Vaccination with DNA containing tat coding sequences and unmethylated CpG motifs protects cynomolgus monkeys upon infection with simian/human immunodeficiency virus (SHIV89.6P)

Recent evidence suggests that a CD8-mediated cytotoxic T cell response against the Tat protein of human immunodeficiency virus (HIV)/simian immunodeficiency virus (SIV) controls primary infection after pathogenic virus challenge, and correlates with the status of long-term nonprogressor in humans. Due to the presence of unmethylated CpG sequences, DNA vaccination can boost the innate immunity driving more potent T cell-mediated immune responses. Therefore, cynomolgus monkeys were vaccinated with a tat-expressing vector containing defined unmethylated CpG sequences (pCV-tat). Here it is shown that the intramuscular inoculation of the pCV-tat contained primary infection with the highly pathogenic SHIV89.6P virus preventing the CD4(+) T cell decline in all the vaccinated monkeys. Undetectable virus replication and negative virus isolation correlated in all cases with the presence of anti-Tat CTLs. However, a CD8-mediated non cytolytic antiviral activity was also present in all protected animals. Of note, this activity was absent in the controls but was present in the monkey inoculated with the CpG-rich vector alone that was partially protected against viral challenge (i.e. no virus replication but positive virus isolation). These results suggest that a CTL response against Tat protects against primary infection by blocking virus replication at its early stage, in the absence of sterilizing immunity. Nevertheless, the boost of the innate immunity by CpG sequences can contribute to this protection both by driving more potent CTL responses and by inducing other CD8-mediated antiviral activities. Thus, the CpG-rich tat DNA vaccine may represent a promising candidate for preventive and therapeutic vaccination against AIDS.

SHIV89.6P pathogenicity in cynomolgus monkeys and control of viral replication and disease onset by human immunodeficiency virus type 1 Tat vaccine

The Tat protein of human immunodeficiency virus (HIV) is produced very early after infection, plays a key role in the virus life cycle and in acquired immunodeficiency syndrome (AIDS) pathogenesis, is immunogenic and well conserved among all virus clades. Notably, a Tat-specific immune response correlates with non-progression to AIDS. Here, we show that a vaccine based on the Tat protein of HIV blocks primary infection with the simian/human immunodeficiency virus (SHIV)89.6P and prevents the CD4 T cell decline and disease onset in cynomolgus monkeys. No signs of virus replication were found in five out of seven vaccinated macaques for almost 1 year of follow-up. Since the inoculated virus (derived from rhesus or from cynomolgus macaques) is shown to be highly pathogenic in cynomolgus macaques, the results indicate efficacy of Tat vaccination in protection against highly pathogenic virus challenge. Finally, the studies of the Tat-specific immunological responses indicate a correlation of protection with a cytotoxic T cell response. Thus, a Tat-based vaccine is a promising candidate for preventive and therapeutic vaccination in humans.

Control of SHIV-89.6P-infection of cynomolgus monkeys by HIV-1 Tat protein vaccine

Vaccine strategies aimed at blocking virus entry have so far failed to induce protection against heterologous viruses. Thus, the control of viral infection and the block of disease onset may represent a more achievable goal of human immunodeficiency virus (HIV) vaccine strategies. Here we show that vaccination of cynomolgus monkeys with a biologically active HIV-1 Tat protein is safe, elicits a broad (humoral and cellular) specific immune response and reduces infection with the highly pathogenic simian-human immunodeficiency virus (SHIV)-89.6P to undetectable levels, preventing the CD4+ T-cell decrease. These results may provide new opportunities for the development of a vaccine against AIDS.

Long-lasting protection by live attenuated simian immunodeficiency virus in cynomolgus monkeys: no detection of reactivation after stimulation with a recall antigen

The infection of cynomolgus monkeys with an attenuated simian immunodeficiency virus (SIV) (C8) carrying a deletion in the nef gene results in a persistent infection associated with an extremely low viral burden in peripheral blood mononuclear cells. The aim of this study was to determine (1) the breadth of the protection after repeated challenges of monkeys with SIV homologous strains of different pathogenicity, (2) the genotypic stability of the live virus vaccine, (3) whether the protection might depend on cellular resistance to superinfection, and (4) whether immunogenic stimuli such as recall antigens could reactivate the replication of the C8 virus. To address these goals, the monkeys were challenged at 40 weeks after C8 infection with 50 MID50 of cloned SIVmac251, BK28 grown on macaque cells. They were protected as indicated by several criteria, including virus isolation, anamnestic serological responses, and viral diagnostic PCR. At 92 weeks after the first challenge, unfractionated peripheral blood mononuclear cells from protected monkeys were susceptible to the in vitro infection with SIVmac32H, spl. At 143 weeks after C8 infection, the four protected monkeys were rechallenged with 50 MID50 of the pathogenic SIVmac32H, spl grown on macaque cells. Once again, they were protected. The C8 virus remained genotypically stable, and depletion of CD4(+) cells was not observed during approximately 3 years of follow-up. In contrast, it was found that the infection with SIVmac32H, spl induced CD4(+) cell depletion in three of three control monkeys. Of importance, stimulation with tetanus toxoid, although capable of inducing specific humoral and T cell proliferative responses, failed to induce a detectable reactivation of C8 virus.

