An investigation of the genetic basis of increased susceptibility to neutralization by anti-fusion glycoprotein antibody arising on passage of human respiratory syncytial virus in cell culture

Human respiratory syncytial virus isolates have previously been shown to exhibit resistance to neutralization by anti-fusion glycoprotein antibodies that is lost on passage in cell culture. Early passage resistant and late passage susceptible stocks of two virus isolates from different epidemics were cloned by plaque purification. Early passage stocks of both isolates yielded predominantly neutralization resistant clones while late passage stocks yielded predominantly susceptible clones. On further characterization of resistant and susceptible clones, resistant virus yields were lower and they were relatively resistant to both neutralization and fusion inhibition by anti-F murine monoclonal antibodies and were also resistant to neutralization by human sera and by Palivizumab. The full genome of resistant and susceptible clones from one of the isolates was sequenced. Four differences, confirmed by sequencing sister clones, were found between resistant and susceptible clones, one in each of the SH, G, F, and L genes.

Apolipoprotein B-associated cholesterol is a determinant of treatment outcome in patients with chronic hepatitis C virus infection receiving anti-viral agents interferon-alpha and ribavirin

BACKGROUND

Hepatitis C virus (HCV) co-opts very-low-density lipoprotein (VLDL) pathways for replication, secretion and entry into hepatocytes and associates with apolipoprotein B (apoB) in plasma. Each VLDL contains apoB-100 and variable amounts of apolipoproteins E and C, cholesterol and triglycerides.

AIM

To determine whether baseline lipid levels predicted treatment outcome.

METHODS

Retrospective analysis was performed of 250 chronic hepatitis C (CHC) patients who had received anti-viral agents interferon-alpha and ribavirin; 165 had a sustained virological response (SVR). Pre- and post-treatment nonfasting lipid profiles were measured and non-high-density lipoprotein (non-HDL) cholesterol (i.e. apoB-associated) was calculated. Binary logistic regression analysis assessed factors independently associated with treatment outcome.

RESULTS

There was an independent association between higher apoB-associated cholesterol (non-HDL-C) and increased odds of SVR (odds ratio 2.09, P = 0.042). In multivariate analysis, non-HDL-C was significantly lower in HCV genotype 3 (g3) than genotype 1 (P = 0.007); this was reversible upon eradication of HCVg3 (pre-treatment non-HDL-C = 2.8 mmol/L, SVR = 3.6 mmol/L, P < 0.001).

CONCLUSIONS

Higher apoB-associated cholesterol is positively associated with treatment outcome in CHC patients receiving anti-viral therapy, possibly due to competition between apoB-containing lipoproteins and infectious low-density HCV lipo-viral particles for hepatocyte entry via shared lipoprotein receptors.

Apolipoprotein B-associated cholesterol is a determinant of treatment outcome in patients with chronic hepatitis C virus infection receiving anti-viral agents interferon-alpha and ribavirin

BACKGROUND

Hepatitis C virus (HCV) co-opts very-low-density lipoprotein (VLDL) pathways for replication, secretion and entry into hepatocytes and associates with apolipoprotein B (apoB) in plasma. Each VLDL contains apoB-100 and variable amounts of apolipoproteins E and C, cholesterol and triglycerides.

AIM

To determine whether baseline lipid levels predicted treatment outcome.

METHODS

Retrospective analysis was performed of 250 chronic hepatitis C (CHC) patients who had received anti-viral agents interferon-alpha and ribavirin; 165 had a sustained virological response (SVR). Pre- and post-treatment nonfasting lipid profiles were measured and non-high-density lipoprotein (non-HDL) cholesterol (i.e. apoB-associated) was calculated. Binary logistic regression analysis assessed factors independently associated with treatment outcome.

RESULTS

There was an independent association between higher apoB-associated cholesterol (non-HDL-C) and increased odds of SVR (odds ratio 2.09, P = 0.042). In multivariate analysis, non-HDL-C was significantly lower in HCV genotype 3 (g3) than genotype 1 (P = 0.007); this was reversible upon eradication of HCVg3 (pre-treatment non-HDL-C = 2.8 mmol/L, SVR = 3.6 mmol/L, P < 0.001).

CONCLUSIONS

Higher apoB-associated cholesterol is positively associated with treatment outcome in CHC patients receiving anti-viral therapy, possibly due to competition between apoB-containing lipoproteins and infectious low-density HCV lipo-viral particles for hepatocyte entry via shared lipoprotein receptors.

Diagnosis of human metapneumovirus by immunofluorescence staining with monoclonal antibodies in the North-East of England

BACKGROUND

Since its discovery in 2001 human metapneumovirus (hMPV) has been shown to be a significant cause of human respiratory disease, responsible for 5-8% of respiratory infections in hospitalised children. Diagnosis hitherto has been largely carried out by reverse tanscriptase polymerase chain reaction (RT-PCR) but immunofluorescence staining of cells from nasopharyngeal secretions (IF) offers advantages for some laboratories and may produce a more rapid result in urgent cases. We have recently demonstrated that IF with a rabbit antiserum gave sensitivity equal to that of RT-PCR. However, monoclonal antibodies offer a more plentiful, uniform IF reagent.

OBJECTIVES

Here we have evaluated a pool of anti-hMPV monoclonal antibodies in the routine diagnosis of respiratory infections in hospitalised infants and children.

STUDY DESIGN

Eight hundred and fifty-seven routine respiratory specimens were tested by IF with rabbit polyclonal antiserum and monoclonal antibody pool in parallel. A further 1003 specimens were tested with the monoclonal antibody pool alone. All specimens were also tested for a panel of other respiratory viruses by IF.

RESULTS

Both rabbit polyclonal antiserum and monoclonal antibody pool gave positive results in 56 and negative results in 797 specimens. The rabbit polyclonal antibody detected virus in a further two specimens which were negative when tested with the monoclonal pool giving a concordance of 96.6% and a specificity of 100% for the monoclonal antibody pool. Overall hMPV was detected in 5% of specimens whilst 18.4% were positive for hRSV.

CONCLUSIONS

The monoclonal antibody pool-based IF is a robust assay suitable for routine use with a sensitivity only slightly less than that of the other major diagnostic methodologies available.

Purification of human respiratory syncytial virus by ultracentrifugation in iodixanol density gradient

Ultracentrifugation in sucrose density gradient remains the most commonly used technique for hRSV purification. However, the high viscosity and hyper-osmotic property of sucrose can cause damage to the extremely labile virus leading to loss of infectivity. To overcome these limitations, an alternative purification technique was developed using iodixanol as gradient medium, incorporating MgSO₄ as a stabilizing agent and EDTA to disaggregate the virus prior to infectivity assay. Virus particles were banded at the 20–36% interface after purification of polyethylene glycol-concentrated viruses by rate zonal ultracentrifugation on a 20–52% discontinuous iodixanol gradient. The presence of the virus was confirmed by viral fusion glycoprotein content using ELISA. After further purification by buoyant density ultracentrifugation on a 20–52% continuous gradient, the virus was recovered in the region of density 1.15–1.19 g/ml and this was confirmed by the coincidence of the infectivity titre, viral genome and fusion glycoprotein peaks. Analysis of recovery rates showed that the use of iodixanol increased the virus yield up to 69%. Iodixanol was also found to be non-toxic to HeLa cells used in infectivity assay, eliminating the need of its downstream removal by dialysis.

