Biomedical subjects

E S Rosenberg

Publications and source records attributed to E S Rosenberg.

At least 19 recordsLinked to original sources

PubMed2007

Estimation and prediction with HIV-treatment interruption data.

We consider longitudinal clinical data for HIV patients undergoing treatment interruptions. We use a nonlinear dynamical mathematical model in attempts to fit individual patient data. A statistically-based censored data method is combined with inverse problem techniques to estimate dynamic parameters. The predictive capabilities of this approach are demonstrated by comparing simulations based on estimation of parameters using only half of the longitudinal observations to the full longitudinal data sets.

Antiretroviral Therapy, Highly Active↗

PubMed2003

Comprehensive epitope analysis of human immunodeficiency virus type 1 (HIV-1)-specific T-cell responses directed against the entire expressed HIV-1 genome demonstrate broadly directed responses, but no correlation to viral load.

Cellular immune responses play a critical role in the control of human immunodeficiency virus type 1 (HIV-1); however, the breadth of these responses at the single-epitope level has not been comprehensively assessed. We therefore screened peripheral blood mononuclear cells (PBMC) from 57 individuals at different stages of HIV-1 infection for virus-specific T-cell responses using a matrix of 504 overlapping peptides spanning all expressed HIV-1 proteins in a gamma interferon-enzyme-linked immunospot (Elispot) assay. HIV-1-specific T-cell responses were detectable in all study subjects, with a median of 14 individual epitopic regions targeted per person (range, 2 to 42), and all 14 HIV-1 protein subunits were recognized. HIV-1 p24-Gag and Nef contained the highest epitope density and were also the most frequently recognized HIV-1 proteins. The total magnitude of the HIV-1-specific response ranged from 280 to 25,860 spot-forming cells (SFC)/10(6) PBMC (median, 4,245) among all study participants. However, the number of epitopic regions targeted, the protein subunits recognized, and the total magnitude of HIV-1-specific responses varied significantly among the tested individuals, with the strongest and broadest responses detectable in individuals with untreated chronic HIV-1 infection. Neither the breadth nor the magnitude of the total HIV-1-specific CD8+-T-cell responses correlated with plasma viral load. We conclude that a peptide matrix-based Elispot assay allows for rapid, sensitive, specific, and efficient assessment of cellular immune responses directed against the entire expressed HIV-1 genome. These data also suggest that the impact of T-cell responses on control of viral replication cannot be explained by the mere quantification of the magnitude and breadth of the CD8+-T-cell response, even if a comprehensive pan-genome screening approach is applied.

Acquired Immunodeficiency Syndrome↗

PubMed2002

Cellular immune responses in transplantation-associated chronic viral infections.

Viral pathogens are important causes of morbidity following transplantation. Cytomegalovirus (CMV) and Epstein-Barr virus (EBV) infections represent two major viral complications in transplant recipients. Recent advances in methodology have led to a better understanding of host immune responses directed against chronic viral infections. We review the nature of antiviral immunity involved in control of CMV and EBV. Viral mechanisms of immune evasion and immunotherapeutic strategies in the transplantation setting will also be addressed.

Animals↗

PubMed2002

Cytotoxic T-lymphocyte (CTL) responses directed against regulatory and accessory proteins in HIV-1 infection.

