Virus population dynamics, fitness variations and the control of viral disease: an update

Viral quasispecies dynamics and variations of viral fitness are reviewed in connection with viral disease control. Emphasis is put on resistance of human immunodeficiency virus and some human DNA viruses to antiviral inhibitors. Future trends in multiple target antiviral therapy and new approaches based on virus entry into error catastrophe (extinction mutagenesis) are discussed.

[Bioartificial liver support for acute liver failure. First case treated in Spain]

BACKGROUND

Research aimed at developing artificial liver support systems has experienced a notable increase in the last decade. Hybrid systems including bioreactors containing hepatocytes which are perfused by liver failure patients blood or plasma have been deviced for the first time. The purpose of such a strategy is to substitute, at least in part, the impaired hepatic function thus improving the prognosis of patients with severe acute or chronic liver diseases.

CASE REPORT

In the present paper, we report the first such a case treated in Spain in the context of a controlled, randomized, multicenter international study aimed at investigating the usefulness and safety of a bioartificial liver support system based on cryopreserved porcine hepatocytes in patients with acute liver failure or having a non-functioning primary graft after liver transplantation.

RESULTS

In this first experience, two sessions of treatment could be completed before a patient with acute liver failure underwent a successful emergency liver transplantation. After more than two years of follow-up, the patient is in her normal life activities and she has not presented any adverse event related to the bioartificial liver support therapy so far.

CONCLUSION

Bioartificial liver support systems are starting to be available for use in clinical practice. Yet it is mandatory to establish their safety and efficacy before a widespread recommendation.

Renal failure after upper gastrointestinal bleeding in cirrhosis: incidence, clinical course, predictive factors, and short-term prognosis

To assess the incidence, clinical course, predictive factors, and prognosis of renal failure in patients with cirrhosis and gastrointestinal bleeding, 175 consecutive episodes of gastrointestinal bleeding in 161 patients were analyzed. Renal failure occurred in 20 (11%) episodes and was transient in 8 episodes and nontransient in 12. Renal failure was more common in patients with cirrhosis than in a control population of bleeding patients without cirrhosis matched by age and severity of the bleeding episode. Among 39 clinical and laboratory variables obtained at admission or during hospitalization related with the bleeding episode or with liver and renal function, the presence of hypovolemic shock, number of packed red blood cells transfused, Child-Pugh class at admission, and baseline platelet count were independent predictors of renal failure. The development of renal failure and hypovolemic shock was the only independent predictors of in-hospital mortality. Mortality rate among the 20 episodes with renal failure was 55% (11 deaths) as compared with only 3% (5 deaths) in the 155 episodes without renal failure (P <.01). The development of nontransient renal failure entailed a much greater mortality as compared with transient renal failure (10 of 12 [83%] vs. 1 of 8 [12%]; P <.01). In conclusion, renal failure is a common event in patients with cirrhosis and gastrointestinal bleeding, the occurrence of which is mainly related to the severity of bleeding and baseline liver function. Renal failure is a strong predictor of mortality in patients with cirrhosis and gastrointestinal bleeding.

Yeast population dynamics in spontaneous fermentations: comparison between two different wine-producing areas over a period of three years

Yeast ecology, biogeography and biodiversity are important and interesting topics of research. The population dynamics of yeasts in several cellars of two Spanish wine-producing regions was analysed for three consecutive years (1996 to 1998). No yeast starter cultures had been used in these wineries which therefore provided an ideal winemaking environment to investigate the dynamics of grape-related indigenous yeast populations. Non-Saccharomyces yeast species were identified by RFLPs of their rDNA, while Saccharomyces species and strains were identified by RFLPs of their mtDNA. This study confirmed the findings of other reports that non-Saccharomyces species were limited to the early stages of fermentation whilst Saccharomyces dominated towards the end of the alcoholic fermentation. However, significant differences were found with previous studies, such as the survival of non-Saccharomyces species in stages with high alcohol content and a large variability of Saccharomyces strains (a total of 112, all of them identified as Saccharomyces cerevisiae) with no clear predominance of any strain throughout all the fermentation, probably related to the absence of killer phenotype and lack of previous inoculation with commercial strains.

