Detection of enterovirus-specific total and polymeric IgA antibodies in serum using a synthetic peptide or heated virion antigen in ELISA

The presence of enterovirus-specific total and polymeric IgA antibodies was assessed in serum from different groups of patients and healthy controls by indirect ELISA using heated virions and synthetic peptide, both enteroviral broad reactive antigens. Total IgA antibody response against a synthetic peptide, representing an enterovirus group-common epitope, was detected in 52% of the patients with an acute enterovirus infection and in 12% of the patients with other infections (P = 0.02). We also found a significant difference (P = 0.005) in the prevalence of peptide IgA antibodies between serum samples collected from blood donors during summer (20%), the prevalent season of enterovirus infections, and winter (6%). A polymeric IgA activity against the peptide was detected in only three patients with an enterovirus infection. In contrast, when a heated coxsackie B5 (coxB5) virus antigen was used, the prevalence of total serum IgA antibodies was not significantly different between patients with an acute enterovirus infection and patients with other infections (71% vs. 53% respectively; P = 0.3). Also no difference was found between the two groups of blood donors (47% in summer vs. 51% in winter; P = 0.7). However, the prevalence of serum polymeric IgA antibodies against coxsackie B5 antigen was significantly greater (P = 0.02) in patients with an acute enterovirus infection (57%) than in patients with other infections (18%). These findings suggest that the presence (18%). These findings suggest that the presence of total peptide-IgA or of polymeric coxsackie B5-IgA in serum is a specific marker of acute enterovirus infection. Finally, we show that the total peptide-IgA- and polymeric coxsackie B5-ELISAs may have a diagnostic value for the serodiagnosis of enterovirus infections when they are used in combination with enteroviral IgG-ELISA.

High levels of IgA in HIV-1-perinatally-infected children. Antigen specificity and possible role of increased substance P plasma levels

The specificity of IgA against food, inhalant, bacterial and fungine antigens as well as for HIV-1 proteins was investigated in 14 HIV-1-infected children (CDC stage P-2) and 15 controls. IgA against food- and inhalant antigens as well as against tetanus toxoid were significantly more often present in the HIV positive children than in controls. No difference between the two groups was present for IgA against Candida albicans. A significant increase of substance P, a strong IgA synthesis inducing neuropeptide, was demonstrated in the plasma of HIV-1 infected children. In conclusion, high levels of IgA seem to reflect a complex immune dysfunction in which many factors are involved. The importance of neuroimmune dysregulation is discussed.

Uses of flow cytometry in virology

This article reviews some of the published applications of flow cytometry for in vitro and in vivo detection and enumeration of virus-infected cells. Sample preparation, fixation, and permeabilization techniques for a number of virus-cell systems are evaluated. The use of flow cytometry for multiparameter analysis of virus-cell interactions for simian virus 40, herpes simplex viruses, human cytomegalovirus, and human immunodeficiency virus and its use for determining the effect of antiviral compounds on these virus-infected cells are reviewed. This is followed by a brief description of the use of flow cytometry for the analysis of several virus-infected cell systems, including blue tongue virus, hepatitis C virus, avian reticuloendotheliosis virus, African swine fever virus, woodchuck hepatitis virus, bovine viral diarrhea virus, feline leukemia virus, Epstein-Barr virus, Autographa californica nuclear polyhedrosis virus, and Friend murine leukemia virus. Finally, the use of flow cytometry for the rapid diagnosis of human cytomegalovirus and human immunodeficiency virus in peripheral blood cells of acutely infected patients and the use of this technology to monitor patients on antiviral therapy are reviewed. Future prospects for the rapid diagnosis of in vivo viral and bacterial infections by flow cytometry are discussed.

Use of PCR to study epidemiology of Serratia marcescens isolates in nosocomial infection

A method to characterize strains of Serratia marcescens based on the PCR amplification of enterobacterial repetitive intergenic consensus sequences has been developed. The PCR fingerprints were generated from boiled supernatants prepared directly from bacterial colonies without the need for DNA extraction. The technique was applied to isolates obtained during an outbreak of pneumonia from seven mechanically ventilated patients, and its result indicated that the outbreak was due to the spread of two epidemic strains. This technique was validated by comparison with rRNA gene restriction analysis. There was complete concordance between these two techniques in discriminating the outbreak-related strains from epidemiologically unrelated isolates. Typing with both biochemical profile and antibiogram profile, though simple, was found to be less reliable than genotyping. The results show that this enterobacterial repetitive intergenic consensus PCR provides a rapid and simple means of typing S. marcescens isolates for epidemiologic studies.

Role of the French drug licensing authority in the prevention of influenza pandemics

The French Drug Agency is responsible for the control and delivery of batch release certificates. In the case of an influenza pandemic, the use of inactivated vaccines, produced according to well-established procedures and controlled according to the European Pharmacopea and FDA requirements, will be strictly dependent on the necessary delays for production and controls. Mutual recognition between the National Control Laboratories in Europe might help in shortening the delays. If new, inactivated vaccines are produced either on cell cultures or by using genetically modified organisms, and if live attenuated vaccines are needed, it would be suitable to organize ad hoc working groups and international collaborative studies in fields of both research and regulation.

