Homotypic Antibody Research Articles

Anti-rotavirus G type-specific and isotype-specific antibodies in children with natural rotavirus infections.

Serum VP7 (G) type- and isotype-specific anti-rotavirus antibodies were assessed among children monitored longitudinally over one or two rotavirus seasons in day care centers. Seventy-five pairs of blood specimens from 63 children were tested for anti-rotavirus antibodies. Stool specimens were collected weekly and tested for rotavirus antigen. G typing of detected rotaviruses showed that seven outbreaks of G1 and one of G3 occurred during the two seasons. G type-specific responses to the outbreak strain occurred among 79% of infected children and 9% of children with infection not detected (P < .001). Of children infected with G1, 54% had a heterotypic response; they were older (P = .048) and had higher preexisting G1 antibody levels than children who had only homotypic responses (P = .012). Higher IgA, IgG, and homotypic antibody levels to the antigenic site C of the G1 and G3 VP7s correlated with protection against infection and illness, homotypic antibody independently of IgA or IgG titers.

Homotypic and heterotypic immune responses to group A rotaviruses in parenterally immunized sheep

Immune responses to human rotaviruses were investigated in sheep with a view to obtaining antibodies for passive immunotherapy of humans. Eighteen adult sheep with previous natural exposure to rotavirus serotypes G3 and G6 were immunized parenterally with purified preparations of either individual rotavirus serotypes G1, G2, G3, G4 and G8, or a mixture thereof. Two additional sheep were kept as control animals with the flock. The antibody responses were measured on serial serum samples by neutralization tests. The homotypic antibody response ranged from 100-fold (rarely) up to 100,000-fold increases in titre. Heterotypic responses against serotypes G3 and G6 were demonstrated in 7/12 and 15/18 sheep, respectively, but the increases in titre were lower than the homotypic responses, ranging from 10- to 100-fold in most cases and were 1000-fold in two sheep. Interestingly, no heterotypic response against the human rotavirus serotypes was raised after 3 months; moderate titres of cross-neutralizing antibodies for the human serotypes were only observed after a third inoculation.

Characterization of serum antibody responses to natural rotavirus infections in children by VP7-specific epitope-blocking assays.

Knowledge of the immune response to rotavirus is crucial for vaccine development. We compared an epitope-blocking assay (EBA) that uses VP7-specific monoclonal antibodies with neutralization assays (NAs) with polyclonal antisera for detecting serum antibody responses after natural rotavirus infection in children. Twenty-six serum pairs from children living in an orphanage with and without symptoms during two rotavirus outbreaks were evaluated for VP7 type 1-, 2-, 3-, and 4-specific antibody responses. In the first outbreak, which was caused by a VP7 type 3 strain, homotypic antibody responses were detected in 11 of 11 symptomatic children by NA and in 10 of 11 symptomatic children by EBA. Heterotypic antibody responses were detected more frequently (12 of 15 children) by NA than by EBA, and the heterotypic epitope-blocking antibody responses occurred in children older than 14 months of age. Antibody responses in asymptomatic children were more commonly detected by EBA than by NA. EBA results from the sera of children in the second outbreak indicated that it was caused by VP7 type 4, whereas NA results suggested it was caused by VP7 type 3. Our results confirm that EBA is a sensitive and specific method for determining VP7 type-specific immune responses after natural rotavirus infections.

