Neutralizing activity and cellular immune responses induced in mice after immunization with apoptotic HIV-1/murine leukemia virus infected cells.

Dendritic cells present microbial antigens to T cells after uptake of apoptotic vesicles from infected cells. We previously reported that immunizations with apoptotic HIV-1/murine leukemia virus (MuLV) infected cells lead to induction of both cellular and humoral immune responses as well as resistance to mucosal challenge with live HIV-1/MuLV infected cells. Here we extended those studies and investigated whether apoptotic cells from HIV-1/MuLV infected cells stimulate the production of HIV-1 neutralizing activity. We compared different routes of administration and were able to induce p24- and Nef-specific cellular proliferation after intraperitoneal (i.p.), intranasal (i.n.), subcutaneous (s.c.) and intramuscular (i.m.) immunizations. Serum IgG and IgA antibodies directed against gp160, p24, or Nef were also produced regardless of immunization route used. However, the induction of mucosa-associated IgAs from faeces or vaginal secretions were detected only after either i.p. or i.n. immunizations. We were able to measure neutralizing activity in sera of mice after i.p. and i.n. immunization. Neutralizing reactivity was also detected after s.c. and i.m. immunizations in the presence of the cytokine adjuvant granulocyte macrophage-colony stimulating factor (GM-CSF). Conclusively we show induction of cellular and humoral immune responses including neutralizing activity after immunization with apoptotic HIV-1/MuLV infected cells in mice. The results from this study support further evaluations using apoptotic cells as antigen delivery system for vaccination against HIV-1 in other animal models.

Selection of human immunodeficiency virus type 1 R5 variants with augmented replicative capacity and reduced sensitivity to entry inhibitors during severe immunodeficiency.

Early in human immunodeficiency virus 1 (HIV-1) infection CCR5-using (R5) viruses predominate. With disease progression, approximately 50% of infected individuals develop viruses able to use CXCR4. In the present work, the evolution of the biological properties of HIV-1 was studied in patients who retain viruses with an R5 phenotype despite AIDS onset. A panel of primary R5 HIV-1 isolates sequentially obtained at an asymptomatic stage and after AIDS diagnosis was examined. The viruses were selected based on our previous observation that R5 variants with reduced sensitivity to RANTES inhibition may appear during disease progression. Biological properties of the early and late R5 viruses, including infectivity, replicative capacity, impact of cationic polymer and sensitivity to inhibition by the entry inhibitors T-20 and TAK-779, were evaluated. R5 viruses isolated after AIDS onset displayed elevated replicative capacity and infectivity, and did not benefit from cationic polymer assistance during infection. Late R5 isolates also exhibited reduced sensitivity to inhibition by T-20 and TAK-779, even though the included patients were naïve to treatment with entry inhibitors and the isolates had not acquired mutations within the gp41 HR1 region. In addition, CD4+ T-cell counts at the time of R5 virus isolation correlated with infectivity, replicative capacity and sensitivity to inhibition by entry inhibitors. The results indicate that R5 HIV-1 variants with augmented replicative capacity and reduced sensitivity to entry inhibitors may be selected for during severe immunodeficiency. At a time when the clinical use of entry inhibitors is increasing, this observation could be of importance in the optimal design of such treatments.

Coevolution of RANTES sensitivity and mode of CCR5 receptor use by human immunodeficiency virus type 1 of the R5 phenotype.

The evolution of human immunodeficiency virus type 1 (HIV-1) coreceptor use has been described as the acquisition of CXCR4 use linked to accelerated disease progression. However, CXCR4-using virus can be isolated only from approximately one-half of individuals with progressive HIV-1 disease. The other half continue to yield only CCR5-using viruses (R5 phenotype) throughout the course of disease. In the present work, the use of receptor chimeras between CCR5 and CXCR4 allowed us to study the evolution of HIV-1 with the R5 phenotype, which was not revealed by studies of wild-type coreceptor use. All together, 246 isolates (173 with the R5 phenotype) from 31 individuals were tested for their ability to infect cells through receptor chimeras. R5(narrow) virus was able to use only wild-type CCR5, whereas R5(broad(1)) to R5(broad(3)) viruses were able to use one to three chimeric receptors, respectively. Broad use of chimeric receptors was interpreted as an increased flexibility in the mode of receptor use. R5(broad) isolates showed higher infectivity in cells expressing wild-type CCR5 than R5(narrow) isolates. Also, the increased flexibility of R5(broad) isolates was concomitant with a lower sensitivity to inhibition by the CC chemokine RANTES. Our results indicate a close relationship between HIV-1 phenotypic changes and the pathogenic process, since the mode and efficiency of CCR5 use as well as the decrease in the RANTES sensitivities of isolated viruses are significantly correlated with CD4(+)-T-cell decline in a patient. One possible explanation is that ligand competition at the CCR5 receptor or changed CCR5 availability may shape the outcome of HIV-1 infection.