The HIV-1 regulatory proteins Tat and Rev and the accessory proteins Vpr, Vpu, and Vif are essential for viral replication, and their cytoplasmic production suggests that they should be processed for recognition by cytotoxic T lymphocytes. However, only limited data is available evaluating to which extent these proteins are targeted in natural infection and optimal cytotoxic T lymphocyte (CTL) epitopes within these proteins have not been defined. In this study, CTL responses against HIV-1 Tat, Rev, Vpr, Vpu, and Vif were analyzed in 70 HIV-1 infected individuals and 10 HIV-1 negative controls using overlapping peptides spanning the entire proteins. Peptide-specific interferon-gamma (IFN-gamma) production was measured by Elispot assay and flow-based intracellular cytokine quantification. HLA class I restriction and cytotoxic activity were confirmed after isolation of peptide-specific CD8+ T-cell lines. All regulatory and accessory proteins served as targets for HIV-1- specific CTL and multiple CTL epitopes were identified in functionally important regions of these proteins. In certain individuals HIV-1-specific CD8+ T-cell responses to these accessory and regulatory proteins contributed up to a third to the magnitude of the total HIV-1-specific CTL response. These data indicate that despite the small size of these proteins regulatory and accessory proteins are targeted by CTL in natural HIV-1 infection, and contribute importantly to the total HIV-1-specific CD8+ T-cell responses. These findings are relevant for the evaluation of the specificity and breadth of immune responses during acute and chronic#10; infection, and will be useful for the design and testing of candidate human immunodeficiency virus (HIV) vaccines.

CD8-Positive T-Lymphocytes↗

PubMed2001

Mother-to-child transmission of HIV infection and CTL escape through HLA-A2-SLYNTVATL epitope sequence variation.

Cytotoxic T lymphocytes (CTL) play a central role in containment of HIV infection. Evasion of the immune response by CTL escape is associated with progression to disease. It is therefore hypothesised that transmitted viruses encode escape mutations within epitopes that are required for successful control of viraemia. In order to test this hypothesis, escape through the dominant HLA-A2-restricted CTL epitope SLYNTVATL (p17 Gag residues 77-85 SL9) in the setting of mother-to-child-transmission (MTCT) was investigated. Initial data from two families in which the HIV-infected mother expressed HLA-A*0201 and had transmitted the virus to other family members were consistent with this hypothesis. In addition, analysis of the gag sequence phylogeny in one family demonstrated that CTL escape variants can be successfully transmitted both horizontally and vertically. To test the hypothesis further, a larger cohort of transmitting mothers (n=8) and non-transmitters (n=14) were studied. Variation within the SL9 epitope was associated with expression of HLA-A2 (P=0.04) but overall no clear link between variation from the SL9 consensus sequence and MTCT was established. However, the high level of background diversity within p17 Gag served to obscure any possible association between escape and MTCT. In conclusion, these studies highlighted the obstacles to demonstrating CTL escape arising at this particular epitope. Alternative strategies likely to be more definitive are discussed.

Amino Acid Sequence↗

PubMed2001

Vpr is preferentially targeted by CTL during HIV-1 infection.

The HIV-1 accessory proteins Vpr, Vpu, and Vif are essential for viral replication, and their cytoplasmic production suggests that they should be processed for recognition by CTLs. However, the extent to which these proteins are targeted in natural infection, as well as precise CTL epitopes within them, remains to be defined. In this study, CTL responses against HIV-1 Vpr, Vpu, and Vif were analyzed in 60 HIV-1-infected individuals and 10 HIV-1-negative controls using overlapping peptides spanning the entire proteins. Peptide-specific IFN-gamma production was measured by ELISPOT assay and flow-based intracellular cytokine quantification. HLA class I restriction and cytotoxic activity were confirmed after isolation of peptide-specific CD8(+) T cell lines. CD8(+) T cell responses against Vpr, Vpu, and Vif were found in 45%, 2%, and 33% of HIV-1-infected individuals, respectively. Multiple CTL epitopes were identified in functionally important regions of HIV-1 Vpr and Vif. Moreover, in infected individuals in whom the breadth of HIV-1-specific responses was assessed comprehensively, Vpr and p17 were the most preferentially targeted proteins per unit length by CD8(+) T cells. These data indicate that despite the small size of these proteins Vif and Vpr are frequently targeted by CTL in natural HIV-1 infection and contribute importantly to the total HIV-1-specific CD8(+) T cell responses. These findings will be important in evaluating the specificity and breadth of immune responses during acute and chronic infection, and in the design and testing of candidate HIV vaccines.

