In-hospital mortality risk stratification in children aged under 5 years with pneumonia with or without pulse oximetry: A secondary analysis of the Pneumonia REsearch Partnership to Assess WHO REcommendations (PREPARE) dataset

OBJECTIVES

We determined the pulse oximetry benefit in pediatric pneumonia mortality risk stratification and chest-indrawing pneumonia in-hospital mortality risk factors.

METHODS

We report the characteristics and in-hospital pneumonia-related mortality of children aged 2-59 months who were included in the Pneumonia Research Partnership to Assess WHO Recommendations dataset. We developed multivariable logistic regression models of chest-indrawing pneumonia to identify mortality risk factors.

RESULTS

Among 285,839 children, 164,244 (57.5%) from hospital-based studies were included. Pneumonia case fatality risk (CFR) without pulse oximetry measurement was higher than with measurement (5.8%, 95% confidence interval [CI] 5.6-5.9% vs 2.1%, 95% CI 1.9-2.4%). One in five children with chest-indrawing pneumonia was hypoxemic (19.7%, 95% CI 19.0-20.4%), and the hypoxemic CFR was 10.3% (95% CI 9.1-11.5%). Other mortality risk factors were younger age (either 2-5 months [adjusted odds ratio (aOR) 9.94, 95% CI 6.67-14.84] or 6-11 months [aOR 2.67, 95% CI 1.71-4.16]), moderate malnutrition (aOR 2.41, 95% CI 1.87-3.09), and female sex (aOR 1.82, 95% CI 1.43-2.32).

CONCLUSION

Children with a pulse oximetry measurement had a lower CFR. Many children hospitalized with chest-indrawing pneumonia were hypoxemic and one in 10 died. Young age and moderate malnutrition were risk factors for in-hospital chest-indrawing pneumonia-related mortality. Pulse oximetry should be integrated in pneumonia hospital care for children under 5 years.

Assembling a global database of child pneumonia studies to inform WHO pneumonia management algorithm: Methodology and applications

Background

The existing World Health Organization (WHO) pneumonia case management guidelines rely on clinical symptoms and signs for identifying, classifying, and treating pneumonia in children up to 5 years old. We aimed to collate an individual patient-level data set from large, high-quality pre-existing studies on pneumonia in children to identify a set of signs and symptoms with greater validity in the diagnosis, prognosis, and possible treatment of childhood pneumonia for the improvement of current pneumonia case management guidelines.

Methods

Using data from a published systematic review and expert knowledge, we identified studies meeting our eligibility criteria and invited investigators to share individual-level patient data. We collected data on demographic information, general medical history, and current illness episode, including history, clinical presentation, chest radiograph findings when available, treatment, and outcome. Data were gathered separately from hospital-based and community-based cases. We performed a narrative synthesis to describe the final data set.

Results

Forty-one separate data sets were included in the Pneumonia Research Partnership to Assess WHO Recommendations (PREPARE) database, 26 of which were hospital-based and 15 were community-based. The PREPARE database includes 285 839 children with pneumonia (244 323 in the hospital and 41 516 in the community), with detailed descriptions of clinical presentation, clinical progression, and outcome. Of 9185 pneumonia-related deaths, 6836 (74%) occurred in children <1 year of age and 1317 (14%) in children aged 1-2 years. Of the 285 839 episodes, 280 998 occurred in children 0-59 months old, of which 129 584 (46%) were 2-11 months of age and 152 730 (54%) were males.

Conclusions

This data set could identify an improved specific, sensitive set of criteria for diagnosing clinical pneumonia and help identify sick children in need of referral to a higher level of care or a change of therapy. Field studies could be designed based on insights from PREPARE analyses to validate a potential revised pneumonia algorithm. The PREPARE methodology can also act as a model for disease database assembly.

Derivation and validation of a novel risk assessment tool to identify children aged 2–59 months at risk of hospitalised pneumonia-related mortality in 20 countries

Introduction

Existing risk assessment tools to identify children at risk of hospitalised pneumonia-related mortality have shown suboptimal discriminatory value during external validation. Our objective was to derive and validate a novel risk assessment tool to identify children aged 2–59 months at risk of hospitalised pneumonia-related mortality across various settings.

Methods

We used primary, baseline, patient-level data from 11 studies, including children evaluated for pneumonia in 20 low-income and middle-income countries. Patients with complete data were included in a logistic regression model to assess the association of candidate variables with the outcome hospitalised pneumonia-related mortality. Adjusted log coefficients were calculated for each candidate variable and assigned weighted points to derive the Pneumonia Research Partnership to Assess WHO Recommendations (PREPARE) risk assessment tool. We used bootstrapped selection with 200 repetitions to internally validate the PREPARE risk assessment tool.

