A case of haemolytic disease of the fetus and newborn attributed to a novel antigen in the RHAG blood group system

BACKGROUND AND OBJECTIVES

A newborn presented with jaundice in Thailand. The cord red cells tested positive by direct antiglobulin test (DAT) for an unknown maternal red cell antibody. Initial blood group sequencing suggested that the infant carried a novel variant RHAG c.140T>C, responsible for a low-prevalence antigen in the RHAG blood group system (ISBT 030). We report here on testing of samples from the infant's parents and older sibling to define a new antigen in the RHAG system.

MATERIALS AND METHODS

Massive parallel sequencing (MPS) using a custom-designed panel was performed on all four family members. Extended serological testing was also performed to determine whether family members with the same variant as the infant showed reactivity with the antibody in the maternal plasma.

RESULTS

We identified a novel single nucleotide variant (SNV) (RHAG c.140T>C, p.[Phe47Ser]) in samples from three of the four family members tested (the infant, the older sibling and the father). The variant was not detected in the mother's sample. Maternal plasma showed positive agglutination with all family members tested; however, when tested with routine panel cells, no reactivity was observed.

CONCLUSION

This case study showed that the presence of the novel variant (RHAG c.140T>C), encoding a p.(Phe47Ser) change in the RhAG glycoprotein, was the apparent cause of incompatibility between maternal plasma and that of red cells from the proband, father and older sibling of the proband. We propose this variant to be a new low-prevalence antigen in the RHAG blood group system.

Next generation sequencing to identify iron status and individualise blood donors' experience

BACKGROUND

Young adults form the majority of first-time blood donors to Australian Red Cross Lifeblood. However, these donors pose unique challenges for donor safety. Young blood donors, who are still undergoing neurological and physical development, have been found to have lower iron stores, and have higher risks of iron deficiency anaemia when compared to older adults and non-donors. Identifying young donors with higher iron stores may improve donor health and experience, increase donor retention, and reduce the burden on product donation. In addition, these measures could be used to individualise donation frequency.

MATERIALS AND METHODS

Stored DNA samples from young male donors (18-25 years; No.=47) were sequenced using a custom panel of genes identified in the literature to be associated with iron homeostasis. The custom sequencing panel used in this study identified and reported variants to human genome version 19 (Hg19).

RESULTS

82 gene variants were analysed. Only one of which, rs8177181, was found to have a statistically significant (p<0.05) association with plasma ferritin level. Heterozygous alleles of this Transferrin gene variant, rs8177181T>A, significantly predicted a positive effect on ferritin levels (p=0.03).

DISCUSSION

This study identified gene variants involved in iron homeostasis using a custom sequencing panel and analysed their association with ferritin levels in a young male blood donor population. Additional studies of factors associated with iron deficiency in blood donors are required if a goal of personalised blood donation protocols is to be achieved.

Recommendation for validation and quality assurance of non-invasive prenatal testing for foetal blood groups and implications for IVD risk classification according to EU regulations

BACKGROUND AND OBJECTIVES

Non-invasive assays for predicting foetal blood group status in pregnancy serve as valuable clinical tools in the management of pregnancies at risk of detrimental consequences due to blood group antigen incompatibility. To secure clinical applicability, assays for non-invasive prenatal testing of foetal blood groups need to follow strict rules for validation and quality assurance. Here, we present a multi-national position paper with specific recommendations for validation and quality assurance for such assays and discuss their risk classification according to EU regulations.

MATERIALS AND METHODS

We reviewed the literature covering validation for in-vitro diagnostic (IVD) assays in general and for non-invasive foetal RHD genotyping in particular. Recommendations were based on the result of discussions between co-authors.

RESULTS

In relation to Annex VIII of the In-Vitro-Diagnostic Medical Device Regulation 2017/746 of the European Parliament and the Council, assays for non-invasive prenatal testing of foetal blood groups are risk class D devices. In our opinion, screening for targeted anti-D prophylaxis for non-immunized RhD negative women should be placed under risk class C. To ensure high quality of non-invasive foetal blood group assays within and beyond the European Union, we present specific recommendations for validation and quality assurance in terms of analytical detection limit, range and linearity, precision, robustness, pre-analytics and use of controls in routine testing. With respect to immunized women, different requirements for validation and IVD risk classification are discussed.

