Insulin-stimulated translocation of GLUT4 to the plasma membrane in rat hippocampus is PI3-kinase dependent

In the central nervous system (CNS) insulin mediates a variety of effects including feeding, metabolism and cognition. The cognitive enhancing effects of insulin are proposed to be mediated through activation of insulin receptors in the hippocampus, an important integration center for learning and memory in the mammalian brain. Since less is known regarding insulin signaling events in the hippocampus, the aim of the current study was to determine whether insulin stimulates similar signaling cascades and GLUT4 translocation in the rat hippocampus as has been described in peripheral tissues. Intracerebroventricular administration of insulin increases hippocampal insulin levels and also stimulates the phosphorylation of Akt in a time-dependent manner. Insulin also stimulates the translocation of GLUT4 to hippocampal plasma membranes in a time course that mirrors the increases in glucose uptake observed during the performance of hippocampal-dependent tasks. Insulin stimulated phosphorylation of Akt and translocation of GLUT4 were blocked by pretreatment with the PI3-kinase inhibitor LY294002. Confocal immunofluorescence determined that insulin stimulated phosphorylation of Akt was localized to neurons and colocalized with the insulin receptor and GLUT4 in the rat hippocampus, thereby identifying the functional anatomical substrates of insulin signaling in the hippocampus. These results demonstrate that insulin-stimulated translocation of GLUT4 to the plasma membrane in the rat hippocampus occurs via similar mechanisms as described in peripheral tissues and suggests that insulin-mediated translocation of GLUT4 may provide a mechanism through which hippocampal neurons rapidly increase glucose utilization during increases in neuronal activity associated with hippocampal-dependent learning.

Serotyping HIV-1 with V3 peptides: detection of high avidity antibodies presenting clade-specific reactivity

The main objective of the present study was to assess the specificity and sensitivity of a modified assay using short synthetic peptides of the V3 region of HIV-1 gp120, which is the main target for neutralizing antibodies. Results from an enzyme immunoassay (EIA) employing a panel of synthetic peptides of HIV-1 subtypes and using urea washes to detect high avidity antibodies (AAV3) were compared with those obtained by the heteroduplex mobility assay and DNA sequencing. The EIA correctly typed 100% of subtype B (sensitivity = 1.0; specificity = 0.95), 100% of HIV-1 E samples (sensitivity = 1.0; specificity = 1.0), and 95% of subtype C specimens (sensitivity = 0.95; specificity = 0.94). In contrast, only 50% of subtype A (sensitivity = 0.5; specificity = 0.95), 60% of subtype D (sensitivity = 0.6; specificity = 1.0), and 28% of subtype F samples (sensitivity = 0.28; specificity = 0.95) were correctly identified. This approach was also able to discriminate in a few samples antibodies from patients infected with B variants circulating in Brazil and Thailand that reacted specifically. The assays described in this study are relatively rapid and simple to perform compared to molecular approaches and can be used to screen large numbers of serum or plasma samples. Moreover, the classification in subtypes (genotypes) may overestimate HIV-1 diversity and a classification into serotypes, based on antigenic V3 diversity or another principal neutralization domain, may be more helpful for vaccine development and identification of variants.

Characterization of the HIV-1 specific humoral immune response during highly active antiretroviral therapy (HAART)

Plasma samples from 19 patients were analyzed for HIV-1 directed humoral immune responses prior to and 1 year after initiation of HAART. Eight of the subjects were classified as virologic successes, defined by a >100-fold decrease in viral load (VL) over the 1-year study period and a final VL <500 copies/ml. The eleven HAART failures were defined as subjects with <10-fold decrease in VL. At study entry (before HAART), VL and CD4 counts were similar between the two groups. Humoral immune responses before therapy and after 1 year of therapy were measured by V3 peptide antibody binding titers and neutralization of HIV-1 MN and four subtype B clinical isolates. Before HAART, neutralizing antibody titers to the clinical isolates and HIV(MN), as well as HIV V3 envelope binding titers to several V3 peptides, were significantly higher among treatment successes compared with treatment failures. After 1 year on HAART, neutralization declined in titer and narrowed in specificity among the HAART successes. In contrast, a significant increase in both neutralizing titer and breadth was seen among HAART failures.

Adenovirus type 3 viremia in an adult with toxic shock-like syndrome

Surveillance by the Unexplained Deaths and Critical Illnesses Project (UNEX) uncovered a novel presentation of adenovirus type 3 infection that satisfied the criteria for toxic shock-like syndrome in a 28-year-old immunocompetent man. Adenovirus may be a cause of toxic shock syndrome; surveillance systems such as UNEX may uncover additional causes of this and other clinically defined infectious syndromes.

Predominant kidney involvement in a fatal case of hantavirus pulmonary syndrome caused by Sin Nombre virus

A 27-year-old woman presented to a hospital with symptoms resembling pyelonephritis; respiratory distress did not develop until nearly a day after admission and she subsequently died. The Unexplained Deaths and Critical Illnesses Project of the Centers for Disease Control and Prevention confirmed Sin Nombre virus infection by the results of serological testing and sequencing of the viral genome; staining of Sin Nombre virus antigen in the pulmonary capillaries was relatively weak.