Results

A total of 27 388 children were included in the analysis (mean age 14.0 months, pneumonia-related case fatality ratio 3.1%). The PREPARE risk assessment tool included patient age, sex, weight-for-age z-score, body temperature, respiratory rate, unconsciousness or decreased level of consciousness, convulsions, cyanosis and hypoxaemia at baseline. The PREPARE risk assessment tool had good discriminatory value when internally validated (area under the curve 0.83, 95% CI 0.81 to 0.84).

Conclusions

The PREPARE risk assessment tool had good discriminatory ability for identifying children at risk of hospitalised pneumonia-related mortality in a large, geographically diverse dataset. After external validation, this tool may be implemented in various settings to identify children at risk of hospitalised pneumonia-related mortality.

External validation of the RISC, RISC-Malawi, and PERCH clinical prediction rules to identify risk of death in children hospitalized with pneumonia

BACKGROUND

Existing scores to identify children at risk of hospitalized pneumonia-related mortality lack broad external validation. Our objective was to externally validate three such risk scores.

METHODS

We applied the Respiratory Index of Severity in Children (RISC) for HIV-negative children, the RISC-Malawi, and the Pneumonia Etiology Research for Child Health (PERCH) scores to hospitalized children in the Pneumonia REsearch Partnerships to Assess WHO REcommendations (PREPARE) data set. The PREPARE data set includes pooled data from 41 studies on pediatric pneumonia from across the world. We calculated test characteristics and the area under the curve (AUC) for each of these clinical prediction rules.

RESULTS

The RISC score for HIV-negative children was applied to 3574 children 0-24 months and demonstrated poor discriminatory ability (AUC = 0.66, 95% confidence interval (CI) = 0.58-0.73) in the identification of children at risk of hospitalized pneumonia-related mortality. The RISC-Malawi score had fair discriminatory value (AUC = 0.75, 95% CI = 0.74-0.77) among 17 864 children 2-59 months. The PERCH score was applied to 732 children 1-59 months and also demonstrated poor discriminatory value (AUC = 0.55, 95% CI = 0.37-0.73).

CONCLUSIONS

In a large external application of the RISC, RISC-Malawi, and PERCH scores, a substantial number of children were misclassified for their risk of hospitalized pneumonia-related mortality. Although pneumonia risk scores have performed well among the cohorts in which they were derived, their performance diminished when externally applied. A generalizable risk assessment tool with higher sensitivity and specificity to identify children at risk of hospitalized pneumonia-related mortality may be needed. Such a generalizable risk assessment tool would need context-specific validation prior to implementation in that setting.

Interference with the production of infectious viral particles and bimodal inhibition of replication are broadly conserved antiviral properties of IFITMs

IFITMs are broad antiviral factors that block incoming virions in endosomal vesicles, protecting target cells from infection. In the case of HIV-1, we and others reported the existence of an additional antiviral mechanism through which IFITMs lead to the production of virions of reduced infectivity. However, whether this second mechanism of inhibition is unique to HIV or extends to other viruses is currently unknown. To address this question, we have analyzed the susceptibility of a broad spectrum of viruses to the negative imprinting of the virion particles infectivity by IFITMs. The results we have gathered indicate that this second antiviral property of IFITMs extends well beyond HIV and we were able to identify viruses susceptible to the three IFITMs altogether (HIV-1, SIV, MLV, MPMV, VSV, MeV, EBOV, WNV), as well as viruses that displayed a member-specific susceptibility (EBV, DUGV), or were resistant to all IFITMs (HCV, RVFV, MOPV, AAV). The swapping of genetic elements between resistant and susceptible viruses allowed us to point to specificities in the viral mode of assembly, rather than glycoproteins as dominant factors of susceptibility. However, we also show that, contrarily to X4-, R5-tropic HIV-1 envelopes confer resistance against IFITM3, suggesting that viral receptors add an additional layer of complexity in the IFITMs-HIV interplay. Lastly, we show that the overall antiviral effects ascribed to IFITMs during spreading infections, are the result of a bimodal inhibition in which IFITMs act both by protecting target cells from incoming viruses and in driving the production of virions of reduced infectivity. Overall, our study reports for the first time that the negative imprinting of the virion particles infectivity is a conserved antiviral property of IFITMs and establishes IFITMs as a paradigm of restriction factor capable of interfering with two distinct phases of a virus life cycle.