Homotypic antibody responses to fresh clinical isolates of human immunodeficiency virus

Human immunodeficiency virus type 1 (HIV-1) exhibits extensive genomic and antigenic diversity, which is thought to contribute to the failure of the host's immune response to control infection and prevent clinical progression. Part of this failure may be due to utilization by the virus of antigenic variation as a means to escape protective immune responses. Antibody-escape variants of HIV-1 were studied here using fresh clinical isolates and autologous plasmas. HIV-1 was isolated from the plasma of seven people who were all seropositive for at least 2 years, and symptomatic sometime during that period. Isolated viruses were confirmed as HIV-1 by the presence of reverse transcriptase activity in infected culture supernatants, and by positive immunofluorescence using human monoclonal antibody to HIV-1 core protein. Plasma from these people were positive by Western immunoblot (DuPont) for most major HIV-1 (strain IIIB) antigens. These plasmas neutralized three laboratory strains of HIV-1 (i.e., IIIB, RF, and MN) but did not neutralize the homotypic strain in five cases, and had greatly reduced neutralizing titers against the homotypic strain in two cases. Homotypic neutralizing antibodies were absent in autologous plasma obtained 3 months later. When antibody titers were measured by fixed-cell indirect immunofluorescence assays (IFAs), high titers of IgG (1:6400 to 1:25,600) were detected against HIV-1 IIIB, while low titers of only 1:20 to 1:160 were detected against homotypic viral antigens at the time of virus isolation, and remained low 12 and 16 weeks later. No class IgA, IgD, IgE, or IgM antibodies to homotypic viral antigens, as possible IgG-blocking antibodies, were detected by fixed-cell IFAs. Cross-reactions with heterologous donor's plasmas were observed in some cases, and in these cases the cross-reactions were unidirectional. Live-cell IFAs detected IgG in patient's plasma to HIV-1 IIIB-infected cells but not to cells infected with homotypic isolates. These results suggest that it is common for neutralization-resistant HIV-1 variants to appear during the course of infection, and that all or most antigens of these variants are capable of escaping antibody recognition.

Homotypic and heterotypic serum and milk antibody to rotavirus in normal, infected and vaccinated horses

The homotypic and heterotypic antibody response to rotavirus was determined in three pony mares and their foals. The normal concentrations of anti-rotavirus antibodies in mares ‘milk and mares’ and foals′ serum over the first 10 weeks post-partum were measured using IgA, IgG and rotavirus sero-type-specific enzyme linked immunosorbent assays. Experimental infection of the foals with serotype 3 equine rotavirus produced a rapid, serotype-specific response which peaked 10 days after infection and a slower heterotypic response which peaked 32 days later. In contrast, vaccination of the mares with an inactivated, adjuvanted serotype 6 bovine rotavirus produced a heterotypic response similar to that of the homotypic response in both serum and milk, although the predominant response in serum was IgG, while in milk it was IgA. These results suggest that non serotype-restricted passive protection of foals against rotavirus may be achieved by parenteral vaccination of mares.

Homotypic serum antibody responses to rotavirus proteins following primary infection of young children with serotype 1 rotavirus

The class-specific antibody responses to serotype 1 rotavirus structural proteins were examined by immunoblotting with sera obtained from young children hospitalized with acute rotavirus diarrhea caused by serotype 1. All were believed to be primary infections. Three consecutive samples were obtained from 16 patients during the acute and convalescent phases of the disease and then approximately 4 months later. Immunoglobulin G (IgG)-class antibody responses to two inner capsid proteins (VP2 and VP6) and to the major homologous outer capsid protein (VP7) were detected in all patients. Antibody responses to VP6 were rapid, increased in intensity during 20 to 40 days after the onset of symptoms, and persisted for more than 4 months. Responses to VP2 and VP7 were more delayed, were maximal in convalescent-phase sera, and decreased markedly in intensity 4 months after the onset of symptoms in the majority of children. Two patients with evidence of mixed infection showed persisting high levels of antibody to VP7. Responses to the outer capsid protein VP4 were detected in 67% of patients, peaked at 20 to 40 days after the onset of symptoms, and were no longer detected at 4 months in the majority of patients. It is likely that the immunoblotting technique underestimated responses to VP4. Acute- and convalescent-phase sera (known to contain antirotavirus IgM or IgA measured by enzyme immunoassay) were also examined by immunoblotting. IgM- and IgA-class antibody responses to viral proteins VP2, VP4, and VP7 appeared to be qualitatively identical to those observed for IgG in the same serum samples.