Immune response to influenza vaccine in adult liver transplant recipients

Influenza virus infection may cause significant complications in liver transplant recipients, and whether vaccination is effective in these patients is controversial. We performed a study to assess the immune response to influenza vaccine in liver transplant recipients and patients with cirrhosis compared with healthy controls. Liver transplant recipients (n = 20), patients with compensated cirrhosis awaiting transplantation (n = 14), and healthy volunteers (n = 9) were administered the standard dose of the 1999 to 2000 inactivated trivalent vaccine (A/Bejing/262/95[H1N1]; A/Sidney/5/97[H3N2]; B/Yamanashi/166/98). Antibody responses to each component of the vaccine were measured at baseline and after 6 weeks by hemagglutination inhibition. Vaccination was well tolerated, and no major side effects were observed. A significant postvaccination increase in antibody titer to all 3 vaccine components was obtained in all groups. However, liver transplant recipients had significantly lower postvaccination geometric mean titers and geometric mean increases to the H3N2 component compared with patients with cirrhosis and controls. The rate of seroconversion to H3N2 after vaccination was also significantly lower in liver transplant recipients (15% v. 89%). We conclude that liver transplant recipients have a significantly impaired immune response to the influenza vaccine, and some patients may remain unprotected from influenza infection after vaccination. Further studies of modified protocols of influenza vaccination for these patients are recommended.

Influenza infection in patients before and after liver transplantation

Infection with influenza virus poses specific problems in pediatric and adult liver transplant recipients, both before and after liver transplantation. These include a higher rate of pulmonary and extrapulmonary complications, development of rejection with graft dysfunction, prolonged shedding of influenza virus, and increased drug-resistance. Hepatic decompensation may occur during influenza infection in patients with cirrhosis. Current prophylaxis includes yearly vaccination with trivalent inactivated vaccine. Appropriate diagnosis and prompt treatment of any upper respiratory infections are indicated in these patients. In this review, we describe a case of influenza viral pneumonia in an adult liver transplant recipient, review basic and clinical aspects of influenza infection in this patient population, and discuss current modes of prevention and treatment in detail.

Hepatic decompensation in patients with cirrhosis during infection with influenza A

BACKGROUND

Patients with chronic liver disease can develop hepatic decompensation during systemic infections. Although gram-negative and gram-positive bacteria are well recognized as causes of decompensation, the effect of influenza virus infection on patients with chronic liver disease is poorly documented.

METHODS

Retrospective analysis of patients with positive viral cultures who were seen at a liver transplantation clinic in a tertiary care referral center during the 1997-1998 influenza A (H3N2) epidemic in San Diego, Calif.

RESULTS

Three patients with end-stage liver disease (1 with Wilson disease and 2 with alcoholic liver disease) developed hepatic decompensation and required hospitalization during infection with influenza A. Two patients had biochemical and clinical evidence of hepatic decompensation, including ascites, hepatic encephalopathy, and peripheral edema, and the third had acute hepatocellular damage, with elevated levels of aminotransferases. Viral hepatitis serologic test results, acetaminophen levels, drug and alcohol screening findings, and bacterial and fungal cultures were negative in all 3 patients. Hepatic decompensation resolved without the need for transplantation in the 2 patients with liver failure, and all patients recovered to their baseline liver function levels within 1 month of onset of acute illness.

CONCLUSIONS

Influenza A infection can cause hepatic decompensation and hospitalization in patients having cirrhosis or who are awaiting liver transplantation. Effective prevention with vaccination and early recognition and treatment of influenza are strongly recommended in these individuals.

Identification of a linear heparin binding domain for human respiratory syncytial virus attachment glycoprotein G

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract disease in infants and young children worldwide. Infection is mediated, in part, by an initial interaction between attachment protein (G) and a highly sulfated heparin-like glycosaminoglycan (Gag) located on the cell surface. Synthetic overlapping peptides derived from consensus sequences of the G protein ectodomain from both RSV subgroups A and B were tested by heparin-agarose affinity chromatography for their abilities to bind heparin. This evaluation identified a single linear heparin binding domain (HBD) for RSV subgroup A (184A-->T198) and B (183K-->K197). The binding of these peptides to Vero cells was inhibited by heparin. Peptide binding to two CHO cell mutants (pgsD-677 and pgsA-745) deficient in heparan sulfate or total Gag synthesis was decreased 50% versus the parental cell line, CHO-K1, and decreased an average of 87% in the presence of heparin. The RSV-G HBD peptides were also able to inhibit homologous and heterologous virus infectivity of Vero cells. These results indicate that the sequence 184A/183K-->198T/K197 for RSV subgroups A and B, respectively, defines an important determinant of RSV-G interactions with heparin.

Prevalence of HTLV-I and HTLV-II infections among HIV-1-infected asymptomatic individuals in São Paulo, Brazil

Human immunodeficiency virus (HIV-1)-infected subjects with acquired immunodeficiency syndrome (AIDS) are often infected with multiple pathogens. In particular, HTLV-I and HTLV-II infections have been found more frequently in AIDS patients than in asymptomatic individuals in Europe and Japan. We carried out a serosurvey among asymptomatic HIV-1-infected subjects in São Paulo, Brazil and compared our results with those of other investigators. In this study, we found HTLV infection in 1.5% of 266 asymptomatic and 14% of 28 AIDS patients. Epidemiological data obtained from patients pointed out the use of intravenous drugs as the principal risk factor for acquiring retroviruses. In conclusion, our results are in accordance with other studies done in Brazil and elsewhere where the principal risk group for HIV/HTLV-I/II coinfection was IDU.