Increased susceptibility of human respiratory syncytial virus to neutralization by anti-fusion protein antibodies on adaptation to replication in cell culture

Subgroup A respiratory syncytial viruses present in respiratory secretions and low passage level cell culture isolates were found to be markedly less susceptible to neutralization with monoclonal antibodies (MAbs) to the F glycoprotein than the cell culture adapted A2 virus strain. Low passage virus isolates collected over a 20 year period and belonging to several sub-group A lineages were refractory to neutralization with antibodies recognizing two major neutralizing antigenic sites located sub-terminally at opposite ends of the F(1) glycoprotein sub-unit. On further passage in cell culture, virus isolates exhibited both increased infectivity titers and increased susceptibility to neutralization by antibodies to both antigenic sites. The consensus nucleotide sequence of the membrane associated proteins M and of the SH, G and F glycoprotein genes, and their intergenic regions were compared for neutralization resistant and susceptible stocks of one virus strain, R17532. No changes were observed in the known monoclonal antibody epitopes on the F glycoprotein. In line with this, the increase in susceptibility was not found to be associated with any increased binding of monoclonal antibody to isolated F glycoprotein in a BIAcore assay, thus excluding the possibility that passage in cell culture selected for viruses with mutations in the antibody binding sites. M and SH genes were conserved but a number of sites in the G and F glycoprotein genes were found to vary on adaptation to cell culture suggesting that change in susceptibility to neutralization was associated with a change in the prevalent quasispecies present in the virus population. The genetic basis of phenotypic change in susceptibility remains to be determined.

Detection of human metapneumovirus in respiratory secretions by reverse-transcriptase polymerase chain reaction, indirect immunofluorescence, and virus isolation in human bronchial epithelial cells

Over two winters in Newcastle upon Tyne, respiratory secretions, negative by immunofluorescence staining for other respiratory viruses, were tested for the presence of human metapneumovirus (HMPV) by RT-PCR. In the second winter, specimens were also tested by immunofluorescence staining with an anti-HMPV polyclonal rabbit antiserum and immunofluorescence positive specimens were inoculated into a line of human bronchiolar cells, 16HBE140. Overall, 55 of 549 (10%) specimens tested were positive for HMPV by RT-PCR. Of 162 specimens tested by both RT/PCR and immunofluorescence staining, 23 were positive by both techniques. Of five specimens positive by RT-PCR alone, only one was confirmed with a second set of primers. Of three specimens positive by immunofluorescence alone, only one was confirmed by virus culture. All four previously recognized sub-genotypes of the virus were identified by both RT-PCR and immunofluorescence staining. Sub-genotype A1 was prevalent in the first winter and B1 prevalent in the second. HMPV replication and virus isolation rates were higher in 16HBE140 cells than in monkey kidney cells and did not require exogenous trypsin. Low passage isolates of both sub-genotypes A2 and B1 replicated slowly reaching peak titers only 12 days after inoculation. In summary, single round RT/PCR and immunofluorescence staining with a polyclonal rabbit antiserum proved of equal sensitivity in the diagnosis of HMPV infection in respiratory secretions both detecting 96% of confirmed positive specimens. 16HBE40 cells provided a significant improvement on monkey kidney cells for the isolation and propagation of the virus.

Apolipoprotein epsilon3 allele is associated with persistent hepatitis C virus infection

BACKGROUND

Host genetic factors may significantly influence the ability to clear hepatitis C virus (HCV) following infection. HCV is associated with very low density lipoproteins (VLDL) and low density lipoproteins (LDL) in the host's circulation. Apolipoprotein E (APOE) is found in VLDL and binds to potential receptors involved in HCV entry into cells, the LDL receptor, and the scavenger receptor protein SR-B1. The APOE gene is polymorphic with three alleles coding for three isoforms: Apo-epsilon2, Apo-epsilon3, and Apo-epsilon4. The aim of this study was to assess if these functional polymorphisms determine disease outcome in HCV infected individuals.

METHODS

The APOE genotype was determined in 420 Northern European patients with evidence of exposure to HCV. Genotype and allele distribution were compared with those of 288 healthy controls and progression of liver disease and viral clearance were analysed according to APOE allele status.

RESULTS

The APOE*E2 and APOE*E4 alleles were both associated with a reduced likelihood of chronic infection (odds ratio (OR) 0.39 (95% confidence interval (CI) 0.211-0.728), p = 0.003; and OR 0.6 (95% CI 0.38-0.96), p = 0.032) and there was a notable absence of the E2E2 genotype in the HCV antibody positive group compared with the control population (p = 0.0067). Overall the genotypes carrying the E2 allele (E2,E3 and E2,E4) were associated with the equivalent of a 3-5-fold reduction in the risk of chronic HCV infection (genotype relative risk 0.36 and 0.20, respectively).

CONCLUSION

This study indicates that functional APOE gene polymorphisms may be a determinant of outcome in HCV infection. We hypothesise that the E2 allele may protect against viral persistence via defective binding of HCV lipoviral particles to the cellular receptors involved in entry of these infectious particles.

Protection of mice against Human respiratory syncytial virus by wild-type and aglycosyl mouse–human chimaeric IgG antibodies to subgroup-conserved epitopes on the G glycoprotein

Monoclonal antibodies (mAbs) to conserved epitopes on the G glycoprotein of human respiratory syncytial virus (HRSV) subgroup A fail to neutralize the virus in cell culture in the absence of complement, but are protective in rodent models of infection. They may have potential as prophylactic agents in human infants. In order to investigate the role of Fc-dependent pathways in protection by one such antibody, 1C2, the VH and VL genes were isolated by RT-PCR and assembled with human κ light-chain and human γ1 heavy-chain constant-region genes to form two mouse–human chimaeras, which were expressed in NS0 cells. One of the chimaeras carried a wild-type γ1 chain, whilst the other had an aglycosyl mutation in the CH2 domain rendering the antibody defective in complement activation and FcγR binding. Whilst both chimaeric antibodies exhibited similar avidity for HRSV in ELISA, only the fully glycosylated wild type was capable of neutralizing the virus in the presence of complement. In mice passively immunized with either murine or wild-type γ1 chimaeric antibody, no virus could be recovered from the lungs 4 days after intranasal inoculation of HRSV. In mice immunized with the aglycosyl γ1 chimaera, however, virus was present in the lungs following challenge, although virus titres were significantly reduced compared with controls (P<0·005). These results indicate that the protective effect of this antibody is mediated by both Fc-dependent and Fc-independent pathways.

Immunohistochemical assessment of hepatitis C virus antigen in cholestatic hepatitis after liver transplantation

BACKGROUND

Patients with common variable immunodeficiency may exhibit rapidly progressive hepatitis when infected with hepatitis C virus (HCV), leading to cirrhosis and liver failure. Liver transplantation in these patients may result in a cholestatic form of HCV reinfection with exceptionally high virus loads.

AIMS

To report an immunohistochemical investigation of the pretransplant and post-transplant liver of one such patient.

