Binding Antibody Responses Research Articles

Development of a Surface Plasmon Resonance–Based Immunoassay for Listeria monocytogenes

A polyclonal antibody was produced against Internalin B (InlB)–enriched extract and used to develop an inhibition assay to detect Listeria monocytogenes cells in solution using surface plasmon resonance. The gene sequence encoding for the InlB protein was cloned into a Qiagen pQE-60 vector, expressed in Escherichia coli, and purified by immobilized metal affinity chromatography. Protein G–purified anti-InlB–enriched extract polyclonal antibody was incubated with various concentrations of L. monocytogenes cells and subsequently injected over a purified-recombinant InlB (rInlB)–immobilized CM5 sensor chip surface. A decrease in antibody binding response was observed with increasing L. monocytogenes cell concentrations. Intraday and interday assay variability studies were carried out to evaluate precision and reproducibility. The assay had a limit of detection of less than 2 × 105 cells per ml and could be successfully reproduced with coefficients of variation of between 2.5 and 7.7%.

Correlation between Immunologic Responses to a Recombinant Glycoprotein 120 Vaccine and Incidence of HIV‐1 Infection in a Phase 3 HIV‐1 Preventive Vaccine Trial

An objective of the first efficacy trial of a candidate vaccine containing recombinant human immunodeficiency virus (HIV) type 1 envelope glycoprotein 120 (rgp120) antigens was to assess correlations between antibody responses to rgp120 and the incidence of HIV-1 infection. Within the randomized trial (for vaccinees, n=3598; for placebo recipients, n=1805), binding and neutralizing antibody responses to rgp120 were quantitated. A case-cohort design was used to study correlations between antibody levels and HIV-1 incidence. Peak antibody levels were significantly inversely correlated with HIV-1 incidence. The relative risk (RR) of infection was 0.63 (95% confidence interval, 0.45-0.89) per log(10) higher neutralization titer against HIV-1(MN), and the RRs of infection for second-, third-, and fourth-quartile responses of antibody blocking of gp120 binding to soluble CD4 versus first-quartile responses (the lowest responses) were 0.35, 0.28, and 0.22, respectively. Despite inducing a complex, robust immune response, the vaccine was unable to reduce the incidence of HIV-1. Two interpretations of the correlative results are that the levels of antibodies (i) caused both an increased (low responders) and decreased (high responders) risk of HIV-1 acquisition or (ii) represented a correlate of susceptibility to HIV-1 but had no causal effect on susceptibility. Although the data cannot definitively discriminate between these 2 explanations, (ii) appears to be more likely.

Humoral immunity to HIV-1: kinetics of antibody responses in chronic infection reflects capacity of immune system to improve viral set point

AbstractWe analyzed the humoral immune response in 46 patients following structured treatment interruption (STI) to investigate the general potential of therapeutic vaccination in chronic HIV-1 infection. Evoked antibody titer increases to glycoprotein 120 (gp120) and p24 were low during 4 short-term STIs and only reached significance during a fifth long-term interruption. Although induction of binding antibodies to viral antigens was not associated with potent suppression of viremia, we observed that individuals with a rapid and high response to p24, and to a lesser extent also to gp120, lowered their viral set points significantly. Of note, the increase of the anti-p24 response correlated with specific CD4 T helper frequency to this antigen. Despite induction of binding antibody responses, which correlated with improved viral control, the increase in neutralizing activity was marginal and did not lead to this enhanced viral suppression. However, a subgroup of patients who potently suppressed viremia independently of STI had significantly higher pre-existing neutralization titers, suggesting a role of humoral immunity in conferring potent protection. In summary, measuring the kinetics of antibody responses provided a marker to validate the responsiveness and capacities of the immune system of HIV-1-infected individuals and reflected the patients' ability to decrease viral set points. (Blood. 2004;104:1784-1792)

Evaluation of the safety, immunogenicity, and protective efficacy of whole inactivated simian immunodeficiency virus (SIV) vaccines with conformationally and functionally intact envelope glycoproteins.