Neutralization of primary HIV-1 isolates by anti-envelope monoclonal antibodies

OBJECTIVE

To evaluate human monoclonal antibodies (MAb) for neutralizing activity against primary HIV-1 isolates in peripheral blood mononuclear cells.

DESIGN

Neutralization activity data were obtained from 11 laboratories on a coded panel consisting of six human MAb to HIV envelope V3, CD4-binding region or gp41. Hyperimmune globulin against HIV-1 and normal human immunoglobulin G were supplied as controls. Each laboratory received pre-titered virus for use in the studies.

METHODS

Each laboratory measured neutralization of the MAb against laboratory strain HIVMN, genomic clone HIVJR-CSF, two subtype B and one subtype D primary isolates.

RESULTS

The titers of the centrally supplied virus stocks as determined by re-titration or back-titration varied among laboratories and were generally 10-100-fold less than provided. The neutralizing activity of each MAb varied by as much as a 1000-fold among laboratories. These differences may result from varying sensitivity in neutralization assay protocols and the differing susceptibility of primary cells to infection with HIV-1.

CONCLUSIONS

To consolidate the data from multiple laboratories, the neutralization titers were compared by classifying antibodies as neutralizing if the antibody concentration for 50% virus inhibition was < or = 10 micrograms/ml. By this criterion, the CD4-binding region and gp41 MAb neutralized all four subtype B viruses and the subtype D isolate in a few of the laboratories. The V3 MAb neutralized only HIVMN and the closely related HIVJR-CSF viruses.

Neutralizing recombinant human antibodies to a conformational V2- and CD4-binding site-sensitive epitope of HIV-1 gp120 isolated by using an epitope-masking procedure

As part of the goal of assembling a mixture of neutralizing human mAbs for possible prophylaxis and therapy of HIV-1 disease, we describe a strategy by which neutralizing human Abs to a weakly immunogenic epitope can be accessed. From a phage display library derived from an asymptomatic HIV-1 seropositive donor, a panel of recombinant Fabs against the CD4 binding site (CD4bs) of gp120 was retrieved by affinity selection using recombinant gp120 (strain LAI). Two Fabs corresponding to the dominant clones were used to mask the CD4bs epitope(s) before repeating the selection procedure. Four Fabs were then retrieved that had novel heavy chain sequences. Three recognized a novel epitope distinct from that recognized by conventional CD4bs Abs and were defined by the following criteria: 1) second V region (V2 region) dependence indicated by sensitivity to amino acid changes in the V2 loop and by competition with murine anti-V2 mAbs; 2) CD4bs dependence indicated by sensitivity to amino acid changes usually associated with CD4 binding and by inhibition of Fab binding to gp120 by soluble CD4; this dependence seemed to arise via conformational changes rather than by direct binding, as CD4bs Abs enhanced binding of two of the novel Fabs and, in a reversal of the competition format, the novel Fabs did not inhibit soluble CD4 binding to gp120; and 3) equivalent binding to glycosylated and deglycosylated gp120 and significant, although much reduced, binding to denatured gp120 in contrast with CD4bs Abs, which do not bind to deglycosylated or denatured gp120. One of the novel Fabs efficiently neutralized the MN and LAI strains of HIV-1. These results indicate the presence of a novel neutralizing conformational epitope on gp120 sensitive to the V2 loop and the CD4bs and further highlight the conformational flexibility of gp120. The strategy of masking highly immunogenic epitopes with Abs to rescue a broader range of specific Abs from combinatorial libraries should be widely applicable.

Neutralizing recombinant human antibodies to a conformational V2- and CD4-binding site-sensitive epitope of HIV-1 gp120 isolated by using an epitope-masking procedure

As part of the goal of assembling a mixture of neutralizing human mAbs for possible prophylaxis and therapy of HIV-1 disease, we describe a strategy by which neutralizing human Abs to a weakly immunogenic epitope can be accessed. From a phage display library derived from an asymptomatic HIV-1 seropositive donor, a panel of recombinant Fabs against the CD4 binding site (CD4bs) of gp120 was retrieved by affinity selection using recombinant gp120 (strain LAI). Two Fabs corresponding to the dominant clones were used to mask the CD4bs epitope(s) before repeating the selection procedure. Four Fabs were then retrieved that had novel heavy chain sequences. Three recognized a novel epitope distinct from that recognized by conventional CD4bs Abs and were defined by the following criteria: 1) second V region (V2 region) dependence indicated by sensitivity to amino acid changes in the V2 loop and by competition with murine anti-V2 mAbs; 2) CD4bs dependence indicated by sensitivity to amino acid changes usually associated with CD4 binding and by inhibition of Fab binding to gp120 by soluble CD4; this dependence seemed to arise via conformational changes rather than by direct binding, as CD4bs Abs enhanced binding of two of the novel Fabs and, in a reversal of the competition format, the novel Fabs did not inhibit soluble CD4 binding to gp120; and 3) equivalent binding to glycosylated and deglycosylated gp120 and significant, although much reduced, binding to denatured gp120 in contrast with CD4bs Abs, which do not bind to deglycosylated or denatured gp120. One of the novel Fabs efficiently neutralized the MN and LAI strains of HIV-1. These results indicate the presence of a novel neutralizing conformational epitope on gp120 sensitive to the V2 loop and the CD4bs and further highlight the conformational flexibility of gp120. The strategy of masking highly immunogenic epitopes with Abs to rescue a broader range of specific Abs from combinatorial libraries should be widely applicable.