Analysis of Legionella pneumophila strains associated with nosocomial pneumonia in a neonatal intensive care unit

A premature child received continuous mechanical ventilation in a neonatal intensive care unit. On day 10 of his life he developed pneumonia due to Legionella pneumophila serogroup 1, monoclonal subtype Bellingham. The strain was cultured from a tracheal secretion taken on day 10 and detected by immunofluorescence using monoclonal antibodies on days 10, 12 and 17. Legionella pneumophila serogroups 1 and 6 (10(2)-4 x 10(4) cfu/l) were cultured from both central and peripheral hot water systems. Monoclonal antibody testing, macrorestriction analysis of the genomic DNA using pulse-field electrophoresis, and electrophoretic alloenzyme typing showed the isolate from the child to be identical to the serogroup 1 strains from the hot water system. Four unrelated Legionella strains of the same monoclonal subgroup Bellingham were studied for comparison. Legionellae were also isolated from two other incubators, but no clinical or microbiological indications of legionellosis were found in the neonates hospitalised there. Serogroup 1 strains isolated from the patient and from the hot water system and serogroup 6 isolates from the hot water supply were able to multiply in cultured Acanthamoeba castellanii cells and in guinea pigs. The serogroup 6 strain, although prevalent in the incubators, was not found in any of the clinical specimens by either culture of immunofluorescence.

Use of ribotyping in epidemiological surveillance of nosocomial outbreaks

Over the past few years, genotypic methods based on the study of bacterial DNA polymorphism have shown high discriminatory power for strain differentiation and superiority over most phenotypic methods commonly available in the clinical microbiology laboratory. Some of the methods used, however, required either a high level of technology and sophisticated equipment (e.g., pulsed-field gel electrophoresis) or species-specific reagents of restricted availability (randomly cloned DNA probes or gene-specific probes). Because ribotyping uses a universal probe (rRNA) and is a rather simple technology, particularly since the advent of nonradioactive labelling systems, it has been widely used for strain differentiation of most bacterial species involved in nosocomial outbreaks. In vitro and in vivo stability of the markers studied has been demonstrated. Although there may be limitation to this approach, ribotyping was found to be highly discriminative, particularly for typing members of the family Enterobacteriaceae, Pseudomonas cepacia, and Xanthomonas maltophilia. In many cases, it has improved the understanding of the mechanism of nosocomial acquisition of organisms by allowing a distinction between endogenous and exogenous infections. Among exogenous infections, it has distinguished between individual and epidemic strains, thus differentiating cross-infection from independent acquisition.

Is there IgA of gut mucosal origin in the serum of HIV1 infected patients?

This study was performed in 77 HIV1 seropositive adult patients to characterise the IgA hyperglobulinaemia seen in the serum during the course of HIV infection. It was shown that both IgA1 and IgA2 subclass concentrations were simultaneously increased but the IgA1 increase was predominant. Secretory IgA (SIgA) concentration was significantly increased and IgA activity to gliadin, bovine serum albumin, and casein could be detected and was correlated with SIgA concentration. In contrast, IgA activity to cytomegalovirus and to tetanus toxoid did not correlate with total IgA concentration. These data suggest the presence of IgA from gut mucosal origin in the serum of these patients. Hyper IgA was inversely correlated with the CD4+ cell number. The increase of all parameters studied varied according to the total IgA concentration in the serum but was also directly related to the stage of immune deficiency in patients with hyper IgA.

Class and subclass distribution of Hantavirus-specific serum antibodies at different times after the onset of nephropathia epidemica

Sera from Dutch and Belgium individuals who suffered from nephropathia epidemica (NE), a mild form of haemorrhagic fever with renal syndrome (HFRS), were tested for the distribution of classes and subclasses of Hantavirus (HV)-specific antibodies at different times after the onset of the disease, with class- and subclass-specific Ig capture enzyme-linked immunosorbent assays (ELISAs). In the acute, early convalescent, and convalescent phases, predominantly specific IgA, IgM, and IgG3 antibodies were detected. Specific IgG2 antibodies were only detected at low levels in the early convalescent and convalescent phases. In the late convalescent phase specific IgG1 and IgG3 antibodies were found, whereas in the late postconvalescent phase only specific IgG1 antibodies proved to be present. Specific IgG4 antibodies were not detected in any of the respective phases. These data show that the simultaneous determination of classes and subclasses of HV specific serum antibodies allows the estimation of the time elapsed after the onset of NE.

Bacterial resistance to fluoroquinolones: lessons to be learned

Resistance to fluoroquinolone antibacterials has emerged in a limited form, largely amongst certain specific species and often restricted to single clones of these pathogens. Mediated by chromosomal mutation, the major mechanisms are alterations in gyrase subunits and reduced penetration associated with decreased outer membrane protein production. Resistance is most commonly seen to emerge amongst pathogens with higher than average initial MICs, particularly affected species being Pseudomonas aeruginosa and the staphylococci. Resistance is more likely to be encountered when such pathogens are exposed to concentrations at or below the MIC, which may result either from underdosage, the presence of the organism in a sequestered site, e.g. bone or prostate, or from confounding factors such as the presence of pus, indwelling prostheses or interactions which reduce absorption from the gastrointestinal tract. Repetitive use of these agents and continued use of fluoroquinolone precursors, such as nalidixic acid, may also contribute to resistance emergence. Most resistance is appearing amongst hospitalised patients and much of the apparent burden reflects horizontal cross-infection of many patients by a single resistant clone. There is very limited data linking increasing community use of fluoroquinolones with resistance emergence amongst pathogens such as Escherichia coli. In the main, the emergence of resistance can be anticipated and perhaps prevented or avoided for the sorts of risk groups and pathogens described. The use of adequate dosage by appropriate routes of administration in suitable patients and implementation of surveillance procedures for those at risk will minimise such problems. Policies for the effective use of these valuable agents should be part of everyday practice in hospitals.