CONCLUSION

These recommendations should be followed to ensure appropriate assay performance and applicability for clinical use of both commercial and in-house assays.

The role of non-invasive prenatal testing (NIPT) for fetal blood group typing in Australia

Maternal alloimmunisation against red blood cell antigens can cause haemolytic disease of the fetus and newborn (HDFN). Although most frequently caused by anti-D, since the implementation of rhesus D (RhD) immunoglobulin prophylaxis, other alloantibodies have become more prevalent in HDFN. Recent advances in non-invasive prenatal testing (NIPT) have allowed early prediction of HDFN risk in alloimmunised pregnancies and allow clinicians to focus health resources on those pregnancies that require intervention. This article aims to provide updates on the current status of NIPT in Australia as both a diagnostic and screening tool in pregnancy.

Targeted exome sequencing designed for blood group, platelet, and neutrophil antigen investigations: Proof-of-principle study for a customized single-test system

BACKGROUND

Immunohematology reference laboratories provide red blood cell (RBC), platelet (PLT), and neutrophil typing to resolve complex cases, using serology and commercial DNA tests that define clinically important antigens. Broad-range exome sequencing panels that include blood group targets provide accurate blood group antigen predictions beyond those defined by serology and commercial typing systems and identify rare and novel variants. The aim of this study was to design and assess a panel for targeted exome sequencing of RBC, PLT, and neutrophil antigen-associated genes to provide a comprehensive profile in a single test, excluding unrelated gene targets.

STUDY DESIGN AND METHODS

An overlapping probe panel was designed for the coding regions of 64 genes and loci involved in gene expression. Sequencing was performed on 34 RBC and 17 PLT/neutrophil reference samples. Variant call outputs were analyzed using software to predict star allele diplotypes. Results were compared with serology and previous sequence genotyping data.

RESULTS

Average coverage exceeded 250×, with more than 94% of targets at Q30 quality or greater. Increased coverage revealed a variant in the Scianna system that was previously undetected. The software correctly predicted allele diplotypes for 99.5% of RBC blood groups tested and 100% of PLT and HNA antigens excepting HNA-2. Optimal throughput was 12 to 14 samples per run.

CONCLUSION

This single-test system demonstrates high coverage and quality, allowing for the detection of previously overlooked variants and increased sample throughput. This system has the potential to integrate genomic testing across laboratories within hematologic reference settings.

International Society of Blood Transfusion Working Party on Red Cell Immunogenetics and Blood Group Terminology: Report of the Dubai, Copenhagen and Toronto meetings

BACKGROUND AND OBJECTIVES

The International Society of Blood Transfusion (ISBT) Working Party for Red Cell Immunogenetics and Blood Group Terminology meets in association with the ISBT congress and has met three times since the last report: at the international meetings held in Dubai, United Arab Emirates, September 2016 and Toronto, Canada, June 2018; and at a regional congress in Copenhagen, Denmark, June 2017 for an interim session.

METHODS

As in previous meetings, matters pertaining to blood group antigen nomenclature and classification were discussed. New blood group antigens were approved and named according to the serologic and molecular evidence presented.

RESULTS AND CONCLUSIONS

Fifteen new blood group antigens were added to eight blood group systems. One antigen was made obsolete based on additional data. Consequently, the current total of blood group antigens recognized by the ISBT is 360, of which 322 are clustered within 36 blood groups systems. The remaining 38 antigens are currently unassigned to a known system. Clinically significant blood group antigens continue to be discovered, through serology/sequencing and/or recombinant or genomic technologies.

International society of blood transfusion working party on red cell immunogenetics and terminology: report of the Seoul and London meetings

The Working Party has met twice since the last report: in Seoul, South Korea 2014, and in London, UK 2015, both in association with the International Society of Blood Transfusion (ISBT) Congress. As in previous meetings, matters pertaining to blood group antigen nomenclature were discussed. Eleven new blood group antigens were added to seven blood group systems. This brings the current total of blood group antigens recognized by the ISBT to 346, of which 308 are clustered within 36 blood groups systems. The remaining 38 antigens are currently unassigned to a known blood group system.

Optical measurement of the temporal delay between two ultra-short and focussed laser pluses

Temporal overlapping of ultra-short and focussed laser pulses is a particularly challenging task, as this timescale lies orders of magnitude below the typical range of fast electronic devices. Here we present an optical technique that allows for the measurement of the temporal delay between two focussed and ultra-short laser pulses. This method is virtually applicable to any focussing geometry and relative intensity of the two lasers. Experimental implementation of this technique provides excellent quantitative agreement with theoretical expectations. The proposed technique will prove highly beneficial for high-power multiple-beam laser experiments.