METHODS/RESULTS

On immunohistochemical staining of frozen sections with anti-HCV core monoclonal antibody or fluorescein labelled human polyclonal anti-HCV IgG, no HCV antigens were demonstrated in the native cirrhotic liver removed at transplant, despite a viral load of 10(6.4) genomes/g. The transplanted liver, collected six weeks post-transplant, exhibited cholestatic recurrent hepatitis, had an HCV virus load of 10(10) genomes/g of liver, and revealed HCV antigen in the cytoplasm of most hepatocytes, with a pronounced periportal distribution. No virus antigen was demonstrable in other cell types. The core antigen was also detected in paraffin wax embedded, formaldehyde fixed tissue of this liver after high temperature antigen retrieval, but not in the native cirrhotic liver or a selection of HCV positive livers collected pretransplant from immunocompetent patients. Attempts to delineate the distribution of E1, NS3, and NS4 antigens were unsuccessful because monoclonal antibodies to these antigens produced "false positive" staining of foci of hepatocytes in the post-transplant livers of HCV seronegative patients with cholestasis.

CONCLUSION

This case provided an opportunity to study the natural development of HCV during acute infection in the absence of an immune response, and may help to elucidate the pathogenesis of HCV recurrence in liver allografts.

Analysis of the binding of monoclonal and polyclonal antibodies to the glycoproteins of antigenic variants of human respiratory syncytial virus by surface plasmon resonance

The surface glycoproteins of human respiratory syncytial virus (hRSV), F and G, are the major protective antigens of the virus. Both are antigenically variable, although to different degrees, but the role of antigenic variation in the pathogenesis of hRSV disease has not been fully evaluated. Assessment of immunity to different virus strains is difficult with conventional antibody assays where differing properties of the virus antigens, other than antigenicity, may influence the outcome of the assay. Here, we have developed BIAcore surface plasmon resonance based assays for antibodies to the glycoproteins of hRSV which allow valid comparison of antibody titres against multiple hRSV strains. Glycoproteins from a number of lineages of hRSV sub-group A were captured from lysates of infected cells onto the dextran coated surface of a BIAcore sensor chip via primary monoclonal antibodies (MAbs) to conserved epitopes. For the G glycoprotein, primary MAbs were conjugated directly to the dextran of the sensor chip via free amide groups. For the F glycoprotein, direct conjugation was found to inactivate the MAb and primary MAb was immobilised on the chip via rabbit anti-mouse Fc antibody fragments in an indirect system. Using monoclonal antibodies as secondary MAbs, the glycoproteins in both systems were shown to exhibit a sub-set of conserved and variable epitopes, with some epitopes of both sorts being unavailable, presumably blocked by the primary antibody. Polyclonal anti-hRSV sera raised against viruses of different genotype bound equally to both F and G glycoproteins from homologous and heterologous viruses suggesting that mice immunised systemically with lysates of cells infected with recent isolates of virus do not respond well to genotype specific epitopes.

Detection of human respiratory syncytial virus genotype specific antibody responses in infants

Infection and reinfection of infants with human respiratory syncytial virus (HRSV) occur despite the presence of serum anti-viral glycoprotein antibodies similar to those, which afford protection in animal models of infection. Antigenic variation of the viral glycoproteins between different genotypes of the virus which co-circulate in the population may contribute to the ability of the virus to escape from antibody-mediated protection. In this study, we have investigated whether human infants infected with HRSV produced antibody responses recognising the antigenic differences between different contemporary genotypes of virus. Acute and convalescent sera from 26 infants were analysed for antibody responses to the glycoproteins of the virus isolated from their respiratory tract and to representative viruses of homologous and heterologous genotypes. All infants developed antibodies with similar reactivity for viruses of all contemporary isolates and genotypes when measured in an immunofluorescence assay against unfixed virus infected cells. However, when antibody responses to the individual glycoproteins were measured in a surace plasmon resonance (SPR) assay, although all infants developed genotype cross-reactive antibodies to the F glycoprotein, anti-G antibodies were detectable in only half of the infants and in all cases these were genotype specific. Possession of no or only genotype specific antibodies to the G glycoprotein may contribute to the susceptibility of infants to reinfection. In both assays, reactivity of anti-glycoprotein antibodies with the sub-group A archetypal strain, A2, was markedly lower than with any contemporary virus tested indicating that this strain alone is unsuitable for accurate assessment of infant antibody responses. .

Measurement of antibody against contemporary virus lineages of human respiratory syncytial virus sub-group A in infants and their mothers

BACKGROUND

Human respiratory syncytial virus (hRSV) infects the majority of infants in their first year of life. Maternal antibodies offer some protection although a small proportion of infected infants develop bronchiolitis and require admission to hospital. A number of lineages of the virus co-circulate in the population and the prevalent virus lineage changes from epidemic to epidemic. The effect of antigenic variation between virus lineages upon the protection offered by maternal antibodies has not been assessed.

OBJECTIVES

To explore the possibility that infants may develop bronchiolitis because of a virus lineage-specific deficiency in their maternal antibodies.

STUDY DESIGN

Virus isolates from infants admitted to hospital in Newcastle upon Tyne with hRSV infection during two consecutive winter epidemics were classified into lineages by genotypic analysis. Antibodies to the surface glycoproteins of contemporary sub-group A lineages and to the A2 virus strain were assayed in the acute sera of infected infants, in a group of uninfected infants and in the mothers of both groups.

RESULTS

Four lineages of sub-group A hRSV were found circulating during the study period. Antibody titres measured against all virus lineages in the acute serum of infants with hRSV bronchiolitis were similar. In the uninfected infants and in the mothers of both infected and uninfected groups antibody titres to all four contemporary virus lineages were also similar. However, in these groups antibodies to the A2 virus strain were four-fold lower than those to contemporary isolates.

CONCLUSIONS

Infants admitted to hospital with hRSV bronchiolitis exhibited no apparent selective deficiency in maternal antibodies to the viral glycoproteins of the infecting virus strain or lineage.

Respiratory Syncytial Virus and Other Pediatric Respiratory Virus Infections

Infants and young children undergoing their primary infection with common human respiratory viruses are at risk of serious, even life-threatening, lower respiratory tract infection, A multiplicity of viruses infect the human respiratory tract but a relatively small number are responsible for the majority of significant illness. Of these the most commonly diagnosed in the pediatric population is respiratory syncytial virus (RSV), which infects essentially all children in their first or second year of life, bringing approx 1% into the hospital with bronchiolitis or pneumonia (1). Children with underlying cardiac or pulmonary disease, or born prematurely are particularly at risk. The virus also causes problems in the immunosuppressed and mortality rates are alarmingly high for RSV pneumonia after bone marrow transplantation (2). The availability of therapy with ribavirin (3) or high titer anti-RSV γ-globulin (4), which may be of benefit in these at risk groups, places a premium on rapid and accurate, but cost effective, diagnosis.