Eight cDNA encoding putative aquaporins in Vitis hybrid Richter-110 and their differential expression

The nucleotide sequences of eight cDNAs encoding putative aquaporins obtained from a leaf Vitis hybrid Richter-110 cDNA library are reported. They encode proteins ranging from 249 to 287 amino acids with characteristic sequences that clearly include them within the MIP family. According to available database sequence homologies, they can be classified into four groups belonging to two subfamilies: PIP (PIP1 and PIP2) and TIP (gamma-TIP and delta-TIP). In order to elucidate the expression patterns of these putative aquaporins in the plant, specific probes were developed and tissue specific differential expression was tested by reverse Northern and compared with two reference genes (malic enzyme and glutamate dehydrogenase). Clearly, most of the putative aquaporins had higher expression in roots, whereas expression in shoot and leaves was generally weaker than the reference genes.

Functional characterization of chimeric reverse transcriptases with polypeptide subunits of highly divergent HIV-1 group M and O strains

Human immunodeficiency virus (HIV)-1 strains have been divided into three groups: main (M), outlier (O), and non-M non-O (N). Biochemical analyses of HIV-1 reverse transcriptase (RT) have been performed predominantly with enzymes derived from HIV-1 group M:subtype B laboratory strains. This study was designed to optimize the expression and to characterize the enzymatic properties of HIV-1 group O RTs as well as chimeric RTs composed of group M and O p66 and p51 subunits. The DNA-dependent DNA polymerase activity on a short heteropolymeric template-primer was similar with all enzymes, i.e. the HIV-1 group O and M and chimeric RTs. Our data revealed that the 51-kDa subunit in the chimeric heterodimer p66(M:B)/p51(O) confers increased heterodimer stability and partial resistance to non-nucleoside RT inhibitors. Chimeric RTs (p66(M:B)/p51(O) and p66(O)/p51(M:B)) were unable to initiate reverse transcription from tRNA(3)(Lys) using HIV-1 group O or group M:subtype B RNA templates. In contrast, HIV-1 group O and M RTs supported (-)-strand DNA synthesis from tRNA(3)(Lys) hybridized to any of their corresponding HIV-1 RNA templates. HIV-2 RT could not initiate reverse transcription on tRNA(3)(Lys)-primed HIV-1 genomic RNA. These findings suggest that the initiation event is conserved between HIV-1 groups, but not HIV types.

Transfusion of incompatible RBCs to a patient with alloanti-Kp(b)

BACKGROUND

The finding of an antibody that reacts against a high-incidence blood group antigen always constitutes a complex transfusion problem because of the difficulty in finding compatible units. When the transfusion of incompatible RBCs is imperative, it would be of great interest to have access to techniques facilitating the prediction of the transfusion outcome.

STUDY DESIGN AND METHODS

The case of a patient with alloanti-Kp(b) who required RBC transfusions is reported. The functional activity of this antibody was assessed by both the chemiluminescence test (CLT) and the survival of 51Cr-labeled RBCS:

RESULTS

The CLT showed an opsonic index of 0.8 with Kp(b)-positive RBCs (normal values up to 1.6) in pretransfusion studies. During an elective surgical procedure, the patient required the transfusion of one incompatible unit of RBCs, which did not produce hemolysis. Two weeks after this incompatible transfusion, the opsonic index had risen to 11. Results of the 51Cr in vivo study, also performed at that time, indicated 24.3 percent survival of Kp(b)-positive RBCs at 60 minutes and 2.0 percent at 24 hours.

CONCLUSION

Results of the CLT correlated with the in vivo transfusion outcome and later with the 51Cr survival study.