IFITMs are interferon-regulated proteins that inhibit a broad range of viruses. Until recently, IFITMs had been described to arrest incoming viral particles in target cells, by inducing their retention in endosomal vesicles. More recently in the case of HIV-1, ours and other laboratories have highlighted the existence of an additional antiviral mechanism with which IFITMs could act in virus-producing cells, leading to the production of virion particles of reduced infectivity. In the present study, we assessed whether the negative imprinting of the virion particles infectivity was a conserved antiviral property of IFITMs by examining a panel of fourteen different DNA or RNA viruses. Our results indicate that a wide spectrum of viruses is susceptible to this antiviral mechanism of inhibition, although some are able to resist it. Swapping of elements between susceptible and resistant viruses strongly suggests that specificities in the mode of virion assembly and not the viral glycoprotein are the dominant factor in the susceptibility of a given virus to this inhibition. However, we also show that HIV-1 strains that engage the CCR5 co-receptor display a notable resistance towards IFITM3, indicating that at least in the case of HIV-1, co-receptor usage is likely to add an additional layer of complexity in the relationship established between IFITMs and the virus, that may or may not extend to other viral families as well. In the context of spreading infections, the results of this study highlight that the overall antiviral effect of IFITMs is mechanistically caused by a previously unappreciated dual mode of action in which they act both in target cells and in virus-producing cells, by respectively forcing endosome trapping of incoming viruses and by commandeering the formation of new virion particles of reduced infectivity. Overall, the results presented here indicate that the negative imprinting of viral particles is a largely conserved antiviral feature of IFITMs and point to IFITMs as a novel paradigm of innate defense proteins capable of interfering with viral replication at two distinct steps of a virus life cycle.

Prevalence of human metapneumovirus in adults with acute respiratory tract infection in Beijing, China

Objective

To evaluate the prevalence and clinical manifestations of human metapneumovirus (hMPV) in immunocompetent Chinese adults with acute respiratory tract infections (ARTIs).

Methods

A reverse transcription PCR (RT-PCR) assay targeting the P gene was developed in this study and used to detect hMPV in nasal and throat swabs collected from 2936 immunocompetent adult patients with ARTIs in Beijing, China between July 2008 and June 2010.

Results

Among the 2936 patients studied, 49 (1.7%) were positive for hMPV, of whom 14 (28.6%) were positive for hMPV_A2b, 19 (38.8%) for hMPV_B1, and 16 (32.6%) for hMPV_B2. hMPV_A1 was not detected. An average detection rate of 6.6% was observed in the peak months of the two epidemic seasons studied. The hMPV prevalence was higher in the sampled elderly (>65 years, 3.2%) than in middle aged adults (25–65 years; 2.0%) and teenagers (14–25 years; 0.9%). During the study period, hMPV infections showed a biennial rhythm of seasonality, peaking from November to March in 2008/09 and from March to June in 2010.

Conclusion

hMPV infection plays an important role in immunocompetent adults in its epidemic season. The demographic and clinical data presented in this study improves our understanding of the pathogenesis and clinical burden of hMPV infection in adults.

Saffold cardiovirus in children with acute gastroenteritis, Beijing, China

To understand Saffold cardiovirus (SAFV) distribution, prevalence, and clinical relevance in China, we retrospectively studied SAFV in children with acute gastroenteritis and found SAFV in 12 (3.2%) of 373. Sequence homology of virus protein 1 genes suggested these strains belong to the SAFV-1 sublineage. SAFVs were found in samples positive for other diarrhea-causing viruses.

Expression of the alternative reading frame protein of Hepatitis C virus induces cytokines involved in hepatic injuries

Hepatitis C virus (HCV) Core has been implicated in immune-mediated mechanisms associated with the development of chronic hepatic diseases. Discovery of different alternative reading frame proteins (ARFPs) expressed from the HCV Core coding sequence challenges properties assigned to Core. This study was designed to evaluate the immunomodulatory functions of Core and ARFPs in monocytes, dendritic cells (DCs), macrophages (Mphi) and hepatocytes, cells that are all capable of supporting HCV replication. THP-1 cells, monocyte-derived Mphi and DCs, and Huh7 cells were infected by using adenoviruses (Ad) encoding Core, CE1E2 and a Core sequence modified so that the Core protein is wild type, but no ARFPs are expressed (CDeltaARFP). THP-1 cells and DCs infected with Ad encoding Core or CE1E2 produced significant levels of interleukin-6 (IL-6), IL-8, MCP-1 and MIP-1beta, whereas production of these chemokines with AdCDeltaARFP was reduced or abolished. Similar effects on IL-8 production were observed in Huh7 cells and on IL-6 and MIP-1beta in Mphi. Wild-type Core sequence, but not CDeltaARFP, could trans-activate the IL-8 promoter and this activation was not associated with activation of p38/p42-44MAPK. This study illustrates, for the first time, the critical importance of ARFP expression in immunomodulatory functions attributed to Core expression and suggests a potential involvement of ARFP in mechanisms associated with HCV pathogenesis.