Hepatitis C virus particles of different density in the blood of chronically infected immunocompetent and immunodeficient patients: Implications for virus clearance by antibody

The purpose of this study was to analyse the influence of the humoral immune response on the generation and clearance of hepatitis C virus (HCV) RNA containing particles in the blood of chronically infected patients. Blood samples were fractionated by sequential flotation ultracentrifugation and HCV RNA was recovered in three fractions: low density of < 1.063 g/ml, intermediate density of 1.063-1.21 g/ml, and high density of > 1.21 g/ml. Serum low-density lipoproteins co-fractionated with the low-density particles, and high-density lipoproteins co-fractionated with the intermediate-density particles. Immunoglobulins were found exclusively in the high-density fractions. In patients with congenital immunodeficiencies, with no or low serum antibodies to the virus, mean HCV RNA titres were equal in each fraction, at approximately 10(5) IU/ml. In antibody-positive, immunocompetent patients, however, virus titres in the low-density fraction and those in the high-density fraction were reduced or absent in most patients, suggesting that virus particles in these fractions are subject to antibody-mediated clearance. Particles of intermediate density were approximately equal in titre in both patient groups, suggesting that these particles are neither generated by, nor cleared, as a result of the humoral immune response. Immunoprecipitation experiments indicated that particles of intermediate density were not complexed with either high-density lipoprotein or immunoglobulins. Elucidation of the mechanisms by which these particles are generated and maintained in the blood may provide valuable insight into the mechanism of virus persistence.

Comparison of human respiratory syncytial virus A2 and 8/60 fusion glycoprotein gene sequences and mapping of sub-group specific antibody epitopes

The fusion glycoprotein, F, of human respiratory syncytial virus is a principal target of neutralising antibodies and an important protective immunogen. Among sub-group A strains of the virus the F gene is highly conserved. A comparison of F gene sequences of two sub-group B strains, 8/60 and 18537, indicates that the gene also is conserved within this sub-group. However, both limited sequence variability and antigenic variation occurs between F genes from different virus sub-groups. Such variability may be important in the failure of natural- and vaccine-induced immunity and it is thus important to identify the variable epitopes. Three anti-F MAbs exhibiting sub-group specific neutralisation and binding to recombinant F glycoprotein were studied. Comparison of A2 and 8/60 F gene sequences revealed 64 predicted variant amino acids. In order to map the variant amino acids responsible for sub-group specific binding, three sets of chimaeric genes, in which different domains of A2 and 8/60 F were exchanged, were created and expressed. Sub-group specificity mapped to the N-terminal region of F1 for two MAbs (RS2B8 and RS348) and to the C-terminal region for the third. By using site-directed mutagenesis, sub-group specific binding of MAbs RS2B8 and RS348 was attributed to a predicted loop region between residues 200 and 216. This loop carried four residues variant between the sub-groups. Change of at least two was necessary to abrogate MAb binding.

Comparison of cytotoxic T-lymphocyte responses to hepatitis C virus core protein in uninfected and infected individuals

Cytotoxic T lymphocytes have been implicated in the control of hepatitis C virus (HCV) infection. Recognition by cytotoxic T lymphocytes of epitopes within HCV core protein has been defined previously by in vitro stimulation with synthetic peptides. The aim of this study has been to examine cytotoxic T-lymphocyte responses generated against peptides produced naturally following intracellular processing of viral protein. Antigen-specific cytotoxic T-lymphocyte lines were generated from both HCV uninfected and infected individuals by culturing CD8+ T cells with autologous dendritic cells loaded intracytoplasmically with recombinant HCV core protein. Analysis of the epitopes recognized by core protein-specific cytotoxic T lymphocytes used synthetic peptides that were selected based on their predicted binding to HLA-A*0201 molecules. Core protein-specific cytotoxic T lymphocytes derived from HCV uninfected and infected individuals were able to lyse autologous target cells pulsed with each of 5 predicted epitopes. Generation of HCV-specific cytotoxic T lymphocytes using dendritic cells as antigen presenting cells provides a method of comparing the potential repertoire of cytotoxic T-lymphocyte responses to the responses that occur in chronically infected individuals. No evidence of a qualitatively different response by patient cytotoxic T lymphocytes was apparent which might explain persistence of the virus.

Comparison of cytotoxic T-lymphocyte responses to hepatitis C virus core protein in uninfected and infected individuals

Cytotoxic T lymphocytes have been implicated in the control of hepatitis C virus (HCV) infection. Recognition by cytotoxic T lymphocytes of epitopes within HCV core protein has been defined previously by in vitro stimulation with synthetic peptides. The aim of this study has been to examine cytotoxic T-lymphocyte responses generated against peptides produced naturally following intracellular processing of viral protein. Antigen-specific cytotoxic T-lymphocyte lines were generated from both HCV uninfected and infected individuals by culturing CD8+ T cells with autologous dendritic cells loaded intracytoplasmically with recombinant HCV core protein. Analysis of the epitopes recognized by core protein-specific cytotoxic T lymphocytes used synthetic peptides that were selected based on their predicted binding to HLA-A*0201 molecules. Core protein-specific cytotoxic T lymphocytes derived from HCV uninfected and infected individuals were able to lyse autologous target cells pulsed with each of 5 predicted epitopes. Generation of HCV-specific cytotoxic T lymphocytes using dendritic cells as antigen presenting cells provides a method of comparing the potential repertoire of cytotoxic T-lymphocyte responses to the responses that occur in chronically infected individuals. No evidence of a qualitatively different response by patient cytotoxic T lymphocytes was apparent which might explain persistence of the virus.

New monoclonal antibodies to oestrogen and progesterone receptors effective for paraffin section immunohistochemistry

Assessment of oestrogen and progesterone receptors (ER and PgR) in breast cancer is widely used for the prediction of response to endocrine therapy and as a prognostic marker. Cytosolic assays have been replaced in many centres by immunochemical techniques, which have many advantages including applicability to small samples, simplicity, and cost-effectiveness. This study describes the generation and characterisation of two novel murine monoclonal antibodies recognizing ER and PgR, designated NCL-ER-6F11 and NCL-PGR respectively, which are effective in heat-treated formalin-fixed, paraffin-embedded tissue. The antibodies have been characterized by Western blotting and by immunohistochemistry on normal and pathological breast and other tissues. NCL-ER-6F11 has been shown to compare favourably with a currently available ER antibody. These antibodies may prove of value in the assessment of hormone receptor status in human breast cancer.

Outcome of post-transfusion hepatitis C: disease severity in blood-component recipients and their implicated donors

The UK 'Look-back Program' identifies recipients of blood products from hepatitis C antibody (anti-HCV) positive donors. Of 60 such recipients tested by the Newcastle Transfusion Service, 28(46.7%) were anti-HCV-negative, 25(41.7%) were anti-HCV-positive, and seven (11.6%) had equivocal serology. We studied 29 anti-HCV-positive/indeterminate recipients and eight of their implicated donors, using serial liver function tests (LFTs), liver histology when clinically indicated, HCV RNA and serotyping. Presumed resolved hepatitis C, with persistently normal LFTs and negative HCV RNA, was found in 28%, of whom 63% had indeterminate anti-HCV by RIBA (1 band of 4 detected on third-generation recombinant immunoblot assay). Resolved hepatitis C was significantly more common in women (p < 0.05) and tended to be associated with younger age at transfusion. There was complete concordance in serotype between donor-recipient pairs. There was no correlation in disease severity between recipients and their implicated donors, nor between recipients from the same donor. A history of alcohol consumption above recommended 'safe' limits (median 30 units) was associated with more severe histological disease (p < 0.01). Host factors, including gender and alcohol consumption, may be important in determining the wide variability in outcome of post-transfusion hepatitis C.