Effects of copper exposure upon nitrogen metabolism in tissue cultured Vitis vinifera

The present study analyses the effects of copper treatment on nitrogen metabolism in a closed system. Sauvignon grapevines were cultured in agar and exposed to copper levels ranging from 0.07 (control) to 5 µg Cu g(-1) medium. Ammonium, nitrate, nitrite, individual and total amino acids and protein contents were determined in root, and leaves. Enzyme activities of nitrate and nitrite reductases, glutamine synthetase, glutamate synthase and glutamate dehydrogenase were also determined. Copper exposure produces a dramatic change in nitrogen metabolism, with a reduction of total nitrogen, which reflects the reduction on nitrate and free amino acid contents in both root and leaves. The assimilation of nitrate the main nitrogen source in the medium, requires nitrate reductase, which is reduced to negligible activity as response to copper exposure. Primary nitrogen metabolism is also reduced in leaves, although to a lesser extent than in roots, which may explain the differences between the two organs in response to copper exposure. An alternative system for assimilation of nitrogen through glutamate dehydrogenase in roots is proposed, while higher levels of ammonium and glutamine may fullfil the needs of organic nitrogen in the leaves.

Role of a dipeptide insertion between codons 69 and 70 of HIV-1 reverse transcriptase in the mechanism of AZT resistance

The 3'-azido-3'-deoxythymidine (AZT)-resistant pheno type of a heavily mutated human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) carrying a dipeptide (Ser-Ser) insertion between codons 69 and 70 as well as other mutations related to resistance to RT inhibitors has been studied. Recombinant virus carrying this variant RT (termed SS RT) showed reduced susceptibility to all nucleoside RT inhibitors in clinical use, particularly to AZT. In the presence of ATP, recombinant SS RT had an increased ability to remove the 3'-terminal nucleotide from AZT- terminated primers and extend the unblocked primer, compared with wild-type HIV-1 RT (BH10 isolate). Insertion of two serines in the sequence context of BH10 RT did not affect the ATP-dependent phosphorolytic activity of the enzyme, and had no influence in resistance to RT inhibitors. However, SS RT mutants lacking the dipeptide insertion or bearing a four-serine insertion showed reduced ATP-dependent phosphorolytic activity that correlated with increased AZT sensitivity, as determined using a recombinant virus assay. Therefore, the insertion appears to be critical to enhance AZT resistance in the sequence context of multidrug-resistant HIV-1 RT.

Identification of acetic acid bacteria by RFLP of PCR-amplified 16S rDNA and 16S-23S rDNA intergenic spacer

DNA corresponding to 16S rDNA and the 165-23S rDNA intergenic spacer (ITS) from 22 reference strains of acetic acid bacteria, representing the diversity of the family Acetobacteraceae, and 24 indigenous acetic acid bacteria isolated from wine fermentations were analysed by PCR-RFLP. Frateuria aurantia LMG 1558T and Escherichia coli ATCC 11775T were included as outgroups. PCR-amplified products of about 1450 bp were obtained from the 16S rDNA of all the strains and products of between 675 and 800 bp were obtained from the 16S-23S rDNA ITS. PCR products were digested with 4-base-cutting restriction enzymes in order to evaluate the degree of polymorphism existing among these strains. Of the enzymes tested, Taql and Rsal were the most discriminatory and showed no intraspecific variations in the restriction patterns. Restriction analysis of the 16S rDNA with these enzymes is proposed as a rapid and reliable method to identify acetic acid bacteria at the level of genus and species (or related species group) and its applicability to identification of indigenous acetic acid bacteria was demonstrated. The same degree of distinction as that for the 16S rDNA analysis was obtained within reference strains of acetic acid bacteria by PCR-RFLP of the 16S-23S rDNA ITS. However, 16S-23S rDNA ITS restriction patterns of strains isolated from wine did not match those of any of the reference strains. Thus, PCR-RFLP of the 16S-23S rDNA ITS is not a useful method to identify isolates of acetic acid bacteria at the species level, although it may be an adequate method to detect intraspecific differentiation.