Vaccine-induced early control of hepatitis C virus infection in chimpanzees fails to impact on hepatic PD-1 and chronicity

Broad T cell and B cell responses to multiple HCV antigens are observed early in individuals who control or clear HCV infection. The prevailing hypothesis has been that similar immune responses induced by prophylactic immunization would reduce acute virus replication and protect exposed individuals from chronic infection. Here, we demonstrate that immunization of naïve chimpanzees with a multicomponent HCV vaccine induced robust HCV-specific immune responses, and that all vaccinees exposed to heterologous chimpanzee-adapted HCV 1b J4 significantly reduced viral RNA in serum by 84%, and in liver by 99% as compared to controls (P=0.024 and 0.028, respectively). However, despite control of HCV in plasma and liver in the acute period, in the chronic phase, 3 of 4 vaccinated animals developed persistent infection. Analysis of expression levels of proinflammatory cytokines in serial hepatic biopsies failed to reveal an association with vaccine outcome. However, expression of IDO, CTLA-4 [corrected] and PD-1 levels in liver correlated with clearance or chronicity.

CONCLUSION

Despite early control of virus load, a virus-associated tolerogenic-like state can develop in certain individuals independent of vaccination history.

Usefulness of the phage display technology for the identification of a hepatitis C virus NS4A epitope recognized early in the course of the disease

A dodecapeptide phage-displayed library was screened with the mouse monoclonal antibody (mAb) 2E3C2 which competed with human antibodies for the binding to the HCV c100 recombinant protein. Four mimotopes shared a consensus motif with the HCV 1701-1707 sequence corresponding to the carboxyl-terminal domain of the non-structural protein NS4A. However, these mimotopes reacted with 2E3C2 only, whereas the corresponding NS4 epitope defined at the sequence 1698-1709 and displayed on phage was recognized by both 2E3C2 and sera from HCV infected patients. Using the Spot method of multiple peptide synthesis and alanine replacement analysis, the respective reactivities of mAb 2E3C2 and anti-NS4A human antibodies against NS4 were shown to be directed against two slightly different overlapping minimal linear sequences and to involve different critical residues. The phage clone displaying the NS4 epitope was used to study the specific recognition of this epitope by different individual HCV positive sera as well as by two seroconversion panels of sera from HCV infected patients. Compared with the detection by RIBA of the different HCV antigens and c100 particularly, these results indicated that the antibodies directed against the NS4 (1698-1709) epitope were produced early during the course of the disease and decreased later.

Full-breadth analysis of CD8+ T-cell responses in acute hepatitis C virus infection and early therapy

Multispecific CD8(+) T-cell responses are thought to be important for the control of acute hepatitis C virus (HCV) infection, but to date little information is actually available on the breadth of responses at early time points. Additionally, the influence of early therapy on these responses and their relationships to outcome are controversial. To investigate this issue, we performed comprehensive analysis of the breadth and frequencies of virus-specific CD8(+) T-cell responses on the single epitope level in eight acutely infected individuals who were all started on early therapy. During the acute phase, responses against up to five peptides were identified. During therapy, CD8(+) T-cell responses decreased rather than increased as virus was controlled, and no new specificities emerged. A sustained virological response following completion of treatment was independent of CD8(+) T-cell responses, as well as CD4(+) T-cell responses. Rapid recrudescence also occurred despite broad CD8(+) T-cell responses. Importantly, in vivo suppression of CD3(+) T cells using OKT3 in one subject did not result in recurrence of viremia. These data suggest that broad CD8(+) T-cell responses alone may be insufficient to contain HCV replication, and also that early therapy is effective independent of such responses.

Modulation of Vaccine‐Induced Immune Responses to Hepatitis C Virus in Rhesus Macaques by Altering Priming before Adenovirus Boosting

BACKGROUND

Preventive and therapeutic vaccine strategies aimed at controlling hepatitis C virus (HCV) infection should mimic the immune responses observed in patients who control or clear HCV, specifically T helper (Th) type 1 and CD8+ cell responses to multiple antigens, including nonstructural protein (NS) 3. Given the experience with human immunodeficiency virus, the best candidates for this are based on DNA prime, pox, or adenovirus boost regimens.

