Denis David

Rapid Effect of Interleukin-2 Therapy in Human Immunodeficiency Virus–Infected Patients whose CD4 Cell Counts Increase Only Slightly in Response to Combined Antiretroviral Treatment

Combined antiretroviral treatment in some human immunodeficiency virus-infected persons does not lead to a rapid increase in CD4 cell counts, and these patients may remain susceptible to opportunistic infections. A group of 13 patients with CD4 cell counts <200 cells/mm3 after > or =9 months of combined antiretroviral treatment received interleukin (IL)-2 immunotherapy (4.5x106 IU twice daily for 5 days every 6 weeks). After only 3 cycles, their CD4 cell counts increased from 123 cells/mm3 (range, 104-134 cells/mm3) to 229 cells/mm3 (range, 176-244 cells/mm3). A marked increase was noted in the naive CD45RA subpopulation of CD4 T lymphocytes. Furthermore, the magnitude of the CD4 cell count response correlated with the baseline expression levels of the antiapoptotic molecule Bcl-2. This study demonstrates that IL-2 immunotherapy can accelerate the recovery of CD4 lymphocytes in persons whose CD4 cell counts fail to increase rapidly in response to combined antiretroviral treatment.

ANALYSIS OF HUMAN VH GENE REPERTOIRE EXPRESSION IN PERIPHERAL CD19+ B CELLS

Using CD19 B-cell selection and polymerase chain reaction-amplified cDNA libraries, we analyzed the peripheral immunoglobulin heavy chain variable repertoire of three healthy adult donors. Here we report that most of the CD19+ circulating B cells expressed unmutated VH-D-JH rearrangements. By specific VH family hybridization, we show that VH gene family utilization in the periphery roughly corresponds to the complexity of these families in the germline and appears to be relatively constant among the analyzed subjects. However, sequence data of clones picked at random from one IgM cDNA library reveals that in spite of this “random” utilization, the VH gene expression in naive circulating B cells is highly biased towards the expression of a limited set of VH genes. As previously reported by others, this restricted mechanism is also found for the D and JH segments.

VARIABLE REGION LIGHT CHAIN GENES ENCODING HUMAN ANTIBODIES TO HIV-1

In previous work, it was found that the heavy chain variable gene (VH) repertoire of human antibodies to HIV is markedly skewed and that the gp120 molecule is a ligand for VH3 gene products. Here, we have analysed the light chain (L-chain) variable region genes (VL) expressed by a panel of human monoclonal antibodies derived from an immunized volunteer, an AIDS patient and seropositive asymptomatic donors, and specific for HIV-1 p25, gp41 and gp120 proteins. We found that, in contrast to VH gene-family use, the VL repertoire does not exhibit a family-bias. We noticed however, a tendency to the use of VL genes that map to the downstream portion of the kappa locus. The VL genes expressed have mutated at lower rates than the corresponding VH genes and show no clustering of the replacement mutations in the hypervariable regions. We also found that the third hypervariable regions (CDR3) of the L-chains have undergone a marked diversification, with addition of untemplated nucleotides, frequent truncation at the 3 end of the VLs and somatic mutation. These molecular events result in a length heterogeneity of the CDR3s and an apparently positive selection of specific highly reactive amino acids. We conclude that the specificity of, at least some of the anti-HIV antibodies, is dictated by the L-chain CDR3 regions which bear the imprints of antigenic selection.

MOLECULAR CHARACTERIZATION OF HUMAN MONOCLONAL ANTIBODIES SPECIFIC FOR SEVERAL HIV PROTEINS : ANALYSIS OF THE VH3 FAMILY EXPRESSION

We have analyzed the heavy-chain variable (VH) region genes expressed by a panel of human monoclonal antibodies derived from an immunized volunteer, an AIDS patient and seropositive asymptomatic donors, and specific for HIV-1 env, pol and gag gene products. The third complementarity-determining regions show a high complexity with unconventional gene recombination events. Most of the VH genes utilized are also frequently encountered in other immune responses. Their sequences are, in general, typical of an antigen-driven immune response. Molecular mechanisms that generate high-affinity antibodies are then effective during HIV infection. Remarkably, VH3 family, which dominates the human antibody repertoire, is barely encountered among anti-HIV antibodies.