A monoclonal antibody pool for routine immunohistochemical detection of human respiratory syncytial virus antigens in formalin-fixed, paraffin-embedded tissue

Four monoclonal antibodies (MAbs) with specificities for epitopes on human respiratory syncytial virus (RSV) proteins preserved after formalin fixation and paraffin embedding were identified in fixed and embedded virus-infected HEp-2 cell pellets. The MAbs bound epitopes on the fusion protein, the nucleoprotein, the phosphoprotein, and the M2 protein of the virus. Following high-temperature antigen unmasking, immunohistochemical staining revealed RSV antigens in the lungs of five of seven children who died with confirmed RSV infection and in none of nine children who died for other reasons, with no evidence of RSV infection. Staining was cytoplasmic, granular, and confined to epithelial cells. Intense staining was seen at the apex of ciliated bronchial and bronchiolar epithelial cells in all five positive cases. In one case, of pneumonitis, infected pneumocytes were present in the alveoli and in several cases, CD68-positive, cytokeratin-negative alveolar macrophages stained for viral antigens. These antibodies may prove useful in studies of the pathogenesis of RSV infection.

Hepatitis C virus density heterogeneity and viral titre in acute and chronic infection: a comparison of immunodeficient and immunocompetent patients

BACKGROUND

Heterogeneities in the buoyant density of hepatitis C virus RNA have been reported in different groups of patients, and have been attributed to differential binding of viral particles to beta-lipoproteins and IgG, and the presence of hepatitis C virus nucleocapsids in circulation. It may be that hepatitis C virus density heterogeneity correlates with the severity of liver disease, hepatitis C virus RNA titre, and the immunocompetence of the patient.

METHODS AND RESULTS

We have analysed five immunodeficient patients (one with hypogammaglobulinaemia and selective IgA deficiency, one with X-linked agammaglobulinaemia, three with common variable immunodeficiency) who have been acutely infected with the same batch of intravenous immunoglobulin contaminated with hepatitis C virus (genotype 1a). The course of hepatitis C virus infection in these patients was compared to one immunocompetent patient who presented with acute hepatitis C virus and progressed to chronic disease, and seven immunocompetent patients with chronic hepatitis C. Serum samples were analysed by differential flotation ultracentrifugation in NaCl solution (density 1.063 g/ml). The high and low density fractions were tested for the presence of RNA by RT-PCR. Serum samples were also quantified for hepatitis C virus RNA (Amplicor HCV Monitor kit, Roche Diagnostic Systems). Three quarters of the acutely infected patients analysed presented with low density hepatitis C virus. Low density hepatitis C virus was absent in most chronic infections but persisted in two patients with common variable immunodeficiency. High density hepatitis C virus was detected in the chronic phase in all acutely infected patients in whom the disease persisted, and was present in all samples from PCR-positive patients with chronic infection. Immunodeficient patients had significantly higher hepatitis C virus RNA titres on presentation than immunocompetent patients, but there was no correlation between titre and clinical course of infection.

CONCLUSIONS

Heterogeneities in the buoyant density of hepatitis C virus RNA have been identified in the patient groups studied. Low density hepatitis C virus is detected more often in acute infection and high density hepatitis C virus is detected more often in chronic infection. Despite acute infection via the same route of infection with the same hepatitis C virus strain, the five immunodeficient patients studied all followed a different clinical course.

Undetectable IgE responses after respiratory syncytial virus infection

Sequential nasopharyngeal secretions were collected from 81 infants from one day to three months after admission to hospital with respiratory syncytial virus (RSV) infection. Samples from 21 infants were assayed for anti-RSV IgE in an antigen capture ELISA assay. No IgE antibodies were detected although an assay of IgA antibodies carried out in parallel by a similar technique detected IgA antibodies in the secretions of all patients tested. Neither prior absorption of IgA or IgG, concentration of the secretions by freeze drying, nor enzyme amplification of the assay revealed any virus specific IgE. Using an antibody capture ELISA with a sensitivity of 0.85 IU/ml, IgE could be detected in sequential secretions of only one of the 81 RSV infected infants studied. Further testing of the secretions from 12 of these patients and those of a further 15 using an enzyme amplified assay with a sensitivity of 0.1 IU/ml revealed no further positives. Low concentrations of IgE were found in the sera of the majority of infants with RSV infection but they did not differ from those of virus negative children of a similar age collected between RSV epidemics. No rise in mean serum IgE concentrations between acute and convalescent samples was observed. No virus specific IgE was detected in the sera of any infant using the enzyme amplified antigen capture ELISA.

Comparison of the T helper cell response induced by respiratory syncytial virus and its fusion protein in BALB/c mice

Specific proliferative T-cell responses were induced in the lymph node cells (LNC) of mice immunised with a sucrose density gradient purified preparation of respiratory syncytial (RS) virus or an immunoaffinity purified preparation of the F glycoprotein. Inhibition studies and flow cytometric analysis showed that the responding cell population were CD4+ T cells. The cytokines produced by virus-specific and F-specific cells were assessed using the CTLL cell line. Peak quantities of cytokine were consistently detected in the supernatants of stimulated cultures 24 h prior to maximum proliferation. The proportion of IL-2 released was determined by blocking IL-2 activity with an anti-IL-2 monoclonal antibody. In cultures of RS virus primed LNC challenged with whole virus there was a switch of cytokine production from 70% IL-2 at day 3 to 80% IL-4 by 6 days of culture. In contrast, LNC cultures from mice immunised with F protein secreted 75-100% IL-2 throughout the culture period. These data suggest that after 6 days of challenge with viral antigen, the RS virus-primed LNC response consists of T helper cells which are predominantly of the Th2 subset, secreting IL-4, whilst F protein-primed LNC secrete large quantities of IL-2 and can therefore be classified as predominantly of the Th1 subset.

Prokaryotic expression and analysis of the antibody response to a Newcastle isolate of the core gene of hepatitis C

The full length hepatitis C virus (HCV) core gene was isolated from a Newcastle strain and expressed in E. coli. A truncated HCV core gene which lacks the hydrophobic carboxyl-terminal sequence was also expressed. The truncated HCV core was expressed at higher levels with fewer cleavage products. Antibody reactivity to the recombinant HCV core antigen was analysed by ELISA and Western blotting in 60 HCV antibody-positive patients with a broad spectrum of liver disease. There was no significant difference between the presence of IgG to recombinant HCV core and reactivity to the core antigen in the RIBA-2 test. There was also no significant difference between the presence of IgG to recombinant core and diagnostic PCR as a marker for active liver inflammation.