Human pharmacology of 3,4-methylenedioxymethamphetamine ("ecstasy"): psychomotor performance and subjective effects

3,4-Methylenedioxymethamphetamine (MDMA, "ecstasy") is a recreational drug of increasing use among youth because of its apparent entactogenic properties, such as euphoria, friendliness, closeness, and empathy. However, experimental studies have shown MDMA to be neurotoxic. Data on pharmacologic actions of MDMA in humans are limited. The authors conducted a randomized, double-blind, crossover, controlled trial to assess psychomotor performance and subjective effects in eight healthy male volunteers. MDMA was given in the same range of doses used for recreational purposes (75 and 125 mg). Amphetamine (40 mg) and placebo were used as reference compounds. For the digit-symbol substitution test (DSST), MDMA-125 produced a mild decrease in responses, and amphetamine produced a mild improvement. For the Maddox wing device, MDMA-125 induced esophoria compared with the other drug conditions. MDMA-125 and MDMA-75 produced increases in feelings of euphoria and well-being, as noted by increases in scores on the Addiction Research Center Inventory (ARCI) MBG and A scales, as well as scores of "stimulated," "good effects," "liking," and "high" on the visual analog scales. Amphetamine administration induced similar effects. At the same time, MDMA-125 enhanced sedation- and dysphoria-related effects (ARCI-PCAG and LSD, "confusion," "drunken," and Profile of Mood States Confusion scale). Mild changes in some body perception-related feelings were also reported after MDMA use, but hallucinations or psychoses were not present. In summary, the short-term administration of MDMA produced marked euphoria, a slight impairment in the performance of psychomotor tasks, and mild changes in body perceptions without hallucinations. These data support the abuse liability of MDMA.

Terlipressin plus albumin infusion: an effective and safe therapy of hepatorenal syndrome

BACKGROUND/AIM

Ornipressin, a vasopressin analog with potent splanchnic vasoconstrictor action, has been shown to reverse hepatorenal syndrome. However, its usefulness in clinical practice is limited by frequent ischemic complications. The aim of this study was to assess the efficacy of terlipressin, an analog of vasopressin with a low profile of side effects, plus albumin in this condition.

METHODS

Nine consecutive patients with cirrhosis and hepatorenal syndrome were included in a pilot study of terlipressin (0.5-2 mg/4 h i.v.) therapy associated with iv albumin.

RESULTS

Treatment (9 days, range 5-15) was associated with a marked reduction of serum creatinine (3.9+/-0.7 to 1.3+/-0.1 mg/dl, p<0.001, mean+/-SE). Reversal of hepatorenal syndrome (reduction of creatinine below 1.5 mg/dl) was observed in seven of the nine patients. There was a remarkable improvement in circulatory function, with an increase in mean arterial pressure (68+/-2 to 80+/-4 mmHg, p<0.05) and suppression of vasoconstrictor systems activity (plasma renin activity and plasma norepinephrine decreased from 23+/-12 ng/ml x h and 1549+/-373 pg/ml to 3.5+/-2 ng/ml x h and 373+/-98 pg/ml, respectively, p<0.01 for both). No patient developed signs of intestinal, myocardial or distal ischemia.

CONCLUSIONS

Terlipressin associated with albumin appears to be a safe and effective treatment of hepatorenal syndrome.

Identification of acetic acid bacteria by restriction fragment length polymorphism analysis of a PCR-amplified fragment of the gene coding for 16S rRNA

Acetic acid bacteria (AAB) irreversibly spoil wines and represent a serious problem. Limited studies on the ecology of AAB during winemaking have been done due to the lack of rapid and precise techniques for their identification. RFLP analysis of PCR-amplified fragment of 16S rDNA was performed on AAB reference strains. The amplified rDNAs were approximately 870-bp long for all AAB species while no amplicons were detected for lactic acid bacteria and yeasts. Out of the four restriction enzymes tested, TaqI was the most efficient one and divided the studied AAB into six groups. However, complete differentiation among collection strains of Acetobacter pasteurianus and Gluconoacetobacter hansenii was not possible.