Group- and Type-Specific Serologic Response in Infants and Children with Primary Rotavirus Infections and Gastroenteritis Caused by a Strain of Known Serotype

Antibody response to group A rotavirus (RV), investigated in paired sera from 72 infants and young children with acute gastroenteritis caused by an RV infection, was diagnosed on the basis of a fourfold or greater rise in group A common RV IgG antibody titer. Virus-specific IgM was detected in sera from 64 patients showing seroconversion; these were considered primary infection. RV was detected in stools of 56 (77.8%) patients with serologic evidence of infection and 54 were considered primary infection isolates: 39, serotype 1; 11, serotype 4; and 2, serotype 2. Two could not be typed. Neutralizing antibody studies showed that in primary infections serotype 1 induced an antibody response to serotype 4 at least fourfold lower than the homotypic response; serotype 2 elicited antibody titers to serotypes 1 and 4 at least fourfold lower than homotypic titer; and serotype 4 infections produced a response to serotype 1 as high as the homotypic response. Of 12 patients with primary infection, virus was not typed in 2 or detected in 10; however, the infecting serotype was identified on the basis of distinct patterns of homotypic and heterotypic antibody response.

Homotypic and Heterotypic Epitope-Specific Antibody Responses in Adult and Infant Rotavirus Vaccinees: Implications for Vaccine Development

Sera from infants and adults who received a live, attenuated monovalent rotavirus vaccine of serotype 1, 2, 3, or 4 VP7 specificity and rhesus rotavirus (RRV) VP4 specificity were analyzed for serotype-specific antibody responses by an epitope blocking immunoassay (EBA) and by neutralization. Although the assays correlated well, responses to the individual neutralization proteins or to different defined antigenic sites on the same protein could be distinguished only by EBA. In general, adult vaccinees exhibited both a homotypic response to the immunizing strain and a heterotypic response to other serotypes. Infant vaccinees less than 6 months old also had a homotypic antibody response but developed significantly fewer heterotypic responses than adults (1.2% and 59%, respectively; P less than .0001). In addition, postvaccination sera from vaccinees who developed naturally occurring rotavirus diarrhea during an efficacy trial of RRV (MMU-18006) or RIT 4237 vaccine were analyzed for serotype-specific responses. The data suggest that the inability to mount a heterotypic antibody response to the infecting serotypes in young infants may have been an important factor in failure of the vaccines to induce protection.

RHINOVIRUSES IN SEATTLE FAMILIES, 1975–1979

Rhinovirus infections in Seattle families with schoolchildren (1975-1979) and in selected outpatients were revealed by virus shedding or antibody rise. These observations extend those in the Seattle Virus Watch (1965-1969). Analysis of rhinovirus serotype prevalence again revealed certain "common" persisting serotypes but provided no further evidence that new serotypes are continuing to emerge. Two seasonal peaks, spring higher than fall, were again evident. Infection rates, again inversely related to age, were lower overall than in the Virus Watch (0.42 vs. 0.64 per person-year), probably because there were fewer young children. Frequencies of antibody response by virus shedders again varied widely by serotype but differed greatly from those in the Virus Watch in rank order of response rate, suggesting that immunogenicity is not a stable serotype characteristic. The frequency and magnitude of antibody response of virus shedders increased with age. Antibody-related protection against infection was evident only in persons age greater than or equal to 10 years. Observations in 7 families during successive homotypic infection episodes indicate that postinfection immunity to natural challenge requires persistence of antibody. Of all reported respiratory illness, 11.9% (0.31 per person-year) were due to rhinoviruses and 6.9% to influenza viruses. Of viruses recovered from family members, rhinoviruses, herpes simplex, and influenza comprised 56%, 12.6%, and 12.4%, respectively. Although households often experienced greater than or equal to 2 concurrent or closely consecutive episodes of infection with different viruses, only 29 individuals were shown to shed 2 viruses at the same time. Most of the second viruses, include 3 rhinoviruses and 18 other nonhemadsorbing viruses, appeared when 582 rhinovirus-positive specimens were retested after treatment with homotypic antibody. These results suggest that rhinoviruses interfere with nonhemadsorbing viruses in cell culture but mostly with other rhinoviruses in humans.