Biological activity, binding site and affinity of monoclonal antibodies to the fusion protein of respiratory syncytial virus

The neutralizing activity and fusion-inhibition activity per unit weight of immunoglobulin were determined for each of a panel of 20 monoclonal antibodies (MAbs) to the fusion (F) protein of respiratory syncytial (RS) virus. Neutralization did not correlate with fusion-inhibiting activity, suggesting that the F protein plays at least two independent, antibody-sensitive roles in viral infection. Antibodies with the highest biological activity against A2, a subgroup A strain of RS virus, neutralized a subgroup B strain (8/60) poorly, suggesting a degree of antigenic variation that may be important in human infection. All but one fusion-inhibiting MAb bound to protein blots and binding was mapped to two areas on overlapping F protein fragments. One MAb with relatively poor fusion-inhibiting activity bound only to fragments C-terminal of amino acid 384, the remainder bound only to fragments containing residues 253 to 289. MAbs directed to the latter site were heterogeneous in neutralizing activity, subgroup specificity and fusion-inhibiting activity. These variations between MAbs could not be accounted for by differences in their binding avidities. We suggest that this binding site is not the complete antibody epitope which probably includes conformation-dependent elements.

Binding of neutralizing monoclonal antibodies to regions of the fusion protein of respiratory syncytial virus expressed in Escherichia coli

cDNA containing the entire coding sequence of the respiratory syncytial (RS) virus fusion (F) protein gene (574 amino acids) and two large PstI restriction fragments, encoding amino acids 18 to 212 and 214 to 574, were expressed in Escherichia coli as C-terminal chimeras with beta-galactosidase (beta-gal) in the pEX expression vector system. A further cDNA fragment, overlapping the PstI restriction site and encoding amino acids 190 to 289, was derived by PCR and expressed in a similar manner. Polyclonal rabbit serum raised against RS virus bound to all four chimeric proteins but most strongly to those containing C-terminal sequences. Two monoclonal antibodies (MAbs), 1E3 and RS348, capable of neutralizing the virus and inhibiting the viral fusion function, bound to all chimeras except that derived from the N-terminal PstI fragment, suggesting that their binding sites were located between amino acids 214 and 289. Further analysis of binding to expressed fragments from restriction enzyme digests and PCR amplification demonstrated that both antibodies bound to amino acids 253 to 289. MAb RS348 bound to 12-mer overlapping synthetic peptides containing the sequence 265 to 272 (PITNDQKK) but MAb 1E3 failed to bind to any 12-mer peptide derived from the F protein sequence. Immunization of mice with chimeric proteins containing the whole F protein coding sequence or amino acids 253 to 384, which includes the binding site of the two MAbs identified here, failed to induce antibodies that recognized the native RS virus F protein or could neutralize the virus. This suggests that either the beta-gal partner inhibits the immune response to the protein or that elements missing from the protein expressed in E. coli, perhaps conformational or added post-translation, contribute to the neutralizing antibody epitope.

T cell function in children with acute lymphoblastic leukaemia

Modern intensive chemotherapy has dramatically improved the prognosis of acute lymphoblastic leukaemia (ALL) in children. However, once remission has been established, quality of life and even survival may be threatened by exacerbation of viral infections in the prolonged period of continuation therapy necessary to prevent relapse. Often the viruses involved in the most severe infections are from the herpesvirus and paramyxovirus groups, suggesting that patients suffer from a defect in the cellular immunity thought essential to control such cell-associated infections. This may result from a T cell defect and, in this study, T cell responsiveness of patients under therapy for leukaemia has been investigated. In vitro proliferative responses of peripheral blood leucocytes (PBL) to the T cell mitogen phytohaemagglutinin (PHA) were impaired in children with ALL before treatment and in the induction of remission. Impairment was attributable to reduced T cell numbers, the presence of inhibitors in the patient's serum and direct damage to lymphocytes. On achieving remission, proliferative responses to PHA of both CD4+ and CD8+ T cell subsets quickly returned to normal levels with the switch to continuation chemotherapy. Proliferative responses to Herpes simplex virus antigens were also apparently normal in the majority of patients tested in remission. Further investigations, however, have suggested a persisting defect in CD8+ lymphocyte function. Gamma interferon secretion by PHA-stimulated PBLs was severely reduced for children with ALL in remission when compared with control children of similar age. Further, cytotoxic T lymphocyte responses to allogeneic cells could only be induced in PBL isolated from two of 13 children in remission from ALL whilst all control children of similar age and adults produced anti-allogeneic responses.

Recognition of respiratory syncytial (RS) virus proteins by human and BALB/C CD4+ lymphocytes

Lymphocyte proliferation assays were used to determine the ability of human and BALB/c T-lymphocytes to recognise and respond to in vitro challenge with purified preparations of four respiratory syncytial (RS) virus proteins. Human peripheral blood lymphocytes (PBLs) collected from adult donors as well as primed BALB/c mouse splenocytes each responded specifically to challenge with intact RS virus and preparations of the fusion (F), attachment (G), 23 kilodalton (23K), and 34K phospho- (P) proteins of the virus. F protein was recognised most frequently by human PBLs, and elicited higher levels of response than equivalent concentrations of the other protein preparations examined. The human PBL proliferative responses elicited by in vitro challenge with intact virus antigen as well as with each of the four protein preparations were found to be confined to the CD4+ T-helper (Th) sub-population of lymphocytes. However, proliferative responses to intact virus and F protein were found to be accompanied by only modest and inconsistent production of Interleukin-2 (IL-2). Finally, no evidence was obtained to indicate that any of the challenge antigens employed in this study were intrinsically mitogenic, as neither naive human cord blood lymphocytes, nor un-primed BALB/c mouse splenocytes proliferated when challenged with intact RS virus or with F, G, 23K, or P protein preparations.

Respiratory syncytial virus: virology, diagnosis, and vaccination

Attempts to develop a respiratory syncytial virus vaccine have revealed the antigenic heterogeneity of the virus and have highlighted the difficulties of inducing protective responses in very young infants. Of the two subgroups of the virus, A and B, that cocirculate, A appears to be the most aggressive in infants, but protection against both will be required. Although a degree of protection is transferred from mother to the infant via the placenta and by breast feeding, the mechanisms of protection remain ill-understood and early hopes of exploiting this phenomenon have not been realized. The immune response to the virus in the very young is depressed but disease severity is not demonstrably linked to failure to control virus replication. Rather, immune mechanisms contribute directly to the development of bronchiolitis. The involvement of the immune response in the pathologic process increases the hazards of vaccination. Research is currently focused on the definition of viral epitopes necessary to induce only a protective immune response and their incorporation into a suitable vaccine vector.

Analysis of the local and systemic immune responses induced in BALB/c mice by experimental respiratory syncytial virus infection

Pulmonary A2 strain respiratory syncytial virus infection of BALB/c laboratory mice persisted for up to 7 days after initial infection with peak virus titres being recovered on day 4. Virus antigen within the lungs was found to be restricted essentially to the alveolar regions. Similarly, pulmonary histopathological changes remained confined to the peri-alveolar regions being consistent with mild pneumonia. Infection was found to elicit a pulmonary major histocompatibility complex-restricted cytotoxic T lymphocyte (CTL) response which was first detectable 6 days after infection and optimal 7 to 9 days after infection. This local CTL response was preceded by a rapid transient virus-specific lymphocyte transformation response which was detectable only 3 days after intranasal infection. In addition, infection induced rapid interferon production within the lungs which was accompanied by an equally rapid rise in pulmonary natural killer (NK) cell cytotoxic activity. Enhanced NK cell cytotoxicity could be detected after only 1 day post-infection and continued to rise to maximum levels on day 3. This response like the acute CTL response was found to be restricted to the lower respiratory tract. IgG was the first class of virus-specific immunoglobulin to be detected in the lungs of infected animals after experimental infection. However, IgG was not detected until day 10 post-infection, 5 days after the initial decline of virus shedding. Virus-specific IgA although detectable did not appear in the lung until day 24.