Evaluation of a new automated microneutralization assay for the quantitative detection of neutralizing antibodies against enteroviruses

An automated microneutralization assay for the quantitative detection of neutralizing antibodies (NA) against polioviruses and non-polio enteroviruses (NPEV) using a pipetting roboter (Tecan RSP 5072) was established and compared to the conventional manually performed test procedure. The qualitative neutralizing antibody detection was not significantly influenced by the assay system (manual or automated assay). Concerning the quantitative antibody detection, two-fold titre differences between the two test systems were observed in only 2.3% of the 260 serum samples investigated. The intra-assay and inter-assay variability of the quantitative detection of neutralizing antibodies using the automated assay proved to be very low. The quantitative detection of neutralizing antibodies using an automated pipetting robot permitted the testing of large numbers of samples within a shorter period and with less labour intensity as compared to the manually performed assay. Therefore it represents a valuable alternative to the conventional microneutralization test, especially for the serodiagnosis of non-polio enterovirus infections in large sample collectives, assessment of immunity to polioviruses and for seroepidemiological surveys.

Pseudomonas aeruginosa serotype O12 outbreak studied by arbitrary primer PCR

A total of 16 colonizing and infecting ofloxacin-resistant Pseudomonas aeruginosa strains and two strains isolated from ventilation equipment fluids, all with similar colonial morphologies and with minor but distinct susceptibility differences, were suspected of belonging to a single outbreak and were studied by arbitrary primer (AP) PCR. Thirteen nonrelated strains were included to evaluate the discriminatory capacity of the technique. AP PCR fingerprinting was compared with serotyping, phage typing, and antibiotic susceptibility testing. AP PCR was performed independently with three different primers. The different AP PCR typing systems yielded almost identical patterns for the epidemic strains and enabled us to differentiate most of the nonrelated strains from each other and from the outbreak strains. The combination of AP PCR typing and the phenotyping techniques that we used enabled us to conclude that an outbreak was occurring. In general, the typeability of AP PCR was greater than those of phage typing and serotyping, while the discriminatory powers of the three methods were comparable.

Evaluation of Staf-Sistem 18-R for identification of staphylococcal clinical isolates to the species level

The accuracy and efficiency of Staf-Sistem 18-R (Liofilchem s.r.l., Roseto degli Abruzzi, Teramo, Italy) were compared with those of conventional biochemical methods to identify 523 strains belonging to 16 different human Staphylococcus species. Overall, 491 strains (93.9%) were correctly identified (percentage of identification, > or = 90.0), with 28 (5.4%) requiring supplementary tests for complete identification. For 14 isolates (2.8%), the strains did not correspond to any key in the codebook and could not be identified by the manufacturer's computer service. Only 18 isolates (3.4%) were misidentified. The system is simple to use, is easy to handle, gives highly reproducible results, and is inexpensive. With the inclusion of more discriminating tests and adjustment in supplementary code numbers for some species, such as Staphylococcus lugdunensis and Staphylococcus schleiferi, Staf-Sistem 18-R is a suitable alternative for identification of human coagulase-positive and coagulase-negative Staphylococcus species in microbiological laboratories.

Arbitrarily primed PCR, ribotyping, and plasmid pattern analysis applied to investigation of a nosocomial outbreak due to Enterobacter cloacae in a neonatal intensive care unit

In December 1992, Enterobacter cloacae was isolated from the oropharynx and respiratory tract of six ventilated neonates hospitalized in the intensive care unit (ICU) of our hospital. To establish the spread of the outbreak, 41 strains of E. cloacae were analyzed for genotypic markers by three methods: plasmid profile analysis, ribotyping with EcoRI or PvuII endonuclease, and arbitrarily primed (AP) PCR. The tested strains included 12 isolates from the 6 epidemic cases, 4 isolates from the respiratory tract of 4 children hospitalized in other wards during the same period, 13 isolates from 12 children hospitalized in pediatric units before or after the outbreak, and 12 epidemiologically unrelated isolates. Ribotyping and AP PCR demonstrated that each of the last 12 strains exhibited distinct genomic patterns, as did each of the strains isolated from neonates hospitalized before or after the epidemic peak. Conversely, two clones of strains were found among the isolates recovered in December, with concordant results being obtained by the three typing methods: the first clone included seven strains from five ventilated children in the ICU and two children from another ward; another clone was shared by one neonate in the ICU and an infant from another ward. These results indicate that ribotyping and AP PCR-the latter applied, to our knowledge, for the first time to the genotypic analysis of E. cloacae--represent very discriminatory tools for the investigation of nosocomial outbreaks caused by this species.

Clotting activity in Staphylococcus schleiferi subspecies from human patients

Staphylococcus schleiferi subsp. schleiferi is a coagulase-negative staphylococcus, usually present as a contaminant in human specimens. A near relative, S. schleiferi subsp. coagulans, possesses coagulase activity but has not been reported from humans. We here describe three isolates of pseudocoagulase-positive S. schleiferi subsp. schleiferi and one isolate of S. schleiferi subsp. coagulans from human patients. The pseudocoagulase from the S. schleiferi subsp. schleiferi isolates differs from S. aureus staphylocoagulase by being sensitive to a combination of protease inhibitors (aprotinin, N-ethylmaleimide, and heparin). These isolates could all easily be confused with S. aureus in a typical clinical laboratory, since they all possess a heat-stable DNase and promote clotting formation. Moreover, S. schleiferi subsp. coagulans produces protein A, and S. schleiferi subsp. schleiferi expresses a clumping factor (fibrinogen affinity factor). Southern blot hybridization with an S. aureus coa-specific probe revealed no sequence related to the coa gene in any of the S. schleiferi isolates, and their riboprobe profiles and biochemical characteristics were typical of S. schleiferi subspecies, not of S. aureus. This study demonstrates that both subspecies of S. schleiferi can promote clotting of rabbit plasma in the standard tube test for coagulase.

