Comparison of hepatitis C viral loads in patients with or without coinfection with different genotypes

Hepatitis C virus genotyping was assessed for 257 chronic hepatitis C patients with viral loads above 1,000 IU/ml. Twelve patients were coinfected with more than one genotype. Their median viral loads did not differ significantly from those observed for monoinfected patients, which in turn did not vary significantly among different genotypes.     

Kinetic analysis of interactions between bispecific monoclonal antibodies and immobilized antigens using a resonant mirror biosensor

A resonant mirror biosensor (IAsys) protocol is described for the comparative kinetic analysis of the ability of monoclonal antibodies (Mabs) and bispecific antibodies (Babs) to bind immobilized antigens. The protocol has been optimized and validated using the panel of affinity-purified antibodies, including two parental Mabs, one specific to human immunoglobulin G (hIgG) and another specific to horseradish peroxidase (HRP), and a Bab derived thereof by cell fusion (anti-hIgG/HRP Bab). The real-time kinetic analysis of antigen–antibody interactions using this protocol allows to demonstrate the differences in the avidity of bivalently binding Mabs and monovalent Babs. As shown in our previous study [J. Immunol. Methods 261 (2002) 103], the observed equilibrium association constants (K_ass) determined by IAsys using this protocol yield figures almost overlapping with those obtained by solid-phase radioimmunoassay (RIA). The described protocol is suited for the investigation of the effects of valency on the binding properties of antibodies. It also may be applied for the selection of Mabs and Babs with desired features, for different fields of application.     

Identifying recent HIV infections using the avidity index and an automated enzyme immunoassay

We evaluated a procedure for identifying recent HIV infections, using sequential serum samples from 47 HIV-positive persons for whom the seroconversion date could be accurately estimated. Each serum sample was divided into two aliquots: one diluted with phosphate-buffered saline and the other diluted with 1 M guanidine. We assayed the aliquots with the automated AxSYM HIV1/2gO test (Abbott Diagnostics Division), without modifying the manufacturer's protocol. We then calculated the avidity index (AI): the ratio of the sample/cutoff value for the guanidine aliquot to that of the phosphate-buffered saline aliquot. We analyzed 216 serum samples: 34 samples were collected within 6 months of seroconversion (recent seroconversions), and 182 were collected after 6 months. The mean AIs, by time from seroconversion, were 0.68 +/- 0.16 (within 6 months) and 0.98 +/- 0.10 (after 6 months) (P < 0.0001). AI of <0.90 correctly identified 88.2% of recent infections but misclassified as recent infections 13.2% of serum samples collected afterward. The probability of an infection being classified as recent and having AI of > or = 0.90 would be 0.7% in a population with 5% recent infections. AI can identify with a certain degree of accuracy recent HIV infections, and being a quantitative index, it provides different levels of sensitivity and specificity, depending on the selected cutoff value. The standard assay procedure is not modified. This test is simple and inexpensive and could be used for surveillance, decision-making in treatment, and prevention.     

Memory for object and object-location after lesions to the ventromedial prefrontal cortex in humans

The aim of the present study was to investigate the effect of small unilateral lesions to the ventromedial portion of the prefrontal cortex on two memory functions: memory for objects and memory for object locations. Patients, who had undergone surgery of the anterior communicating artery aneurysm, and normal control subjects, participated in the study. The patients were subdivided into two groups: with and without unilateral resection of the gyrus rectus. Subjects were presented with two memory tests, that required remembering either simultaneously presented visual stimuli (object memory test; OMT) or locations of the stimuli (location memory test; LMT). In the OMT, patients with resection of the gyrus rectus were impaired in comparison to patients without resection and normal control subjects. In the LMT, the three groups did not differ from each other. Our results suggest that the ventromedial prefrontal cortex is specifically involved in memory for objects.     

