increase in plasma glucose when compared to values of fasted control rats. However, early illness caused similar or increased rates of glucose production from alanine in vivo. Similar reduced rates of glucose formation were observed when the isolated livers or hepatocytes from rats during the agonal stages of infection were perfused with excess quantities of gluconeogenic substrates. Thus, in the rat, gluconeogenic capacity (ability to form glucose from excess substrates) appears to decrease only during the agonal stages of pneumococcal infection. During acute pneumococcal sepsis in the rhesus monkey, alanine production and utilization were significantly elevated and it was estimated that over 90% of the newly produced alanine was utilized for glucose synthesis. When arterial--venous differences were measured across the hindquarters, significantly more alanine was released, presumably from skeletal muscle of the septic monkey, compared to the recovery period or in the control groups. Thus, the increase in glucose synthesis in both rat and monkey appears to be correlated with substrate availability and kinetic rate, rather than gluconeogenic capacity of the liver. The major increase in glucose utilization during both S. pneumoniae and Francisella tularensis live vaccine strain (LVS) infections in rat was a progressive elevation in the rate of oxidation via the pentose phosphate shunt in the rat. Further, the rate of oxidation appeared to be correlated with the magnitude of the bacteremia, which is an indication of the severity of the infection...

Role of the liver in regulation of ketone body production during sepsis

During caloric deprivation, the septic host may fail to develop ketonemia as an adaptation to starvation. Because the plasma ketone body concentration is a function of the ratio of hepatic production and peripheral usage, a pneumococcal sepsis model was used in rats to measure the complex metabolic events that could account for this failure, including the effects of infection on lipolysis and esterification in adipose tissue, fatty acid transport in plasma and the rates of hepatic ketogenesis and whole body oxidation of ketones. Some of the studies were repeated with tularemia as the model infection. From these studies, it was concluded that during pneumococcal sepsis, the failure of rats to become ketonemic during caloric deprivation was the result of reduced ketogenic capacity of the liver and a possibly decreased hepatic supply of fatty acids. The latter appeared to be a secondary consequence of a severe reduction in circulating plasma albumin, the major transport protein for fatty acids, with no effect on the degree of saturation of the albumin with free fatty acids. Also, the infection had no significant effect on the rate of lipolysis or release of fatty acids from adipose tissue. Ketone body usage (oxidation) was either unaffected or reduced during pneumococcal sepsis in rats. Thus, a reduced rate of ketone production in the infected host was primarily responsible for the failure to develop starvation ketonemia under these conditions. The liver of the infected rat host appears to shuttle the fatty acids away from beta-oxidation and ketogenesis and toward triglyceride production, with resulting hepatocellular fatty metamorphosis.

The effect of T3 and reverse T3 administration on muscle protein catabolism during fasting as measured by 3-methylhistidine excretion

Since recent studies have indicated that measurement in urine of the amino acid, 3-methylhistidine, accurately reflects the extent of muscle catabolism, and because it has been suggested that thyroid hormones may influence muscle breakdown, especially during fasting, the effect of T3 and reverse T3 (rT3) administration on the excretion of 3-methylhistidine was examined in obese subjects during fasting. The mean (+/- SE) 3-methylhistidine excretion in patients fed an egg protein diet (devoid of meat protein) was 256 +/- 35 mumoles/day and decreased to 190 +/- 14 mumoles/day during fasting. T3 administration (100 microgram/day x 5 days) increased 3-methylhistidine excretion to 304 +/- 37 mumoles/day during its ingestion and to 485 +/- 46 mumoles/day in the T3 posttreatment interval. T3 doses of 10 microgram every 4 hr (q4h) for the first 6 days of fasting also appeared capable of increasing 3-mehis excretion whereas 5 microgram T3 q4h administered during the first 6 days of fasting did not increase 3-mehis excretion. Reverse T3 administration (80 microgram q6h) during fasting was associated with a mean 3-methylhistidine of 130 +/- 13 mumoles/day, a value no higher than in patients fasted alone. These observations suggest that: (1) skeletal muscle catabolism decreases during fasting: and (2) pathophysiologic doses of T3 (60 microgram/day or more), but not reverse T3, enhance muscle catabolism during fasting.