Detection of infectious simian immunodeficiency virus in B- and T-cell lymphomas of experimentally infected macaques

An increasing frequency of malignant lymphomas occurs among patients infected by human immunodeficiency virus. Because of the close similarities to human malignancies, we used a nonhuman primate model to study the pathogenesis of simian immunodeficiency virus (SIV)-associated malignancies. Specifically, we investigated (1) the presence of the SIV genome in tumor cells, (2) the presence of coinfecting viruses, and (3) the presence of a rearrangement of the immunoglobulin and c-myc genes. We observed 5 cases of non-Hodgkin's lymphomas (4 of B- and 1 of T-cell origin) among 14 SIV-infected cynomolgus monkeys. No c-myc translocation was observed in the tumors, whereas B-cell lymphomas were characterized either by a monoclonal (in 2 of 4) or by an oligoclonal (in 2 of 4) VDJ rearrangements of the immunoglobulin heavy chain gene. Molecular, biological, and immunological analyses did show the presence of infectious SIV in the tumor cells of 1 T-cell and 2 oligoclonal B-cell lymphomas. Neither Simian T-lymphotropic nor Epstein-Barr viruses were detectable, whereas Simian herpes virus Macaca fascicularis-1 was detectable at a very low copy number in 3 of 4 B-cell lymphomas; however, only 1 of these also harbored the SIV genome. These results support the possibility that SIV may be directly involved in the process of B or T lymphomagenesis occurring in simian acquired immunodeficiency syndrome.

Live attenuated simian immunodeficiency virus prevents super-infection by cloned SIVmac251 in cynomolgus monkeys

The ability of a live attenuated simian immunodeficiency virus (SIV) to protect against challenge with cloned SIVmac251/BK28 was evaluated in four cynomolgus macaques. The intravenous infection of the C8 variant of the SIVmac251/32H virus, carrying an in-frame 12 bp deletion in the nef gene, did not affect the CD4+ and CD8+ cell counts, and a persistent infection associated with an extremely low virus burden in peripheral blood mononuclear cells (PBMCs) was established. After 40 weeks, these monkeys were challenged intravenously with a 50 MID50 dose of SIVmac251/BK28 virus grown on macaque cells. Four naive monkeys were infected as controls. Monkeys were monitored for 62 weeks following challenge. Attempts to rescue virus from either PBMCs or bone marrow from the C8-vaccinated monkeys were unsuccessful, but in two cases virus was re-isolated from lymph node cells. The presence of the SIV provirus with the C8 variant genotype maintaining its original nef deletion was shown by differential PCR in PBMCs, lymph nodes and bone marrow. Furthermore, in contrast to the control monkeys, the vaccinated monkeys showed normal levels for CD4+ and CD8+ cells, minimal lymphoid hyperplasia and no clinical signs of infection. Our results confirm that vaccination with live attenuated virus can confer protection. This appears to be dependent on the ability of the C8 variant to establish a persistent but attenuated infection which is necessary for inducing an immune response, as suggested by the persistence of a strong immune B cell memory and by the over-expression of interleukin (IL)-2, interferon-gamma and IL-15 mRNAs in PBMCs of C8-vaccinated monkeys but not in those of control monkeys.

AIDS-related complex treated by antiviral drugs and allogeneic bone marrow transplantation following conditioning protocol with busulphan, cyclophosphamide and cyclosporin

A 26-year-old man with AIDS-related complex (ARC) was treated with high-dose busulphan and cyclophosphamide, followed by allogeneic bone marrow transplantation. For 3 months before transplantation he received a combination of four drugs considered active against human immunodeficiency virus (HIV) to reduce the viral burden: zidovudine, acyloguanosine, fusidic acid and phenylidantoin. Although in reduced doses in coincidence with marrow engraftment, zidovudine therapy was scheduled after transplantation in order to protect donor cells from infection with HIV. Engraftment rapidly occurred and was documented by cytogenetic analyses. The post-transplant course was characterized by severe acute GvHD with irreversible hepatorenal failure. The patient died on day 48 after transplantation. Polymerase chain reaction analyses for detecting HIV DNA showed the persistence of positivity at day +30 and +45 after transplantation. Antibodies to specific HIV proteins evaluated with Western blot testing also persisted at days +21 and +35 after transplantation. Circulating immunocomplexes disappeared on day +31, and an increase in the CD4/CD8 ratio occurred. The short survival of the patient, affected by chronic hepatitis too, does not allow final conclusions about the role of BMT in HIV disease.

Interaction of HIV-1 with susceptible lymphoblastoid cells. 1H NMR studies

Different strains of HIV susceptible lymphoblastoid cells have been infected by HIV-1 and examined by means of 1H NMR spectroscopy at different times after infection, taking advantage of the presence of high resolution lipid signals from the plasma membrane of tumor cells. A transient decrease in intensity of fatty acid signals, originated by changes in membrane structure, has been observed early after viral infection. Marked alterations in membrane-dependent steps of phospholipid synthesis can also be inferred by the observed transient depression in peaks from choline-based metabolites. Spectral modifications deriving from changes in lipid metabolism are also produced both in infected cells a few days after infection and in permanently infected cells. 1H NMR can, therefore, monitor structural and metabolic effects induced by HIV infection.