Convalescent Antibody Research Articles

A serological survey on neutralizing antibody titer of SARS convalescent sera.

A seroepidemiologic study was conducted in North China in 2003 to determine the neutralizing antibody titer of severe acute respiratory syndrome (SARS) convalescent sera. A total of 99 SARS convalescent serum samples were collected from patients from the Inner Mongolia Autonomous Region, Hebei Province, and Beijing 35–180 days after the onset of symptoms. The anti‐SARS antibodies were detected by enzyme‐linked immunosorbent assay (ELISA), neutralization assay, and Western blot. Eighty‐seven serum samples were confirmed to be positive for SARS antibodies. The neutralizing antibody titer of the 87 positive sera was analyzed quantitatively by neutralization assay. The geometric mean titer (GMT) of the 87 convalescent sera was 1:61. The Kolmogorov–Smirnov test showed that the neutralizing antibody titers conform to normal distribution, which suggests that the average anti‐SARS antibody level in this study was representative of the convalescent antibody level of the SARS population. This result could be useful for the development and quality control of SARS vaccines. J. Med. Virol. 77:147–150, 2005. © 2005 Wiley‐Liss, Inc.

Characterization of antibodies to PspA and PsaA in adults over 50 years of age with invasive pneumococcal disease

We characterized antibody responses to two Streptococcus pneumoniae surface proteins, PspA and PsaA, in 14 adults over 50 years of age hospitalized with invasive pneumococcal disease (IPD), and in two groups of age-matched controls (18 patients with invasive disease due to other microorganisms and 35 patients hospitalized for non infectious conditions). All patients with IPD and all control subjects had detectable antibodies to both proteins on hospital admission. Three weeks later, the geometric mean concentrations of antibodies to PspA and PsaA in IPD patients were respectively 10 and 25 times higher than on admission. In contrast, acute and convalescent antibody levels were similar in control patients with invasive diseases due to other microorganisms.