Genotyping confirms inheritance of the rare At(a-) type in a case of haemolytic disease of the newborn

The At(a) blood group antigen (now AUG2 in the Augustine system) is a high-frequency antigen with negative phenotype At(a-) found only in individuals of African ancestry. In a twin pregnancy, the fifth pregnancy in a woman of African origin, serological investigations confirmed that the mother was At(a-) and anti-At(a) was detected. DNA samples were exome sequenced and alignment was performed to allow variant calling. It was confirmed that the single nucleotide polymorphism, rs45458701, within the SLC29A1 gene encoding the ENT1 protein, recently reported to be a basis of the At(a-) phenotype was also the basis of the phenotype in this family. The reagents for serological analysis required to identify the rare blood type present in this mother are held in only a few reference laboratories worldwide. This case highlights the utility of genetic methods in resolving complex investigations involving blood grouping and demonstrates that genotyping of variants associated with blood types present in specific ethnic groups may be the fastest method available for identification of the basis of fetomaternal incompatibilities.

International Society of Blood Transfusion Working Party on red cell immunogenetics and blood group terminology: Cancun report (2012)

The International Society of Blood Transfusion Working Party on red cell immunogenetics and blood group terminology convened during the International congress in Cancun, July 2012. This report details the newly identified antigens in existing blood group systems and presents three new blood group systems.

Heterogeneous drying stresses in stratum corneum

We study the drying of stratum corneum, the skin's outermost layer and an essential barrier to mechanical and chemical stresses from the environment. Even though stratum corneum exhibits structural features across multiple length-scales, contemporary understanding of the mechanical properties of stratum corneum is based on the assumption that its thickness and composition are homogeneous. We quantify spatially resolved in-plane traction stress and deformation at the interface between a macroscopic sample of porcine stratum corneum and an adherent deformable elastomer substrate. At length-scales greater than a millimeter, the skin behaves as a homogeneous elastic material. At this scale, a linear elastic model captures the spatial distribution of traction stresses and the dependence of drying behavior on the elastic modulus of the substrate. At smaller scales, the traction stresses are strikingly heterogeneous and dominated by the heterogeneous structure of the stratum corneum.

Seroprevalence of 2009 pandemic influenza A(H1N1) virus in Australian blood donors, October - December 2009

Assessment of the severity of disease due to the 2009 pandemic influenza A(H1N1) in Australian states and territories has been hampered by the absence of denominator data on population exposure. We compared antibody reactivity to the pandemic virus using haemagglutination inhibition assays performed on plasma specimens taken from healthy adult blood donors (older than 16 years) before and after the influenza pandemic that occurred during the southern hemisphere winter. Pre-influenza season samples (April – May 2009, n=496) were taken from donation collection centres in North Queensland (in Cairns and Townsville); post-outbreak specimens (October – November 2009, n=779) were from donors at seven centres in five states. Using a threshold antibody titre of 40 as a marker of recent infection, we observed an increase in the influenza-seropositive proportion of donors from 12% to 22%, not dissimilar to recent reports of influenza A(H1N1)-specific immunity in adults from the United Kingdom. No significant differences in seroprevalence were observed between Australian states, although the ability to detect minor variations was limited by the sample size. On the basis of these figures and national reporting data, we estimate that approximately 0.23% of all individuals in Australia exposed to the pandemic virus required hospitalisation and 0.01% died. The low seroprevalence reported here suggests that some degree of prior immunity to the virus, perhaps mediated by broadly reactive T-cell responses to conserved influenza viral antigens, limited transmission among adults and thus constrained the pandemic in Australia.

Dengue viremia in blood donors from Honduras, Brazil, and Australia

BACKGROUND

Dengue fever and hemorrhagic disease are caused by four dengue virus (DENV) serotypes (DENV-1 to -4), mosquito-borne flaviviruses with increasing incidence, and expanding global distributions. Documented transfusion transmission of West Nile virus raised concern regarding transfusion-transmitted DENV.