Local antibody production and respiratory syncytial virus infection in children with leukaemia

Children undergoing therapy for acute lymphoblastic leukaemia (ALL) are at increased risk of severe viral respiratory infection, and some find it difficult to terminate virus secretion. This increased severity may result from a defect in the mucosal immune response. To test this hypothesis, nasal immunoglobulin secretion and specific antiviral antibody responses to infection with respiratory syncytial (RS) virus in children with ALL have been compared with those in a normal age-matched comparison group. Children with leukaemia secreted normal levels of IgA and slightly raised IgM levels. IgG levels were depressed. Following RS virus infection, the majority of children with leukaemia secreted normal amounts of IgA and IgG nasal antibody and successfully cleared the virus. However, three of the 13 children studied made poor or undetectable nasal antibody responses, which correlated with their inability to clear the virus.

Interferon alfa, infectious virus, and virus antigen secretion in respiratory syncytial virus infections of graded severity

Interferon alfa was measured by an immunoradiometric assay in the nasopharyngeal secretions of a group of infants admitted to hospital with respiratory syncytial virus infection. Virus replication in the upper respiratory tract was assessed by infectivity assay and by an enzyme linked immunoadsorbent assay for the viral fusion protein on the same nasopharyngeal secretions. All infants were examined daily while in hospital and allocated a score based upon a subjective assessment of the severity of their illness. There was no significant correlation between interferon, virus, or fusion (F) protein secretion and severity of illness or age of infant. It is concluded that poor interferon alfa secretion does not underly the susceptibility of infants to severe infections with this virus.

IgG and IgM antibodies to viral glycoproteins in respiratory syncytial virus infections of graded severity

Serum antibodies to the fusion (F) and large glycoprotein (G) of respiratory syncytial virus in the serum of 57 infected infants were measured by enzyme linked immunosorbent assay (ELISA). Most serum samples taken at the time of admission to hospital contained antibodies to both glycoproteins, and overall there was no significant evidence of a selective deficiency of antibody to either viral antigen. Less than a quarter of the infants showed rising IgG antibody titres to either glycoprotein after infection, whereas over threequarters produced an IgM response. There was a significant correlation between IgG response to viral glycoproteins and the age of the infant. The correlation of age with the IgM response was less pronounced, and there was no correlation between serum IgG antibody derived transplancentally in the acute phase of infection and IgM response to either glycoprotein. Neither IgG or IgM responses correlated with a clinical assessment of the severity of infection in the infants. IgM responses, however, were weakly correlated with reduced secretion of infectious virus in the upper respiratory tract.

Monoclonal antibodies to feline calicivirus

We have prepared monoclonal antibodies to the capsid protein of feline calicivirus (FCV). These antibodies are directed against two close but distinct epitopes, only one of which is involved in virus neutralization. We have used these antibodies and immune cat serum in immunoprecipitation and Western blotting experiments and have identified novel proteins in FCV-infected cells which we term P78, P41, P35 and P29. The number and sizes of FCV proteins now known resemble those made by other caliciviruses.

The effect of foster feeding and bottle feeding expressed breast-milk on the susceptibility of guinea-pig infants to influenza virus

Infant guinea-pigs born to mothers immunized against influenza virus by infection during pregnancy were reared from birth by non-immune foster mothers. As a control for the effects of fostering, a similar group were fostered to immune mothers. Fostering, regardless of the immune state of the foster-mother, increased the susceptibility of the infant to upper respiratory tract infection. Increased susceptibility was associated with ablation of the infants IgM and IgA antibody responses and reduced secretion of transplacentally acquired IgG antibody in nasal secretions. In the reciprocal experiment, infants of non-immune mothers fostered to immune mothers cleared virus more rapidly than their peers who were fed by their own mothers. This protective effect was associated with an enhanced nasal IgM and IgA antibody response. Infants of immune mothers separated from their mothers at birth and hand-reared on a cow's-milk-based formula feed suffered an increased susceptibility to the virus similar to that seen in fostered infants. Addition of a pool of expressed milk from a group of immune mothers, including their own, to the feed of hand-reared infants did not reduce their susceptibility. However, a further group of infants fed a non-cellular whey fraction of the same milk pool secreted significantly lower titres of virus. This increased protection was associated with elevated levels of IgG antibody secretion into nasal washes early in infection.

The susceptibility of breast-fed and cow's milk formula-fed infant guinea pigs to upper respiratory tract infection with influenza virus

Breast-fed infant guinea pigs from immune mothers were partially protected against infection with influenza virus when compared to those from nonimmune mothers. Virus titres in nasal washes at 24 h post-infection were reduced and virus clearance from the upper respiratory tract accelerated. When infants of immune mothers were deprived of colostrum and hand-reared on a formula-feed their ability to reduce virus yields at 24 h post-infection was lost. Infants partially breast-fed and partially formula-fed gave total virus yields similar to their fully breast-fed peers. Infants of immune mothers possessed high titres of serum IgG antibody to the virus prior to infection. Post-infection, IgG antibodies appeared on the mucosal surface of breast-fed seropositive infants earlier than for seronegative infants of nonimmune mothers but IgM and IgA responses of seropositive infants were less vigorous than those of seronegative infants. There was little evidence that antibody present in a mother's milk was transmitted to the nasal mucosa of her offspring. Fully and partly formula-fed seropositive infants showed enhanced transudation of serum IgG antibody on to the mucosal surface and this effect was most marked in the partly formula-fed group which showed greater protection. In both formula-fed groups serum and nasal IgM and IgA responses were completely suppressed.

The purification of four respiratory syncytial virus proteins and their evaluation as protective agents against experimental infection in BALB/c mice

The fusion (F) glycoprotein, large glyco- (G) protein, phospho- (P) protein and 22K protein of respiratory syncytial (RS) virus A2 strain were purified by a combination of immunoaffinity adsorption and preparative SDS-PAGE. All four proteins elicited serum antibody in mice after repeated inoculation in adjuvant, although the magnitude of the response as measured by ELISA varied from mouse to mouse. The F protein generated neutralizing antibodies in only 50% of the mice determined to be seropositive by ELISA. The G protein also induced neutralizing antibodies but in this instance neutralization tests and ELISA titres were more closely correlated. No neutralizing activity was detected in mice immunized with the P or 22K proteins although all produced antibody detectable by ELISA. Mice immunized with either the F or the G protein were found to be protected against subsequent RS virus challenge, whether they had developed neutralizing antibody or not. Mice inoculated with the P or 22K proteins were not protected.