Efficient neutralization of primary isolates of HIV-1 by a recombinant human monoclonal antibody

The ability of antibodies to neutralize diverse primary isolates of human immunodeficiency virus-type 1 in vitro has been questioned, with implications for the likely efficacy of vaccines. A recombinant human antibody to envelope glycoprotein gp120 was generated and used to show that primary isolates are not refractory to antibody neutralization. The recombinant antibody neutralized more than 75 percent of the primary isolates tested at concentrations that could be achieved by passive immunization, for example, to interrupt maternal-fetal transmission of virus. The broad specificity and efficacy of the antibody implies the conservation of a structural feature on gp120, which could be important in vaccine design.

V3 region polymorphisms in HIV-1 from Brazil: prevalence of subtype B strains divergent from North American/European prototype and detection of subtype F

Viral DNA sequences were determined over the V3 region of env from 28 infected individuals living in the high HIV-1 prevalence Brazilian cities of Rio de Janeiro and São Paulo. Twenty-six belonged to envelope sequence subtype B, prevalent in North America and Europe, and one was classified as subtype F, found recently in Brazil and in Romania (one appeared to be a B/F recombinant). Octameric sequences at the tip of the subtype B V3 loops were variable and distinct from those prevalent in North America and Europe. The GPGR motif, prevalent in North American/European strains, was found in only 8 (28.5%) sequences, whereas GWGR was found in 12 (43%) and novel sequences in 8 (28.5%). Brazilian subtype B sequences also diverged from the consensus North American/European strains over the remainder of the V3 loop. These results suggest that Brazilian HIV-1 B strains may have important antigenic differences from prototype subtype B strains currently being evaluated for use in HIV vaccines. These results should be taken into account for future vaccine programs in Brazil.

In vitro evolution of a neutralizing human antibody to human immunodeficiency virus type 1 to enhance affinity and broaden strain cross-reactivity

A method is described that allows for the improvement of antibody affinity. This method, termed complementary-determining region (CDR) walking, does not require structural information on either antibody or antigen. Complementary-determining regions are targeted for random mutagenesis followed by selection for fitness, in this case increased binding affinity, by the phage-display approach. The current study targets a human CD4-binding-site anti-gp120 antibody that is potently and broadly neutralizing. Evolution of affinity of this antibody demonstrates in this case that affinity can be increased while reactivity to variants of human immunodeficiency virus type 1 is broadened. The neutralizing ability of this antibody is improved, as assayed with laboratory and primary clinical isolates of human immunodeficiency virus type 1. The ability to produce human antibodies of exceptional affinity and broad neutralizing ability has implications for the therapeutic and prophylactic application of antibodies for human immunodeficiency virus type 1 infection.

Evaluation of monoclonal antibodies to HIV-1 envelope by neutralization and binding assays: an international collaboration

OBJECTIVE

To characterize a purified panel of monoclonal antibodies (MAb) to epitopes in HIV-1 envelope V3, CD4-binding region, C4 and gp41.

DESIGN

Neutralization and/or binding activity data were obtained from 21 laboratories on a coded panel consisting of seven human MAb, seven mouse MAb, recombinant human CD4 immunoadhesin [CD4-immunoglobulin G (IgG)], normal human and normal murine Ig.

METHODS

Laboratories performed a variety of neutralization assays and antigen binding assays with HIVIIIB, HIVMN and other laboratory strains of HIV-1.

RESULTS

For a single MAb, there was up to a 10(3) range of neutralizing antibody titers between laboratories. The range in titers appeared to depend on the sensitivity of the neutralization assay. Two methods were used to consolidate the data from all laboratories, the geometric mean titer (GMT) and the median neutralizing titer (MNT). The panel of MAb were also analyzed by a variety of assays that measure binding activity to native or denatured epitopes. The relative binding activity of the MAb did not appear to correlate with neutralizing activity.

CONCLUSION

Neutralization results from any single laboratory did not correlate with the collective data. The relative potency (rank order) of the MAb in the panel were equivalent when determined by GMT or MNT. These values may be useful to individual laboratories for estimating the sensitivity of their neutralization assays. The study also identified potential reference reagents with which neutralizing activity could be compared.