Hepatitis B immunoglobulin discontinuation followed by hepatitis B virus vaccination: A new strategy in the prophylaxis of hepatitis B virus recurrence after liver transplantation

It is widely agreed that hepatitis B virus immunoglobulin (HBIG) should be administered for at least 12 months to patients transplanted for hepatitis B virus (HBV)-related diseases to prevent HBV recurrence. No data are available, however, on how long this treatment should be used, and most centers currently administer HBIG on a life-long basis. Herein, we report the results of a new prophylactic strategy aiming at the discontinuation of HBIG treatment and consisting of the administration of double dose recombinant HBV vaccine (0, 1-, and 6-month schedule) to liver transplant recipients fulfilling the following criteria: (1) liver transplantation for conditions related to nonreplicative HBV infection (hepatitis B surface antigen [HBsAg] positive, hepatitis B e antigen [HBeAg] negative, and HBV DNA negative); (2) at least 18 months of HBIG administration; and (3) no HBV infection recurrence, normal or slightly altered liver graft function, and low-grade immunosuppression at the time of vaccination. Seventeen patients received HBV vaccination and 14 of them (82%) developed protective serum titers of anti-HBs (>10 IU/L). Six patients seroconverted after a first course of vaccination, whereas 8 patients required a second course (3 additional doses of vaccine). Responding patients were followed for a median of 14 months (range, 3-50) after seroconversion. During this period no HBV recurrence occurred and in only 2 patients a decrease of anti-HBs titers below 10 UI/L was observed. Our data suggest that in selected liver transplant recipients, posttransplantation HBV vaccination may be a useful and cost-effective strategy in the prophylaxis of HBV recurrence, allowing the discontinuation of life-long HBIG treatment.

Effect of acute moderate changes in PaCO2 on global hemodynamics and gastric perfusion

OBJECTIVE

To describe global hemodynamics and splanchnic perfusion changes in response to acute modifications in Paco2 in hemodynamically stable patients.

DESIGN

Prospective, randomized crossover study.

SETTING

Medical-surgical intensive care unit at a community hospital (400,000 inhabitants).

PATIENTS

Ten critically ill patients who were sedated, paralyzed, and mechanically ventilated.

INTERVENTIONS

Hypercapnia and hypocapnia were obtained by increasing and reducing instrumental deadspace in random order. After each intervention, patients returned to the basal condition. Each period lasted 80 min: 20 min to achieve stable Paco2 and 60 min for tonometer equilibration. In each period, global hemodynamic variables and tonometric data were collected. The periods were compared using analysis of variance.

MEASUREMENTS AND MAIN RESULTS

Acute hypercapnia (Paco2 from 40+/-3 to 52+/-3 torr, p<.05) increased cardiac index (3.43+/-0.37 vs. 3.97+/-0.43 mL/min/m2, p<.05), heart rate (95+/-6 vs. 105+/-3 beats/min, p<.05), and mean pulmonary artery pressure (21+/-1 vs. 24+/-1 mm Hg, p<.05) and reduced systemic vascular resistance (992+/-98 vs. 813+/-93 dyne x sec/ cm5, p<.05) and oxygen extraction ratio (27+/-3% vs. 22+/-2%, p<.05). Standardized intramucosal Pco2 increased from 49+/-2 to 61+/-3 torr (p<.05) with an associated decrease in calculated intramucosal pH ([pHi] 7.35+/-0.03 vs. 7.25+/-0.02, p<.05), but the gastro-arterial Pco2 gradient (deltaPco2) did not change. Acute hypocapnia (Paco2 from 41+/-3 to 34+/-3 torr, p<.05; pH 7.41+/-0.01 to 7.47+/-0.02, p<.05) induced slight increments in systemic vascular resistance (995+/-117 vs. 1088 +/- 160 dyne x sec/cm5, p<.05) and oxygen extraction ratio (28+/-2% vs. 30+/-2%, p<.05). Standardized intramucosal Pco2 decreased (50+/-4 vs. 44+/-3 torr, p<.05), pHi increased (7.33+/-0.03 vs. 7.36+/-0.02; p<.05), but deltaPco2 did not change.