Treatment of severe acute respiratory syndrome in health-care workers

There is still no proven therapy for severe acute respiratory syndrome (SARS). The protocol reported by Loletta So and colleagues1So LK Lau AC Yam LY et al.Development of a standard treatment protocol for severe acute respiratory syndrome.Lancet. 2003; 361: 1615-1617Summary Full Text Full Text PDF PubMed Scopus (289) Google Scholar emphasised the combination use of ribavirin and high-dose cortico-steroid. However, if given very early in the course of the disease, this approach could suppress the generation of host immunity to the novel coronavirus. We observed a biphasic pattern of illness in SARS and postulated that the first stage represents a viraemic phase and the second phase is an immune phase.2JT Wang, JL Wang, CT Fang, SC Chang: Temporary defervescence in the first week of disease course does not indicate recovery of disease in a patient with severe acute respiratory syndrome. Emerg Infect Dis (in press).Google Scholar Acute respiratory distress syndrome seems to be a complication in the second phase.2JT Wang, JL Wang, CT Fang, SC Chang: Temporary defervescence in the first week of disease course does not indicate recovery of disease in a patient with severe acute respiratory syndrome. Emerg Infect Dis (in press).Google Scholar If this hypothesis is true, antiviral agents will be most beneficial in the first phase, whereas corticosteroids should be delayed until the onset of the second phase to maximise benefit and keep the negative effects of immune suppression to a minimum. We, therefore, developed a treatment protocol3Department of Internal MedicineGuidelines for management of severe acute respiratory syndrome (SARS).http://ntuh.mc.ntu.edu.tw/med/sarsGoogle Scholar that emphasises early use of ribavirin but delayed introduction of corticosteroids until the second week, if possible. One oral 2000 mg loading dose of ribavirin was given to patients as soon as they received medical attention, followed by 600 mg ribavirin twice daily for patients with a bodyweight greater than 75 kg or 1000 mg daily for those with a bodyweight of 75 kg or less (400 mg in morning, 600 mg in evening) for 10 days. For patients who developed pneumonia, intravenous methylprednisolone (2 mg/kg daily for 5 days) was started on day 8 of fever or later. If rapid deterioration occurred before day 8, steroid treatment was started upon development of dyspnoea. If respiratory distress was not responsive to this dose, 500 mg methylprednisolone daily for 3 days was given. Upon improvement, the dose of steroid was tapered off over the next 2 weeks as recovery warranted. In Taipei between April 23 and May 31, 2003, 17 health-care workers at our hospital contracted SARS.4WHOCase definitions for surveillance of severe acute respiratory syndrome (SARS).http://www.who.int/csr/sars/casedefinition/enGoogle Scholar PCR of serum or nasopharyngeal swab proved positive in seven of the 17 health-care workers, and convalescent serum antibodies were positive in 13 health-care workers. All 17 health-care workers received our treatment protocol (table). The median starting day of ribavirin was day 2 of fever (range 1–7 days). Only one health-care worker needed subsequent intubation and respiratory support. All 17 individuals recovered without major sequelae or subsequent relapse. With prompt identification and early treatment, mortality from SARS can be avoided among previously healthy health-care workers.TableCharacteristics and timing of treatment for 17 health-care workers with SARSAge (years)/sex/occupationProtection usedSARS categoryRibavirin started*Oral ribavirin 2000 mg loading then 600 mg twice daily.Steroid started†Intravenous methylprednisolone 2 mg/kg daily.Minipulse started‡Intravenous methylprednisolone 500 mg daily.ICU stayMaximum oxygen demandDischargePatient number133/M/doctorN95 maskProbableD1D7–NoRoom airD24228/F/nurseN95 maskSuspectedD2––NoRoom airD18326/F/nurseN95 maskProbableD3D9–NoRoom airD28445/F/nurseN95 maskProbableD3D10–NoNasal cannula 3 L/minD27526/F/nurseN95 maskProbableD2D8D13NoNasal cannula 2 L/minD28649/F/registerSurgical maskProbableD2D6D15YesIntubated with FiO2 0·6D52751/F/porterSurgical maskProbableD7D13–NoNasal cannula 3 L/minD33849/F/porterSurgical maskProbableD4D7–NoNasal cannula 3 L/minD25934/M/doctorN95 maskSuspectedD6––NoRoom airD61053/F/doctorN95 maskSuspectedD2––NoRoom airD141141/F/nurseN95 maskProbableD1D10–NoRoom airD201227/F/nurseN95 maskSuspectedD4––NoRoom airD101335/F/nurseN95 maskProbableD2D9–NoRoom airD201428/F/nurseN95 maskSuspectedD3––NoRoom airD121530/F/doctorN95 maskProbableD2D8–NoRoom airD261642/M/technicianN95 maskProbableD2D11–NoNasal cannula 3 L/minD291757/F/porterN95 maskProbableD3D13–NoRoom airD23F=female. M=male. D=day since onset of fever. ICU=intensive care unit; FiO2=fractional concentration of oxygen in inspired gas.* Oral ribavirin 2000 mg loading then 600 mg twice daily.† Intravenous methylprednisolone 2 mg/kg daily.‡ Intravenous methylprednisolone 500 mg daily. Open table in a new tab F=female. M=male. D=day since onset of fever. ICU=intensive care unit; FiO2=fractional concentration of oxygen in inspired gas.

Immunologic memory in Haemophilus influenzae type b conjugate vaccine failure

Aims: To compare the convalescent antibody response to invasive Haemophilus influenzae type b (Hib) disease between conjugate vaccine immunised and unimmunised children, to look for evidence of priming for immunologic...

Antibody response to pneumococcal capsular polysaccharides in children with acute otitis media.

To describe the antibody response to pneumococcal capsular polysaccharides in children <2 years of age with pneumococcal acute otitis media (AOM) caused by serotypes 6A, 6B, 11A, 14, 19F or 23F. These serotypes were commonly found in both nasopharyngeal carriage and AOM in children of the study population in Finland. Serum antibody concentrations to pneumococcal capsular polysaccharides of types 6B, 11A, 14, 19F and 23F were measured by enzyme immunoassay in acute and convalescent sera from children with AOM. Responses (at least 2-fold increase of antibody concentration) were relatively infrequent and varied with both the age of the child and the serotype of the Streptococcus pneumoniae isolated from the middle ear fluid. Children older than 12 months were more likely to have antibody responses than were younger children. Responses were seen only infrequently to types 6A, 6B or 19F (1 of 14, 1 of 9 and 2 of 25, respectively), more often to types 11A and 14 (2 of 8 and 3 of 8) and relatively frequently to type 23F (8 of 18). However, the convalescent antibody concentrations to type 23F were low and usually declined after the infection, whereas responders to 14 AOM had antibodies that persisted at a high concentration through the follow-up. The results emphasize the differences between Streptococcus pneumoniae serotypes in their immunogenicity and quantitative and qualitative differences of antibodies produced after infection.