Protein-sparing therapy during pneumococcal infection in rhesus monkeys

A model was developed in the rhesus monkey to determine if the marked wasting of body proteins associated with sepsis could be prevented by an intravenous supply of various nutritional substrates. All monkeys were given a basic infusion of 0.5 gm of amino acid nitrogen/kg body weight via an indwelling catheter in the jugular vein. Three groups were given diets with no added calories, 85 calories/kg from dextrose or 85 calories from lipid. In each group, six monkeys were inoculated with 3 x 10(8) Streptococcus pneumoniae and four with heatkilled organisms. In the monkeys infused with the amino acids alone, pneumococcal sepsis resulted in a fourfold increase in loss of body proteins compared with calorie-restricted controls. Addition of 85 calories/kg/day of either dextrose or lipid reduced body wasting associated with infectious disease. The calories from lipid were utilized bythe septic host as a source of energy, with a slightly reduced efficiency when compared with the isocaloric infusion of dextrose. The nitrogen sparing of the fat emulsion could not be accounted for by its glycerol content. Therefore, the septic monkey seemed to utilize fatty acids as an energy substrate. It appears that the carbohydrate calories tend to favor the synthesis of peripheral proteins (associated mainly with skeletal muscle), while lipid calories favor synthesis of visceral proteins such as plasma albumin and acute-phase proteins.

Involvement of hepatic metallothioneins in hypozincemia associated with bacterial infection

Hypozincemia was induced in rats by Salmonella typhimurium and live vaccine strain Francisella tularensis (LVS) infections. Hepatic synthesis of zinc-binding proteins (ZBP) was studied in order to elucidate the mechanisms involved in the redistribution of zinc from plasma to liver occurring during infectious illness. ZBP, labeled in vivo with 65Zn, were isolated and identified as metallothioneins based, in part, on their heat stability, dimorphism, and amino acid composition. Cysteine was the major amino acid found in both forms of metallothionein and constituted 28-31% of total residues. The apparent half-life of these proteins as measured by disappearance of 65Zn was determined to be 19 h in a relatively mild infection (LVS) and 38 h in a more severe S. typhimurium infection. Results provide evidence that metallothioneins not only have the previously postulated regulatory role in normal zinc homeostasis but are intimately involved in the zinc redistribution occurring during the acute stage of infectious illness.

Total body protein catabolism in starved and infected rats

The catabolic effects of starvation alone, or starvation in the presence of pneumococcal sepsis, were compared in rats whose skeletal muscle protein had been tagged 14 days earlier with 14C-phenylalanine. In a fed rat, protein catabolism (as estimated by expired 14CO2) is not constant throughout the day but is highest during the dark hours. Starvation is associated with accelerated protein catabolism and a gradual loss of periodicity. Infection increases the rate of catabolism still further and results in a complete loss of periodicity.

Specific muscle protein-sparing postoperative dextrose-free amino acid infusions

The protein-sparing and ketogenic effect of postoperative infusion of maintenance solutions containing either 3.5% amino acids or 5% dextrose in 0.33 normal (N) saline was compared by nitrogen balance and urinary acetone determination in 31 patients. A specific muscle protein sparing effect was determined by quantitation of excretion of 3-methylhistidine in seven patients of the amino acid group and eight patients in the dextrose group. In addition, an extensive hormone and substrate profile was determined. It was found that amino acid infusions not only produce a less negative nitrogen balance but also significantly reduce excretion of 3-methylhistidine indicating specific preservation of the muscle compartment.

Effect of glucose infusion on the concentration of individual serum free amino acids during sandfly fever in man

After an intravenous glucose load in man, total serum amino acid concentrations are rapidly depressed and remain below baseline values for at least 2 to 3 hr after serum glucose and insulin have returned to preload concentrations. Despite the presence of basal hypoaminoacidemia, a decreased glucose disappearance rate, and hyperinsulinemia in volunteers who were ill with sandfly fever, an intravenous glucose load resulted in a further depression of serum amino acids which was equal to or slightly greater than that observed in the same individuals before exposure to the virus. Although the infectious process may have some effect on insulin-stimulated hepatic disposal of a glucose load, it does not appear to influence the ability on insulin to decrease the rate of release of certain amino acids from skeletal muscle.