Risk factors for acquisition of multiply drug-resistant gram-negative bacteria

Some bacteria are naturally resistant to many antibiotics and most can become multiply resistant. Multiply resistant gram-negative bacteria have proved a particular problem over the last 30 years, but the development of new agents has lessened their significance for most clinicians. Now, however, clinical practice is threatened by the lack of new classes of antibiotics, the widespread emergence of resistance and the advent of plasmid-mediated cephalosporinases by which the spread of resistance is likely to be rapid. Increased use of prophylaxis in immunosuppressed and intensive care patients is likely to aggravate the problem, as is the use of new broad-spectrum agents in the community. More directed and restricted antibiotic use and better education of patients and prescriber are necessary to contain the problem of antibiotic resistance. Improved surveillance of sensitivity trends is essential. Many outbreaks also are associated with poor infection control techniques. The cost of outbreaks due to multiply resistant organisms and lack of compliance with infection control procedures needs to be properly studied. While many predisposing factors for the acquisition of these organisms and the development of infection are understood, the multifactorial nature of illness in many patients complicates the issue, necessitating further study of risk factors and preventative and therapeutic measures.

Does the gender difference in interferon production seen in picornavirus-infected spleen cell cultures from ICR Swiss mice have any in vivo significance?

Splenocyte cultures from female ICR Swiss mice produced greater interferon (IFN) levels, particularly IFN-gamma, than did cultures from males by 12 h post-infection (pi) with the D variant of encephalomyocarditis virus (EMCV-D). This early IFN-gamma is produced by natural killer (NK)-like cells and is dependent on plastic adherent cells and IFN-alpha/beta. In this study, we evaluated the significance of this observation on the innate resistance of ICR Swiss females to EMCV-D-mediated disease. Treatment of females with rabbit anti-mouse IFN-alpha/beta serum rendered them susceptible to the diabetogenicity of EMCV-D. Although sera from both sexes of ICR Swiss mice exhibited peak IFN levels day 3 pi, IFN-gamma was present in the sera of males at only 1 day pi and in the sera of females at days 1-3 pi. Females cleared virus from the circulation by day 2 pi, 1 day earlier than did males. Flow cytometric evaluations of lymphoid cell phenotypes in spleens and pancreata of infected mice revealed that percentages of L3T4+ cells were significantly decreased only in spleens from males at day 1 pi and were diminished along with Ly2+ cells in pancreata of males at 7 days pi, suggesting that T-cell responses were impaired in virus-infected males.

Infection by echoviruses 1 and 8 depends on the alpha 2 subunit of human VLA-2

Anti-VLA-2 antibodies protected HeLa cells from infection by echoviruses 1 and 8 but not from infection by other echovirus serotypes. Echoviruses 1 and 8 bound to and infected nonpermissive hamster cells transfected with the alpha 2 subunit of human VLA-2. These results indicate that the human alpha 2 subunit is critical for infection by echoviruses 1 and 8 but that other echovirus serotypes must bind receptors other than VLA-2.

Ventilator temperature sensors: an unusual source of Pseudomonas cepacia in nosocomial infection

A prospective study was undertaken to determine the source of Pseudomonas cepacia colonization and infection that had affected ventilated patients in an Intensive Care Unit (ICU) for three years. Thirty-eight patients undergoing mechanical ventilation were enrolled during a six-week period. Samples were taken from patients, ventilator circuits and the environment for culture. P. cepacia was isolated from the condensate formed in the ventilator circuit and the source of the contamination was shown to be the temperature sensor. Ribotyping of the representative strains of P. cepacia performed with two endonucleases, EcoRI and PvuII, confirmed the homogeneity of the isolates from patients and ventilator circuits. A modification of the procedure for disinfection of the temperature sensors resulted in the eradication of P. cepacia from the ICU.

Diagnosis of enteroviral meningitis with IgG-EIA using heat-treated virions and synthetic peptides as antigens

Two recently developed enzyme immunosorbent assays (EIA) for the detection of significant titre increases in enteroviral IgG-antibodies were evaluated as diagnostic tools in 127 etiologically well-characterized patients with aseptic meningitis. One assay was based on heat-treated virions (H-EIA) and one on synthetic peptides (P-EIA) as antigens. The sensitivities, with virus isolation as reference method, were 0.67 by H-EIA and 0.62 by P-EIA, which were higher than by a routinely used complement fixation test (CFT, 0.51) but somewhat lower than the sensitivities found by two previously presented IgM-assays, mu-capture EIA, and solid-phase reverse immunosorbent test (SPRIST). The specificities of the two IgG-EIA techniques and CFT were apparently high, whereas the two IgM-assays showed positive reactions in some non-enteroviral cases. A relatively rapid increase in enteroviral IgG-antibodies was apparent using H-EIA and P-EIA. The two IgG-EIA tests contributed with considerable additional etiological information since significant IgG-rises were obtained in 13 patients by H-EIA and in 19 by P-EIA, respectively, out of the 56 individuals in whom enterovirus isolation was negative and a non-enteroviral diagnosis was not found. Thus, detection of enteroviral IgG-antibodies by H-EIA and P-EIA seems to be a valuable alternative to CFT for the routine diagnosis of enteroviral meningitis. The IgM-assays, mu-capture EIA, and SPRIST, may allow a relatively rapid report of an enteroviral infection. However, since both the IgM-tests are hampered by incomplete specificities, a confirmation of positive results by an IgG-assay should be carried out.