High prevalence of antibodies to the gp120 V3 region principal neutralizing determinant of HIV-1MN in sera from Africa and the Americas

Neutralizing antibodies (NA) against HIV-1MN and HIV-1IIIB, and antibodies binding to synthetic peptides (BA) derived from the gp120 envelope V3 region principal neutralizing determinants (PND) of the HIV-1MN, HIV-1IIIB, and HIV-1Z3 virus strains were assayed in HIV-1 antibody-positive sera from the United States, Haiti, Brazil, Zaire, and Zimbabwe. The ability of soluble PND peptide to block neutralization of the corresponding virus by representative sera was also tested. In each country, NA and BA titers were highest against the HIV-1MN strain, and compared with other countries, NA and BA titers against HIV-1MN were higher in sera from the United States and Haiti. When NA titers were compared with BA titers against either HIV-1MN or HIV-1IIIB, no correlation was found for the HIV-1IIIB strain, but there was a significant correlation for HIV-1MN. Addition of the HIV-1MN strain peptide to a neutralization assay for HIV-1MN resulted in a four- to tenfold reduction in NA titers in sera from the United States, Zaire, and Brazil. The results suggest that HIV-1MN and closely related variants are prevalent in many parts of the world, and that antibodies directed against the PND account for most of the neutralizing activity in sera of infected individuals.

Multicenter study of strains of respiratory syncytial virus

Two major groups of respiratory syncytial virus (RSV) strains, A and B, have been identified and their patterns of isolation determined in different communities but not simultaneously in multiple communities. In this study, we tested 483 RSV isolates from 14 university laboratories in the United States and Canada for the 1984/1985 and 1985/1986 RSV seasons; 303 (63%) isolates were group A, 114 (24%) were group B, and 66 (14%) could not be grouped. Isolates were subdivided into six subgroups within group A and three within group B; up to six and often four or more different subgroups were isolated in the same laboratory during the same RSV season. The pattern of group and subgroup isolations varied among laboratories during the same year and between years for the same laboratory. These differences suggest that RSV outbreaks are community, possibly regional, but not national phenomena. The ability to identify group and subgroup differences in isolates is a powerful tool for epidemiologic studies of RSV.

Possible beneficial effects of neutralizing antibodies and antibody-dependent, cell-mediated cytotoxicity in human immunodeficiency virus infection

We studied the relationship between early human immunodeficiency virus type 1 (HIV-1) specific immune responses and pathogenesis of infection in participants enrolled in the multicenter AIDS cohort study (MACS). Sera collected at 6-month intervals for 2 years (visit 1-5) from 39 persons who seroconverted by enzyme-linked immunosorbent assay (ELISA) 6 months (visit 2) after enrollment were examined for isotype-specific Western blot reactivity, neutralizing antibodies (NA) against two divergent strains of HIV-1 (HIV-1IIIB and HIV-1RF), and for antibodies capable of participating in antibody-dependent, cell-mediated cytotoxicity (ADCC). These results were compared with changes in CD4+ cell number and episodes of lymphadenopathy. Twenty-five subjects had antibodies of at least one isotype reactive to at least one HIV-1 protein by Western blot at visit 1, before they became ELISA positive. NA reactive with HIV-1IIIB were detected before those reactive with HIV-1RF. NA were first observed in 11 sera at visit 2, in 22 sera at visit 3, and in 3 sera at visit 4; sera from three patients remained nonneutralizing through visit 5. In most cases, NA were detected after a decline in CD4+ cell numbers. The data are consistent with the interpretation that NA develop after about 16 to 18 months of declining CD4+ cell numbers, following which the rate of decline in CD4+ cell numbers slows. In contrast, HIV-1 envelope antigen-specific ADCC responses were first observed in 11 subjects at visit 1 when all 39 were NA and ELISA negative, in 12 subjects at visit 2, in 13 subjects at visit 3, and 1 subject at visit 4. Early ADCC responses were associated with high mean % CD4+ cell numbers and absence of lymphadenopathy throughout the 2-year observation period. Not all subjects who developed ADCC developed NA. In some subjects, ADCC and NA were detectable for the first time at the same visit, for others ADCC was detectable prior to NA, and for a few NA was detectable prior to ADCC. These findings suggest that ADCC and neutralization are mediated by different antibody populations, that they may partially inhibit the progress of HIV-1 infection, and that the late appearance of NA may relate to the failure of immunity to effect recovery from this infection.

Characterization of the serologic profile of children with human immunodeficiency virus infection: correlation with clinical status

Serum samples from 28 children with symptomatic human immunodeficiency virus (HIV) infection were studied for the presence of HIV antigen. Their humoral immune response profile, including anti-HIV specific isotypic responses and neutralizing titers, was characterized. Additionally, serum specimens from 12 of these children were tested for their ability to mediate antibody-dependent cellular cytotoxicity (ADCC) against HIV envelope antigens. Analysis of our results showed that children with acquired immunodeficiency syndrome (AIDS) were much more likely to have serum antigenemia and an absence of anti-p24 antibodies than those with AIDS-related complex (ARC). A significant association was also noted between a more stable clinical status and a strong anti-p24 antibody response with detectable antibodies to other HIV antigens in multiple antibody subclasses. This suggests that the longitudinal evaluation of antigen/antibody profiles may aid in the assessment of prognosis for children with HIV infection. Sera from 6/6 patients with ARC and 4/6 patients with AIDS were able to mediate ADCC. No correlation was found between clinical status and the titers of neutralizing antibodies.