The significance and mechanism of an increased serum phenylalanine-tyrosine ratio during infection

Infections or inflammatory states often cause significant increases in serum phenylalanine and the phenylalanine-tyrosine ratio. More than 95% of samples obtained during inflammatory diseases in man showed phenylalanine-tyrosine ratio increases greater than the maximum normal values. An increase in this ratio also occurred in monkeys with induced Rocky Mountain spotted fever, viral encephalitis, yellow fever, or pneumococcal and Salmonella infections, as well as in rats with pneumococcal and Salmonella infections, as well as in rats with pneumococcal, Salmonella or tularemia infections. A similar ratio increase occurred in rats inoculated with unpurified mediator substances (released by activated leukocytes) that appear to initiate many of the secondary metabolic phenomena associated with infection and/or inflammation. To identify responsible mechanisms, rats were given lethal doses of Streptococcus pneumoniae; serum phenylalanine and phenylalanine-tyrosine ratios increased significantly. Hepatic phenylalanine hydroxylase activities were slightly decreased when compared to noninfected controls. Infected and noninfected rats showed comparable oxidation rates for 14C-phenylalanine given with an oral phenylalanine load, as a pulse-oral dose, or as an intraperitoneal injection. After 8 hr, both infected and control rats had similar amounts of radioactivity in total body protein, but tissue distributions were markedly altered during pneumococcal sepsis. Serum proteins of infected rats contained almost twice as much total radioactivity as that found in controls, while the amount of labeled phenylalanine in skeletal muscle protein was significantly reduced in the infected group. Isolated muscles from infected rats released more phenylalanine and less tyrosine than control muscles. Infection-related increases in serum phenlalanine could not be explained by decreased hydroxylation or oxidation. Rather, the data were consistent with an increased flux of phenylalanine into serum, most likely as the result of increased skeletal muscle catabolism. Elevations in the serum phenylalanine-tyrosine ratio have potential value for estimating the presence of an inflammatory fisease and the catabolic state of a patient.

Influence of the adrenal glucocorticoids on the stimulation of synthesis of hepatic ribonucleic acid and plasma acute-phase globulins by leucocytic endogenous mediator

An injection of unpurified leucocytice endogenous mediator into rats results in an increased incorporation of [6(-14)C]orotate into hepatic RNA, an increase in the concentration of RNA associated with the bound ribosomal fraction of liver, and increases in the concentrations in serum of acute-phase proteins such as alpha2-macrofoetoprotein and haptoglobin. If given 3 days after adrenalectomy or 7 days after hypophysectomy,, leucocyte factor did not induce the increase in RNA synthesis or alpha2-macrofoetoprotein concentrations but did stimulate an increase in serum haptoglobin. When hypophysectomized or adrenalectomized rats received daily subcutaneous injections of 0.5mg of cortisol, leucocyte factor again induced a significant increase in the synthesis of hepatic RNA and an increase in the concentration of serum alpha2-macrofoetoprotein. These observations suggest that leucocyte factor can regulate acute-phase-protein synthesis at several different sites, one or more of which requires permissive action of the glucocorticoid hormones. Futher, leucocyte factor will stimulate an increase rate of incorporation of orotate into hepatic ribosomes when added in vitro in the presence of cortisol to a liver-perfusion system. Thus the stimulatory effect of leucocyte factor may be directy on liver but may require the presence of other hormones to stimulate the incorporation of orotate into RNA.

Distribution and metabolism of phenylalanine and tyrosine during tualraemia in the rat

Tularaemia in rats causes a doubling of the serum phenylalanine/tyrosine ratio and a more than twofold increase in muscle phenylalanine which cannot be accounted for by decreased hepatic phenylalanine hydroxylase (EC 1.14.16.1) activity, but appear to result from a generalized movement of amino acids from muscle to liver during infection.

Amino acid flux and protein synthesis after exposure of rats to either Diplococcus pneumoniae or Salmonella typhimurium

At 26 h after inoculation of rats with Diplococcus pneumoniae, the serum concentrations of 10 and 20 individual amino acids were lower than corresponding values observed in pair-fed controls. In contrast, only 2 of 20 serum amino acids were similarly decreased in rats inoculated with Salmonella typhimurium. Despite these serum differences, a greater accumulation of labeled non-metabolizable amino acids occurred in the livers of rats infected with S. typhimurium. These data suggested a greater increase in the flux of amino acids from muscle to liver in the rats infected with S. typhimurium as compared to those infected with D. pneumoniae. A similar increase in serum protein synthesis was observed in rats infected with D. pneumoniae or S. typhimurium. However, with the latter infection, a larger percentage of the amino acids appeared to be utilized as a source of energy in addition to their role as precursors of proteins.