Amino Acid Sequence↗

PubMed2001

Investigation of primary human immunodeficiency virus infection in patients who test positive for heterophile antibody.

In light of a recent report of 3 false-positive results of Epstein-Barr virus heterophile tests caused by HIV infection, we sought to assess the frequency of this occurrence. One hundred thirty-two positive heterophile antibody-tested serum samples were obtained from 2 tertiary care facilities in Boston to assess for HIV, and all tested negative for HIV plasma RNA. This study shows that false-positive results of heterophile tests are not frequently associated with primary HIV infection.

Antibodies, Heterophile↗

PubMed2001

Evolution and transmission of stable CTL escape mutations in HIV infection.

Increasing evidence indicates that potent anti-HIV-1 activity is mediated by cytotoxic T lymphocytes (CTLs); however, the effects of this immune pressure on viral transmission and evolution have not been determined. Here we investigate mother-child transmission in the setting of human leukocyte antigen (HLA)-B27 expression, selected for analysis because it is associated with prolonged immune containment in adult infection. In adults, mutations in a dominant and highly conserved B27-restricted Gag CTL epitope lead to loss of recognition and disease progression. In mothers expressing HLA-B27 who transmit HIV-1 perinatally, we document transmission of viruses encoding CTL escape variants in this dominant Gag epitope that no longer bind to B27. Their infected infants target an otherwise subdominant B27-restricted epitope and fail to contain HIV replication. These CTL escape variants remain stable without reversion in the absence of the evolutionary pressure that originally selected the mutation. These data suggest that CTL escape mutations in epitopes associated with suppression of viraemia will accumulate as the epidemic progresses, and therefore have important implications for vaccine design.

Adult↗

PubMed2001

Control of HIV-1 viremia and protection from AIDS are associated with HLA-Bw4 homozygosity.

Certain HLA-B antigens have been associated with lack of progression to AIDS. HLA-B alleles can be divided into two mutually exclusive groups based on the expression of the molecular epitopes HLA-Bw4 and HLA-Bw6. Notably, in addition to its role in presenting viral peptides for immune recognition, the HLA-Bw4, but not HLA-Bw6, motif functions as a ligand for a natural killer cell inhibitory receptor (KIR). Here, we show that profound suppression of HIV-1 viremia is significantly associated with homozygosity for HLA-B alleles that share the HLA-Bw4 epitope. Furthermore, homozygosity for HLA-Bw4 alleles was also significantly associated with the ability to remain AIDS free and to maintain a normal CD4 T cell count in a second cohort of HIV-1-infected individuals with well defined dates of seroconversion. This association was independent of the presence of a mutation in CC chemokine receptor 5 (CCR5) associated with resistance to HIV-1 infection, and it was independent of the presence of HLA alleles that could potentially confound the results. We conclude that homozygosity for HLA-Bw4-bearing B alleles is associated with a significant advantage and that the HLA-Bw4 motif is important in AIDS pathogenesis.

Acquired Immunodeficiency Syndrome↗

PubMed2001

The HIV-1 regulatory proteins Tat and Rev are frequently targeted by cytotoxic T lymphocytes derived from HIV-1-infected individuals.

The HIV-1 regulatory proteins Rev and Tat are expressed early in the virus life cycle and thus may be important targets for the immune control of HIV-1-infection and for effective vaccines. However, the extent to which these proteins are targeted in natural HIV-1 infection as well as precise epitopes targeted by human cytotoxic T lymphocytes (CTL) remain to be defined. In the present study, 57 HIV-1-infected individuals were screened for responses against Tat and Rev by using overlapping peptides spanning the entire Tat and Rev proteins. CD8+ T cell responses against Tat and Rev were found in up to 19 and 37% of HIV-1-infected individuals, respectively, indicating that these regulatory proteins are important targets for HIV-1-specific CTL. Despite the small size of these proteins, multiple CTL epitopes were identified in each. These data indicate that Tat and Rev are frequently targeted by CTL in natural HIV-1 infection and may be important targets for HIV vaccines.