A novel, general approach to chemical inactivation of retroviruses was used to produce inactivated simian immunodeficiency virus (SIV) particles with functional envelope glycoproteins. Inactivated virions of three different virus isolates (SIVmne E11S, SIVmac239, and SIVmac239 g4,5), prepared by treatment with 2,2'-dithiodipyridine (aldrithol-2, AT-2), were not detectably infectious, in vitro or in vivo. Immunization of pigtailed macaques with inactivated SIVmne E11S particles, without adjuvant, induced both humoral and cellular immune responses. Four of six animals immunized with the inactivated particles did not show measurable SIV RNA in plasma (<100 copy Eq/ml) following intravenous challenge with pathogenic, homologous virus (SIVmne E11S), compared to peak values of > or =10(6) copy Eq/ml in challenged SIV-naive control animals (p = 0.0001). Despite the absence of measurable viral RNA in plasma in these animals, culturable virus and viral DNA were initially detectable in blood and lymph node specimens; in contrast to control animals, SIV DNA could no longer be detected in PBMC by 10 weeks postchallenge in five of six SIV-immunized animals (p = 0.0001). However, vaccines did not resist a sequential rechallenge with the heterologous pathogenic virus SIVsm E660. AT-2-inactivated virus with functional envelope glycoproteins is a novel class of vaccine immunogen and was noninfectious, under conditions of rigorous in vivo challenge, and induced both binding and neutralizing antibody responses, along with cellular immune responses. Results suggest that immunization facilitated effective containment of pathogenic homologous challenge virus. With further optimization, AT-2-inactivated viral particles may be a useful class of immunogen in the development of a vaccine to prevent AIDS.

Independent but not synergistic enhancement to the immunogenicity of DNA vaccine expressing HIV-1 gp120 glycoprotein by codon optimization and C3d fusion in a mouse model

The ability to elicit humoral and cell-mediated immune (CMI) responses from DNA immunization by combinational use of codon optimization and C3d component of complement was evaluated in this study. DNA vaccines that express either the wild type or the codon optimized gp120 gene coding for the envelope (Env) glycoprotein of human immunodeficiency virus (HIV-1) from the primary isolate JR-FL strain were compared to the same forms fused to three tandem copies of the murine C3d genes. Either codon optimization or C3d fusion alone was effective at generating early appearance, higher binding and neutralizing antibody responses. We also observed that cell-mediated immune responses against HIV Env could also be enhanced by C3d fusion. However, for both humoral and CMI responses, there were no synergistic effects when the combination of codon optimization and C3d fusion was employed.

Long-term memory B-cell responses in recipients of candidate human immunodeficiency virus type 1 vaccines

The efficacy and practical application of human immunodeficiency virus type 1 (HIV-1) vaccines may depend in part on the longevity of the immune responses generated, particularly those in the memory compartment. Candidate vaccines based on the HIV-1 envelope glycoproteins generate binding and neutralizing antibodies in humans but there have been no prior studies on the long-term persistence and recall of those responses. We evaluated six healthy, HIV non-infected adults who had received a combination of recombinant canarypox HIV-1 vaccines boosted by gp120 and who had achieved a high serum titer of neutralizing antibody to HIV-1 MN. These individuals were administered a gp160 boost 4–5 years after their last vaccination. Four volunteers had detectable binding and neutralizing antibodies at the time of boosting and all six volunteers exhibited a recall binding and neutralizing antibody response. The antibodies neutralized multiple T cell line-adapted (TCLA) strains of virus, including the vaccine strain, but not primary isolates. These results demonstrate that memory B-cell responses can last for many years following HIV-1 envelope glycoprotein immunization. In principle, similar long-term memory may be possible with improved immunogens that generate broadly cross-reactive neutralizing antibodies.

Sensitivity and specificity of isolated antigen fromPlasmodium falciparum culture supernatant.

Immunological sensitivity and specificity properties of isolated Plasmodium falciparum (GPL) antigen from culture supernatant have been measured and compared with malarial antigens and non malarial filtered paper blood sera for potency and efficacy. Latex bead coded GPL, Pf and RESA antigens immunoreaction properties of human filter paper blood samples (FPB) were studied by laser light scattering immunoassay (LIA) and Enzyme linked immunoabsorbent assay (ELISA) techniques. Results of GP. antigen sensitivity study by LIA method showed a very high malaria antibody binding response (MABR) i.e. 6% compared with 78% with RESA and 88% Pf antigens. Malaria detection by ELISA method also found similar results. Specificity study of GPL antigen for different non malarial filter paper blood sera (NMFS) showed no immunoreaction however Pf and RESA antigen showed few positive immunological responses. These results suggest that sensitivity and specificity properties of isolated GPL antigen is better than other antigens.