Intrathecal administration of amikacin for treatment of meningitis secondary to cephalosporin-resistant Escherichia coli

OBJECTIVE

To report a case of gram-negative bacillary meningitis (GNBM) secondary to cephalosporin-resistant Escherichia coli that was treated with intrathecal and intravenous amikacin and intravenous imipenem/cilastatin (I/C).

CASE SUMMARY

A patient who had undergone two recent neurosurgical procedures developed GNBM and bacteremia. He was treated empirically with ceftazidime. Both bloodstream and cerebrospinal fluid isolates were identified as E. coli, resistant to third-generation cephalosporins, penicillins, tobramycin, and gentamicin. The patient was subsequently treated with intravenous and intrathecal amikacin plus intravenous I/C. He experienced subjective and objective improvement on days 2-4 of antimicrobial therapy; two generalized tonic-clonic seizures occurred on days 7 and 12. Intrathecal amikacin was discontinued after 6 days, and intravenous amikacin and I/C were discontinued after 23 and 27 days, respectively. The patient's mental status did not completely return to premeningitis baseline.

DISCUSSION

Third-generation cephalosporins are the treatment of choice for GNBM. In the case reported herein, bacterial resistance to these agents prompted the use of a therapy that has not been well studied and is also considered to be less safe and perhaps less efficacious. Treatment of GNBM with an intrathecally administered aminoglycoside or with intravenous I/C plus an aminoglycoside is reviewed.

CONCLUSIONS

Patients with GNBM secondary to third-generation cephalosporin-resistant organisms may require therapies that may be less effective and more toxic. Further study of alternative agents is warranted.

Ciprofloxacin-induced, low-level resistance to structurally unrelated antibiotics in Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus

The effects of ciprofloxacin on the rates of development of low-level resistance to other antibiotics were determined in vitro. Three methicillin-resistant Staphylococcus aureus and two Pseudomonas aeruginosa clinical strains were grown overnight in Mueller-Hinton broth with or without subinhibitory concentrations (1/2, 1/4, and 1/8 MICs) of ciprofloxacin or an aminoglycoside and then quantitatively plated onto medium containing 4 or 8 times the MICs of various antibiotics. The spontaneous mutational frequencies were determined and compared with those of cells not exposed to ciprofloxacin. Exposure of methicillin-resistant S. aureus strains to ciprofloxacin resulted in a > 100-fold increase in the isolation of variants with decreased susceptibilities to ciprofloxacin, tetracycline, imipenem, fusidic acid, and gentamicin, but not vancomycin. Likewise, a > 100-fold increase in the isolation of variants with decreased susceptibilities to ciprofloxacin and imipenem (35-fold) in P. aeruginosa A21213 was observed, and a > 100-fold increase in the isolation of variants with decreased susceptibilities to ciprofloxacin, amikacin, and cefepime in P. aeruginosa A22379 was observed. On the other hand, exposure of these strains to an aminoglycoside did not influence the development of resistance to nonaminoglycoside drugs. These results indicate that exposure to subinhibitory levels of ciprofloxacin can promote the development of low-level resistance to antibiotics with different modes of action.

Transient erythroblastopenia of childhood presenting with echovirus 11 infection

We report a case of transient erythroblastopenia in a three-year-old girl presenting with echovirus 11 infection. Viral infection was demonstrated by isolation of echovirus 11 in stool cultures and the presence of echovirus 11-specific IgM antibody in serum. We suggest that echovirus may have played a role in the pathogenesis of transient erythroblastopenia of childhood in this patient.

Identification of group-common linear epitopes in structural and nonstructural proteins of enteroviruses by using synthetic peptides

Synthetic peptides were employed in enzyme-linked immunosorbent assays to identify group-common linear epitopes in the structural and nonstructural proteins of enteroviruses. Nine linear epitopes were recognized by using sera from patients with heterotypic immunoglobulin G antibody responses to enterovirus infections. The most-reactive peptides were derived from conserved regions of the amino-terminal part of VP1, whereas peptides representing sequences from other conserved regions of VP1, as well as VP2, VP3, and VP4, and from a nonstructural region showed no or poor reactivity. These findings may be useful in the development of serological tests for the diagnosis of infections caused by a broad range of enteroviruses.

Comparison of excretory/secretory and circulating antigens of Toxoplasma gondii by enzyme immunoassay and immunoblotting

Toxoplasma gondii trophozoites (RH strain) were cultured in embryonic fibroblasts in order to study the kinetics of production of excretory/secretory antigens, and the results were compared to the production of circulating antigens in an in vivo mouse model. By capture-ELISA, excretory/secretory antigens were first detected on the fourth day of culture whereas circulating antigens were first detected 1 day after infection. Similar concentrations of antigens were detected in both models as evidenced by comparable absorbance values. By immunoblotting, the excretory/secretory antigens were also detected later compared to circulating antigens (day 4 vs day 1). Seven major polypeptides were detected in both antigen preparations, six of them having the same molecular mass (110, 75, 48, 30, 24 and 22 kDa).