CD8-Positive T-Lymphocytes↗

PubMed2001

Cellular immune responses and viral diversity in individuals treated during acute and early HIV-1 infection.

Immune responses induced during the early stages of chronic viral infections are thought to influence disease outcome. Using HIV as a model, we examined virus-specific cytotoxic T lymphocytes (CTLs), T helper cells, and viral genetic diversity in relation to duration of infection and subsequent response to antiviral therapy. Individuals with acute HIV-1 infection treated before seroconversion had weaker CTL responses directed at fewer epitopes than persons who were treated after seroconversion. However, treatment-induced control of viremia was associated with the development of strong T helper cell responses in both groups. After 1 yr of antiviral treatment initiated in acute or early infection, all epitope-specific CTL responses persisted despite undetectable viral loads. The breadth and magnitude of CTL responses remained significantly less in treated acute infection than in treated chronic infection, but viral diversity was also significantly less with immediate therapy. We conclude that early treatment of acute HIV infection leads to a more narrowly directed CTL response, stronger T helper cell responses, and a less diverse virus population. Given the need for T helper cells to maintain effective CTL responses and the ability of virus diversification to accommodate immune escape, we hypothesize that early therapy of primary infection may be beneficial despite induction of less robust CTL responses. These data also provide rationale for therapeutic immunization aimed at broadening CTL responses in treated primary HIV infection.

Acute Disease↗

PubMed2001

Substantial differences in specificity of HIV-specific cytotoxic T cells in acute and chronic HIV infection.

Cytotoxic T lymphocytes (CTLs) play a vital part in controlling viral replication during human viral infections. Most studies in human infections have focused on CTL specificities in chronic infection and few data exist regarding the specificity of the initial CTL response induced in acute infection. In this study, HIV-1 infection in persons expressing human histocompatibility leukocyte antigen (HLA)-A*0201 was used as a means of addressing this issue. In chronic infection, the dominant HLA-A*0201-restricted CTL response is directed towards the epitope SLYNTVATL ("SL9") in p17 Gag (residues 77-85). This epitope is targeted by 75% of HLA-A*0201-positive adults, and the magnitude of this A*0201-SL9 response shows a strong negative association with viral load in progressive infection. Despite using the highly sensitive peptide-major histocompatibility complex tetramer and intracellular cytokine assays, responses to the SL9 epitope were not detectable in any of 11 HLA-A*0201-positive subjects with acute HIV-1 infection (P = 2 x 10(-6)), even when assays were repeated using the SL9 peptide variant that was encoded by their autologous virus. In contrast, multiple responses (median 3) to other epitopes were evident in 7 of the 11 A*0201-positive subjects. Longitudinal study of two subjects confirmed that the A*0201-SL9 response emerged later than other CTL responses, and after viral set point had been reached. Together, these data show that the CTL responses that are present and that even may dominate in chronic infection may differ substantially from those that constitute the initial antiviral CTL response. This finding is an important consideration in vaccine design and in the evaluation of vaccine candidates.

Acute Disease↗

PubMed2001

Cellular immune response to human immunodeficiency virus.