Immunologic responses of children to serious infections with Streptococcus pneumoniae.

Antibody responses (as measured by radioimmunoassay), alterations in serum levels of complement, and the presence of circulating immune complexes (as measured by the fluid-phase C1Q-binding assay, the fluid-phase conglutinin assay, and the activation of C1 were evaluated in 15 children after meningitis and/or bacteremia caused by Streptococcus pneumoniae. The ages of the children ranged from two months to 16 years; the duration of follow-up ranged from 18 to 189 days (mean, 78 days). Increases in levels of homotypic antibody were found in only three (25%) of the 12 children in whom this response could be assessed, and all of these responses were transient. Eight (53%) of the 15 children had evidence of a heterotypic antibody response to S pneumoniae serotypes other than those causing their infections. The activation of C1 and C1q-binding activity were detected at the early stage of disease and were generally transient. The result of the fluid-phase conglutinin assay was positive for 14 (93%) of the 15 children later in the course of disease; this result was consistently positive throughout the follow-up period in the majority of children. Depressed concentrations of C4 were noted in nine children, depressed levels of C3 in four, and depressed levels of factor B in two.

Antigenic drift in visna: virus variation during long-term infection of Icelandic sheep.

A group of 20 Icelandic sheep were infected intracerebrally with visna virus strain 1514, and 209 virus isolates were obtained from the blood, cerebrospinal fluid, and central nervous system (CNS) over a period of 7 years, during which eight animals developed clinical signs of visna necessitating sacrifice. (i) Using type-specific antisera, it was found that 12 (16%) of 76 isolates tested escaped neutralization. These 12 variant viruses were distributed randomly among animals and over time, and did not replace the infecting strain even though all sheep developed homotypic antibody within 3 months of infection. The one exception was sheep no. 1557 (an animal without clinical visna), where the last six isolates were variants. (ii) A total of 35 blood and CNS isolates from seven of these sheep (including five with clinical visna) were tested against serial samples of their own sera. Autologous antisera neutralized all isolates tested with the exception of isolates from sheep 1557. None of the isolates obtained at sacrifice from the five sheep with clinical visna escaped neutralization with autologous antisera. These data suggest that although variant viruses are encountered at considerable frequency during long-term infection of Icelandic sheep, the variants usually do not replace the infecting strain. Antigenic drift does not appear to be essential for virus persistence or for the development of clinically evident CNS lesions.

Immunological enhancement and the pathogenesis of dengue haemorrhagic fever.

Laboratory studies have provided evidence that the replication of dengue viruses in preparations of primary peripheral blood mononuclear cells of human or simian origin, or in macrophage-like cell lines of human or murine origin, may be enhanced by sub-neutralizing concentrations of homotypic dengue antibody, by heterotypic dengue antibody, or by antibody against heterologous flaviviruses. The mechanism underlying this phenomenon is discussed in the context of dengue haemorrhagic fever and the dengue shock syndrome.

Epidemiologic studies of Streptococcus pneumoniae in infants: antibody response to nasopharyngeal carriage of types 3, 19, and 23.

The relationship between nasopharyngeal carriage of Streptococcus pneumoniae types 3, 19, and 23 and the development of homotypic serum antibody was examined in 17 infants followed prospectively from birth. Serially drawn sera from these children and single serum samples from 18 normal adolescents were assayed for opsonizing antibody using reduction of nitroblue tetrazolium to measure phagocytosis of killed whole pneumococci. Selected sera were also tested for quantitative antibody level by a radioimmunoassay, which correlated quite well with the nitroblue tetrazolium assay. All but one of the adolescents had antibody to type 19, and all 18 had antibody to type 23. None of the 12 infants tested for antibody to type 19 pneumococci showed evidence of an antibody response. Two of 10 infants responded to type 23 pneumococci, as did two of three infants tested to type 3 pneumococci.