Prolonged Cough in Adolescents and Adults Due to Pertussis

Infectious Diseases| September 01 2001 Prolonged Cough in Adolescents and Adults Due to Pertussis AAP Grand Rounds (2001) 6 (3): 27–28. https://doi.org/10.1542/gr.6-3-27 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Prolonged Cough in Adolescents and Adults Due to Pertussis. AAP Grand Rounds September 2001; 6 (3): 27–28. https://doi.org/10.1542/gr.6-3-27 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search nav search search input Search input auto suggest search filter All AAP SitesAll PublicationsAll JournalsAAP Grand RoundsPediatricsHospital PediatricsPediatrics In ReviewNeoReviewsAAP News Search Advanced Search Topics: cough, pertussis Source: Senzilet LD, Halperin SA, Spika JS, et al. Pertussis is a frequent cause of prolonged cough illness in adults and adolescents. Clin Infect Dis. 2001;32:1691–1696. Researchers in Canada conducted a multicenter study to determine the prevalence of laboratory-confirmed pertussis in a convenience sample of adolescents and adults (≥12 years old) who had a cough-related illness of 1 to 8 weeks’ duration. Nasopharyngeal aspirates and acute and convalescent antibody titers to Bordetella pertussis antigens were collected from 442 symptomatic patients. Results for each of the 5 criteria for laboratory confirmation of pertussis infection were as follows: positive nasopharyngeal (NP) aspirate culture 2/440;positive polymerase chain reaction (PCR) of NP aspirate 3/314;4-fold increase between acute- and convalescent-phase antibody titers to B pertussis antigens 7/393;antibody titers higher than the 99.99th percentile for 575 healthy... Copyright © 2001 by the American Academy of Pediatrics2001 You do not currently have access to this content.

Antibody Neutralization of the Extracellular Enveloped Form of Vaccinia Virus

The extracellular enveloped form (EEV) of vaccinia virus (VV) is important for the long-range dissemination of the virus inside the host. Early work suggested that both IMV and EEV infectivity could be inhibited by antibodies, although two other studies reported that EEV was resistant to neutralization. Here, we readdressed this question, using four VV-immune antisera and their purified IgG, and showed that EEV infectivity can be inhibited by antibody produced from a live infection in plaque-reduction assays, although EEV is more resistant to neutralization by convalescent antibodies than is IMV. In parallel, indirect immunofluorescent staining and confocal microscopy showed that antibody aggregated EEV and prevented it from binding to cells. Using the IgG and Fab fragments prepared from this antiserum, we tested whether EEV made by VV mutants lacking genes A33R, A34R, A36R, A56R, B5R, F12L, or F13L can be inhibited in plaque-reduction assays. Although vΔB5R was slightly more resistant than other mutants, none of these mutants escaped neutralization completely, suggesting that multiple virus proteins are involved in the inhibition. Using an antibody specific to B5R protein and B5R mutants with consecutive short consensus repeat (SCR) domains deleted, the neutralization epitopes on B5R were mapped to within the SCR domain 1.

Identification of immunodominant and conformational epitopes in the capsid protein of hepatitis E virus by using monoclonal antibodies.

Antibody to the capsid (PORF2) protein of hepatitis E virus (HEV) is sufficient to confer immunity, but knowledge of B-cell epitopes in the intact capsid is limited. A panel of murine monoclonal antibodies (MAbs) was generated following immunization with recombinant ORF2.1 protein, representing the C-terminal 267 amino acids (aa) of the 660-aa capsid protein. Two MAbs reacted exclusively with the conformational ORF2.1 epitope (F. Li, J. Torresi, S. A. Locarnini, H. Zhuang, W. Zhu, X. Guo, and D. A. Anderson, J. Med. Virol. 52:289-300, 1997), while the remaining five demonstrated reactivity with epitopes in the regions aa 394 to 414, 414 to 434, and 434 to 457. The antigenic structures of both the ORF2.1 protein expressed in Escherichia coli and the virus-like particles (VLPs) expressed using the baculovirus system were examined by competitive enzyme-linked immunosorbent assays (ELISAs) using five of these MAbs and HEV patient sera. Despite the wide separation of epitopes within the primary sequence, all the MAbs demonstrated some degree of cross-inhibition with each other in ORF2. 1 and/or VLP ELISAs, suggesting a complex antigenic structure. MAbs specific for the conformational ORF2.1 epitope and a linear epitope within aa 434 to 457 blocked convalescent patient antibody reactivity against VLPs by approximately 60 and 35%, respectively, while MAbs against epitopes within aa 394 to 414 and 414 to 434 were unable to block patient serum reactivity. These results suggest that sequences spanning aa 394 to 457 of the capsid protein participate in the formation of strongly immunodominant epitopes on the surface of HEV particles which may be important in immunity to HEV infection.