Despite recent success with the use of highly active antiretroviral therapy, eradication of HIV type 1 appears beyond the capabilities of presently available therapy. Therefore, greater emphasis has been given to finding mechanisms that promote immunologic control of viral replication rather than eradication. Although the correlates of immune protection in HIV-1 infection remain undefined, increasing evidence indicates that HIV-1-specific cellular immune responses may play a critical role in antiviral control. Vigorous HIV-1-specific CD4+ T-helper cell and CD8+ cytotoxic T-lymphocyte responses may play a critical role in control of viral replication in the absence of antiretroviral therapy, which has been demonstrated in individuals with long-term nonprogressive infection. However, in chronic, progressive HIV-1 infection, virus-specific T-helper cell responses are typically weak or absent in all stages of disease, and HIV-1-specific cytotoxic T-lymphocyte responses wane over time, presumably due to the lack of HIV-1-specific T helper cells. Effective treatment of individuals during acute HIV-1 seroconversion syndrome appears to restore HIV-1-specific T-helper cell responses, which are otherwise only observed in persons with long-term nonprogressive infection. This observation, along with anecdotal reports of individuals successfully controlling viral replication after treating acute HIV-1 infection, provides immunologic rationale for structured treatment interruption and other immunotherapeutic approaches designed to augment HIV-1-specific immune responses.

Acquired Immunodeficiency Syndrome↗

PubMed2001

Relative dominance of epitope-specific cytotoxic T-lymphocyte responses in human immunodeficiency virus type 1-infected persons with shared HLA alleles.

Cytotoxic T lymphocytes (CTL) target multiple epitopes in human immunodeficiency virus (HIV)-infected persons, and are thought to influence the viral set point. The extent to which HLA class I allele expression predicts the epitopes targeted has not been determined, nor have the relative contributions of responses restricted by different class I alleles within a given individual. In this study, we performed a detailed analysis of the CTL response to optimally defined CTL epitopes restricted by HLA class I A and B alleles in individuals who coexpressed HLA A2, A3, and B7. The eight HIV-1-infected subjects studied included two subjects with acute HIV infection, five subjects with chronic HIV infection, and one long-term nonprogressor. Responses were heterogeneous with respect to breadth and magnitude of CTL responses in individuals of the same HLA type. Of the 27 tested epitopes that are presented by A2, A3, and B7, 25 were targeted by at least one person. However, there was wide variation in the number of epitopes targeted, ranging from 2 to 17. The A2-restricted CTL response, which has been most extensively studied in infected persons, was found to be narrowly directed in most individuals, and in no cases was it the dominant contributor to the total HIV-1-specific CTL response. These results indicate that HLA type alone does not predict CTL responses and that numerous potential epitopes may not be targeted by CTL in a given individual. These data also provide a rationale for boosting both the breadth and the magnitude of HIV-1-specific CTL responses by immunotherapy in persons with chronic HIV-1 infection.

Alleles↗

PubMed2001

Multiple effector functions mediated by human immunodeficiency virus-specific CD4(+) T-cell clones.

Mounting evidence suggests that human immunodeficiency virus type 1 (HIV-1) Gag-specific T helper cells contribute to effective antiviral control, but their functional characteristics and the precise epitopes targeted by this response remain to be defined. In this study, we generated CD4(+) T-cell clones specific for Gag from HIV-1-infected persons with vigorous Gag-specific responses detectable in peripheral blood mononuclear cells. Multiple peptides containing T helper epitopes were identified, including a minimal peptide, VHAGPIAG (amino acids 218 to 226), in the cyclophilin binding domain of Gag. Peptide recognition by all clones examined induced cell proliferation, gamma interferon (IFN-gamma) secretion, and cytolytic activity. Cytolysis was abrogated by concanamycin A and EGTA but not brefeldin A or anti-Fas antibody, implying a perforin-mediated mechanism of cell lysis. Additionally, serine esterase release into the extracellular medium, a marker for cytolytic granules, was demonstrated in an antigen-specific, dose-dependent fashion. These data indicate that T helper cells can target multiple regions of the p24 Gag protein and suggest that cytolytic activity may be a component of the antiviral effect of these cells.

Amino Acid Sequence↗

PubMed2001

Neutralizing antibodies associated with viremia control in a subset of individuals after treatment of acute human immunodeficiency virus type 1 infection.