Evidence for T-cell involvement during the acute phase of echovirus meningitis

Little is known about the cellular immune response during the acute phase of enterovirus infection. This was studied in patients with echovirus meningitis by analysing changes in the lymphocyte subset distribution both in blood and in cerebrospinal fluid (CSF) and their stage of activation. A significant increase of whole T-cell and CD4+ T-cell counts was observed in CSF in parallel with a slight decrease of T-cell percentage in blood. Activation of the cellular immune response is supported by the observation of elevated neopterin levels in serum and CSF. However, the phenotypic markers of T-cell activation, IL-2 receptor (CD25), and HLA-DR antigens were not detected in blood or in CSF.

Evaluation of four methods for rapid detection of adenovirus

Four methods for rapid detection of adenovirus were evaluated by testing retrospectively 28 frozen clinical specimens from which an adenovirus strain had been isolated. After thawing all specimens were retested for the presence of adenovirus by conventional culture on KB cells and found to be positive. The four tests used for rapid detection of adenovirus were a 48-hour culture technique, and an immunoassay, a latex agglutination test and an immunofluorescence assay for direct detection of viral antigen using commercially available reagents. Of the 28 specimens all were positive in the 48-hour culture, 25 (89%) positive in the immunoassay and 10 (36%) positive in the latex agglutination test. Six of eight nasopharyngeal aspirate specimens were positive in the immunofluorescence assay. Twenty-five clinical specimens negative for adenovirus on conventional culture were also negative in the 48-hour culture technique. Overall, the rapid (48-hour) culture technique was 100% sensitive and 100% specific compared to conventional culture. The direct detection of viral antigen by immunoassay was less sensitive, however results were available within a few hours. Prospective comparative studies are warranted to determine whether these rapid techniques could replace conventional culture in the routine diagnosis of adenovirus infection.

A method for detecting specific anti-C100 protein antibodies of IgM isotype in hepatitis C virus infection

A method for the determination of specific IgM antibodies to C100 protein, a hepatitis C virus-associated antigen, was developed which employed fractionation of serum proteins by gel chromatography and an enzyme-linked immunosorbent assay. Detection of IgM anti-C100 proved to be specific and reproducible in purified IgM fractions. Separation of IgM from IgG was necessary before IgM could be measured, because of the detrimental effect of the simultaneous presence of IgG antibodies with anti-C100 rectivity on IgM determination. IgM anti-C100 was not found in sera containing rheumatoid factors or IgM antibodies to other hepatotropic viruses. IgM anti-C100 was detected in 19 (44%) of 43 patients with hepatitis C virus-related chronic liver disease. When compared with the histological picture of liver disease, IgM anti-C100 was absent in patients with minimal changes and was most common (66.7%) in patients with progressive disease. It is suggested that IgM anti-C100 could reflect an active state of hepatitis C virus infection.

Early diagnosis of enteroviral meningitis by detection of specific IgM antibodies with a solid-phase reverse immunosorbent test (SPRIST) and mu-capture EIA

A solid-phase reverse immunosorbent test (SPRIST) and a mu-capture enzyme immunosorbent assay (EIA) for detection of enterovirus-specific IgM antibodies were evaluated for enterovirus diagnosis of aseptic meningitis in 160 consecutive patients from whom enterovirus (11 different serotypes) were isolated in 64. In patients with an enterovirus isolate and/or four-fold titre rise in the complement fixation test (CFT) for enterovirus, specific enterovirus IgM antibodies were detected on the day of admission to hospital in 48% by SPRIST and in 50% by EIA and 4-6 days after onset of symptoms in 71% by SPRIST and 79% by EIA. A significant increase in titre was observed between serum sampled on the day of admission and 2 days later in 38% by SPRIST and in 41% by EIA. These results indicate that the IgM antibody response appears early in the course of aseptic meningitis. Since both SPRIST and EIA provide rapid results the tests may be of differential diagnostic value and the IgM antibody kinetics may be utilized for diagnosis during the acute phase of aseptic meningitis. With optimized serum sampling the positive outcome was 76% in SPRIST and 82% in EIA among patients with positive virus isolation and/or CFT for enterovirus. In 67 patients virus isolation and CFT for enterovirus yielded negative results as well as all non-enteroviral diagnostic tests. Thirty-eight of these patients were positive by SPRIST and/or EIA and in half of these 38 a significant titre rise and/or fall in SPRIST and/or EIA was recorded. The majority of these IgM-positive patients became ill in the late summer or autumn, i.e., the "enterovirus season."(ABSTRACT TRUNCATED AT 250 WORDS)

[The role of the bacteriological laboratory in the criteria for choosing and monitoring antibiotic treatment]

The constant development of clinical bacteriology and the consequence this has on the way an infected patient is approached and treated require that be examined a bacteriology laboratory's contribution in choosing and monitoring an antibiotic treatment. In the economic context of hospitals, one of the aims is to rationalize the prescription of biological investigations, as well as that of antibiotic treatments. The patient's history, his clinical state as well as the place where he has been admitted must be taken into account to establish, together with microbiologists, a hierarchy of the biological investigations required and to adapt the antibiotic treatment. In the laboratory, both the bacteriostatic and bactericidal sensitivity to antibiotics may be assessed in vitro. The best therapeutic antibiotic concentrations may be obtained by monitoring the pharmacokinetics of antibiotics.