Natural infection with influenza A (H3N2). The development, persistence and effect of antibodies to the surface antigens

A technique for estimating antibodies to the neuraminidase antigens of influenza A is described. The antibody response to the haemagglutinin and neuraminidase antigens of influenza A (H3N2) was studied in a boys' public school over the four-year period 1970--4. During this time there were two outbreaks of influenza A and the effect of antibody on the result of natural challenge was investigated. No boy who had homotypic neuraminidase antibody had clinical influenza.

Neutralization of poliovirus: A hypothesis to explain the mechanism and the one-hit character of the neutralization reaction

Poliovirus capsid protein undergoes pH-dependent reversible conformational transitions between state A (isoelectric point about 7) and state B (isoelectric point about 4.5). When virus reacts with homotypic antibody, the virion becomes stabilized in state B. In this respect, the multiplicity of antibody per virion is not a variable factor since the smallest amount of antibody, based on the smallest measurable degree of neutralization, induces the same effect on the virion as a saturating amount. No conformational states intermediate between A and B are seen under any conditions of neutralization. The same result was seen with each antiserum from several rabbits, with human antiserum, with antibody obtained from rabbit serum by ammonium sulfate precipitation, with IgG and IgM types of antibody, and with the Fab fragment of rabbit antibody. Although small differences in isoelectric points exist among the different serotypes of poliovirus, they share the basic observations, namely, the property of conformational transitions, and stabilization in the B-state upon reacting with homotypic antibody. Failure to be stabilized in the B-state was found not to be the underlying cause for nonneutralizability. A system has been developed for in vitro uncoating of poliovirus. The essential component of the system is an extract of HeLa cell plasma membrane. It was found that neutralized virus is resistant to uncoating in this system. Based on the above results an attempt has been made to explain both neutralization and its one-hit characteristic in terms of conformational transitions and cooperativity among the capsid subunits.

Type specificity of complement-requiring and immunoglobulin M neutralizing antibody in initial herpes simplex virus infections of humans.

Studies comparing the enhancing effect of guinea pig complement on homotypic and heterotypic neutralizing antibodies produced in initial herpes simplex virus (HSV) infections of humans indicated that antibodies to HSV type 1 and HSV type 2 were enhanced to about the same extent, and there was no signigicant difference in the degree to which complement enhanced homotypic and heterotypic HSV-neutralizing antibody. Homotypic and heterotypic immunoglobulin G neutralizing antibodies were enhanced by complement to as great, or greater, an extent as immunoglobulin M (IgM) HSV antibodies in the same sera. In patients with initial HSV type 1 infections, the IgM neutralizing antibody response was type specific. On the other hand, patients with initial HSV type 2 infections produced both homotypic and heterotypic IgM neutralizing antibody. An initial HSV type 2 infection in an individual previously infected with HSV type 1 elicited the production of IgM neutralizing antibody to both HSV type 1 and HSV type 2. However, patients with recurrent HSV type 1 infections failed to produce IgM antibody to either HSV type during reactivation of the virus.