Immediate treatment of acute human immunodeficiency virus type 1 (HIV-1) infection has been associated with subsequent control of viremia in a subset of patients after therapy cessation, but the immune responses contributing to control have not been fully defined. Here we examined neutralizing antibodies as a correlate of viremia control following treatment interruption in HIV-1-infected individuals in whom highly active antiretriviral therapy (HAART) was initiated during early seroconversion and who remained on therapy for 1 to 3 years. Immediately following treatment interruption, neutralizing antibodies were undetectable with T-cell-line adapted strains and the autologous primary HIV-1 isolate in seven of nine subjects. Env- and Gag-specific antibodies as measured by enzyme-linked immunosorbent assay were also low or undetectable at this time. Despite this apparent poor maturation of the virus-specific B-cell response during HAART, autologous neutralizing antibodies emerged rapidly and correlated with a spontaneous downregulation in rebound viremia following treatment interruption in three subjects. Control of rebound viremia was seen in other subjects in the absence of detectable neutralizing antibodies. The results indicate that virus-specific B-cell priming occurs despite the early institution of HAART, allowing rapid secondary neutralizing-antibody production following treatment interruption in a subset of individuals. Since early HAART limits viral diversification, we hypothesize that potent neutralizing-antibody responses to autologous virus are able to mature and that in some persons these responses contribute to the control of plasma viremia after treatment cessation.

Acquired Immunodeficiency Syndrome↗

PubMed2001

Identification of novel HLA-A2-restricted human immunodeficiency virus type 1-specific cytotoxic T-lymphocyte epitopes predicted by the HLA-A2 supertype peptide-binding motif.

Virus-specific cytotoxic T-lymphocyte (CTL) responses are critical in the control of human immunodeficiency virus type 1 (HIV-1) infection and will play an important part in therapeutic and prophylactic HIV-1 vaccines. The identification of virus-specific epitopes that are efficiently recognized by CTL is the first step in the development of future vaccines. Here we describe the immunological characterization of a number of novel HIV-1-specific, HLA-A2-restricted CTL epitopes that share a high degree of conservation within HIV-1 and a strong binding to different alleles of the HLA-A2 superfamily. These novel epitopes include the first reported CTL epitope in the Vpr protein. Two of the novel epitopes were immunodominant among the HLA-A2-restricted CTL responses of individuals with acute and chronic HIV-1 infection. The novel CTL epitopes identified here should be included in future vaccines designed to induce HIV-1-specific CTL responses restricted by the HLA-A2 superfamily and will be important to assess in immunogenicity studies in infected persons and in uninfected recipients of candidate HIV-1 vaccines.

Acquired Immunodeficiency Syndrome↗

PubMed2001

Rapid definition of five novel HLA-A*3002-restricted human immunodeficiency virus-specific cytotoxic T-lymphocyte epitopes by elispot and intracellular cytokine staining assays.

Human immunodeficiency virus (HIV)-specific cytotoxic T lymphocytes (CTL) play a major role in control of viral replication. To understand the contribution of this antiviral response, an initial step is to fully define the specific epitopes targeted by CTL. These studies focused on CTL responses restricted by HLA-A*3002, one of the HLA-A molecules most prominent in African populations. To avoid the time-consuming effort and expense involved in culturing CTL prior to defining epitopes and restricting alleles, we developed a method combining Elispot assays with intracellular gamma interferon staining of peripheral blood mononuclear cells to first map the optimal epitopes targeted and then define the HLA restriction of novel epitopes. In two A*3002-positive subjects whose CTL responses were characterized in detail, the strongest response in both cases was to an epitope in p17 Gag, RSLYNTVATLY (residues 76 to 86). Using this method, CTL epitopes for which there were no motif predictions were optimized and the HLA restriction was established within 48 to 72 h of receipt of blood. This simple and convenient approach should prove useful especially in the characterization of CTL responses specific to HIV and other viruses, particularly in localities where performing cytotoxicity assays would be problematic.

Amino Acid Sequence↗