Prevalence of respiratory syncytial virus subgroups over six consecutive outbreaks: 1981-1987

Indirect immunofluorescence with strain-specific monoclonal antibodies was used to determine the phenotype of respiratory syncytial virus (RSV) isolates obtained from infants hospitalized in greater Boston over six successive outbreaks from 1981 to 1987. Of 981 isolates, 591 (60%) were classified as subgroup A and 383 (39%) as subgroup B. The prevalence of subgroups varied both between and within yearly outbreaks. In 1983-84 and 1984-85, both subgroups circulated concurrently and in almost equal proportions; in 1981-82, 1982-83, and 1985-86 subgroup A was dominant, accounting for 93% of all RSV isolates; and in 1986-87 subgroup B accounted for 89% of all RSV isolates. In some outbreaks both geographic and temporal clustering of subgroups occurred. No major differences in age, gender, or frequency of nosocomially acquired RSV between infants infected with either subgroup were seen, either overall or between or within yearly outbreaks. An expanded panel of monoclonal antibodies revealed further heterogeneity among subgroup A isolates. Comparison of these results with similar studies from other geographic locations indicated that the pattern of RSV subgroup prevalence is a localized phenomenon.

Strain-specific serum antibody responses in infants undergoing primary infection with respiratory syncytial virus

We sought to characterize the human respiratory syncytial virus (RSV) subgroup-specific antibody response to primary infection with RSV. RSV isolates from 43 infants and young children were typed as either subgroup A (Long strain-like) or B (18537 strain-like) based on reactivity with monoclonal antibodies. Acute-phase or preinfection and convalescent-phase sera were collected from the 43 subjects and tested in an enzyme-linked immunosorbent assay using purified F and G glycoproteins from RSV subgroups A and B and by neutralization assay against both subgroups of RSV. Twenty-six individuals had rises in titer of antibody to F glycoprotein, 27 to G glycoprotein, and 28 had rises in titer of neutralizing antibody. The antibody responses to homologous and heterologous F glycoproteins were not significantly different. In contrast, homologous vs. heterologous antibody responses to G glycoprotein were significantly different, with 7.3% relatedness between the G glycoproteins of subgroups A and B. Analysis of neutralizing antibody responses revealed 31% relatedness.

Respiratory virus infection of peripheral blood monocytes: correlation with ageing of cells and interferon production in vitro

The ability of respiratory syncytial virus (RSV) and parainfluenza virus type 3 (PIV3) to replicate in peripheral blood monocytes cultured in vitro for 1, 2, 4 or 7 days prior to infection was investigated. Inoculation of 1-day old monocytes produced at least tenfold less new virus than infection of the older, more macrophage-like cells for both viruses. PIV3 induced extensive syncytium formation, whereas RSV caused a cytopathic effect manifest by increased rounding of the cells with minimal syncytium formation. Supernatants of infected monocytes were assayed for human interferon-alpha (HuIFN-alpha) in an attempt to explain the restricted viral replication in the youngest monocytes. In PIV3-infected cells, HuIFN-alpha production was inversely correlated with new virus formation. Monocytes infected after 1 day in culture produced 800 IU/ml of HuIFN-alpha; the older cells produced 100 to 200 IU/ml. In contrast, monocytes infected on day 1 with RSV produced minimal amounts (1.5 IU/ml) of HuIFN-alpha. Increasing amounts of HuIFN-alpha were detected in cells infected with RSV after 2, 4 or 7 days in culture, reaching a maximum of 400 IU/ml on day 7. Further investigation of the apparent restriction of replication in young monocyte cultures may be helpful in understanding the pathogenesis of these respiratory infections.

Concurrent circulation of antigenically distinct strains of respiratory syncytial virus during community outbreaks

Respiratory syncytial virus (RSV) is considered to be of a single serotype. Antigenic variants are detectable both by neutralization and monoclonal antibodies and have been divided into two broad categories, groups 1 and 2. Group 2 isolates have been considered to be uncommon. We used indirect immunofluorescence with strain-specific monoclonal antibodies to study RSV isolates from hospitalized infants in the greater Boston area. Of 223 RSV isolates recovered over a five-month period in 1983-1984, 125 (56%) were group 1, 92 (41%) were group 2, and 6 (3%) were of an intermediate character. Among 181 community-acquired RSV isolates, both temporal and geographic clustering was observed: group 1 isolates were common from January through March and predominated in central Boston; group 2 isolates were found principally in February and were acquired in outlying, particularly northern, areas. Strain-specific differences were not found with respect to sex, age, or clinical findings. An analysis of 82 RSV isolates from the 1981-1982 season showed 75 (91%) group 1 isolates and 7 (9%) group 2 isolates. We conclude that at least two antigenically distinct groups of RSV isolates may circulate concurrently in the community and that the prevalence of group 2 isolates appears greater than previously suspected.

Comparison of washed nasopharyngeal cells and whole nasal secretions for detection of respiratory syncytial virus antigens by enzyme-linked immunosorbent assay

We compared washed nasal epithelial cells with unfractionated nasal secretions as sources of respiratory syncytial virus (RSV) antigens in an indirect enzyme-linked immunosorbent assay (ELISA). Of 28 infants positive for RSV by virus isolation or direct immunofluorescence or both, 27 (96%) were positive by ELISA with whole nasal secretions, whereas only 19 (68%) were positive by ELISA with the matching washed-cell fractions. Furthermore, the ELISA absorbances obtained with nasal secretions were significantly greater than those seen with washed-cell fractions, indicating that whole nasal secretions contain relatively greater amounts of RSV antigens as measured by ELISA.