Spread of Streptococcus pneumoniae in Families. II. Relation of Transfer of S. pneumoniae to Incidence of Colds and Serum Antibody

Factors that affect the spread of Streptococcus pneumoniae and the antibody responses associated with colonization were studied in 64 families for periods of eight to 52 weeks. Surveillance included daily recording of respiratory symptoms and bimonthly pharyngeal cultures for identification of the pneumococcal carrier state. Rhinovirus cultures were included for a portion of the study period. Intrafamilial carriage of a single type of S. pneumoniae and simultaneous spread to more than one family member were commonmspread often occurred in association with an upper respiratory tract infection; simultaneous transmission of S. pneumoniae and a rhinovirus was documented. Preexisting, type-specific serum antibody did not prevent acquisition of homotypic S. pneumoniae but did appear to shorten the duration of pharyngeal carriage. Sera of all 11 adults had greater than 150 ng of antibody nitrogen/ml of homotypic serum antibody (measured by a radioimmunoassay) before colonization. In contrast, only one of 13 preschool children had homotypic antibody concentrations of this magnitude before colonization. A threefold or greater rise in the concentration of homotypic antibody occurred in 13 of 24 children (54%) after acquisition of S. pneumoniae; the increase in antibody concentration was associated with illness in six of the children. On the other hand, acquisition of S. pneumoniae in adults was not associated with an increase in concentration of homotypic serum antibody.

EXPERIMENTAL REOVIRUS INFECTION IN MONKEYS: II. SEROLOGIC STUDIES1

Groups of bonnet monkeys (Macaca radiata) were experimentally infected with the three serotypes of reoviruses. Reovirus types 1 and 2 induced the production of high levels of homotypic hemagglutination-inhibiting antibody in all monkeys and, in addition, heterotypic antibodies to the other two serotypes in some. Type 3 virus induced only homotypic antibody response. A second infection with type 3 virus also induced only a homotypic response. In monkeys previously infected with reovirus type 2, type 3 infection caused a fourfold or greater rise in type 3 antibody but no enhancement of type 1 or 2 antibody. In monkeys previously infected with reovirus type 3, type 2 infection induced the production of antibodies reactive to types 1 and 2 in some, but no rise of type 3 antibody in any. In monkeys previously infected with type 1, type 3 infection induced a fourfold or greater rise in antibody to all three serotypes. Among those previously infected with type 3, type 1 infection caused an enhancement of antibodies to types 1 and 3 in all and to type 2 in a few.

Parenteral inactivated rhinovirus vaccine: minimal protective effect.

SummaryAn inactivated preparation of rhinovirus type 13 administered subcutaneously to 29 antibody-free volunteers in three 1.0-ml doses at two week intervals resulted in rapid appearance of high titers of homotypic serum neutralizing antibody in 100% of volunteers. Parallel responses were observed in 17 other volunteeers with preexisting antibody. Antibody in nasal secretions was detected in 38% and 59% of vaccinees, respectively. Challenge of 14 vaccinees with 3 TCid50 of live rhinovirus type 13 resulted in similar rates of infection and illness, as compared to 13 nonvaccinated controls, but there was significant reduction in virus shedding, severity of illness and duration of illness in the vaccinees.We wish to thank Terrel D. Hutto, Warden, Clive Aldridge and Hudie Cottrell, Medical Officers, Ramsey Unit, Texas Department of Corrections, for their help in the volunteer program; Peggy Kleyle for her technical work; and Dr. David Alling for the statistical tests.

A Sensitive Neutralization Test for the Adeno-Associated Satellite Viruses

Abstract A highly sensitive neutralization test for the four satellite serotypes was developed by selecting particularly effective combinations of adenovirus helper and cell system. Neutralizing antibody titers were measured by inhibition of satellite replication as assayed in terms of complement-fixation-producing units (CFPU) of virus. Neutralizing antibody measured by this method was more type-specific, and the antibody titers were much higher than those obtained by the direct complement-fixing antibody test. Homotypic neutralizing antibody titers of 103 were common, and in some instances titers as high as 106 were observed. The neutralizing activity against satellite virus was found to reside in the λ globulin fraction of post-infection human and post-immunization rabbit sera. The frequency of individuals with neutralizing antibodies but without CF antibodies suggests that the CF antibody titer falls off more rapidly than the neutralizing titer. Both neutralization and CF tests revealed significant intertypic crossing, especially between types 2 and 3.