Induction of Immune Responses and Break of Tolerance by DNA against the HIV-1 Coreceptor CCR5 but No Protection from SIVsm Challenge

An inactivating mutation in the human CCR5 gene reduces the risk of HIV-1 infection in individuals with homozygous alleles. We explored whether genetic immunization would induce an immune response directed to CCR5 structures and if immunological tolerance toward endogenous CCR5 could be broken. We also studied whether this immunization approach could protect cynomolgus monkeys from an infection, with SIVsm, which primarily uses CCR5 as a coreceptor. Epidermal but not intramuscular delivery of the CCR5 gene to mice elicited strong IgG antibody binding responses to CCR5. Intramucosal immunization of cynomolgus macaques with CCR5 DNA followed by boosts with CCR5 peptides induced prominent IgG and IgA antibody responses in serum and vaginal washings. The CCR5-specific antibodies neutralized the infectivity of primary human R5 HIV-1 strains, and the macaque SIVsm but not that of a tissue culture-adapted X4 HIV-1 strain. The consecutive CCR5 gene and CCR5 peptide immunizations induced B- and T-cell responses to peptides representing both human and macaque amino acid sequences of the respective CCR5 proteins. This indicates that tolerance was broken against endogenous macaque CCR5, which has a 98% homology to the human CCR5 gene. After the final boost, the vaccinated monkeys together with two control monkeys were challenged with SIVsm. Neither protection against nor enhancement of SIVsm infection was achieved.

Immunodominant peptide epitopes of allergen, Asp f 1 from the fungus aspergillus fumigatus

Aspergillus fumigatus ribotoxin Asp f 1 is a major allergen with IgE binding activity to serum of a majority of patients with allergic bronchopulmonary aspergillosis (ABPA). The IgE binding epitopes or the T-cell stimulatory peptides of this molecule have not been studied. In the present investigation, we have synthesized linear decapeptides spanning the whole molecule of Asp f 1 and analyzed their IgE binding properties. We have also synthesized peptides based on their possible T-cell stimulatory properties and studied the stimulation of peripheral blood mononuclear cells from ABPA patients and normal controls. Several peptides demonstrated distinct IgE antibody binding response against sera from ABPA patients and proliferative response against peripheral blood mononuclear cells from the patients. From the results, it can be concluded that the carboxy-terminal region of Asp f 1 representing amino acid residues 115–149 involved in both humoral and cell mediated immunoresponses in ABPA.

Repair analysis of promutagenic (+)- anti-BPDE DNA adduct in transcriptionally active sequences of plasmid DNA in Escherichia coli

The extent of formation and repair of promutagenic (+)- anti-BPDE-N 2-dG in transcriptionally active thymidine kinase ( tk) gene insert and vector DNA fragments was assessed in the (±)- anti-BPDE treated plasmid p220- tk within the Escherichia coli hosts of varying repair potential. Polyclonal antibody (BP1), specific for (+)- anti-BPDE DNA adduct, was utilized for quantitative estimation of this bulky lesion in nanograms amounts of membrane transblotted DNA fragments. A carcinogen dose-dependent quantitative antibody binding response, due to selective recognition of the major (+)- anti-BPDE adduct, was seen with various DNA fragments separated by gel electrophoresis. The sensitivity of the immunodetection at 0.2 fmol (+)- anti-BPDE DNA adduct, allowed a linear detection in the range of modification level of 0.64×10 −7 to 86×10 −7 adducts per nucleotide in plasmid DNA. Based on this sensitivity, detection of 0.07 and 0.46 (+)- anti-BPDE DNA adducts in respective tk and vector DNA fragments was achieved upon immunoanalysis of the in vitro modified DNA. Adduct concentration dependent antibody binding was independent of size of the vector or insert fragments. Antibody binding response, to DNA modified in vivo, was dependent upon the dose of (±)- anti-BPDE to plasmid DNA replicating within bacterial hosts. The repair of (+)- anti-BPDE DNA adducts was determined as the loss of antibody binding sites in the specific fragments of plasmid DNA within host E. coli. About 50% of the initial DNA damage was repaired from the individual fragments during 15 min post-incubation in the repair-proficient (wild-type) E. coli cells. Complete adduct removal occurred in approx. 60 min of post-incubation period. A significant (91%) decrease in the survival of mutant ( uvrA − recA −) cells was observed at 4 μM (±)- anti-BPDE treatment without any reduction in the colony forming units in the wild-type cells. On the contrary, no repair was seen in the excision repair-deficient ( uvrA − ) E. coli cells. The results indicate (1) the selectivity of the immunological method and the unique ability of the (+)- anti-BPDE specific antibodies to monitor the direct loss of this promutagenic base lesion from the in vivo modified DNA (2) the role of host excision repair pathway in efficient removal of adducts from bacterial genome determines the survival of the bacterial cells and (3) the repair of (+)- anti-BPDE DNA adducts in episomally replicating, transcriptionally active sequences occur at a rapid rate presumably due to the ease of accessibility of repair enzymes to lesions within DNA.