METHODS

A DENV RNA assay was developed based on transcription-mediated amplification (TMA) blood screening assays routinely used by blood centers worldwide. Sensitivity was established by endpoint dilution analyses of DENV-1 RNA transcript and pedigreed tissue culture standards for all four DENV-serotypes. Frozen plasma samples were tested from 2994 donations from Honduras (September 2004-January 2005), 4858 donations from Brazil (February-April 2003), and 5879 donations from Australia (March-September 2003). Type-specific polymerase chain reaction (PCR) assays were used to quantify and genotype TMA repeat-reactive samples; viral cultures, type-specific antibody, and antigen assays were also performed.

RESULTS

The TMA assay detected 14.9 copies per mL DENV-1 transcript (95% detection limit), with comparable sensitivity for all four serotypes. Honduran donors yielded 9 TMA repeat-reactive samples (0.30%); 8 were confirmed by PCR, with 3 DENV serotypes detected and viral loads from fewer than 3 x 10(4) to 4.2 x 10(4) copies per mL; and 4 samples yielded infectious virus. Three (0.06%) Brazilian samples tested repeat-reactive; 2 (0.04%) were PCR-positive (serotypes DENV-1 and -3; 12 and 294 copies/mL). No Australian donor samples tested repeat-reactive.

CONCLUSION

Dengue viremia rates among asymptomatic blood donors ranged from 0.30 percent in Honduras to 0.04 percent in Brazil. Future studies are needed to establish rates of transfusion transmission by viremic donations and clinical consequences in recipients.

Follow-up of six blood donors highlights the complementary role and limitations of hepatitis C virus antibody and nucleic acid amplification tests

BACKGROUND AND OBJECTIVES

The purpose of this study was to analyse the follow-up results for six blood donors who screened positive for hepatitis C virus (HCV) by nucleic acid amplification technology (NAT) but were non-reactive in the primary antibody immunoassay (HCV NAT yield).

MATERIALS AND METHODS

Volunteer blood donations were screened, in parallel, for antibodies to hepatitis C virus (anti-HCV) and for human immunodeficiency virus (HIV)/HCV RNA using the Abbott PRISM HCV Chemiluminescent immunoassay (ChLIA) and the Chiron Procleix HIV-1/HCV RNA assays, respectively. NAT yield donor samples were further tested using supplemental assays, including an alternate HCV antibody enzyme immunoassay (EIA) (Abbott Murex anti-HCV Version 4), an immunoblot (Ortho RIBA-3 or Genelabs Diagnostics HCV Blot 3.0) and two alternative HCV NAT assays [Roche HCV Amplicor and an assembled HCV polymerase chain reaction (PCR)]. Five of the six donors were available for follow-up testing.

RESULTS

The six NAT yield donations were identified as constituents of 24-member minipools among 2,212,695 donations screened over the 28-month study period. All samples were positive when tested, undiluted, using the Roche Amplicor and assembled reverse transcription-polymerase chain reaction (RT-PCR) alternate NAT assays. One of the donors, subsequent to seroconversion, showed RNA levels that fluctuated above and below the limit of detection of the NAT screening assay. Three of the six were reactive on the secondary EIA and showed reactivity to the core c22(p) antigen by immunoblot at the index donation. Two others subsequently became reactive in the ChLIA prior to the EIA, showing reactivity against c100 and/or c33c antigens by immunoblot. The remaining donor became reactive in the ChLIA and EIA at the same time, showing RIBA reactivity against all of the following three peptides: c100; c33c; and c22(p).

CONCLUSIONS

This study demonstrated that at least five of six HCV NAT yield donors were in the pre- or early antibody seroconversion phase of infection. The observation that one yield donor demonstrated HCV RNA that fluctuated above and below the limit of detection of the primary NAT-screening assay supports the maintenance of both NAT and antibody screening for HCV. Follow-up testing of suspected yield donors revealed that the primary and alternate anti-HCV immunoassays had different performance characteristics, depending on the specificity of the donor's early anti-HCV response.

Nucleic acid technology screening of Australian blood donors for hepatitis C and human immunodeficiency virus-1 RNA: comparison of two high-throughput testing strategies

BACKGROUND AND OBJECTIVES

The aim of this study was to compare the performance of two high-throughput strategies for hepatitis C virus (HCV) and human immunodeficiency virus-1 (HIV-1) RNA nucleic acid technology (NAT) screening in a volunteer blood-donor population.