ELISA for IgG-class antibody to hepatitis E virus based on a highly conserved, conformational epitope expressed in Eschericia coli

In assays based on most recombinant hepatitis E virus (HEV) antigens, the IgG antibody responses to HEV are observed commonly to wane or disappear after the acute phase of infection. Such IgG assays have therefore been used for the diagnosis of acute HEV infection, but they have limited usefulness in seroepidemiological studies. Using western immunoblotting, it was shown previously that the open reading frame (ORF) 2.1 antigen, representing the carboxy-terminal 267 amino acids (aa) of the capsid protein, exposes a conformational epitope which allows optimal detection of convalescent antibody compared to other proteins expressed in Eschericia coli. This conformational epitope is shown to be highly conserved between divergent human HEV isolates, and the development of a sensitive and highly specific enzyme immunoassay (ELISA) based on this recombinant antigen is described. The ORF2.1 ELISA allows the detection and quantitation of both acute- and convalescent phase HEV-specific IgG, and will help to define better the antibody responses to the virus and the prevalence of HEV infection worldwide.

Identification and characterization of TspA, a major CD4(+) T-cell- and B-cell-stimulating Neisseria-specific antigen.

In search for novel T-cell immunogens involved in protection against invasive meningococcal disease, we screened fractionated proteins of Neisseria meningitidis (strain SD, B:15:P1.16) by using peripheral blood mononuclear cells (PBMCs) and specific T-cell lines obtained from normal individuals and patients convalescing from N. meningitidis infection. Proteins of iron-depleted meningococci produced higher PBMC proliferation indices than proteins of iron-replete organisms, indicating that iron-regulated proteins are T-cell immunogens. Insoluble proteins of the iron-depleted cells, which produced better T-cell stimulation than soluble ones, were fractionated by using sodium dodecyl sulfate-polyacrylamide gels and recovered as five fractions (F1 to F5) corresponding to decreasing molecular weight ranges. The proteins were purified (by elution and precipitation) or electroblotted onto nitrocellulose membranes (dissolved and precipitated) before use in further T-cell proliferation assays. One of the fractions (F1), containing high-molecular-mass proteins (>130 kDa), consistently showed the strongest T-cell proliferation responses in all of the T-cell lines examined. F1 proteins were subdivided into four smaller fractions (F1A to F1D) which were reexamined in T-cell proliferation assays, and F1C induced the strongest responses in patients' T-cell lines. Rabbit polyclonal antibodies to F1C components were used to screen a genomic expression library of N. meningitidis. Two major clones (C1 and C24) of recombinant meningococcal DNA were identified and fully sequenced. Sequence analysis showed that C24 (1,874 bp) consisted of a single open reading frame (ORF), which was included in clone C1 (2, 778 bp). The strong CD4(+) T-cell-stimulating effect of the polypeptide product of this ORF (named TspA) was confirmed, using a patient T-cell line. Immunogenicity for B cells was confirmed by showing that convalescent patients' serum antibodies recognized TspA on Western blots. Additional genetic sequence downstream of C24 was obtained from the meningococcal genomic sequence database (Sanger Centre), enabling the whole gene of 2,761 bp to be reconstructed. The DNA and deduced amino acid sequence data for tspA failed to show significant homology to any known gene, except for a corresponding (uncharacterized) gene in Neisseria gonorrhoeae genome sequences, suggesting that tspA is unique to the genus Neisseria. The DNA and deduced amino acid sequence of the second ORF of clone C1 showed significant homology to gloA, encoding glyoxalase I enzyme, of Salmonella typhimurium and Escherichia coli. Thus, we have identified a novel neisserial protein (TspA) which proved to be a strong CD4(+) T-cell- and B-cell-stimulating immunogen with potential as a possible vaccine candidate.

