Biomedical subjects
D Montefiori
Publications and source records attributed to D Montefiori.
Vaccine protection by a triple deletion mutant of simian immunodeficiency virus.
Twelve rhesus monkeys were vaccinated with SIVmac316 delta nef (lacking nef sequences), and 12 were vaccinated with SIVmac239 delta3 (lacking nef, vpr, and upstream sequences in U3). SIVmac316 and SIVmac239 differ by only eight amino acids in the envelope; these changes render SIVmac316 highly competent for replication in macrophages. Seventeen of the animals developed persistent infections with the vaccine viruses. Seven of the 24 vaccinated animals, however, developed infections that were apparently transient in nature. Six of these seven yielded virus from peripheral blood when tested at weeks 2 and/or 3, three of the seven had transient antibody responses, but none of the seven had persisting antibody responses. The 24 monkeys were challenged in groups of four with 10 rhesus monkey infectious doses of wild-type, pathogenic SIVmac251 at weeks 8, 20, and 79 following receipt of vaccine. None of the seven with apparently transient infections with vaccine virus were protected upon subsequent challenge. Analysis of cell-associated viral loads, CD4+ cell counts, and viral gene sequences present in peripheral blood in the remainder of the monkeys following challenge allowed a number of conclusions. (i) There was a trend toward increased protection with length of time of vaccination. (ii) Solid vaccine protection was achieved by 79 weeks with the highly attenuated SIV239 delta3. (iii) Solid long-term protection was achieved in at least two animals in the absence of complete sterilizing immunity. (iv) Genetic backbone appeared to influence protective capacity; animals vaccinated with SIV239 delta3 were better protected than animals receiving SIV316 delta nef. This better protection correlated with increased levels of the replicating vaccine strain. (v) The titer of virus-neutralizing activity in serum on the day of challenge correlated with protection when measured against a primary stock of SIVmac251 but not when measured against a laboratory-passaged stock. The level of binding antibodies to whole virus by enzyme-linked immunosorbent assay also correlated with protection.
Simian immunodeficiency virus DNA vaccine trial in macaques.
Explore the source record for details and available documents.
Influence of heavy chain constant regions on antigen binding and HIV-1 neutralization by a human monoclonal antibody.
F105, a neutralizing IgG1 kappa human mAb, is reactive with a discontinuous epitope within the gp120 CD4 binding site. Because isotype usage may affect Ab function, we examined the effect of isotype on Ag/Ab interactions and HIV-1 neutralization. An IgG3 kappa Ab was prepared by linking the variable regions of F105 to cloned human kappa and gamma 3 constant regions. Immunoreactivity of F105 IgG1 and IgG3 with IIIB-, MN-, and RF-infected cells was equivalent. Inhibition of binding and fusion of IIIB to uninfected cells and neutralization of IIIB virus was comparable for F105 IgG1 and IgG3, with 14 to 23 micrograms/ml required for 90% neutralization. In contrast, F105 IgG3 was marginally more effective at inhibition of MN binding/fusion and significantly more effective at neutralization of MN virus (62 micrograms/ml for IgG3 and > 100 micrograms/ml for IgG1 to achieve 90% neutralization). Despite high affinity binding to RF-infected cells, F105 IgG1 minimally neutralizes free RF virus. F105 IgG3 is dramatically more effective against the RF isolate, with 2 to 20 micrograms/ml of Ab required for 50% neutralization. Both isotypes were relatively ineffective at inhibition of RF binding/fusion. Thus, whereas affinity with native Ags on the surface of HIV-1-infected cells was unaffected by heavy chain constant regions, Ab isotype can strongly influence virion neutralization. Structural changes in gp120, as a result of increased flexibility conferred by the elongated IgG3 hinge region, are suggested as a possible mechanism to increase neutralization of selected HIV-1 isolates. These results may have significant implications in the design of immunotherapeutic and vaccine agents.
Studies in subjects with long-term nonprogressive human immunodeficiency virus infection.
BACKGROUND: In a small percentage of persons infected with human immunodeficiency virus type 1 (HIV-1), there is no progression of disease and CD4+ T-cell counts remain stable for many years. Studies of the histopathological, virologic, and immunologic characteristics of these persons may provide insight into the pathogenic mechanisms that lead to HIV disease and the protective mechanisms that prevent progression to overt disease. METHODS AND RESULTS: We studied 15 subjects with long-term nonprogressive HIV infection and 18 subjects with progressive HIV disease. Nonprogressive infection was defined as seven or more years of documented HIV infection, with more than 600 CD4+ T cells per cubic millimeter, no antiretroviral therapy, and no HIV-related disease. Lymph nodes from the subjects with nonprogressive infection had significantly fewer of the hyperplastic features, and none of the involuted features, characteristic of nodes from subjects with progressive disease. Plasma levels of HIV-1 RNA and the viral burden in peripheral-blood mononuclear cells were both significantly lower in the subjects with nonprogressive infection than in those with progressive disease (P = 0.003 and P = 0.015, respectively). HIV could not be isolated from the plasma of the former, who also had significantly higher titers of neutralizing antibodies than the latter. There was viral replication, however, in the subjects with nonprogressive infection, and virus was consistently cultured from mononuclear cells from the lymph nodes. In the lymph nodes virus "trapping" varied with the degree of formation of germinal centers, and few cells expressing virus were found by in situ hybridization. HIV-specific cytotoxic activity was detected in all seven subjects with nonprogressive infection who were tested. CONCLUSIONS: In persons who remain free of disease for many years despite HIV infection the viral load is low, but viral replication persists. Lymph-node architecture and immune function appear to remain intact.
A macaque adherent cell line that expresses human CD4 is susceptible to SIV: utility for assessing neutralizing antibody.
A macaque CD4 + adherent cell line was generated by stable expression of the human CD4 gene in a rhesus macaque mammary tumor cell line, CMMT. The resulting cell line CMMT/CD4 expressed surface CD4 and was sensitive to infection by a wide range of isolates of simian immunodeficiency virus (SIV) of different subgroups, but was not susceptible to infection with HIV-1. The CMMT/CD4 cell line was used to develop a microassay for measurement of neutralizing antibody in plasma of SIV-infected or immunized animals. Single infected cells could be detected in a monolayer of CMMT/CD4 by immunoperoxidase and a 90% reduction in the number of positive cells was used as a measure of neutralizing activity of two-fold plasma dilutions. This assay had comparable sensitivity to methods based upon detecting a reduction in reverse transcriptase activity of SIV, reduction of viral antigen, or inhibition of cytopathic effect.
Prolonged clinical latency and survival of macaques given a whole inactivated simian immunodeficiency virus vaccine.
Simian immunodeficiency virus (SIV) infection of macaques is a useful and relevant model for evaluating candidate human immunodeficiency virus (HIV) vaccines. One important feature of this model is that SIV vaccines can be evaluated for their ability to prevent infection as well as to prevent or delay the onset of AIDS. In the present study, a group of macaques was vaccinated with whole inactivated SIV and challenged with peripheral blood mononuclear cells from an SIV-infected macaque. This challenge represented a rigorous and realistic test of the immunization protocol. All macaques became infected after challenge; however, immunized animals survived significantly longer (P < .03) than naive controls. These data suggest that similar vaccines administered to humans at risk for HIV-1 infection might delay or prevent AIDS even if the vaccine failed to prevent infection.
Imidazole acetic acid as a substitute for cAMP.
Explore the source record for details and available documents.