METHODS

In rhesus macaques, we compared NS3-expressing DNA prime and adenovirus boost strategy with 2 alternative priming approaches aimed at modifying Th1 and CD8+ responses: DNA adjuvanted with interleukin (IL)-2- and -12-encoding plasmids or Semliki Forest virus (SFV).

RESULTS

All prime-boost regimens elicited NS3-specific B and T cell responses in rhesus macaques, including CD8+ responses. SFV priming induced higher lymphoproliferation and longer Th1 memory responses. The use of IL-2- and IL-12-expressing vectors resulted in reduced Th2 and antibody responses, which led to increased Th1 skewing but not to an increase in the magnitude of the IFN- gamma and CD8+ responses.

CONCLUSIONS

All strategies induced Th1 cellular responses to HCV NS3, with fine modulations depending on the different priming approaches. When they are developed for more HCV antigens, these strategies could be beneficial in therapeutic vaccine approaches.

Comparative immunogenicity analysis of modified vaccinia Ankara vectors expressing native or modified forms of hepatitis C virus E1 and E2 glycoproteins

We have evaluated in C57/Bl6 and HLA-A2.1 transgenic mice the immunogenicity of three MVA vectors expressing either native HCV E1E2 polyprotein, truncated and secreted E1 (E'1(311)) and E2 (E'2(661)) proteins, or a chimeric E1E2 heterodimer presented at the plasma membrane. Immunization induced mainly a Th1 response in HLA-A2.1 transgenic mice while a Th2-type response was detected in C57/Bl6 mice. Comparison of the three vectors shows an increase in the humoral response when antigens are secreted or membrane bound, and slightly in the cellular response when antigens are exposed on the cell surface.

Memory T-cell-mediated immune responses specific to an alternative core protein in hepatitis C virus infection

In vitro studies have described the synthesis of an alternative reading frame form of the hepatitis C virus (HCV) core protein that was named F protein or ARFP (alternative reading frame protein) and includes a domain coded by the +1 open reading frame of the RNA core coding region. The expression of this protein in HCV-infected patients remains controversial. We have analyzed peripheral blood from 47 chronically or previously HCV-infected patients for the presence of T lymphocytes and antibodies specific to the ARFP. Anti-ARFP antibodies were detected in 41.6% of the patients infected with various HCV genotypes. Using a specific ARFP 99-amino-acid polypeptide as well as four ARFP predicted class I-restricted 9-mer peptides, we show that 20% of the patients display specific lymphocytes capable of producing gamma interferon, interleukin-10, or both cytokines. Patients harboring three different viral genotypes (1a, 1b, and 3) carried T lymphocytes reactive to genotype 1b-derived peptides. In longitudinal analysis of patients receiving therapy, both core and ARFP-specific T-cell- and B-cell-mediated responses were documented. The magnitude and kinetics of the HCV antigen-specific responses differed and were not linked with viremia or therapy outcome. These observations provide strong and new arguments in favor of the synthesis, during natural HCV infection, of an ARFP derived from the core sequence. Moreover, the present data provide the first demonstration of the presence of T-cell-mediated immune responses directed to this novel HCV antigen.

Characterization of mimotopes mimicking an immunodominant conformational epitope on the hepatitis C virus NS3 helicase

The hepatitis C virus (HCV) nonstructural 3 (NS3) protein is composed of an amino terminal protease and a carboxyl terminal RNA helicase. NS3 contains major antigenic epitopes. The antibody response to NS3 appears early in the course of infection and is focused on the helicase region. However, this response cannot be defined by short synthetic peptides indicating the recognition of conformation-dependent epitopes. In this study, we have screened a dodecapeptide library displayed on phage with anti-NS3 mouse monoclonal antibodies (mAbs) that compete with each other and human anti-HCV NS3 positive sera. Two peptides (mimotopes) were selected that appeared to mimic an immunodominant epitope since they were recognized specifically by the different anti-NS3 mAbs of the study and by human sera from HCV infected patients. Homology search between the two mimotopes and the NS3 sequence showed that one of the two peptides shared amino acid similarities with NS3 at residues 1396-1398 on a very accessible loop as visualized on the three-dimensional structure of the helicase domain whereas the other one had two amino acids similar to nearby residues 1376 and 1378. Reproduced as synthetic dodecapeptides, the two mimotopes were recognized specifically by 19 and 22, respectively, out of 49 sera from HCV infected patients. These mimotopes allowed also the detection of anti-NS3 antibodies in sera of HCV patients at the seroconversion stage. These results suggest that the two NS3 mimotopes are potential tools for the diagnosis of HCV infection.