Strain variation of respiratory syncytial virus

Western blotting and immunoperoxidase staining with monoclonal antibodies were employed to analyse epitopic and polypeptide molecular weight variation among isolates of respiratory syncytial (RS) virus collected in Newcastle between 1965 and 1986. One group of isolates resembled the A2 and Long prototype subgroup A strains of RS virus in possessing a P protein of Mr 34,000. Isolates in this subgroup showed two patterns of reactivity with subgroup A-specific monoclonal antibodies to the G glycoprotein and 22K protein. Isolates with both reactivity patterns were isolated throughout the period studied. Isolates in the second group resembled the 8/60 subgroup B prototype strain in their lack of reactivity to subgroup A-specific monoclonal antibodies but were heterogeneous in P protein molecular weight. The earliest isolate only, made in 1965, possessed a P protein of Mr 31,000 resembling the prototype strain. All subsequent subgroup B isolates possessed a higher Mr, 33,000, P protein. Overall, subgroup A viruses were isolated most frequently although subgroup B strains may have predominated in some epidemics.

Mammary immunity in mothers of infants with respiratory syncytial virus infection

Seven of 230 breast fed infants followed prospectively from birth through their first winter contracted RS virus infections. The colostral from five of the mothers of these infants contained antiviral IgA antibodies. In each case antibody levels were above the mean for a group of 36 mothers whose infants were age matched to infected infants but for whom there was no evidence of RS virus infection in their first winter. Four colostral samples from mothers of infected infants also contained antiviral IgG antibody. Colostral lymphocyte reactivity to RS virus antigen was tested in three mothers of infected infants and two showed significant proliferation. There was, therefore, no evidence that mothers of infected infants lacked mammary immunity to the virus. Maternal mammary IgA and IgG responses following diagnosis of RS virus infection in the infant were followed for the seven cases identified prospectively and for a further 23 infants admitted to hospital with RS virus infections of varying severity. There was no evidence that the mothers of more severely affected infants were deficient in IgA or IgG milk antibody.

Heterogeneity of the respiratory syncytial virus 22K protein revealed by Western blotting with monoclonal antibodies

Respiratory syncytial (RS) virus-infected HeLa, HEp-2, Vero and BS-C-1 cell lysates were electrophoresed on SDS-polyacrylamide gels under reducing conditions and analysed by Western blotting and immunoperoxidase using monoclonal antibodies specific for the 22K protein (relative mol. wt. of 23,000 in our gel system). Three novel polypeptides with mol. wt. of 24,000, 21,000 and 17,000 were stained in addition to the 23,000 polypeptide which was present in the greatest amount in all three virus strains tested regardless of host cell line. When samples were electrophoresed under non-reducing conditions each of the three higher mol. wt. polypeptides seen in reducing gels migrated as two bands (total of six bands) with altered electrophoretic mobilities. In experiments using the alkylating agent iodoacetamide under conditions where the novel 24,000, 21,000 and 17,000 polypeptides were not visible, the number of mobility variants of the 23,000 polypeptide which could be detected in non-reducing conditions was increased from two to four. At least one, and possibly three, of these variants was the result of conformational variation in the 23,000 polypeptide caused by the generation or rearrangement of intrachain disulphide bonds after the infected cells were lysed in SDS-PAGE sample buffer. Post-lysis conformational changes were minimized by treatment of the infected cells with iodoacetamide before solubilization or by decreasing the SDS concentration or using milder detergents in the lysis buffer.

Expression of the respiratory syncytial virus 22K protein on the surface of infected HeLa cells

Immunofluorescent staining of unfixed respiratory syncytial virus-infected HeLa cells with monoclonal antibodies (MAbs) demonstrated that the 22K protein is expressed on the cell membrane along with the fusion (F) protein and large glycoprotein (G). All three proteins were detected in the cytoplasm at 17 h post-infection and in the case of the F and G proteins this coincided with their appearance on the cell surface. However, the 22K protein could not be detected on the surface until approximately 16 h after its detection in the cytoplasm, when cytopathic effect was extensive. No evidence for the surface expression of the phosphoprotein (P), matrix (M) or nucleocapsid (N) proteins was found. Trypsin treatment of infected cells prior to unfixed immunofluorescent staining and Western blot analysis indicated that, unlike the G protein, the quantity of 22K protein detected on the cell surface constituted only a small proportion of the total present in the cell. A comparison of the patterns of immunofluorescent staining produced by MAbs on acetone-fixed infected cells suggested that the N, P and 22K proteins, but not the M protein, may be associated with the same intracellular structures.

Virus infections in childhood malignant disease

The viruses isolated during infective episodes over a 5-year period of 93 children with acute lymphoblastic leukemia (ALL) and 107 children with other malignancies have been studied. Viruses were identified by the fluorescent antibody technique (FAT), electron microscopy, and culture. Viruses were isolated on 204 occasions. Rhinovirus and RSV occurred significantly more often in the patients with ALL, and adenovirus more commonly in the solid tumor patients. Viruses were responsible for 4 of the 69 deaths. Multiple different virus isolation during the same infective episode was significantly more common than in a control group. Where paired sera were available, only 10 out of 27 children showed at least a fourfold rise to the isolated virus. A rise in complement-fixing antibody is confirmed as a very unreliable method of detecting virus infection in immunosuppressed children. Viruses are important pathogens in children with cancer and assume greater relevance now that over 60% of malignant disease in childhood can be cured.

Interferon responses of peripheral blood mononuclear cells from normal and leukaemic children

Human peripheral blood mononuclear cell cultures (PBMC) stimulated with Sendai virus or K562 cells produce a mixture of interferons. Temperature and pH stability characteristics and reactions with monospecific antibodies indicate that PBMC cultures from adults produce interferons alpha and gamma in approximately equal proportions. PBMC cultures from children produce lower levels of interferons with a higher proportion of type alpha. The ability of PBMC cultures from children with acute lymphoblastic leukaemia (ALL) to produce interferon was determined. Little or no gamma interferon was induced by either Sendai virus or K562 cells. Cultures from some children with ALL produced alpha interferon but mean levels were significantly lower than from normal children. A group of older children with ALL who had completed their course of therapy and were off treatment produced levels of interferon indistinguishable from those of normal children. This in vitro deficit, possibly induced by chemotherapy, may reflect an in vivo deficit and may contribute to the impaired handling of viruses seen in children being treated for ALL.

Respiratory syncytial virus glycoprotein expression in human and simian cell lines

Glycoproteins synthesized in both human (HeLa and HEp-2) and simian (Vero and BS-C-1) cell lines following infection with two different strains of respiratory syncytial virus (A2 and Long) were analysed by SDS-PAGE following immunoprecipitation with monoclonal antibodies. Minor virus strain-dependent differences in the large glycoprotein, G, and the fusion protein polypeptides F1 and F2 were observed together with minor cell line-dependent differences in the size of the F2 polypeptide. Major quantities of two glycoproteins, termed Ga (50K) and Gb (45K), were detected in A2 strain-, and to a lesser extent in Long strain-, infected simian cells. These proteins were also present in infected human cells, but in much reduced amounts. Immunoprecipitation with anti-G monoclonal antibodies demonstrated that Ga and Gb shared different epitopes with G.