Anxiety Profiles of Mice Selectively Bred for Intermale Aggression

In the present study we compared genetically selected aggressive (TA) and nonaggressive (TNA) male mice, as well as males from an unselected control line (SW), in three tests of anxiety: the elevated plus-maze, the light-dark box, and the staircase test. Males were tested repeatedly for 3 days. In all three tests TA males were found to be more active and less anxious than TNA males, with SW males showing more or less intermediate scores. Furthermore, repeated plus-maze testing induced anxiety-like behavior in both TA and TNA mice, whereas repeated testing in the light-dark and staircase paradigms resulted in different responses. Whereas TNA animals were found to be stable, TA animals showed habituation on the second and third day of testing. The obtained data support the conclusion that a higher-level offensive aggression entails lower level of anxiety.     

Behavioral analysis of the saccharin deprivation effect in rats

The deprivation effect (DE)--an increase in the level of free-choice consumption of alcohol after a period of forced abstinence--may reflect relapselike drinking and be relevant for modeling alcohol abuse. However, the behavioral mechanisms of the DE are unclear. In these experiments, rats had unlimited free-choice access to water and saccharin-containing solutions and underwent repeated episodes of saccharin deprivation. It was found that DE magnitude correlates positively with the deprivation phase duration, expression of the DE is highly context dependent, and the DE can be prevented by extinguishing response to the saccharin-associated stimuli. Thus, DE procedures may be useful for studying the effects of continued exposure to stimuli associated with various primary reinforcers such as drugs of abuse.     

Metallo-beta-lactamase VIM-2 in clinical isolates of Pseudomonas aeruginosa from Portugal

Resistance to carbapenems is emerging, and it is a great problem to therapeutics. Three isolates of Pseudomonas aeruginosa from a Portuguese hospital identified in urine and sputum, in 1995, presented a high-level resistance to imipenem (> 32 mg/L). Afterward, one isolate of P. aeruginosa recovered from urine of an ambulatory patient in 1998 showed high resistance to imipenem and meropenem. The resistance to carbapenems in these strains was associated with the production of a class B beta-lactamase, as was demonstrated by imipenem hydrolysis and inhibition by EDTA. Using primers described for bla(IMP) and bla(VIM), the amplification of the latter was observed in all isolates and a VIM-2 metallo-enzyme was identified. The pulsed-field gel electrophoresis (PFGE) patterns of these isolates were indistinguishable, suggesting dissemination to the community of this VIM-2 producer.     

Differential scanning calorimetric study of the complexes of modified myosin subfragment 1 with ADP and vanadate or beryllium fluoride

Summary The effects of various modifications of rabbit skeletal myosin subfragment 1 on thermal denaturation of subfragment 1 in ternary complexes with Mg-ADP and orthovanadate (V_i) or beryllium fluoride (BeF_x) have been studied by differential scanning calorimetry. It has been shown that specific modifications of SH₁ group of Cys-707 by different sulfhydryl reagents, trinitrophenylation of Lys-83, and reductive methylation of lysine residues promote the decomposition of the S1·ADP·V_i complex and change the character of structural transitions of the subfragment 1 molecule induced by the formation of this complex, but they have much less or no influence on subfragment 1 thermal stability in the S1·ADP·BeF_x complex. Thus, the differential scanning calorimetric studies on modified subfragment 1 preparations reveal a significant difference between S1·ADP·V_i and S1·ADP·BeF_x complexes. It is suggested that S1·ADP·V_i and S1·ADP·BeF_x complexes represent structural analogues of different transition states of the ATPase cycle, namely the intermediate states S1^**·ADP·P_i and S1^*·ATP, respectively. It is also proposed that during formation of the S1·ADP·V_i complex the region containing both Cys-707 and Lys-83 plays an important role in the spread of conformational changes from the active site of subfragment 1 ATPase throughout the structure of the entire subfragment 1 molecule. In such a case, the effects of reductive methylation of lysine residues on the subfragment 1 structure in the S1·ADP·V_i complex are related to the modification of Lys-83.