Yaffa Mizrachi

Progressive specific immune attrition after primary, secondary and tertiary immunizations with bacteriophage ΦX174 in asymptomatic HIV-1 infected patients.

BackgroundAntibody responses to immunization are often compromised in patients infected by HIV-1, and the use of childhood immunization in affected children is controversial. We investigated whether multiple immunizations with a T cell-dependent neoantigen, bacteriophage ΦX174, induce selective immune attrition and post-vaccination viremia. MethodsSeventeen asymptomatic, antiretroviral therapy-naïve HIV-1-infected patients with a CD4 cell count of 450 cells/μl or greater were immunized in 1990/1991 with three intravenous doses of bacteriophage ΦX174. Group 1 received zidovudine (ZDV) during the primary and secondary immunization. Group 2 received ZDV exclusively during the tertiary immunization. Bacteriophage-specific antibodies of the IgM and IgG class, lymphocyte phenotypes (CD4+, CD8+, CD4+DR+, CD8+DR+, CD4+CD45RO+ and CD4+45RA+, CD4+CD45RO+DR+) and HIV-1 plasma viremia were measured sequentially. ResultsIn both patient groups the primary, secondary and tertiary antibody responses, as expressed by geometric mean antibody titres and IgM to IgG switch, were impaired. Booster immunizations resulted in a progressive attrition of specific antibody responses to bacteriophage. Antibodies to tetanus toxoid remained stable. The HIV-1 viral loads, which were evaluated in archived specimens from eight patients, increased after immunization but returned to baseline appoximately 4 weeks later. The humoral immune attrition and increases in plasma viremia were blunted by concomitant short courses of ZDV. DiscussionMultiple boosters of immunizations in asymptomatic treatment-naive HIV-1-infected patients may result in a specific immune attrition and vaccine-induced viremia. Short-term monotherapy with ZDV may have blunted these adverse effects. Hyperimmunization of HIV-1-infected patients may be detrimental unless accompanied by antiretroviral therapy.

Safety and immunogenicity of a V3 loop synthetic peptide conjugated to purified protein derivative in HIV-seronegative volunteers.

Objectives: To develop a peptide‐based model for a preventive vaccine for HIV‐1 infection. Design: Phase I trial in HIV‐1‐seronegative volunteers. Participants: Adult healthy subjects HIV‐1‐antibody‐seronegative in an enzymelinked immunosorbent assay, screened for tuberculin [purified protein derivative (PPD)] reactivity with 2 tuberculin units PPD‐administered intradermally. Interventions: Submicrogram doses of a PPD conjugate with a peptide of the primary neutralizing domain (PND) of HIV‐1MN (PPD‐MN‐PND) were administered intradermally to tuberculin skin‐test‐positive and ‐negative volunteers. Results: Antibodies to the MN‐PND were measured after two immunizations in 10 out of 11 PPD skin‐test‐positive volunteers. After the fourth immunization high‐affinity antibodies were detected, which persisted for over 1 year. High titers of MN‐PND‐specific immunoglobulin (Ig) G and IgA were detected in the serum and saliva of all volunteers tested. Serum antibodies were cross‐reactive with PND peptide from some other HIV‐1 strains but neutralized only the HIV‐1MN prototype. Human leukocyte antigen (HLA)‐B7‐restricted MN‐PND‐specific cytotoxic T lymphocytes (CTL) were also detected. Conclusions: The PPD‐MN‐PND vaccine at submicrogram doses is safe and immunogenic in PPD skin‐test‐positive healthy adult volunteers. Long lasting humoral immune responses in the serum and saliva were possibly accompanied by HLA‐B7‐restricted CTL responses. This is a vaccine prototype that can be rapidly and inexpensively modified to include other peptide epitopes. It is especially suitable for use in a worldwide multibillion Bacillus Calmette‐Guérin (BCG)‐primed or tuberculosis‐exposed population at risk for HIV‐1 infection.

Improved brain delivery and in vitro activity of zidovudine through the use of a redox chemical delivery system.

Objective: Improved therapy for AIDS dementia and related encephalopathies may be achieved through enhanced delivery of effective antiretroviral agents to the central nervous system (CNS). Design: A novel chemical delivery system (CDS) was used, which utilized redox trapping of drugs in the brain. This study was aimed at defining the pharmacokinetics of a zidovudine (ZDV)‐CDS as well as establishing its in vitro antiviral efficacy against HIV in both lymphocytes and in a neural cell line. Results: ZDV‐CDS administered parenterally to rats produced significantly higher brain levels of ZDV [area under the curve (AUC), 425 &mgr;g × min/g] than equimolar ZDV (AUC, 13.5 &mgr;g × min/g). Native ZDV uptake was minimal after 1h when analyzed in CEM lymphocytes and in SKNMC neuroblastoma cell line. By contrast, marked uptake of ZDV‐CDS was followed by biochemical conversion of ZDV‐CDS to its main metabolites (ZDV‐CDS quaternary salt, ZDV‐Q+, and native ZDV). These improved uptake profiles were associated with greater in vitro virucidal effect. ZDV‐CDS at 0.5 &mgr;M was 80% more effective than ZDV in suppressing p24 production in a lymphocyte culture infected with 6000 median tissue culture infective doses (TCID50) of the HIV N1T strain and 50% more effective at 0.05 &mgr;M. Furthermore, syncytia formation was completely suppressed at a ZDV‐CDS dose of 0.5 &mgr;M (600TCID50) but native ZDV at the same dose was ineffective. Finally, while ZDV (at 0.5 &mgr;M) is not active in reducing viral replication in an SKNMC neural cell line, the ZDV‐CDS complex significantly suppressed p24 synthesis. Conclusion: The ZDV‐CDS complex is capable of delivering higher ZDV doses to lymphocytes and neural cells, with improved antiretroviral activity.

