HIV-1 binding and neutralizing antibodies of injecting drug users

Previous studies have demonstrated a stronger seroreactivity against some synthetic peptides responsible for inducing neutralizing antibodies in injecting drug users (IDU) compared to that of individuals sexually infected with HIV-1 (S), but the effectiveness in terms of the neutralizing ability of these antibodies has not been evaluated. Our objective was to study the humoral immune response of IDU by determining the specificity of their antibodies and the presence of neutralizing antibodies. The neutralization capacity against the HIV-1 isolate MN (genotype B), the primary HIV-1 isolate 95BRRJ021 (genotype F), and the seroreactivity with peptides known to induce neutralizing antibodies, from the V2 and V3 loops of different HIV-1 subtypes, were analyzed. Seroreactivity indicates that IDU plasma are more likely to recognize a broader range of peptides than S plasma, with significantly higher titers, especially of V3 peptides. Similar neutralization frequencies of the MN isolate were observed in plasma of the IDU (16/47) and S (20/60) groups in the 1:10 dilution. The neutralization of the 95BRRJ021 isolate was more frequently observed for plasma from the S group (15/23) than from the IDU group (15/47, P = 0.0108). No correlation between neutralization and seroreactivity with the peptides tested was observed. These results suggest that an important factor responsible for the extensive and broad humoral immune response observed in IDU is their infection route. There was very little difference in neutralizing antibody response between the IDU and S groups despite their differences in seroreactivity and health status.

Human immunodeficiency virus type 1 neutralization by plasma from B or F genotype infected individuals

Anti-human immunodeficiency virus type 1 (HIV-1) "binding antibodies" (antibodies capable of binding to synthetic peptides or proteins) occur throughout HIV-1 infection, are high-titered and highly cross-reactive, as confirmed in this study by analyzing plasma from B and F genotype HIV-1 infected individuals. Plasma from individuals infected with clade F HIV-1 displayed the most frequent cross-reactivity, in high titers, while Bbr plasma showed much higher specificity. Similarly, neutralization of a reference HIV-1 isolate (HIV-1 MN) was more frequently observed by plasma from F than B genotype infected individuals. No significant difference was seen in neutralization susceptibility of primary B, Bbr or F clade HIV-1 by plasma from individuals infected with the classical B (GPGR) or F HIV-1, but Bbr (GWGR) plasma were less likely to neutralize the F genotype primary HIV-1 isolates. The data indicate that both B and F genotype derived vaccines would be equally effective against B and F HIV-1 infection, with a slightly more probable effectiveness for F than B genotype. Although the Bbr variant appears to induce a much more specific humoral immune response, the susceptibility in neutralizing the Brazilian HIV-1 B genotype Bbr variant is similar to that observed with the classical B genotype HIV-1.

Analysis of antibody specificity against the third variable region of the envelope glycoprotein gp120 of HIV-1 in plasma from HIV-1-positive individuals residing in Brazil

1. Antibody specificity for the principal neutralization domain (PND) of the human immunodeficiency virus type 1 (HIV-1) was studied in plasma from 122 HIV-1-infected individuals residing in Brazil. 2. Using 8 overlapping sequential pentadecapeptides corresponding to the third variable region (V3) of 5 different HIV-1 isolates in an enzyme-linked immunosorbent assay (ELISA), a preferential recognition of the peptides with amino acid sequences corresponding to the HIV-1 isolates IIIB and MN (maximal reactivities of 60-70) compared to the isolates SC, WMJ-2 or RF (maximal reactivities below 60) was observed. 3. A difference was observed in the overall reactivity pattern to HIV-1 SC peptides of plasma collected from individuals residing in the Brazilian states of Rio de Janeiro and Bahia. However, a statistically significant increased recognition by Bahian plasma was only observed for the HIV-1 SC C55 peptide. 4. The mean CD4/CD8 ratio of the group of plasma with an isolate-restricted recognition of peptides (0.522 +/- 0.074) was significantly lower than that of the total group of plasma (1.00 +/- 0.18).

