Claudine Bruck

Antibodies to soluble CD4 in HIV-1-infected individuals.

A direct enzyme immunoassay (EIA) using the recombinant soluble form of CD4 (sCD4) produced in rodent cells as antigen was applied to detect antibodies to CD4 in sera from HIV-1- and HIV-2-infected patients. High titers of antibodies to sCD4 were found in sera from 12.6% of the HIV-1-infected persons included in this study, but not in 120 normal human sera. The reactivity of these antibodies with sCD4 was confirmed by a Western blot analysis. A possible anti-idiotypic origin of those antibodies was thought to be unlikely in view of the lack of inhibition of the binding of the biotin-labeled monoclonal antibody (mAb) anti-Leu3a by sCD4 positive sera. Attempts to correlate the evolution of the disease with the presence or absence of antibodies to sCD4 in a panel of well documented HIV-1-seropositive cases did not reveal any clear correlation. Sera from HIV-2-infected people (nine sera analysed), sera from HIV-1-infected chimpanzees (10 sera analysed) and sera from humans immunized with a recombinant vaccinia virus expressing gp160 (10 sera analysed) scored negative for antibodies to sCD4. The possible origin and biological significance of the observed antibodies to sCD4 are discussed.

Comparison and fine mapping of both high and low neutralizing monoclonal antibodies against the principal neutralization domain of HIV-1.

SummaryMonoclonal antibodies raised against viral lysate of HIV-1 (strain LAV-1) and against recombinant gp 160 of HIV-1 (strain HTLV IIIB) which neutralized HIV-1 in a type specific manner were mapped with the aid of peptides (Pepscan analysis). Each of these monoclonal antibodies bound to peptides located on the principal neutralizing domain (PND) of HIV-1. We found that the antigenic sites of the MAbs described in this paper are represented by linear peptides of at least 10 amino acids long. The affinity of the MAbs is high for these peptides and in the same order of magnitude as for native gp 160. The fine mapping of the epitopes may reflect structural features of the PND, for instance which amino acid side chains are exposed and which are buried in the protein. Furthermore the fine mapping of the epitopes explained the HIV type-specific neutralizing activity of the MAbs. Antibodies that bound to the tip of the loop (amino acids QRGPGRAF) have a higher neutralizing activity than antibodies that bound to amino acids towards the N-terminal side of the loop (amino acids KSIRI). Furthermore, MAbs that bound to virtually the same amino acids on the tip of the loop (amino acids IQRGPGRAF and RGPGRAFV) had different neutralizing activities due to different affinities for native gp 160. These data reveal that neutralizing activity not only is determined by the affinity of an antibody to the neutralizing site but also by its fine binding specificities to the V 3 loop of gp 120.

Virus load in chimpanzees infected with human immunodeficiency virus type 1: effect of pre-exposure vaccination.

Many reports indicate that a long-term asymptomatic state following human immunodeficiency virus type 1 (HIV-1) infection is associated with a low amount of circulating virus. To evaluate the possible effect of stabilizing a low virus load by non-sterilizing pre-exposure vaccination, a quantitative virus isolation method was developed and evaluated in four chronically infected chimpanzees infected with a variety of HIV-1 related isolates. This assay was then used to monitor a group of chimpanzees (n = 6) challenged with HIV-1 following vaccination with gp120 or gp160. Data indicated that of the three vaccinated animals which became infected after challenge, the animal with the lowest neutralizing titre at the time of challenge acquired a virus load similar to the control animals, whereas the two other chimpanzees had reduced numbers of virus producing cells in their peripheral circulation. One animal became virus isolation negative, developed an indeterminant PCR signal on lymph node DNA and subsequently became negative for HIV-1 DNA as determined by PCR on PBMC (peripheral blood mononuclear cells) and bone marrow DNA. Recently, the second animal has also become PCR negative. To confirm observations from quantitative virus isolations, quantification of HIV-1 DNA in PBMC and virus RNA in serum was performed by PCR on serially diluted samples at two different time points. Comparison of virus load as determined by these three methods confirmed that there was an effect of vaccination in reducing virus load and demonstrated a correlation between decreased numbers of virus producing cells, HIV-1 DNA containing cells and virus RNA molecules in serum.

Temporal development of cross-neutralization between HTLV-III B and HTLV-III RF in experimentally infected chimpanzees

Sera from chimpanzees inoculated respectively with HTLV-III B, LAV, HTLV-III RF and brain tissue from an AIDS patient were analysed for neutralizing activity by two methods: a cell fusion inhibition test (CFI) using HTLV-III B infected cells as inoculum and CD4+ cells as target and a replication inhibition test (RIT) using cell-free HTLV-III B as well as HTLV-III RF as inoculum and also CD4+ cells as target. All chimpanzees seroconverted for HTLV-III B antibodies within 2 months after inoculation and the ten sera included in the study recognized the HTLV-III B core proteins p17 and p24 and the transmembrane protein gp41 by immunoblotting. The HTLV-III B external envelope gp120 was recognized by eight sera with antibodies active in the CFI (CFI-Ab) or in the RIT (VN-Ab) using HTLV-III B as inoculum, while neither of two sera without such reactivity did. HTLV-III B CFI-Ab and HTLV-III B VN-Ab concurred in nine of ten serum samples. LAV and HTLV-III B infection induced HTLV-III B CFI-Ab and HTLV-III B VN-Ab within 9 months after inoculation in all four chimpanzees tested. However, only the serum of one of the four animals also neutralized HTLV-III RF. HTLV-III RF inoculation evoked only HTLV-III RF VN-Ab within nine months. Between 11 and 18 months neutralizing activity to both HTLV-III B and HTLV-III RF was found in all four sera of chimpanzees inoculated with HTLV-III B, LAV or HTLV-III RF.(ABSTRACT TRUNCATED AT 250 WORDS)