Value of the polymerase chain reaction assay in noninvasive respiratory samples for diagnosis of community-acquired pneumonia.

We studied the causes of community-acquired pneumonia (CAP) in 184 patients. Microbiologic evaluation included sputum examination, blood culture, assessment of acute and convalescent antibody titers for Legionella pneumophila, Mycoplasma pneumoniae, Chlamydia pneumoniae, Coxiella psitacci, Coxiella burnetii and respiratory viruses, polymerase chain reaction (PCR) assays for M. pneumoniae and C. pneumoniae in throat swab, and PCR assay based on the amplification of pneumolysin gene fragment in sera. The causative pathogen was identified in 78 patients (Streptococcus pneumoniae, 44; M. pneumoniae, 26; C. pneumoniae, 1; others, 7). S. pneumoniae was detected in serum by the PCR assay in 41 patients, five of whom also had a positive blood culture. PCR assay was negative in two patients with positive blood culture for S. pneumoniae. C. pneumoniae was detected by PCR in nine patients, but only one showed seroconversion. M. pneumoniae was detected by PCR in only three patients (two without seroconversion). The diagnosis of pneumonia caused by S. pneumoniae was five times greater using PCR in serum than with blood culture. Detection of C. pneumoniae by PCR without fulfilling criteria for acute infection may be considered a prior infection. The PCR assay for the diagnosis of M. pneumoniae has a lower sensitivity than serologic methods.

Seroneutralization of porcine reproductive and respiratory syndrome virus correlates with antibody response to the GP5 major envelope glycoprotein.

To determine the structural protein of the porcine reproductive and respiratory syndrome virus (PRRSV) involved in the production of neutralizing antibodies following clinical infection, correlation was studied between virus neutralization capability of convalescent pig sera and antibody response to the open reading frames (ORFs) 3-, 4-, 5-, and 7-encoded proteins GP3, GP4, GP5, and N, respectively. Individual virus genes were cloned into the pGEX-4T-1 vector, and the recombinant viral proteins were expressed in Escherichia coli fused to the glutathione S-transferase (GST) protein. The resulting GST-ORF3, GST-ORF4, GST-ORF5, and GST-ORF7 recombinant fusion proteins were purified by electroelution and used as antigens for serologic testing by indirect enzyme-linked immunosorbent assay and western immunoblotting. The overall antibody (IgG and IgM) titers to PRRSV of pooled convalescent pig sera were first determined by indirect immunofluorescence, and then sera with specific IgG titers > 1:1,024 were tested for their specific virus neutralization activity and reactivity to individual recombinant fusion proteins. Except for the early immune response (as revealed by the presence of specific IgM), neutralizing titers were correlated with anti-GP5 titers but not with anti-GP3 and anti-GP4 titers. The correlation between virus neutralization and anti-GP5 titers was significant (r = 0.811, P < or = 0.001).

Evaluation of bluetongue virus diagnostic tests in free-ranging bighorn sheep

Five bluetongue virus (BTV) diagnostic tests were evaluated for use in free-ranging bighorn sheep. We sampled one bighorn sheep population four times between 1989 and 1995. The tests evaluated included virus isolation (VI), polymerase-chain reaction (PCR), serum neutralization (SN), agar-gel immunodiffusion (AGID), and competitive enzyme-linked immunosorbent assay (c-ELISA). The c-ELISA, AGID and SN tests had high levels of agreement in determining serogroup exposure in bighorn sheep. We used maximum-likelihood algorithms to estimate the parameters of each diagnostic test used. Although the c-ELISA and AGID had high sensitivity and specificity, the SN had perfect specificity but lower apparent sensitivity. Due to the potential of cross-reactions among multiple serotypes, results of the SN must be interpreted with caution when assessing serotype exposure in an area where multiple serotypes are endemic. The PCR assay delineated convalescent antibody titers from more-recent infections, and consequently, was pivotal in distinguishing a different exposure pattern between the bighorn sheep and cattle in an adjacent herd. Based on an increasing seroprevalence (50% to 100%), BTV circulated through this bighorn sheep population between 1989 and 1993. This increase in seroprevalence coincided with a bighorn die-off due to BTV infection in June, 1991. An adjacent cattle herd was sampled in 1995 for comparison. The bighorn sheep and adjacent cattle had different patterns of exposure to BTV between 1994 and 1995. There was no evidence that BTV circulated through the bighorn sheep population from 1994 to 1995. In 1995, seroprevalence to BTV decreased to 72%, none of yearling bighorn was seropositive, and all of the 39 bighorn sheep were PCR-negative. In contrast, all adult cattle were seropositive to BTV by c-ELISA and SN, and 4 of the calves were seropositive; 11 of the 24 cattle were PCR-positive, including all five calves. Overall, the pattern of temporal herd immunity in the bighorn sheep appeared to follow a classic epidemic curve, with the appearance and subsequent disappearance of herd immunity coinciding with the 1991 die-off in this population. As low levels of herd immunity and high proportions of susceptible animals are key factors in the development of epidemics, this population of bighorn sheep may be at increased risk for a BTV epidemic in the future.