Quantification of respiratory syncytial virus polypeptides in nasal secretions by monoclonal antibodies

An indirect enzyme-linked immunosorbent assay (ELISA) which uses monoclonal antibody as solid-phase immunosorbent was developed to measure specific polypeptides of respiratory syncytial virus (RSV). The assay was used to examine 43 nasopharyngeal (NP) aspirates from RSV-positive infants that had been examined previously for RSV by culture, direct immunofluorescence, and polyclonal antibody ELISA. Frozen NP aspirates were serially diluted and examined for the 66K mol. wt. fusion glycoprotein (F), the 84K large surface glycoprotein (G) and the 41K nucleoprotein (N) by monoclonal capture ELISA. F protein was detected in all 43 specimens, G protein was detectable in 20 (47%) and N protein in 22 (51%) of 43 NP aspirates. In specimens with detectable G and N proteins, F was detected by endpoint titration at approximately tenfold greater dilutions than either G or N. In 19 sequential NP aspirates from five patients with RSV infection, F was present in higher titre throughout infection. In 20 cases, matching cell culture isolates were examined by immunofluorescence with strain-specific monoclonal antibodies. Three of 20 isolates showed strain-specific differences by their lack of reaction with anti-G monoclonal antibody. Titration of the 20 cell culture isolates by monoclonal antibody capture ELISA showed the relative amount of F and N proteins to be equal in all cases, whereas levels of G protein tended to be slightly lower. Reconstruction experiments with NP aspirates demonstrated that degradation of F and N proteins did not occur in NP aspirates, but that G protein antigenicity appeared to be affected by nasal secretions. When compared with cell culture-grown material, nasal secretions contained abundant F protein but a surprisingly low concentration of N protein.

Antigenic characterization of respiratory syncytial virus strains with monoclonal antibodies

To study the antigenic characteristics of respiratory syncytial virus (RSV), we developed and evaluated monoclonal antibodies (MAbs) to three strains of RSV: 11 to Long, 4 to 18537, and 9 to A2. Six of these MAbs immunoprecipitated the nucleoprotein, six the large glycoprotein, and 11 the fusion protein. By the pattern of the reactions of these MAbs to 16 strains of RSV in an indirect immunofluorescence assay or enzyme-linked immunosorbent assay, we were able to distinguish three subgroups. With a panel of 10 of these 24 MAbs, we tested 26 strains isolated between 1979 and 1982 in Boston and found that 22 belonged to group 1, 4 to group 2, and none to group 3. The pattern of the reactions of the MAbs against representative strains from the three groups identified nine epitopes by indirect immunofluorescence assay: three of each on the nucleoprotein, the large glycoprotein, and the fusion protein. These results, along with those of previous studies, suggest that groups 1 and 3 are antigenically similar and group 2 is antigenically more distinct.

Monoclonal capture antibody ELISA for respiratory syncytial virus: detection of individual viral antigens and determination of monoclonal antibody specificities

An enzyme-linked immunosorbent assay (ELISA) for respiratory syncytial virus (RSV) that employs solid-phase monoclonal antibodies was developed. RSV antigens bound by these monoclonal capture antibodies were detected by addition of a polyclonal bovine antiserum, followed anti-bovine enzyme conjugate and enzyme substrate. The sensitivity and specific of the assay were determined by titrations of the solid-phase antibodies and by antigen titrations with both unpurified RSV-infected cell culture material and purified RSV nucleocapsids. The addition of a competitive binding step prior to the addition of antigen to the solid-phase antibody provides further evidence of the assay's specificity. Furthermore, the competitive binding assay enables the antigen specificity of monoclonal antibodies to be determined or compared without the use of purified antigens. Monoclonal capture ELISA is a convenient, rapid, and sensitive assay that can be used to measure specific RSV antigens in unpurified preparations as well as to determine anti-RSV antibody specificity and should prove useful in examining other complex antigen-antibody systems.

Comparison of enzyme immunoassay with radioimmunoassay for the detection of hepatitis B surface antigen

A direct solid-phase enzyme immunoassay (Auszyme I) and a direct solid-phase radioimmunoassay (Austria II) for detection of hepatitis B surface antigen (HBsAg) were compared in tests with a panel of 347 human sera. Compared with RIA, EIA showed a sensitivity of 98% with 153 HBsAg-positive sera and a specificity of 99% with 194 HBsAg-negative sera. Sera that gave false negative and false positive results by EIA were re-examined by both RIA and EIA to confirm the initial result. Use of less than the recommended volume of serum for EIA produced results inconsistent with RIA in four of 27 sera examined. Quantitative correlation between RIA and EIA was low (r = 0.691). Positive controls used for EIA showed considerable variation from day to day, although intra-assay variation was much less. The sensitivity of the EIA method examined compares favourably with previously published EIA studies and with the RIA used in this study. Auszyme I EIA is a sensitive and specific third generation test for HBsAg that offers several advantages over currently used RIA techniques.

