B-45 Base Rates of Low Scores on a Traditional Battery of Neuropsychological Tests in Soldiers with and without Acute mTBI

Objective

It is not uncommon for healthy individuals to have one or more low scores on a battery of cognitive tests. The number of scores produced by the battery by itself can affect the probability of having low scores. The purpose of this study is to examine the rates of low scores on a battery of commonly used neuropsychological tests in soldiers with and without acute mTBI.

Methods

Data from 246 healthy soldiers and 177 soldiers evaluated within seven days of sustaining a mTBI and who had complete and valid data were used in this analysis. All soldiers completed the TOPF, WAIS-IV, CVLT-II, RCFT, DKEFS, and CPT-II. The CARB was used as a measure of effort. For each group, we determined the proportions of soldiers who had various numbers of scores that were 1.0 or more, 1.5 or more, 2.0 or more standard deviations below the normative means for each score. We used prevalence ratios to compare the proportions with low scores in each group.

Results

Low scores were common in both groups (93.1% and 96.0% of controls and mTBI cases, respectively, had at least one score 1.0+ SDs below norm, 57.7% and 79.1% had at least one score 1.5+ SDs below norm, while 30.5% and 48.0% had at least score 2.0+ SDs below norm). Low scores were more common in the mTBI group.

Conclusion

Examining rates of low scores can help identify clinically meaningful performance decrements across an entire battery when large numbers of scores are available.

B-74 Using Rates of Low Scores to Assess Agreement between ANAM4 TBI-MIL and a Traditional Battery of Neuropsychological Tests

Objective

The Automated Neurological Assessment Metrics (Version 4) Traumatic Brain Injury Military (ANAM4 TBI-MIL) battery is widely used by the US military to assess cognitive function. We compare intra-individual agreement between ANAM4 TBI-MIL and a battery of traditional neuropsychological tests using rates of low scores.

Methods

Complete and valid data from 246 healthy soldiers and 177 soldiers ≤7 days from sustaining mild TBI (mTBI) were used in this analysis. All soldiers were consecutively administered ANAM4 TBI-MIL and a traditional test battery consisting of: TOPF, WAIS-IV, CVLT-II, RCFT, DKEFS, and CPT-II. We performed base rate analyses of both batteries to determine the proportions of soldiers who had various numbers of scores that were 1.0+, 1.5+, and 2.0+ standard deviations below the normative mean. We used those rates to place Soldiers into a “low score hierarchy” ranging from the least poor (i.e. ~≥10th %ile) to the worst overall performance (i.e. ~≤10th %ile). We then compared agreement between the batteries at each of those levels.

Results

More soldiers with mTBI had low scores than healthy soldiers on both batteries. Of the soldiers who performed at the worst level on one battery, 88.1% from ANAM and 100% from traditional had some level of poor performance on the other battery. However, of the soldiers who performed at the worst level on either battery, only 58.3% from ANAM and 50.0% from traditional also performed at the worst level on the other battery.

Conclusion

These batteries similarly identify poor performance to a degree, though with some potentially meaningful differences still present.

Experimental anthrax vaccines: efficacy of adjuvants combined with protective antigen against an aerosol Bacillus anthracis spore challenge in guinea pigs

The efficacy of several human anthrax vaccine candidates comprised of different adjuvants together with Bacillus anthracis protective antigen (PA) was evaluated in guinea pigs challenged by an aerosol of virulent B. anthracis spores. The most efficacious vaccines tested were formulated with PA plus monophosphoryl lipid A (MPL) in a squalene/lecithin/Tween 80 emulsion (SLT) and PA plus the saponin QS-21. The PA+MPL in SLT vaccine, which was lyophilized and then reconstituted before use, demonstrated strong protective immunogenicity, even after storage for 2 years at 4 degrees C. The MPL component was required for maximum efficacy of the vaccine. Eliminating lyophilization of the vaccine did not diminish its protective efficacy. No significant alteration in efficacy was observed when PA was dialyzed against different buffers before preparation of vaccine. PA+MPL in SLT proved superior in efficacy to the licensed United States human anthrax vaccine in the guinea pig model.