Effect of Rimantadine on Induced Specific Serum Haemagglutination-Inhibiting Antibody and Nasal IgA Titres after Experimental Exposure of Adults to Influenza a Virus

Haemagglutination-inhibiting (HI) antibody and specific nasal IgA responses to infection with influenza A (H1N1) virus were compared between 35 rimantadine-treated subjects (100 mg, orally, twice daily from day 2 to day 10, post-challenge) and 36 placebo-treated subjects. Infection was documented in 29 (83%) and 34 (94%), viral shedding in 24 (69%) and 30 (83%), and seroconversion in 21 (60%) and 27 (75%) of the rimantadine- and placebo-treated subjects, respectively. The duration of virus shedding (1.7±1.6 days compared with 3.1±2.1 days) was significantly lower in the rimantadine-treated group. Both groups had significant increases in the HI (21 days post-challenge) and virus-specific nasal IgA antibody (7 days post-challenge) titres. Convalescent HI but not IgA antibody titre was significantly greater in the placebo group. Convalescent HI antibody titre correlated with virus shedding, suggesting that differences between treatment groups are attributable to the reduced duration of viral shedding in rimantadine-treated subjects.

Erythema Migrans—like Rash Illness at a Camp in North Carolina

Borrelia burgdorferi, the causative agent of Lyme disease, has never been isolated from a patient thought to have acquired Lyme disease in any southeastern state. To investigate 14 cases of an erythema migrans (EM)-like rash illness that occurred during 2 summers at an outdoor camp in central North Carolina in an effort to determine the etiologic, epidemiological, and clinical aspects of this illness. Using active surveillance, we identified cases of clinically diagnosed EM in residents and staff of the camp. We collected clinical and demographic information; history of exposure to ticks; acute and convalescent serum antibodies to B. burgdorferi, Rickettsia rickettsii, and Ehrlichia chaffeensis; and cultures for spirochetes from biopsy specimens of skin lesions. Serum samples from a group of residents and staff who did not develop rashes were tested for the same antibodies. We speciated ticks removed from people and collected from vegetation. We identified 14 cases of EM-like rash illness during the 2 summers. Of the 14 case-patients, 10 had associated mild systemic symptoms and 1 had documented fever. All 14 case-patients had removed attached ticks, and 8 remembered having removed a tick from the site where the rash developed a median of 12 days earlier (range, 2-21 days). One tick removed from the site where a rash later developed was identified as Amblyomma americanum, the Lone Star tick; 97% of ticks collected from vegetation and 95% of ticks removed from people were A. americanum. No spirochetes were isolated from skin biopsy specimens. Paired serum samples from 13 case-patients did not show diagnostic antibody responses to B. burgdorferi or other tick-borne pathogens. This investigation suggests the existence of a new tick-associated rash illness. We suspect that the disease agent is carried by A. americanum ticks. In the southern United States, EM-like rash illness should no longer be considered definitive evidence of early Lyme disease.