MATERIALS AND METHODS

The semiautomated Chiron Procleix HIV-1/HCV transcription mediated amplification (TMA) assay was used to screen 1 439 765 donations in two different testing configurations. Three sites (termed PDT sites) performed a mixture of individual donation (ID) and minipool (MP) testing, where 1 113 288 donations were screened as pools of 24 and an additional 32 003 donations were screened in ID format. A further two sites (termed SDT sites) screened 294 474 donations exclusively in ID format.

RESULTS

A significantly higher proportion of initial NAT reactives that failed to react on follow-up testing [termed non-repeatably reactive (NRR)] was observed for ID testing at SDT sites than at PDT sites (0.082 vs. 0.047%: P < 0.01). Within the PDT sites, however, there was no significant difference between the NRR rate for MP or ID samples (0.037 vs. 0.047%; not significant). There was a significant difference in failed run rates between PDT and SDT sites (P < 0.01), with PDT sites having a higher run failure rate owing to non-amplification of the internal control. The PDT sites also had a significantly higher overall invalid sample rate. However, the invalid sample rate, specifically caused by known equipment failure, was significantly higher in the SDT sites, possibly attributable to greater usage (P < 0.0001). Four HCV NAT-positive/antibody-negative samples were identified in the course of the study.

CONCLUSIONS

The comparison of the performance of PDT with SDT sites identified only minor differences that did not adversely impact on the timely release of blood products. Although both ID and MP strategies showed excellent specificity, irrespective of site configuration, the significantly increased NRR rate, observed exclusively for ID testing performed at SDT sites, indicates a potential for contamination that may limit the number of samples that can optimally be processed using ID testing. The performance data for ID testing in particular should serve as a useful benchmark for evaluating candidate NAT systems that are fully automated.

Sensitivity of HCV RNA and HIV RNA blood screening assays

BACKGROUND

The FDA requirement for sensitivity of viral NAT methods used in blood screening is a 95-percent detection limit of 100 copies per mL, whereas the NAT screening system should have a sensitivity of at least 5000 copies per mL per individual donation. According to the Common Technical Specifications of the European Directive 98/79/EC for in vitro diagnostics, viral standard dilutions (calibrated against the WHO standard) should be tested at least 24 times for a statistically valid assessment of the 95-percent detection limit.

STUDY DESIGN AND METHODS

Viral standard dilution panels (PeliCheck, VQC-CLB) were prepared for HCV RNA genotypes 1 and 3 and for HIV RNA genotypes B and E. In a multicenter study, 23 laboratories tested the panels all together in 8 to 91 test runs per NAT method.

RESULTS

The following 95-percent detection limits (and 95% CIs) were found on the HCV RNA genotype 1 reference panels (shown as geq/mL): Gen-Probe TMA, 85 (64-118); AmpliScreen, 126 (83-225); AmpliScreen with NucliSens Extractor, 21 (13-44); Amplicor with NucliSens Extractor, 69 (50-102), and Amplicor with Qiagen extraction technology, 144 (74-102). On HIV RNA genotype B dilution panels, the following 95-percent detection limits were found (shown as geq/mL): Gen-Probe TMA, 31 (20-52); AmpliScreen, 126 (67-311); AmpliScreen with NucliSens Extractor, 37 (23-69), and NucliSens QL assay, 123 (51-566). HIV RNA genotype E panels were detected with equal sensitivity as HIV RNA genotype B panels. In the Gen-Probe TMA assay, the 50-percent detection limits on HIV RNA type B and type E were 3.6 (2.6-5.0) and 3.9 (2.4-5.8) geq per mL, respectively. The HCV RNA genotype 1 and 3 standards were detected with equal sensitivity.

CONCLUSION

The differences in sensitivity between NAT assays can be explained by the input of isolated viral nucleic acid in the amplification reactions. The FDA requirements for sensitivity of NAT blood screening assays can be met by the Gen-probe TMA, as well as by the AmpliScreen assays, particularly when combined with the NucliSens Extractor.

Better care and better teaching. New model of postpartum care for early discharge programs

PROBLEM BEING ADDRESSED

Rapid postpartum discharge has reduced opportunities to detect early newborn or parenting problems and to teach neonatal assessment and maternal postpartum care to medical trainees.

OBJECTIVE OF PROGRAM

Development of a program to not only ensure adequate care of mothers and newborns after early hospital discharge, but also to teach outpatient assessment skills to family medicine residents.