Uptake of diphtheria toxin and its fragment A moiety by mammalian cells in culture

Evidence suggesting that diphtheria toxin reaches the cytoplasm of susceptible mammalian cells by two independent mechanisms is presented. A schematic model describing the two processes of toxin entry into the cell is developed. One process of toxin uptake considered to by physiologically significant is passage of the protein toxin through the plasma membrane. This most likely happens by binding of fragment B to receptors on the membrane and by subsequent toxin-membrane interaction so that ultimately fragment A, the enzymatically active moiety, is transported tothe cell interior. This process, which ultimately leads to cessation of protein synthesis and cell death, involves a comparatively small number of toxin molecules. A second mechanism of toxin uptake is by classical pinocytosis. The majority of toxin taken into the cell is accomplished by this process. The fate of toxin taken into HEp-2 cells via pinocytosis is proteolysis by lysosomal enzymes. Thus, such vesicle-bound toxin is ordinarily not expressed biologically. Evidence suggesting that ammonium chloride provides total protection to diphtheria toxin-susceptible cells by preventing entry of toxin by the specific receptor-associated process is also provided; data showing that the ammonium salt immobilizes bound toxin on the plasma membrane of HEp-2 cells are presented. Finally, it is suggested that actively endocytic cells such as guinea pig macrophages interact with toxin in a significantly different manner than do nonphagocytic cells.

Chemical modulation of diphtheria toxin action on cultured mammalian cells

Ammonium chloride (4 times 10-3 M) rendered HEp-2 monolayers completely insensitive to the action of diphtheria toxin, as measured by de novo protein synthesis. Total protection was observed even with large amounts of toxin (400 minimum lethal doses/ml). Ammonium chloride did not reduce toxicity by direct action on the protein, nor did it prevent the adsorption of toxin to the cell membrane. Although the ammonium salt did not block the initial interaction between cell and toxin, it did maintain the toxin at a site amenable to neutralization with antitoxin. Surface-adsorbed toxin was inactivated by cellular enzymes or alternatively was desorbed from the membrane during a 12-h incubation in the presence of ammonium chloride. In addition, ammonium chloride provided protection to both toxin-sensitive guinea pig peritoneal macrophages and a partially toxin-resistant strain of HEp-2 cells. Sodium arsenite was effective in protecting cell monolayers from the action of diphtheria toxin; unlike ammonium chloride, its action was not dependent upon continued incubation with cells during exposure to toxin. Inhibitors of energy metabolism abolished toxin action either totally (sodium fluoride) or partially (dinitrophenol and sodium cyanide). Inhibitors of cellular proteases, on the other hand, did not modify toxin activity. The ability of several modifiers of membrane function to alter expression of toxicity for HEp-2 cells was also examined. One compound known to enhance endocytic activity, Tuftsin, had no effect, whereas poly-L-ornithine provided partial protection. Of the two compounds known to alter membrane fluidity, cytochalasin B provided partial protection for HEp-2 cell cultures, whereas colchicine had no effect. Agents that bind to sulfhydryl groups on the cell surface had no apparent effect on toxicity, suggesting that the initial toxin-cell interaction does not involve sulfhydryl groups. Those compounds that provide virtually full protection against the action of diphtheria toxic on cell monolayers (i.e., ammonium chloride, sodium fluoride, and sodium arsenite) had no inhibitory effect on the in vitro enzyme activity associated with fragment A of the toxin.

Interaction of cultured mammalian cells with [125I] diphtheria toxin

The characteristics of cell adsorption and pinocytotic uptake of diphtheria toxin by several mammalian cell types were studied. Purified toxin iodinated by a solid-state lactoperoxidase method provided preparations of high specific activity and unaltered biological activity. Dephtheria toxin-sensitive HEp-2 cells and guinea pig macrophage cultures were compared with resistant mouse L-929 cells. At 37 C the resistant cells in monolayer adsorbed and internalized [125I] toxin to a greater extent than did the HEp-2 cell cultures; no significant differences were observed at 5 C. Ammonium chloride protection levels did not alter uptake of toxin by either L-929 OR HEp-2 cells. Biological activity of the iodinated toxin, however, was negated provided the presence of ammonium chloride was maintained. The ammonium salt appears to maintain toxin in a state amenable to antitoxin neutralization. Guinea pig macrophages internalized iodinated toxin to a level 10 times greater than the established cell lines. In spite of the increased uptake of toxin by the endocytic cells, ammonium chloride prevented expression of toxicity. In an artificial system, toxin adsorbed to polystyrene latex spheres and internalized by guinea pig macrophages during phagocytosis did express biological activity. Ammonium chloride afforded some but not total protection against toxin present in the phagocytic vacuoles. The data suggest that two mechanisms of toxin uptake by susceptible cells may be operative. Toxin taken into the cell by a pinocytotic process probably is not ordinarily of physiological significance since it is usually degraded by lysosomal enzymes before it can reach cytoplasmic constituents on which it acts. When large quantities of toxin are pinocytized, toxicity may be expressed before enzymatic degradation is complete. A more specific uptake involving direct passage of the toxin through the plasma membrane may be the mechanism leading to cell death in the majority of instances.