Production of human monoclonal antibodies against HIV-1 peptides

Protocols were evaluated in an attempt to produce human monoclonal antibodies (HumAb) specific for the human immunodeficiency virus type 1 (HIV-1). The first series of experimentls involved in vitro immunization of normal human peripheral blood lymphocytes (PBL) with peptide C57 (HIV-1 strain IIIB clone BH10 gp 120 amino acids 324-338: GNMRQAHCNISRAKW) followed by either fusion to mouse/human heterolhybrids or transformation with Epstein Barr virus (EBV). Using the hybridoma technology, three IgM class (alfa light chain) Human Ab were obtained. In a parallel study, PBL from two HIV-1 infected patients were immortalized after in vitro stimulation with fragments of the HIV-1 envelope glycoprotein (recombinant gp120 fragment of gp 120, amino acids 295-473, or the penv9 fragment of gp160, amino acids 474-757). Five IgG class Human b (three IgG2m alfa; one IgG1, K; one IgG3, alfa) reactive with the antigens used in the in vitro stimulations were obtained

Synergistic signal of an anti-hamster T cell monoclonal antibody on antigen-induced T cell proliferation

1.The use of monoclonal antibodies (mAb) has permitted the identification of T cell surface antigens and the classification of these antigens based upon phenotype and function. Some of these monoclonal antibodies can identify antigens specifically involved in T lymphocyte activation and are also able to induce, under certain conditions, T cell proliferation. 2. We describe a new mAb raised against hamster T cells which binds to a 45-KDa cell surface antigen expressed on 45% of thymic cells and 90% of mature T lymphocytes. This mAb,d esignated X2VA, alone does not cause T cells proliferation, but increases in a synergistic manner T cell proliferation when these cells are cultured in the presence of specific antigens, or used in mixed lymphocyte reactions. 3. When the X2Va mAb is used as single signal for the T cells it induces the production of a T cell growth factor, suggesting that the synergist effect observed during antigen-induced T cell proliferation is mediated by one more cytokines. 4. Our results indicate that the X2Va mAb recognizes an antigen which is expressed during T cell ontogenesis and which is involved in hamster T cell Activation

Isolation and antigenic characterization of human immunodeficiency virus (HIV) in Brazil

Isolamento e caracterizaçäo antigênica do vírus da imunodeficiência humana (VIH/HIV) no Brasil - Um retrovírus foi isolado de um paciente brasileiro com "Síndrome de Imunodeficiência Adquirida" (SIDA/AIDS) e caracterizado em termos de sua reatividade com soros de indivíduos infectados com vírus da imunodeficiência humana dos tipos 1 e 2 (HIV-1 e HIV-2). A análise antigênica por "Western blot" revelou que o isolado brasileiro é bastante similar a uma cepa de HIV-1 bem caracterizada. A identificaçäo do retrovírus como HIV-1 e näo HIV-2 é reforçada pelo fato dos anticorpos do paciente do qual foi isolado o vírus näo terem reagido com a glicoproteínas de envelope de 140 kDa, específica para HIV-2

Trypanosoma cruzi: circulating antigens.

Antigenos circulantes foram detectados em soros de camundongos infectados experimentalmente com elevadas doses de Trypanosoma cruzi pela reacao com soros obtidos de camundongos em fase cronica de infeccao. A reacao de imunodifusao entre soros homologos agudo e cronico produziu quatro linhas de precipitacao.Por reacao com soro cronico de camundongo antigenos circulantes foram detectados em soros de cricetos, caes e coelhos infectados com doses elevadas de Trypanosoma cruzi e em soros de pacientes chagasicos. Uma reacao foi tambem observada com urina de camundongos e caes infectados de forma aguda. Exoantigeno de Trypanosoma cruzi foi detectado em meio de cultura de tripanosomas e em sobrenadantes de culturas de celulas infectadas. Tentativas de isolamento dos antigenos sao descritas