Mucosal immune responses in four distinct compartments of women infected with human immunodeficiency virus type 1: a comparison by site and correlation with clinical information.

Because mucosal immune responses may be important in protection against human immunodeficiency virus type 1 (HIV-1), HIV-1-specific immune responses at mucosal sites in natural infection were compared. Total antibody concentrations and HIV-1-specific binding antibody responses in four distinct mucosal sites and serum were assessed in 41 HIV-infected and 19 HIV-seronegative women. HIV-1 gp160-specific IgG responses were detected in >99% of mucosal samples in infected subjects, with the highest titers in genital secretions. HIV-1-specific IgA was detected in the majority of endocervical secretions (94%) and nasal washes (95%) but less often in vaginal washes (51%) and parotid saliva (38%). There was no significant correlation between mucosal immune response and most clinical factors. Based on methodologic considerations, frequencies of detection, and HIV-1-specific responses, nasal washes and genital secretions may each provide important measures of HIV-1-specific mucosal immune responses in infected women.

DNA repair in human cells: quantitative assessment of bulky anti-BPDE-DNA adducts by non-competitive immunoassays.

Mutagenicity and carcinogenicity of the ubiquitous environmental pollutant benzo[a]pyrene is mediated via its reactive diol epoxide metabolite, anti-BPDE, with the predominant formation of N(2)-deoxyguanine adducts in genomic DNA. Polyclonal and monoclonal antibodies specific for (+/-)-anti-BPDE DNA adducts were used for the quantitative detection of genotoxic damage in DNA treated in vitro and in vivo with ( +/- )-anti-BPDE. In non-competitive enzyme-linked immunosorbent assay the polyclonal antiserum (BP1) exhibited higher affinity, avidity and sensitivity than the monoclonal antibody (5D2). A linear antibody binding response was observed over a wide carcinogen dose range with a detection limit of < 0.1 fmol adducts in immobilized DNA. Non-competitive immuno-slot blot assay could detect 0.2 adducts/10(6) nucleotides induced by < 1 nM ( +/- )-anti-BPDE. The high sensitivity and mono-adduct specificity of non-competitive immunoassays allowed the detailed study of ( +/- )-anti-BPDE-DNA adduct processing human cells exposed to very low levels of the genotoxin. Analysis of polyclonal antiserum binding sites in DNA from repair-proficient human fibroblasts revealed adduct removal rates directly proportional to the initial genotoxic insult. Despite efficient repair, substantial damage persisted in repair-proficient cells exposed to high doses of carcinogen. At low levels of initial damage (0.882 and 3.44 +/- 0.17 adducts/ 10(6) nucleotides) approximately 50% repair was observed after 4 and 8 h respectively. Cells removed approximately 40% of the lesions in 8 h at an intermediate level of damage (20.7 +/- 1.5 adducts/10(6) nucleotides). At higher DNA damage levels (105 +/- 8 and 177 +/- 1 adduct/10(6) nucleotides) 33 and 19% of the lesions respectively were repaired in 24 h. Repair-deficient xeroderma pigmentosum group A fibroblast cells did not show any significant loss of antibody binding sites at high or low initial modification levels. These data suggest that the level of initial DNA damage has a significant impact on the overall efficiency of cellular repair, with potential implications for the biological consequences of deleterious DNA lesions in mammalian cells.

Immunogenicity of recombinant human adenovirus-human immunodeficiency virus vaccines in chimpanzees.