Naturally occurring anti-interferon-alpha 2a antibodies in patients with acute viral hepatitis

The occurrence of antibodies against recombinant human interferon-alpha 2a (IFN-alpha 2a) in patients with acute viral hepatitis (AVH) was examined by ELISA. Naturally occurring IgG anti-IFN-alpha 2a were found in 50% of patients with type A, 50% of those with type B and in 8.3% of those with non-A, non-B AVH. The corresponding frequencies of IgM antibodies were 80%, 30% and 33.3%, respectively. IgM anti-IFN-alpha 2a were found more frequently in patients with AVH type A than in normal control subjects (P less than 0.01). Anti-IFN-alpha 2a were detectable at the highest frequency 3 weeks after acute onset and then became negative. An absorption experiment revealed that IgM anti-IFN-alpha 2a did not cross-react with recombinant human IFN-alpha 2b. Immunoblotting analysis confirmed the binding of antibodies to IFN-alpha 2a. Sera positive for IgG and/or IgM anti-IFN-alpha 2a were unable to neutralize IFN-alpha 2a. The appearance of anti-IFN-alpha 2a was not correlated with disease severity. There was no evidence to suggest that anti-IFN-alpha 2a impaired the elimination of hepatitis virus. This is the first study to demonstrate the occurrence of anti-IFN-alpha 2a in patients with AVH. Detection of anti-IFN-alpha 2a may be useful for clarifying any underlying immune events in various diseases.

Acute infection of encephalomyocarditis (EMC) virus in Syrian hamsters

One-month-old Syrian hamsters of the APA and Std: golden strains were inoculated intraperitoneally with 10(5) PFU/head of the D variant of encephalomyocarditis (EMC) virus and examined virologically and pathologically up to 7 days after inoculation. APA hamsters developed apparent hyperglycemia due to pancreatic islet cell damage while Std:golden hamsters did not. Hamsters of both strains showed clear histopathologic changes in the testis with prominent viral replication as well as in the brain, heart and exocrine pancreas. The susceptibility to EMC virus-infection was higher in males than in females and in APA than in Std: golden hamsters.

Chromosomal locations and gonadal dependence of genes that mediate resistance to ectromelia (mousepox) virus-induced mortality

Four genetic loci were tested for linkage with loci that control genetic resistance to lethal ectromelia virus infection in mice. Three of the loci were selected because of concordance with genotypes assigned to recombinant inbred (RI) strains of mice derived from resistant C57BL/6 and susceptible DBA/2 (BXD) mice on the basis of their responses to challenge infection. Thirty-six of 167 male (C57BL/6 x DBA/2)F1 x DBA/2 backcross (BC) mice died (22%), of which 27 (75%) were homozygous for DBA/2 alleles at Hc and H-2D. Twenty-eight percent of sham-castrated and 6% of sham-ovariectomized BC mice were susceptible to lethal mousepox, whereas 50% of gonadectomized mice were susceptible. There was no linkage evident between Hc or H-2D and loci that controlled resistance to lethal ectromelia virus infection in 44 castrated BC mice. Mortality among female mice of BXD RI strains with susceptible or intermediate male phenotypes was strongly correlated (r = 0.834) with male mortality. Gonadectomized C57BL/6 mice were as resistant as intact mice to lethal ectromelia virus infection. These results indicate that two gonad-dependent genes on chromosomes 2 and 17 and one gonad-independent gene control resistance to mousepox virus infection, that males and females share gonad-dependent genes, and that the gonad-independent gene is fully protective.

Spontaneous interferon-alpha antibodies in a patient with pure red cell aplasia and recurrent cutaneous carcinomas

High-titered spontaneous interferon (IFN) antibodies were detected in a patient with pure red cell aplasia (PRCA), a benign mediastinal tumor, and recurrent cutaneous carcinomas. The circulating IFN antibodies reacted broadly with various human IFN-alpha subtypes (20-140 x 10(3) neutralizing units/ml serum) but not with IFN-beta or IFN-gamma, and they neutralized the antiviral activity of the patient's endogenous IFN-alpha. The IFN-alpha-binding activity was restricted to the IgG1 subclass in a nonmonoclonal manner. Whereas the PRCA repeatedly responded to immunosuppression with high-dose cyclosporin A (CSA) and CSA plus plasmapheresis, IFN antibody production continued during treatment with cyclophosphamide and CSA. Serological analysis revealed past infection with parvovirus B19 and persistent B19 IgM titers. Antibody-mediated impairment of the IFN-alpha system might have favored the development of both PRCA and the various cutaneous carcinomas in this patient.

Enhanced capacity of females for early interferon-gamma production by natural killer-like cells following stimulation by staphylococcal enterotoxin A

Staphylococcal enterotoxin A (SEA) induced the production of interferon-gamma (IFN-gamma) by spleen cells from ICR Swiss mice during the first 24 h of culture. Splenocytes from females produced higher levels of IFN-gamma than did those from males at 8, 12, and 16 h. By 20 h after SEA stimulation, IFN-gamma production by spleen cells from males was similar to that of females. The cell types involved in IFN-gamma production in this SEA/spleen cell system were analyzed by depletion studies. Removal of Thy-1+ cells by panning prevented production of IFN-gamma in the 24 h after SEA stimulation. In vivo depletion of asialo GM1+ (AGM1+) cells prevented production of IFN-gamma through 16 h of culture with SEA, but permitted a modest IFN-gamma response at 20 h that was similar in magnitude in both sexes. Following removal of L3T4+ and Lyt-2+ cells by panning, IFN-gamma production was detected at 12 h after SEA stimulation and maintained through 24 h of culture with cells from females producing higher levels of IFN-gamma. These data suggest that male ICR Swiss mice are deficient in the activity of Thy-1+, AGM1+, L3T4-, and Lyt-2- cells in the early (8-16 h) production of IFN-gamma following SEA stimulation of spleen cells.