RISK OF HEMOLYTIC UREMIC SYNDROME FOLLOWING SPORADIC E. COLI O157 INFECTION: RESULTS OF A CANADIAN COLLABORATIVE STUDY † 760

The risk of hemolytic uremic syndrome (HUS) following E. coli O157 gastroenteritis has been estimated to range widely (from 3-26%), and has been reported as a summary estimate for all ages. The objective of this study was to better estimate the age-specific risk of HUS and hemolytic anemia (HA) following O157 infection among a representative cohort of children from the Province of Alberta, and to compare this to children presenting to tertiary centers in the rest of Canada. Children with HUS or E. coli O157 gastroenteritis were eligible if they were less than 15 years old and stool samples had been submitted to one of 18 participating hospital labs or to one of the two Provincial Health Laboratories (PHL) in Alberta. Samples from the PHL allowed identification of an almost complete cohort of non-referred Alberta children with O157 gastroenteritis. Hemoglobin, blood smear, urinalysis, and serum creatinine were obtained 8-10 days after the onset of diarrhea; subjects were followed for 1 month. Compliance with blood specimens was 92% in Alberta and 90% in the rest of Canada. O157 infection was considered present in those with HUS if the stool culture grew O157 or if the acute or convalescent anti-O157 lipopolysaccharide antibody titer was ≥ 1:500. From June, 1991 to March, 1994 HUS was diagnosed in 205 Canadian children. Of these, 77% (26 in Alberta and 131 in other provinces) had evidence of O157 infection. In addition 586 children had O157 gastroenteritis but no HUS; 4 of these in Alberta and 14 elsewhere had HA. The risk of HUS following O157 infection in Alberta was 26/322, or 8.1% (95% CI, 5.3-11.6); if those with HA are included, the risk increases to 9.3%. In the rest of Canada, the risk of HUS following O157 infection was 31.1%, reflecting referral bias. In Alberta children, the highest age-specific risk of HUS/HA was 13% in those younger than 5 years (95% CI, 7.6-18.5%). These data help guide clinical care and provide a basis for sample size estimates for prevention trials. More than 90% of HUS patients across Canada had been seen by a physician in the two weeks before diagnosis, identifying the potential for intervention at an early phase of the illness.

Neutralization Susceptibility of African Swine Fever Virus Is Dependent on the Phospholipid Composition of Viral Particles

In this study we have investigated the generation of African swine fever (ASF) virus variants resistant to neutralizing antibodies after cell culture propagation. All highly passaged ASF viruses analyzed were resistant to neutralization by antisera from convalescent pigs or antibodies generated against individual viral proteins which neutralized low-passage viruses. A molecular analysis of neutralizable and nonneutralizable virus isolates by sequencing of the genes encoding for neutralizing proteins revealed that the absence of neutralization of high-passage viruses is not due to antigenic variability of critical epitopes. A comparative analysis of phospholipid composition of viral membranes between low- and high-passage viruses revealed differences in the relative amount of phosphatidylinositol in these two groups of viruses, independent of the cells in which the viruses were grown. Further purification of low- and high-passage viruses by Percoll sedimentation showed differences in the phospholipid composition identical to those found with the partially purified viruses and confirmed the susceptibility of these viruses to neutralization. The incorporation of phosphatidylinositol into membranes of high-passage viruses rendered a similar neutralization susceptibility to low-passage viruses, in which this is a major phospholipid. In contrast, other phospholipids did not interfere with high-passage virus neutralization, suggesting that phosphatidylinositol is essential for a correct epitope presentation to neutralizing antibodies. Additionally, the removal of phosphatidylinositol from a low-passage virus by a specific lipase transformed this virus from neutralizable to nonneutralizable. These data constitute clear evidence of the importance of the lipid composition of the viral membranes for the protein recognition by antibodies and may account in part for the past difficulties in reproducibly demonstrating ASF virus-neutralizing antibodies by using high-passage viruses.

Suppression of in vivo cell-mediated immunity during experimental influenza A virus infection of adults