Recombinant human adenovirus (Ad) type 4-, 5-, and 7-vectored vaccines expressing either the HIV env or gag-protease genes were tested for immunogenicity in three chimpanzees. The first phase of the vaccination protocol consisted of a primary and two booster immunizations with Ad-HIVs by the oral route of administration, followed by a single booster immunization with Gag and/or Env subunit vaccines. The second phase of the vaccination protocol consisted of intranasal administration of Ad-HIVs previously administered by the oral route. Following the first phase adenovirus was shed into stools for only 1-7 days and modest type-specific anti-adenovirus neutralizing antibody titers were induced. Strong anti-Env binding antibody responses were detected in all three animals following the second oral booster immunization. One chimpanzee responded with a low-titered type-specific neutralizing antibody response to HIV. Cell-mediated immune responses to Env were not detected after the primary vaccination, but were detected following all booster immunizations. Administration of the Gag subunit vaccine boosted both humoral and cell-mediated immune responses to Gag antigens. In contrast, the Env subunit vaccine boosted cellular but not humoral immune responses. In the second phase of the vaccination protocol, both virus shedding and anti-adenovirus responses were enhanced. All three chimpanzees responded to the intranasal administration of Ad7-HIVs with boosted anti-HIV serum responses, including low-titered type-specific neutralizing antibodies, elicited anti-HIV antibodies at secretory sites, and stimulated cell-mediated immune responses to both Gag and Env antigens.

Localization of virus-specific and group-specific epitopes of plant potyviruses by systematic immunochemical analysis of overlapping peptide fragments.

Virus-specific or group-specific antibody probes to potyviruses can be produced by targeting the immune response to the virus-specific, N-terminal region of the capsid protein (29-95 amino acids depending on the virus) or to the conserved core region (216 amino acids) of the capsid protein, respectively. Immunochemical analysis of overlapping, synthetic octapeptides covering the capsid protein of the Johnsongrass strain of Johnsongrass mosaic virus (JGMV-JG) has delineated the peptide sequences recognized by five polyclonal rabbit antisera and two mouse monoclonal antibodies (mAbs). The antibodies characterized were (i) three virus-specific rabbit polyclonal antisera and one virus-specific mouse mAb (1/25) raised against native virus particles, (ii) one polyclonal antiserum raised against trypsin-derived core particles of JGMV-JG, (iii) one group-specific polyclonal antiserum raised against the denatured, truncated coat protein from trypsin-derived core particles of JGMV-JG, and (iv) one group-specific mouse mAb (1/16) raised against native virus particles. The two epitopes seen by mAb 1/25 occurred at residues 18-27 and 43-52 and overlapped with the two major epitopes seen by the virus-specific polyclonal antiserum. The group-specific epitope seen in JGMV-JG by mAb 1/16 was also recognized strongly in potato virus Y, the type member of the potyvirus group. The multiple epitopes seen by the cross-reactive polyclonal antisera were distributed across the entire core region of the coat protein and their relative antibody binding responses varied between JGMV-JG, potato virus Y, and six other distinct potyviruses.

Studies on the clonality of the response to an epitope of a protein antigen. Randomness of activation of epitope-recognizing clones and the development of clonal dominance.

Syngeneic mice immunized with tobacco mosaic virus protein (TMVP) can differ with respect to their ability to produce antibodies that bind a decapeptide epitope representing residues 103 to 112 of TMVP, and with respect to the fine specificity of the decapeptide binding antibodies as determined by their ability to bind several synthetic analogues of the decapeptide. To elucidate the mechanism responsible for the differences between the syngeneic animals in their ability to make anti-decapeptide antibodies, spleen cells from a large number of naive CSW mice were pooled, and aliquots were transferred (either including or excluding resident T cells) into naive recipients that were subsequently immunized with TMVP. Examination of the frequency and fine specificity of anti-decapeptide antibodies revealed that the recipients exhibited various clonalities of decapeptide binding antibody responses similar to those seen in a normal population of CSW mice. Moreover, the response of each individual mouse was of a restricted clonality despite the availability of a more extensive repertoire of decapeptide-recognizing clones. The results indicate that the selection of the clonality of the antibody response was not determined by the presence (or absence) of particular clones of B or T cells and that the mechanism responsible for generating differences between mice must have acted, subsequent to introduction of the Ag, by activation of a limited number of clones randomly selected by Ag and/or by Ag-driven mutation. The long term nature of the antibody response to the decapeptide epitope was also investigated. The response was shown to be "locked-in" for the life of the immunized individual. Thus, individuals that responded to TMVP but that did not produce antibodies to the decapeptide after the first set of immunizations with TMVP maintained their non-responsiveness to the decapeptide after the second set of immunizations with the protein. However, individuals that responded to an initial set of immunizations with TMVP by producing antibodies to the decapeptide epitope continue to produce antibodies to the decapeptide after a second set of immunizations with TMVP. The fine specificity of the decapeptide-binding antibodies also appeared to be "locked in" throughout the life of the immunized individual. The long term maintenance of the clonability of the antibody response does not appear to be influenced by Ag-specific T cells and is strictly a function of memory B cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Response of adult human volunteers to oral administration of bovine and bovine/human reassortant rotaviruses