Vaccination with an adenoviral vector encoding hepatitis C virus (HCV) NS3 protein protects against infection with HCV-recombinant vaccinia virus

Cellular immune response plays an important role in the clearance of hepatitis C virus (HCV). Thus, development of efficient ways to induce anti-viral cellular immune responses is an important step toward prevention and/or treatment of HCV infection. With this aim, we have constructed a replication-deficient recombinant adenovirus expressing HCV NS3 protein (RAdNS3). The efficacy of RAdNS3 was tested in vivo by measuring the protection against infection with a recombinant vaccinia virus expressing HCV-polyprotein (vHCV1-3011). Immunisation with 10(9)pfu of RAdNS3 induced anti-NS3 humoral, T helper and T cytotoxic responses. We identified eight epitopes recognised by IFN-gamma producing cells, five of them exhibiting lytic activity. Moreover, we show that RAdNS3 immunised mice were protected against challenge with vHCV1-3011 and that this protection was mediated by CD8(+) cells. In conclusion, our results suggest that adenoviral vectors encoding NS3 might be useful for the induction of prophylactic and/or therapeutic anti-HCV immunity.

Hepatitis C virus non-structural protein 3-specific cellular immune responses following single or combined immunization with DNA or recombinant Semliki Forest virus particles

The capacity of recombinant Semliki Forest virus particles (rSFV) expressing the hepatitis C virus non-structural protein 3 (NS3) to induce, in comparison or in combination with an NS3-expressing plasmid, specific cellular and humoral immune responses in murine models was evaluated. In vitro studies indicated that both types of vaccine expressed the expected size protein, albeit with different efficacies. The use of mice transgenic for the human HLA-A2.1 molecule indicated that the rSFV-expressed NS3 protein induces, as shown previously for an NS3 DNA vaccine, NS3-specific cytotoxic lymphocytes (CTLs) targeted at one dominant HLA-A2 epitope described in infected patients. All DNA/rSFV vaccine combinations evaluated induced specific CTLs, which were detectable for up to 31 weeks after the first injection. Overall, less than 1 log difference was observed in terms of the vigour of the bulk CTL response induced and the CTL precursor frequency between all vaccines (ranging from 1:2.6x10(5) to 1:1x10(6)). Anti-NS3 antibodies could only be detected following a combined vaccine regimen in non-transgenic BALB/c mice. In conclusion, rSFV particles expressing NS3 are capable of inducing NS3-specific cellular immune responses targeted at a major HLA-A2 epitope. Such responses were comparable to those obtained with a DNA-based NS3 vaccine, whether in the context of single or combined regimens.

Evaluation of an enzyme immunoassay for hepatitis C virus antibody detection using a recombinant protein derived from the core region of hepatitis C virus genome

This study was undertaken to evaluate an enzyme immunoassay (EIA) for hepatitis C virus antibody detection (anti-HCV), using just one antigen. Anti-HCV EIA was designed to detect anti-HCV IgG using on the solid-phase a recombinant C22 antigen localized at the N-terminal end of the core region of HCV genome, produced by BioMérieux. The serum samples diluted in phosphate buffer saline were added to wells coated with the C22, and incubated. After washings, the wells were loaded with conjugated anti-IgG, and read in a microtiter plate reader (492 nm). Serum samples of 145 patients were divided in two groups: a control group of 39 patients with non-C hepatitis (10 acute hepatitis A, 10 acute hepatitis B, 9 chronic hepatitis B, and 10 autoimmune hepatitis) and a study group consisting of 106 patients with chronic HCV hepatitis. In the study group all patients had anti-HCV detected by a commercially available EIA (Abbott), specific for HCV structural and nonstructural polypeptides, alanine aminotransferase elevation or positive serum HCV-RNA detected by nested-PCR. They also had a liver biopsy compatible with chronic hepatitis. The test was positive in 101 of the 106 (95%) sera from patients in the study group and negative in 38 of the 39 (97%) sera from those in the control group, showing an accuracy of 96%. According to these results, our EIA could be used to detect anti-HCV in the serum of patients infected with hepatitis C virus.