MAIN COMPONENTS OF PROGRAM

In an urban, secondary care, university-affiliated teaching hospital predominantly training family medicine residents, an interdisciplinary committee created and supervised a neonatal and maternal postpartum assessment program. Newborn infants and their mothers are seen by a family physician, a family medicine resident, and a nurse within 48 hours of discharge, after which care is assumed in the community by the child's primary care physician. An assessment protocol developed by the interdisciplinary group promotes standardized mother and child care and a structured learning experience for trainees.

CONCLUSION

Rapid follow up of early discharged infants and their mothers can be facilitated by a program of standardized assessment by a roster of pooled, interacting family physicians and nurses. When this assessment occurs in a teaching milieu, a comprehensive learning experience can be combined with defined objectives that emphasize and encourage newborn and maternal assessment for ambulatory patients.

Membrane interaction of Escherichia coli hemolysin: flotation and insertion-dependent labeling by phospholipid vesicles

The 1,024-amino-acid acylated hemolysin of Escherichia coli subverts host cell functions and causes cell lysis. Both activities require insertion of the toxin into target mammalian cell membranes. To identify directly the principal toxin sequences dictating membrane binding and insertion, we assayed the lipid bilayer interaction of native protoxin, stably active toxin, and recombinant peptides. Binding was assessed by flotation of protein-liposome mixtures through density gradients, and insertion was assessed by labeling with a photoactivatable probe incorporated into the target lipid bilayer. Both the active acylated hemolysin and the inactive unacylated protoxin were able to bind and also insert. Ca(2+) binding, which is required for toxin activity, did not influence the in vitro interaction with liposomes. Three overlapping large peptides were expressed separately. A C-terminal peptide including residues 601 to 1024 did not interact in either assay. An internal peptide spanning residues 496 to 831, including the two acylation sites, bound to phospholipid vesicles and showed a low level of insertion-dependent labeling. In vitro acylation had no effect on the bilayer interaction of either this peptide or the full-length protoxin. An N-terminal peptide comprising residues 1 to 520 also bound to phospholipid vesicles and showed strong insertion-dependent labeling, ca. 5- to 25-fold that of the internal peptide. Generation of five smaller peptides from the N-terminal region identified the principal determinant of lipid insertion as the hydrophobic sequence encompassing residues 177 to 411, which is conserved among hemolysin-related toxins.

Hepatitis G virus genotypes in Australia, Papua New Guinea and the Solomon Islands: a possible new Pacific type identified

BACKGROUND

Hepatitis G Virus (HGV)/GB Virus-C (GBV-C) is a newly discovered RNA virus. Nucleotide sequence comparison and phylogenetic studies of the 5' untranslated region (5'UTR) within the viral genome have identified at least three different types which have provisionally been classified as type 1 (West African origin), type 2 (North American origin) and type 3 (Asian origin).

METHODS AND RESULTS

The products of RT-PCR were sequenced by using blood donors and patients infected with HGV/GBV-C in Australia, Papua New Guinea and the Solomon Islands to investigate the genotype distribution in this area of the world. All the Australian isolates showed strong sequence homology with type 2, while the Papua New Guinea and Solomon Islands sequences were more closely related, but differ from type 3, which has previously been reported from isolates studied within Asia.

CONCLUSIONS

Phylogenetic analysis suggests that these latter sequences are either a new HGV/GBV-C Pacific type or a subtype of the Asian type RNA virus. Isolates homologous with type 1 were not identified in these population groups.

An ordered reaction mechanism for bacterial toxin acylation by the specialized acyltransferase HlyC: formation of a ternary complex with acylACP and protoxin substrates

The 110 kDa haemolysin protoxin (proHlyA) is activated in the Escherichia coli cytosol by acyl carrier protein-dependent fatty acylation of two internal lysine residues, directed by the co-synthesized protein HlyC. Using an in vitro maturation reaction containing purified protoxin peptides and acylACP, we show unambiguously that HlyC possesses an apparently unique acyltransferase activity fully described by Michaelis-Menten analysis. The Vmax of HlyC at saturating levels of both substrates was approximately 115 nmol acyl group min-1 mg-1 with KMacylACP of 260 nM and KMproHlyA of 27 nM, kinetic parameters sufficient to explain why in vivo HlyC is required at a concentration equimolar to proHlyA. HlyC bound the fatty acyl group from acylACP to generate an acylated HlyC intermediate that was depleted in the presence of proHlyA, but enriched in the presence of proHlyA derivatives lacking acylation target sites. HlyC was also able to bind in vivo 4'-phosphopantetheine. Substitution of conserved amino acids that could act as putative covalent attachment sites did not prevent binding of the fatty acyl or 4'-phosphopantetheine groups. These data and substrate variation analyses suggest that the unique acylation reaction does not involve covalent attachment of fatty acid to the acyltransferase, but rather that it proceeds via a sequential ordered Bi-Bi reaction mechanism, requiring the formation of a non-covalent ternary acylACP-HlyC-proHlyA complex.