Small groups of adult volunteers, in sequence, were inoculated orally with inactivated purified bovine rotavirus of strain NCDV, with live NCDV purified or unpurified and with two different NCDV × human rotavirus reassortant viruses. One of five volunteers given 200 μg of ultraviolet-inactivated NCDV developed a virus-neutralizing (VN) and a binding antibody response detected by enzyme-linked immunosorbent assay (ELISA). Four of 10 volunteers given from 1 × 10 6 to 1 × 10 8 p.f.u. of live NCDV developed VN antibody, but nine of 10 responded when ELISA, HAI and radioimmuno-precipitation tests for serum antibody were also considered. Two different NCDV × human serotype I Wa strain virus reassortants, each containing Wa gene segment 9 and the serotype 1 neutralization phenotype, were administered orally in doses up to 10 6 p.f.u. The reassortants were relatively ineffective in eliciting a serum antibody response at the dosage level employed.

5 Respiratory Allergy to Synthetic Resins

Human hypersensitivity responses to acid anhydride compounds have been recognized with increased frequency. The most extensive use of acid anhydride compounds is in the production of synthetic resins. Clinical sensitization to phthalic anhydride (PA), hexahydrophthalic anhydride (HHPA), tetrachlorophthalic anhydride (TCPA) and himic anhydride (HA) usually presents as an asthma/rhinitis syndrome. Workers sensitized to trimellitic anhydride (TMA) may also develop IgE-mediated asthma/rhinitis, but in addition they may exhibit late respiratory symptoms (LRSS) and a unique syndrome characterized by pulmonary infiltrates and anaemia (PDA). Non-immunological irritant effects may also occur after overexposure to any of these compounds. Clinical diagnosis is established by a careful occupational history, skin tests, serial pulmonary function tests and confirmed by bronchial challenge conducted under controlled laboratory conditions. Phthalic anhydride IgE-mediated reaction skin tests can be performed with either unconjugated PA or PA carrier protein reagents. Skin tests with TCPA- or TMA-protein conjugates have been used successfully for in vivo diagnosis of workers developing the asthma/rhinitis syndrome after sensitization to these substances. Several in vitro immunological tests are also useful for diagnosis and serial surveillance studies in the workplace. Total IgE, specific IgE, total antibody binding and specific IgG antibody responses can be measured accurately for these purposes. Total IgE and specific IgE reactions are associated with IgE-mediated asthma while total antibody and specific IgG levels are more apt to be higher in patients with LRSS. Specific IgG antibodies may be protective in some workers who develop high levels of specific IgE without having clinical sensitivity. Antibody responses to these materials probably involve specificities directed toward haptens and new antigenic determinants within the carrier proteins. Patients who develop severe respiratory symptoms to any of these acid anhydride compounds should be removed from further contact or exposure with these materials.

Collaborative study of the effects of human growth hormone in growth hormone deficiency. II. Development and significance of antibodies to human growth hormone during the first year of therapy.

ABSTRACT Fifty-eight serum samples from 71 growth hormone deficient patients treated for 1 yr with Raben and/or Wilhelmi human growth hormone (hGH) were tested for binding antibodies to hGH. The sera of 35 patients (60.3%) were positive for binding antibodies. The growth rate of patients with antibodies (8.3 ± 3.3 SD cm/1 yr) was not different than that of patients without antibodies (8.2 ± 3.8 SD cm/1 yr). The incidence of a response <5.0 cm/1 yr was no greater in patients with antibodies. Binding antibody titrations were performed in 27 sera, and the maximum titer observed was 1:640 in a single serum. There was no correlation between binding antibody titer and response to therapy. No hemagglutinating antibodies to hGH were detectable in the 17 sera tested. These observations indicate that while binding antibodies to hGH develop with high frequency, they do not play a significant role in modifying the response to an initial year of hGH therapy in growth hormone-deficient patients.