Detection and identification of influenza virus antigens by nylon-coupled enzyme-linked immunoassay

A direct solid-phase enzyme-linked immunoassay for rapid detection and typing of influenza virus was developed utilizing antibodies immobilized by covalent linkage to nylon beads. Covalent linkage of antibody to nylon was accomplished by treatment of partially hydrolyzed nylon with glutaraldehyde. For comparison to conventional enzyme-linked immunosorbent assays (ELISA), IgG fractions were adsorbed to polystyrene beads. Influenza type-specific immunoglobulins coupled to nylon beads were used in an enzyme-linked immunoassay to identify influenza A/USSR/77(H1N1), and A/Texas/75 (H3N2). In titrations of viral antigen, antibody coupled to nylon beads detected 1.9 X 10(4) plaque-forming units (PFU) per assay, whereas 2.2 X 10(5) PFU were required in assays utilizing antibody adsorbed to polystyrene beads. Use of fluorogenic or radioactive substrates for alkaline phosphatase-labeled antibodies increased the sensitivity for virus detection 10-fold with this enzyme, but were only slightly more sensitive than chromogenic substrates with peroxidase-labeled antibody.

Enzyme-linked immunosorbent assay for detection of respiratory syncytial virus infection: development and description

An indirect enzyme-linked immunosorbent assay for detection of respiratory syncytial virus (RSV) antigens was developed, using commercially available antisera. Horse anti-RSV and calf antiserum to bovine RSV were used as capture and detector antibodies, respectively. The assay could detect as few as 50 PFU of unpurified RSV per ml in infected cell culture supernatant fluids and as little as 10 ng of affinity-purified RSV antigen per ml. No cross-reactions were observed with heterologous virus types. Freeze-thaw treatment had no effect on RSV enzyme-linked immunosorbent assay titers, but viral transport medium inhibited RSV enzyme-linked immunosorbent assay titers from 10- to 100-fold. The assay can be easily performed in 24 h and is a sensitive and specific method for the detection of RSV antigens.

Enzyme-linked immunosorbent assay for detection of respiratory syncytial virus infection: application to clinical samples

An enzyme-linked immunosorbent assay (ELISA) for respiratory syncytial virus antigens was applied to the rapid diagnosis of acute infections in children and was compared with viral culture and immunofluorescence tests. The ELISA test employed commercially available reagents and was run on a day-to-day basis as specimens were received in the laboratory. Sensitivity and specificity by ELISA were 82 and 95%, respectively, compared with culture. In the same specimens, the sensitivity and specificity by immunofluorescence were 86 and 96%, respectively. Nasopharyngeal aspirates were proven to be a better source of viral antigen than were nasopharyngeal swabs. ELISA-positive samples remained positive even when left unrefrigerated for a week or mailed to the laboratory in plastic containers. Respiratory syncytial virus ELISA, like culture, became negative as the disease progressed and showed no superiority over culture for diagnosis late in the illness.

Immobilization of antibodies on nylon for use in enzyme-linked immunoassay

Antibodies were immobilized by covalent linkage on nylon balls and powder for use in solid-phase enzyme-linked immunoassays. Covalent linkage of antibody to nylon was accomplished by treatment of partially hydrolyzed nylon with glutaraldehyde or carbodiimides. Up to 0.74 microgram of immunoglobulin G per mm2 nylon could be immobilized, whereas only 0.02 microgram per mm2 could be adsorbed to polystyrene, and the binding to nylon was stable. This eliminated the problem of antibody desorption noted in conventional enzyme-linked immunosorbent assay which are based on simple adsorption to plastics, and gave more reproducible results. The method was also more sensitive, detecting levels of approximately 1 ng per ml of immunoglobulin E in clinical samples. Further, antibodies coupled to nylon balls remained bound under conditions that dissociate antibody-antigen complexes, which permitted reuse of the immobilized antibodies for immunoassays.

Factors involved in enzyme-linked immunoassay of viruses and evaluation of the method for identification of enteroviruses

A quantitative enzyme-linked immunosorbent assay was used for identification of selected enteroviruses: poliovirus type 1, echovirus type 6, coxsackievirus A type 9, and coxsackievirus B types 1 through 6. Partially purified viral antigens or virus-specific antibodies were adsorbed to polystyrene spectrophotometer cuvettes, which permitted the assays to be reported and compared in terms of enzyme units specifically reacting. Both the adsorbed antigen and the adsorbed antibody methods were approximately equal in terms of sensitivity and specificity of reaction. By use [14C]leucine-labeled enteroviruses, the amount of virus that bound to the plastics used was shown to be dependent on the purity of the virus preparation used, but it was higher than the amount that was bound by plastics coated with viral antibody. Diluents which contained 0.15% (vol/vol) Tween 20 and 2.0% (wt/vol) bovine serum albumin in phosphate-buffered saline, pH 7.2, were found to be the most effective in inhibiting nonspecific adsorption of immunoreagents. However, the presence of these inhibitors in phosphate-buffered saline solutions also caused desorption of virus or viral antibody during immunoassays; the amount of virus desorption varied with the type of preparation used, and antibody desorption was dependent on the concentration of antibody initially used for adsorption. For specific identification of a given enterovirus type by the enzyme-linked immunosorbent assay method used, approximately 10(5) plaque-forming units of virus per assay tube were required.