Immunodominance of HIV-1 Specific CD8+ T-Cell Responses Is Related to Disease Progression Rate in Vertically Infected Adolescents

BACKGROUND: HIV-1 vertically infected children in the USA are living into adolescence and beyond with the widespread use of antiretroviral drugs. These patients exhibit striking differences in the rate of HIV-1 disease progression which could provide insights into mechanisms of control. We hypothesized that differences in the pattern of immunodomination including breadth, magnitude and polyfunctionality of HIV-1 specific CD8+ T cell response could partially explain differences in progression rate. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we mapped, quantified, and assessed the functionality of these responses against individual HIV-1 Gag peptides in 58 HIV-1 vertically infected adolescents. Subjects were divided into two groups depending upon the rate of disease progression: adolescents with a sustained CD4%≥25 were categorized as having no immune suppression (NS), and those with CD4%≤15 categorized as having severe immune suppression (SS). We observed differences in the area of HIV-1-Gag to which the two groups made responses. In addition, subjects who expressed the HLA- B*57 or B*42 alleles were highly likely to restrict their immunodominant response through these alleles. There was a significantly higher frequency of naïve CD8+ T cells in the NS subjects (p = 0.0066) compared to the SS subjects. In contrast, there were no statistically significant differences in any other CD8+ T cell subsets. The differentiation profiles and multifunctionality of Gag-specific CD8+ T cells, regardless of immunodominance, also failed to demonstrate meaningful differences between the two groups. CONCLUSIONS/SIGNIFICANCE: Together, these data suggest that, at least in vertically infected adolescents, the region of HIV-1-Gag targeted by CD8+ T cells and the magnitude of that response relative to other responses may have more importance on the rate of disease progression than their qualitative effector functions

Generation of CD8(+) T-Cell Responses by a Recombinant Nonpathogenic Mycobacterium smegmatis Vaccine Vector Expressing Human Immunodeficiency Virus Type 1 Env

Because the vaccine vectors currently being evaluated in human populations all have significant limitations in their immunogenicity, novel vaccine strategies are needed for the elicitation of cell-mediated immunity. The nonpathogenic, rapidly growing mycobacterium Mycobacterium smegmatis was engineered as a vector expressing full-length human immunodeficiency virus type 1 (HIV-1) HXBc2 envelope protein. Immunization of mice with recombinant M. smegmatis led to the expansion of major histocompatibility complex class I-restricted HIV-1 epitope-specific CD8(+) T cells that were cytolytic and secreted gamma interferon. Effector and memory T lymphocytes were elicited, and repeated immunization generated a stable central memory pool of virus-specific cells. Importantly, preexisting immunity to Mycobacterium bovis BCG had only a marginal effect on the immunogenicity of recombinant M. smegmatis. This mycobacterium may therefore be a useful vaccine vector

Genetic Alteration of Mycobacterium smegmatis To Improve Mycobacterium-Mediated Transfer of Plasmid DNA into Mammalian Cells and DNA Immunization▿

Mycobacteria target and persist within phagocytic monocytes and are strong adjuvants, making them attractive candidate vectors for DNA vaccines. We characterized the ability of mycobacteria to deliver transgenes to mammalian cells and the effects of various bacterial chromosomal mutations on the efficiency of transfer in vivo and in vitro. First, we observed green fluorescent protein expression via microscopy and fluorescence-activated cell sorting analysis after infection of phagocytic and nonphagocytic cell lines by Mycobacterium smegmatis or M. bovis BCG harboring a plasmid encoding the fluorescence gene under the control of a eukaryotic promoter. Next, we compared the efficiencies of gene transfer using M. smegmatis or BCG containing chromosomal insertions or deletions that cause early lysis, hyperconjugation, or an increased plasmid copy number. We observed a significant—albeit only 1.7-fold—increase in the level of plasmid transfer to eukaryotic cells infected with M. smegmatis hyperconjugation mutants. M. smegmatis strains that overexpressed replication proteins (Rep) of pAL5000, a plasmid whose replicon is incorporated in many mycobacterial constructs, generated a 10-fold increase in plasmid copy number and 3.5-fold and 3-fold increases in gene transfer efficiency to HeLa cells and J774 cells, respectively. Although BCG strains overexpressing Rep could not be recovered, BCG harboring a plasmid with a copy-up mutation in oriM resulted in a threefold increase in gene transfer to J774 cells. Moreover, M. smegmatis strains overexpressing Rep enhanced gene transfer in vivo compared with a wild-type control. Immunization of mice with mycobacteria harboring a plasmid (pgp120hE) encoding human immunodeficiency virus gp120 elicited gp120-specific CD8 T-cell responses among splenocytes and peripheral blood mononuclear cells that were up to twofold (P < 0.05) and threefold (P < 0.001) higher, respectively, in strains supporting higher copy numbers. The magnitude of these responses was approximately one-half of that observed after intramuscular immunization with pgp120hE. M. smegmatis and other nonpathogenic mycobacteria are promising candidate vectors for DNA vaccine delivery

Patient cohort characteristics.

a<p>Log viral load.</p>b<p>H = Hispanic; AA = African American; M = Male; F = Female; Race was not available for 1 subject in the NS group and 2 subjects in the SS group.</p><p>The numbers in parentheses represent 95% confidence intervals.</p

Categorization of subjects into two distinct disease progression groups.

<p>Two examples of representative patients categorized into either long-term survivors with No Immune Suppression (NS) (A) or Severe Immune Suppression (SS) (B). The dotted line is the boundary of the CD4% value of that progression group. The shading shows the window from within which PBMC samples were chosen for study.</p

Association between CD57 expression on CD4 T cells and disease progression.

<p><b>A.</b> Comparison of CD57 expression on CD4 T cells between progression groups. <b>B.</b> Correlation between log viral load (LVL) and CD57 expression on CD4 T cells. <b>C.</b> Correlation between CD4% and expression of CD57 on CD4 T cells.</p

Areas of Gag targeted by CD8+ T cell responses.

<p>The frequency of recognition of individual single peptides are shown for the total cohort in panel A. The NIH AIDS Reagent peptides for HIV-1 Gag are represented by their peptide number. A comparison of the frequency of recognition of single peptides between the two progression groups is shown in panel B. The percentage of each group responding to 6 of the individual Gag peptides is shown in panel C.</p

Comparison of differentiation profiles of total CD4 T cells between progression groups.

<p>We used expression of CCR7 and CD45RA to categorize CD4 T cells into one of four differentiation phenotypes. Filled circles (•) represent LTS-SS patients and empty circles (○) represent LTS-NS patients. The line in each column represents the median and the differentiation phenotype is beneath each column.</p