CONCLUSIONS

In this small group of stable patients, moderate acute variations in Paco2 had a significant effect on global hemodynamics, but splanchnic perfusion, assessed by deltaPco2, did not change. In these conditions, the use of pHi to evaluate gastric perfusion appears unreliable.

Etiology and microbial patterns of pulmonary infiltrates in patients with orthotopic liver transplantation

STUDY OBJECTIVE

To evaluate the etiology and microbial patterns of pulmonary infiltrates in liver transplant patients using a bronchoscopic diagnostic approach and the impact of diagnostic results on antimicrobial treatment decisions.

DESIGN

A prospective cohort study.

SETTING

A 1,000-bed tertiary-care university hospital.

PATIENTS AND METHODS

Fifty consecutive liver transplant patients with 60 episodes of pulmonary infiltrates (33 episodes during mechanical ventilation) were studied using flexible bronchoscopy with protected specimen brush (PSB) and BAL.

RESULTS

A definite infectious etiology was confirmed in 29 episodes (48%). Eighteen episodes corresponded to probable pneumonia (30%), 10 episodes had noninfectious etiologies (17%), and 3 remained undetermined (5%). Opportunistic infections were the most frequent etiology (16/29, 55%, including 1 mixed etiology). Bacterial infections (mainly Gram-negative) accounted for 14 of 29 episodes (48%), including 1 of mixed etiology. The majority of bacterial pneumonia episodes (n = 10, 71%) occurred in period 1 (1 to 28 days posttransplant) during mechanical ventilation, whereas opportunistic episodes were predominant in periods 2 and 3 (29 to 180 days and > 180 days posttransplant, respectively; n = 14, 82%). Microbial treatment was changed according to diagnostic results in 21 episodes (35%).

CONCLUSIONS

Microbial patterns in liver transplant patients with pulmonary infiltrates corresponded to nosocomial, mainly Gram-negative bacterial pneumonia in period 1, and to opportunistic infections in period 2 and, to a lesser extent, period 3. A comprehensive diagnostic evaluation including PSB and BAL fluid examination frequently guided specific antimicrobial therapy.

Dynamics of dominance of a dipeptide insertion in reverse transcriptase of HIV-1 from patients subjected to prolonged therapy

A small proportion (0.8%) of individuals of a cohort of HIV-1 infected patients subjected to prolonged therapy with nucleoside analogues included a recently recognised dipeptide insertion in their RT (Ser-Ser or Ser-Gly between RT codons 69 and 70). To study the dynamics of dominance of genomes with this genetic change, sequential HIV-1 isolates from two patients were analyzed with regard to consensus sequences and complexity of mutant spectra. The two patients displayed completely different, complex evolutionary patterns leading to temporary dominance of dipeptide insertions. In one patient, a virus very closely related to an ancestor virus from the same patient overtook the population at late times, displacing genomes encoding a Ser-Ser insertion. In another patient the sequential dominance of genomes with Ser-Ser insertion-->no insertion-->Ser-Gly insertion was observed. These three types of genomes coexisted in the mutant spectrum of one HIV-1 isolate. Complexity was also reflected in the shape of phylogenetic trees derived with genomes from the mutant spectrum at each time point. The results suggest that HIV-1 genomes encoding a dipeptide insertion between RT codons 69 and 70 do not show a clear selective advantage over other genomes lacking the insertion. Such an absence of a clear selective advantage will favor that such genomes encoding this RT insertion become dominant only in a transient fashion, and following disparate kinetics in different patients.