Detection of immunoglobulin G, M, and A antibodies to enterovirus structural proteins by immunoblot technique in echovirus type 4-infected patients

Paired serum specimens from 24 patients with echovirus (EV) type 4 infection by virus isolation were tested by the immunoblot technique for the presence of IgG, IgM, and IgA antibodies to EV4 structural proteins. Single sera from 20 patients without neutralizing enterovirus IgM were used as controls. All the sera from EV4-infected patients had IgG antibodies to VP1 of EV4 but also 13 out of the 20 controls. 23 out of 24 EV4-infected patients elicited IgM and IgA specific antibodies to VP1, a pattern highly significant as compared with controls (3/20 for IgM and 8/20 for IgA). In 16 out of the 24 EV4-infected patients, the IgM antibodies were also directed against VP2 (versus 2 out of 20 in the control group). Anti-VP2 IgA were detected in 4 out of the 24 EV4 patients (versus 0 in controls). The 24 paired sera from EV4-infected subjects were also tested by immunoblot technique against three other enteroviruses: EV21, coxsackievirus A9 and poliovirus 1. Cross-reactivities were observed to a large extent against VP1 and VP2 proteins with the three classes of antibodies. These results confirm the data of previous studies on the reactivity of IgM antibodies to various structural proteins that IgG antibodies react exclusively to VP1. Furthermore, this study demonstrates the occurrence of circulating IgA antibodies directed to VP1 and sometimes VP2 in the course of enterovirus infection. The potential interest of this latter finding for diagnosis requires further investigation.

Early diagnosis of enteroviral meningitis by a solid-phase reverse immunosorbent test and virus isolation

45 cases of aseptic meningitis/meningoencephalitis were studied with regard to enteroviral etiology by virus isolation and solid-phase reverse immunosorbent test (SPRIST), a cross-reacting test for enterovirus IgM. An etiological diagnosis was reached in 37/45 (82%) patients. Etiological diagnoses other than enteroviruses were found in 8 patients: Borrelia burgdorferi in 4, varicella-zoster virus in 2, herpes simplex virus in 1 and mumps virus in 1 patient. Enteroviruses (echovirus 6, 21 and 30) were isolated from cerebrospinal fluid (CSF) in 26/37 (70%) and from stool samples of 20/21 (95%) of patients with no other etiology. Altogether enteroviruses were isolated from CSF and/or faecal samples in 29 patients. Echovirus 30 dominated as etiologic agent. In 34/40 (85%) of the samples with an enterovirus, a cytopathogenic effect was observed in cell culture within 4 days. In patients with an enterovirus isolate a SPRIST IgM response to echovirus 3, 5, 7 and/or coxsackievirus B3 was detected in 6/13 (46%) sera sampled 3-4 days after the onset of meningeal symptoms and in altogether 17/25 patients (68%). In 4 out of these virus isolation positive and SPRIST negative patients a single serum for SPRIST was available less than 4 days after onset of meningeal symptoms. Antigen from echovirus 5 gave the highest diagnostic yield. The SPRIST IgM test was positive in 2 cases where virus isolation, complement fixation and neutralization tests were negative. Epidemiological data however supported an enteroviral diagnosis in both of them. In conclusion, both SPRIST and virus isolation seem to be valuable for the early diagnosis of enteroviral meningitis.

Detection of neutralizing IgM antibodies in the diagnosis of enterovirus infections

Data are presented of IgM detection by a neutralization test used routinely in 1,062 patients. Antigens isolated during the period of investigation were EV4, EV7, EV11, EV18, EV21, EV24, EV33, CA9, CB2, CB4, and CB5. No difference was observed in the distribution of IgM-positive sera according to age and sex. Total antibodies are at higher titres when IgM antibodies are present. Polytypic IgM responses are not frequent (less than 10%). The frequency of the IgM-positive sera for a given serotype correlated with the frequency of isolates for the serotype except for CA9. Other than for babies under age 6 months, IgM detection is more frequent than is isolation. The susceptibility of the elderly and the frequency of IgM-positive sera among adults over age 40 years suggests possible underestimation of enterovirus infections in adults. The duration of IgM remains a major question.

Characterization of a non-structural 147-kDa precursor polypeptide of echovirus 33 and its immunogenicity in man

Zinc chloride (0.9 mM)--an inhibitor of the processing of the initial polypeptides of Picornaviridae--was used to accumulate large precursors of echovirus 33 (EV33) and notably two proteins of 147- and 97-kDa. Polyclonal hyperimmune sera were raised in mice against these polypeptides and assayed by immunoblotting against EV33-infected cells blocked or not with ZnCl2, showing that protein 147--2ABC3ABCD according to the L434 convention--can be considered to be the precursor of the two non-structural proteins P2 and P3. Sixty-three serum specimens from subjects exhibiting varying antibody status against EV33 by seroneutralization were investigated by immunoblotting against an EV33 ZnCl2-blocked antigen. Some subjects infected with EV33 were shown to elicit antibodies which recognize the non-structural precursor polypeptides, a fact whose clinical significance needs further evaluation.