Chromosomal distribution and coding capacity of the human endogenous retrovirus HERV-W family

Some genomic elements of the multicopy HERV-W endogenous retroviral family have been previously identified in databases. One of them, located on chromosome 7, contains a single complete open reading frame (ORF) putatively encoding an envelope protein. We have experimentally investigated the genomic complexity and coding capacity of the HERV-W family. The human haploid genome contains at least 70, 100, and 30 HERV-W-related gag, pro, and env regions, respectively, widely and heterogeneously dispersed among chromosomes. Using in vitro transcription-translation procedures, three putative HERV-W gag, pro, and env ORFs were detected on chromosomes 3, 6, and 7, respectively, and their sequences analyzed. A 363 amino acid gag ORF containing matrix and carboxy-terminal truncated capsid domains encoded a putative 45-kDa protein. No gag-pro ORF was found, but a pro sequence containing a DTG active site was detected. Finally, the previously described 538 amino acid HERV-W env ORF, located on chromosome 7, was shown to be unique and encoded a putative 80-kDa glycosylated protein. Proteins of molecular mass identical to the one obtained by an in vitro transcription-translation procedure were detected in human placenta, using anti HERV-W Gag- and Env-specific antibodies. The absence of an HERV-W replication-competent provirus versus the existence of HERV-W-related Gag and Env proteins in healthy human placenta is discussed with respect to particle formation, physiology, and pathology.

Identification of a human epitope in hepatitis C virus (HCV) core protein using a molecularly cloned antibody repertoire from a non-symptomatic, anti-HCV-positive patient

Healthy carriers of hepatitis C virus (HCV) infection exhibit a specific antibody response against all HCV antigens, which could play a role in disease control. Generation of panels of human antibodies may permit a thorough characterization of this response and further identify particular antibodies with potential clinical value. To this effect, we have established a human phage-display antibody library from a patient exhibiting a high antibody response against HCV antigens and no clinical symptoms of disease. This library was screened against a recombinant core antigen [amino acids (aa) 1-119] produced in E. coli. Two recombinant Fab-carrying phages (rFabCs) were isolated and characterized. Both rFabC3 and rFabC14 recognize aa 1-48 on core antigen, but rFabC14 is competed out by a synthetic peptide, C(2-20) (aa 1-20), at much lower concentrations than rFabC3. In order to identify more precisely the recognition sites of these antibodies, we produced soluble forms of the rFabs (sFabs), and used them to pan a random phage-display peptide library. A single peptide sequence, QLITKPL, was identified with sFabC3, while two equally represented sequences, HAFPHLH and SAPSSKN, were isolated using sFabC14. The QLITKPL sequence was partially localized between aa 8 and 14 of core protein, but no clear homology was found for the two sFabC14 peptides. However, we confirmed the specificity of these peptides by competition experiments with sFabC14.

Heterologous expression of a Trypanosoma cruzi surface glycoprotein (gp82) in mammalian cells indicates the existence of different signal sequence requirements and processing

Metacyclic trypomastigotes of Trypanosoma cruzi express a developmentally regulated 82 kDa surface glycoprotein (gp82) that has been implicated in the mammalian cell invasion. When the non-infective epimastigote stage of the parasite was transfected with a vector containing the gp82 gene, an 82 kDa surface glycoprotein, which was indistinguishable from the metacyclic stage protein, was expressed. In contrast, when the same gene was expressed in transfected mammalian cells, although a large amount of protein was produced, it was not imported into the endoplasmic reticulum and glycosylated. This blockage in targeting and processing could be partially compensated for by the addition of a virus haemagglutinin signal peptide to the amino terminus of gp82. Thus, the requirements for membrane protein processing are distinct in mammals and T. cruzi, and an intrinsic feature of the gp82 prevents subsequent sorting to the mammalian cell surface. These results could be useful in the development of new DNA vaccines against T. cruzi employing parasite genes encoding immunodominant surface glycoproteins.

Molecular cloning and characterization of MSRV-related sequences associated with retrovirus-like particles

New sequences have been obtained by successive overlapping RT-PCR extensions from the pol region of a retroviral RNA (multiple sclerosis-associated retroviral element, MSRV) amplified in retrovirus-like particles from patients with multiple sclerosis. gag and pol sequences are related to type C oncoviruses, whereas the env sequence is closer to type D. A tryptophan-like (W) tRNA primer-binding site was identified downstream of the RU5 region in the 5'LTR, and the U3R region cloned in the 3'LTR exhibited potent promoter activity. MSRV clones define a novel family of endogenous elements, HERV-W. From our data, HERV-W RNAs are copackaged in extracellular particles which might be produced by replication-competent or transcomplemented HERV-W copies or by an exogenous member of the HERV-W family.