An ELISA for the detection of antibody to the core antigen of hepatitis C virus: use in diagnosis and analysis of indeterminate samples

AIMS

In order to examine more carefully the natural history of hepatitis C virus infection and to determine a role for anti-core in the discrimination of indeterminate samples, a solid phase ELISA to detect antibody of the immunoglobulin G class to the hepatitis C virus core antigen was developed using purified protein expressed in Escherichia coli from a major portion of the core antigen coding region.

METHODS/RESULTS

In a study which examined 651 samples submitted for routine testing by a commercial ELISA (Ortho), only 11 samples showed discrepant results; of these, 10 were Ortho ELISA positive, anti-core negative and one was Ortho ELISA negative anticore positive. Supplemental tests showed that 5/10 of these samples were anti-HCV negative by RIBA and the reciprocal 5 were negative for anti-C22 but positive for anti-C100 and anti-C33. The Ortho ELISA negative, anticore positive sample was weakly positive for anti-C22. The anti-core ELISA was then used to examine 67 indeterminate samples from the blood bank; 11/11 samples which were HCV-RNA positive were anti-core positive and 7/56 samples which were HCV-RNA negative were anti-core positive. The anti-core titre was then examined in two groups of indeterminate samples; group 1, polymerase chain reaction-positive, anti-core positive and group 2, polymerase chain reaction-negative, anti-core positive. The geometric mean anti-core titres in these groups were 1 x 10(-3.6) and 1 x 10(-2.3), respectively. Thus in this group of indeterminate samples, all samples (except one) with an anti-core titre > or = 1/200 were polymerase chain reaction-positive, confirming a close correlation between anti-core levels and hepatitis C viraemia. Anti-core was detected with equal efficiency in patients infected with genotypes which differed to that used to express the recombinant core antigen.

Divergent and invariant HLA class II beta chain isoelectric points

Class II molecules were isolated from consanguineous HTCs (DR1-DRw8) by sequential immunoprecipitation with the monoclonal antibodies 7.3.19.1 (anti-DRw52-like), B8.11.2 (anti-DR backbone), and 7.5.10.1 (anti-HLA class II backbone). Depending upon the DR-serotype of the cell line used, two or three class II antigen families, distinct in molecular weight, could be isolated (see Hum Immunol 9:221, 1984). Immunoprecipitated class II molecules were treated with NaNase and then analyzed on 1D-IEF gels. Each HLA class II antigen family contained two alpha chains conserved in pI. Furthermore, the various haplotypes show distinct electrophoretic beta chain patterns. The number of beta chain charge configurations detected varies from 2 to 5, depending upon the antigen family or haplotype studied. Some of these chains have a pI which is specific for a given class II serotype whereas other beta chain pIs are invariant and shared among more antigen families or haplotypes.

Frozen section diagnosis of pancreatic carcinoma: a prospective study of 64 biopsies

Useful morphologic criteria for frozen section diagnosis of pancreatic and periampullary carcinoma were established by prospective review of 64 frozen sections in this region, with permanent section correlation and patient follow-up. These were divided into three major and five minor criteria based on frequency of occurrence and reproducibility. Major criteria were: 1) nuclear size variation of 4:1 or greater between ductal epithelial cells, 2) incomplete ductal lumens, and 3) disorganized duct distribution. Minor criteria, less frequently and reproducibly observed but valuable diagnostic aids, included: 1) huge, irregular epithelial nucleoli; 2) necrotic glandular debris; 3) glandular mitoses; 4) glands unaccompanied by connective tissue stroma within smooth muscle bundles (periampullary biopsies); and 5) perineural invasion. Combined application of both major and minor criteria is especially helpful in cases complicated by chronic pancreatitis.