A variety of recent evidence documents that otitis media is a frequent complication of upper respiratory tract viral infections. This relationship has been attributed to the interaction of a number of virus-provoked host responses, including eustachian tube dysfunction, changes in nasopharyngeal bacterial flora and suppressed immune function. The present study examined the effect of experimental influenza A virus infection on immune function as assessed by delayed skin test reactivity to Candida, tetanus, and diphtheria/tetanus antigens in healthy adults with ( n = 12) and without ( n = 15) allergic rhinitis. All subjects became infected with the challenge virus as evidenced by viral shedding into nasal secretions and/or a four-fold rise in convalescent serum antibody titers compared to baseline. Intradermal skin tests were placed at baseline and 2, 4, 17, and 24 days after intranasal influenza A inoculation, the reactions were imaged and recorded 48 h after placement, and response areas were calculated by computerized digitization. The average combined areas for the three antigens (±S.T.D.) on each of the 5 study days were 1.4 ± 1.4, 0.7 ± 0.7, 0.6 ± 0.6, 1.4 ± 1.4, and 1.2 ± 1.2 cm 2, respectively. The responses to Candida, but not tetanus and diphtheria/ tetanus, returned to baseline levels by day 17. Repeated measures ANOVA documented significant effects of study day and antigen, but not allergy status. These results show that experimental influenza A infection suppressed delayed hypersensitivity skin tests in both allergic and non-allergic subjects, and suggest that alterations in immune function may contribute to otitis media.

Improved genetic mapping of X linked retinoschisis.

X linked retinoschisis (RS) causes poor vision in affected males owing to radial cystic changes at the macula. Genetic linkage analysis was carried out in 16 British families with X linked retinoschisis using markers from the Xp22 region. Linkage was confirmed between the RS locus and the markers DXS207 (lod score, Zmax = 17.9 at recombination fraction theta = 0.03; confidence interval for theta = 0.007-0.09), DXS1053 (Zmax = 18.0 at theta = 0.01, CI = 0.001-0.06), DXS43 (Zmax = 12.9 at theta = 0.03, CI = 0.004-0.09), DXS1195 (Zmax = 6.4 at theta = 0.00), DXS418 (Zmax = 8.2 at theta = 0.00), DXS999 (Zmax = 21.2 at theta = 0.01, CI = 0.001-0.05), DXS443 (Zmax = 14.2 at theta = 0.03, CI = 0.004-0.09), DXS365 (Zmax = 24.5 at theta = 0.008, CI = 0.001-0.04). Key recombinants placed RS between DXS43 distally and DXS999 proximally. Multipoint linkage analysis gave odds of 344:1 in favour of this location for RS and supported the map Xpter-(DXS207, DXS1053)-DXS43-1 cM-RS-1 cM-DXS999-DXS443-DXS365-DXS1052-Xcen.

Perspective: the problem of non-O157:H7 shiga toxin (Verocytotoxin)-producing Escherichia coli.

Escherichia coli 0157:H7 causes diarrhea, hemorrhagic colitis, and the hemolytic uremic syndrome (HUS) [1, 2]. The cardinal virulence trait of E. coli 0157:H7 is the production of Shiga toxins (Stx, also termed Verocytotoxins) [3,4]. Unlike most coliforms in human feces, E. coli 0157:H7 does not ferment sorbitol after overnight incubation [5]. Therefore, it is easily and economically detected by laboratories using sorbitolMacConkey (s-Mac) agar screening to identify sorbitol-nonfermenting candidate E. coli 0157:H7 [6, 7]. Such colonies are then tested for the presence of the 0157 antigen, which, if detected, presumptively identifies Stx-producing E. coli (STEC) 0157:H7. In contrast, it is not known which of the many STEC belonging to serotypes other than 0157:H7 (non0157:H7 STEC) are pathogens; with rare exceptions [8, 9], such organisms ferment sorbitol and would be overlooked on an s-Mac agar plate. The same difficulty applies to the detection of sorbitol-fermenting Stx-producing E. coli 0157:NM, a pathogen in Germany [10]. In this issue, Ludwig et al. [11], report that 6 of 8 HUS patients from whom non-0157:H7 STEC were isolated produced antibodies to the O-specific lipopolysaccharide of the putatively causative strains. Ludwig et al. also determined that patients infected with E. coli expressing O antigens 26, 55, and 111 did not make antibodies to the 0157 lipopolysaccharide. Humans infected with E. coli 0157:H7 respond briskly with antibodies to the 0157 antigen [12-16], so absence of anti0157 antibodies probably exonerates E. coli 0157:H7 as the pathogen that precipitated the HUS. This is an important point, because children from whom such non-0157:H7 STEC have been isolated sometimes produce convalescent antibodies to the 0157 lipopolysaccharide [12-14], suggesting that E. coli 0157:H7 was missed in the stool culture. Furthermore, simultaneous enteric infections with E. coli 0157:H7 and non-