HCV core immunodominant region analysis using mouse monoclonal antibodies and human sera: characterization of major epitopes useful for antigen detection

Monoclonal antibodies (MAbs) were generated by immunizing mice with a truncated recombinant protein corresponding to the immunodominant region (residues 1-120) of hepatitis C virus (HCV) nucleocapsid protein. The specific recognition by either human sera or mouse monoclonal antibodies of overlapping peptides spanning the core region 1-120 as well as the comparison with epitopes described earlier allowed the fine mapping of HCV core. Within the region 1-120, the major antigenic domain could be restricted to the first 45 amino acids. Indeed, the peptide S42G (residues 2-45) allowed the detection of an anti-HCV core response by all anticore-positive human sera examined. According to their epitope localization, three groups of mouse MABs could be evidenced that were directed against different regions of core. Group II MAbs recognized a strictly linear epitope (QDVKF, residues 20-24), whereas group I MABs were directed against a conformational epitope mainly located at the amino acid residues (QIVGG, 29-33). The epitope of group III MABs was also conformational (PRGRRQPI, residues 58-65). These three epitopes appeared close but different from the three major human epitopes RKTKRNTN, VYLLPR, and GRTWAQPGYPWPLY (residues 7-17, 34-39, and 73-86, respectively). Group II MAB 7G12A8 and group I MAB 19D9D6 were used in a sandwich ELISA for the capture and the detection, respectively, of viral core antigen in sera of patients with chronic HCV infection. After treatment of sera with triton x 100 in acidic conditions, amounts of viral antigen as low as 20 pg/ml of sera could be detected.

A cytotoxic factor for glial cells: a new avenue of research for multiple sclerosis?

A novel retrovirus, provisionally called Multiple Sclerosis RetroVirus (MSRV), was recently described in multiple sclerosis (MS). We report here that monocyte/macrophage culture supernatants from MS patients containing reverse transcriptase activity secrete a cytotoxin which induces death of primary mouse cortical glial cells. This cytotoxin, which was also found in MS cerebrospinal fluid, specifically causes death of mouse immortalized astrocytes and oligodendrocytes in vitro and seems to be associated to MSRV-specific RNA. This toxic factor, called gliotoxin, is present only in active cases of MS and is a stable glycosylated protein of 17 kDa, in CSF as well as in monocyte/macrophage culture supernatants. Since this gliotoxin is highly toxic for glial cells, it may represent an initial pathogenic factor, leading to the neuropathological features of MS, like blood brain barrier disruption and demyelination.

Molecular identification of a novel retrovirus repeatedly isolated from patients with multiple sclerosis. The Collaborative Research Group on Multiple Sclerosis

The partial molecular characterization of multiple sclerosis (MS)-associated retrovirus (MSRV), a novel retrovirus previously called LM7, is reported. MSRV has been isolated repeatedly from leptomeningeal, choroid plexus and from Epstein-Barr virus-immortalized B cells of MS patients. A strategy based on reverse transcriptase PCR with RNA-purified extracellular virions yielded an initial pol fragment from which other regions of the retroviral genome were subsequently obtained by sequence extension. MSRV-specific PCR primers amplified a pol region from RNA present at the peak of reverse transcriptase activity, coinciding with extracellular viral particles in sucrose density gradients. The same sequence was detected in noncellular RNA from MS patient plasma and in cerebrospinal fluid from untreated MS patients. MSRV is related to, but distinct from, the endogenous retroviral sequence ERV9. Whether MSRV represents an exogenous retrovirus with closely related endogenous elements or a replication-competent, virion-producing, endogenous provirus is as yet unknown. Further molecular epidemiological studies are required to determine precisely the apparent association of virions containing MSRV RNA with MS.

Organization and expression of the gene encoding an immunodominant repetitive antigen associated to the cytoskeleton of Trypanosoma cruzi

We have studied the genomic organization and expression of the gene encoding a high molecular mass (300 kDa) repetitive antigen associated with the cytoskeleton of Trypanosoma cruzi. Protease digestion of the native protein, restriction analysis of genomic DNA and sequencing of genomic and cDNA clones indicated that most of the protein is built up by tandemly arranged, nearly identical repeats of 68 amino acids. The gene size was estimated to be approx. 9.4 kb based on the sizes of the transcript and the native protein. The nucleotide sequence conservation among the repeats indicates that selective sequence homogenization, presumably through gene conversion, maintained the amino-acid sequence conservation. Two duplicated allelic forms of this gene were mapped in fragments of about 20 kb. In some strains an additional allele was located in a fragment of 9.4 kb. Our results suggest that this repetitive antigen is a structural protein which could be involved in the attachment of the flagellum to the cell body.