We studied the humoral response of mice immunized with soluble CD4-rgp120 complex, testing polyclonal and monoclonal antibodies (mAbs) with the aim of identifying molecular changes that take place ...after the first interaction between human immunodeficiency virus and the cell surface. The antisera had a paradoxically high syncytia-blocking titer associated with anti-CD4 specificity, while their capacity to inhibit CD4-gp120 binding was relatively modest. One of the mAbs produced from these responders blocks syncytia formation but does not inhibit CD4 interaction with gp120. Apparently, this mAb interacts with the CD4 moiety of CD4-gp120 complex and prevents a post-binding event necessary for membrane fusion and viral infection.
Random copolymers of polyamino acids containing negatively charged and aromatic residues at specific ratios appear to bind HIV type 1 V3 loop and neutralize diverse laboratory isolates. At least the ...putative heparin binding domain and isoleucine residues in the amino half of V3 are involved in the interactions with these polymers. There are a number of interesting features common between these polymer's modes of binding to the V3 and the protease inhibition drug ABT-538.
CD8+ T lymphocytes from HIV+ individuals can potently suppress HIV-1 replication in a noncytolytic manner. This suppression appears to be multifactorial and the molecules contributing have not been ...fully elucidated. As an approach to this question we used herpesvirus saimiri (HVS) to transform CD8+ T lymphocytes from an HIV+ asymptomatic donor to a continuously growing, activation-independent, IL-2-dependent phenotype. The transformed cell population, termed CD8(HVS), had an activated phenotype, contained HVS sequences, did not shed infectious HVS virus, and was polyclonal. The CD8(HVS) cells, despite the absence of detectable CTL activity, potently suppressed HIV-1 production by both autologous and heterologous CD4+ cells from infected donors. The CD8(HVS) cells in coculture also suppressed virus production from PBMCs acutely infected with syncytium-inducing (SI) strains or NSI primary isolates of HIV-1. The supernatants from the CD8(HVS) cells and their concentrates derived from these supernatants were suppressive to NSI primary isolates of HIV-1 but not to SI strains. Fractionation of these concentrates showed that the suppressive activity was associated with low molecular mass (6500- to 19,300-Da) protein species. Western blotting and ELISA indicated that the CC chemokines MIP-1alpha, MIP-1beta, and RANTES were present in these fractions. Antibody-blocking studies with antibodies to the CC chemokines indicated that a significant portion of the soluble HIV-suppressive activity was due to these molecules. However, these experiments also suggested the inhibitory activity of the CD8(HVS) cells in coculture is not due exclusively to the CC chemokines. The HVS-transformed cells provide a useful tool for the study of noncytolytic CD8+ T lymphocyte-mediated suppression of HIV-1.
The V3 loop (residues 303-338) of the human immunodeficiency virus type 1 (HIV-1) gp120 envelope protein represents a principal neutralizing determinant for the virus. An HIV-1 proviral clone ...containing a mutation in the V3 loop was constructed in which the proline residue at position 313 was changed to an alanine (P313-A). This mutation alters the conserved GPGR sequence that is found in the V3 loop sequences of different HIV-1 isolates. The P313-A clone produced virus particles, which were infectious for a number of T-cell lines including MOLT-4, CEM, and SupT1, but demonstrated a relatively low infectivity on the AA5 B-cell line when compared with wild-type viruses, HTLV-IIIB, HXB2/10 (a chimeric molecular clone), and another mutant virus (Q290-T). V3 loop-specific neutralizing polyclonal sera and the 9284 monoclonal antibody, which recognizes the amino side of the V3 loop sequence, effectively blocked infectivity and syncytia formation of all viruses tested. In contrast, the 0.5 beta monoclonal antibody, which is biologically more potent than 9284 and recognizes a different V3 loop determinant, failed to neutralize the P313-A virus. These results suggest that the proline residue in the relatively conserved GPGR "turn" region of the V3 loop is crucial for recognition by the 0.5 beta antibody. The observed variation in sensitivity of the B-cell line to the P313-A virus may reflect the presence of cell-specific factors which could be important in establishing an HIV-1 infection.
We have previously described a synthetic peptide (T1-SP10) derived from two noncontiguous regions of HTLVIIIB envelope gp120 (T1, amino acids 428-443; SP10, amino acids 303-321) that induced ...type-specific anti-HIV neutralizing antibodies and T cell proliferative responses against native HIV gp120 when used as a carrier-free immunogen in goats. In this study, HTLVIIIB T1-SP10 synthetic peptides were used to immunize rhesus monkeys to determine if the peptides were capable of eliciting HIV-specific neutralizing antibody and proliferative responses in primates. Four compounds (alum, polyA:polyU, threonyl-muramyldipeptide (MDP) and IFA) were also compared for efficacy as adjuvants in this system. Rhesus monkeys immunized with T1-SP10 peptides generated high titers of antibodies against the immunogens and also against HTLVIIIB gp120. Sera from all four animals given T1-SP10 in IFA or threonyl-MDP neutralized infection by HTLVIIIB and blocked virus-dependent cell fusion events. A peak neutralization titer of 1:940 was seen in one animal given IFA (19600) and a titer of 1:900 was seen in one of the monkeys (17371) given threonyl-MDP. Proliferative responses of immune rhesus PBMC to T1-SP10 appeared after the first injection. After eight immunizations, two of eight monkeys (one injected with peptides in threonyl-MDP and one given peptides in IFA) had PBMC proliferative responses to native HTLVIIIB gp120. These data demonstrate that the carrier-free T1-SP10 synthetic peptide construct can induce high titers of neutralizing anti-HIV antibody responses and PBMC proliferative responses to HIV in primates.
A series of peptides were synthesized based on various regions of the HIV-1 transmembrane protein gp41 to define the role of HIV-1 envelope proteins in virus infection. Results indicate that one of ...these peptides, DP-178, blocks an early step in the virus life cycle prior to reverse transcription.
PDF