L-cycloserine, an inhibitor of sphingolipid biosynthesis, inhibits HIV-1 cytopathic effects, replication, and infectivity

Drugs that reduce viral production or prevent viral spread by interference with the hosts cellular components are unlikely to induce resistance, in contrast to treatment modalities that interact with the HIV-1 life cycle. Two features make L-cycloserine (L-CS) a candidate drug of this kind: (a) L-CS is a potent inhibitor of the sphingolipid pathway (b) sphingolipids, galactocerebrosides, and sulfatides have been shown, by others, to bind gp120. In a feasibility and efficacy study, we have found that L-CS inhibits HIV-1 replication in a CD4+ lymphoid cell line (CEM) as documented by the reduction of syncytium formation, the number of HIV-1 infected cells, and p24 protein production. This observation may lead to a new strategy for the treatment of HIV-1 infection.

Immunologic responses of HIV-1-infected study subjects to immunization with a mixture of peptide protein derivative-V3 loop peptide conjugates.

V3 loop peptide sequences from several HIV-1 strains were covalently linked to purified protein derivative (PPD) of Mycobacterium tuberculosis. A mixture of PPD conjugates of V3 loop peptides from six different strains of HIV-1 induced a stronger antibody response than a single V3 peptide-conjugate administered to guinea pigs and humans. Sera from animals immunized with a PPD-six peptide-PPD conjugate neutralized multiple primary-isolate strains of HIV-1. Potent immune responses were noted only when animals were primed with bacillus Calmette-Guerin (BCG), PPD was covalently bound to the peptides, and PPD was used as the carrier protein. Based on these animal studies, an immunogen consisting of PPD-conjugated V3 loop peptides from five HIV-1 strains was tested in 7 HIV-1 seropositive PPD skin test positive study subjects. Vaccinees exhibited over time a uniform increase in neutralizing antibodies for both laboratory adapted and primary isolates of HIV-1, including strains from multiple clades. In 3 patients with baseline viral loads between 8000 and 12,000 RNA copies/ml, the viral load declined in 2 patients to <400 copies/ml and in 1 patient to 1200 copies/ml without concurrent administration of highly active antiretroviral therapy (HAART).

V3 variation in HIV-seropositive patients receiving a V3- targeted vaccine.

ObjectiveTo analyze V3 loop sequences of HIV-1 in three seropositive individuals who exhibited declines in viremia while receiving a V3-targeted vaccine. DesignRetrospective analysis of case series at an HIV Clinic, University of Tel Aviv. PatientsThree HIV-1-seropositive, PPD-DTHR-positive (PPD, Siebert purified protein derivative of tuberculin; DTHR, delayed type hypersensitivity reaction) individuals who had been inoculated with a mixture of PPD-cross-linked V3 peptides from five HIV strains and then exhibited declines in HIV-1 viremia during the course of vaccination in the absence of combination antiretroviral therapy and whose virus levels resurged once vaccine boosting was discontinued. ResultsDeclines in viremia were observed even when the viral V3 sequences of the patients’ HIV differed by at least one or two amino acid residues from those of the five peptides in the vaccine. Although viral mutants with amino acid substitutions within V3 appeared during vaccination, plasma virus loads remained at low levels for several months after these variants appeared. About a year after boosting was discontinued, anti-V3 peptide antibodies in the patients had declined and plasma virus returned to the prevaccination levels or higher. Compared with the isolates that predominated during the course of vaccination, the resurgent viruses contained zero to six amino acid residue differences in the V3 loop but few synonymous substitutions. ConclusionsViruses with altered V3 sequences did emerge but did not result in increased viremia during the course of vaccination. In two individuals where V3 mutations were absent in the virus that re-emerged after vaccine boosting ceased, resurgence could not have been a consequence of V3 changes.

Receptor-mediated maternofetal transfer of immunoglobulins. Inhibition of transport of anti-HIV-1 immunoglobulin by generic immunoglobulins in the in vitro perfused placenta.

Objectives: The passage of immunoglobulin G (IgG) across the placenta is thought to involve Fc’ receptors on the syncytiotrophoblast. To confirm the receptor dependency of this process we have studied the changes in the tissue content and transfer kinetics of immunoglobulins and hyperimmune serum to HIV (HIVIG) during in vitro dual placental perfusion. Methods: Isolated lobules of term placentae from normal pregnancies were perfused in a model of maternal and fetal circulation. The perfused tissue was compared to fresh tissue samples from the same placenta for the content of IgG, IgG subclasses, IgM, cytokeratin, human placental lactogen and SP1 antigen by immunohistochemistry and by protein elution. Results: The immunoglobulin staining faded by an average of 40% during the 1st hour of perfusion. In contrast, staining for cytokeratin, human placental lactogen and SP1 remained unchanged. During a 4-hour recycling of endogenous immunoglobulins in the maternal circulation, IgG and HIVIG crossed to the fetal side in a steady rate. The transport of HIVIG could be inhibited by preperfusion with an intravenous gammaglobulin preparation (IVIG). Discussion: The transfer of IgG across the placenta occurs in a steady state rate consistent with a receptor-mediated mechanism. Furthermore, inhibition of HIVIG maternofetal transfer by IVIG further establishes the receptor-mediated transfer of immunoglobulins through the placenta.