NK cells stimulated with IL-15 or CpG ODN enhance rituximab-dependent cellular cytotoxicity against B-cell lymphoma

Phase II study of a TLR-9 agonist (1018 ISS) with rituximab in patients with relapsed or refractory follicular lymphoma

Toll-like receptor-9 (TLR-9) agonists have pleotropic effects on both the innate and adaptive immune systems, including increased antigen expression, enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) and T helper cell type 1 shift in the immune response. We combined a TLR-9 agonist (1018 ISS, 0.2 mg/kg sc weekly x 4 beginning day 8) with standard rituximab (375 mg/m(2) weekly x 4) in patients (n = 23) with relapsed/refractory, histologically confirmed follicular lymphoma, and evaluated immunological changes following the combination. Treatment was well-tolerated with no significant adverse events attributable to therapy. Clinical responses were observed in 48% of patients; the overall median progression-free survival was 9 months. Biologically relevant increases in ADCC and circulating CD-3 positive T cells were observed in 35% and 39% of patients, respectively. Forty-five percent of patients had increased T cells and dendritic cells in skin biopsies of 1018 ISS injection sites 24 h post-therapy. Pre- and post-biopsies of tumour tissue demonstrated an infiltration of CD8(+) T cells and macrophages following treatment. This group of patients had favourable clinical outcome despite adverse prognostic factors. This study is the first to histologically confirm perturbation of the local immune microenvironment following systemic biological therapy of follicular lymphoma.

Lipid-based delivery of CpG oligonucleotides enhances immunotherapeutic efficacy

There has been significant interest in the potential of cytosine-guanine (CpG) containing oligodeoxynucleotides (ODN) as an immunotherapy for malignant, infectious and allergic diseases. While human trials have yielded promising results, clinical use of free CpG ODN still faces several challenges which limit their effectiveness. These include suboptimal in vivo stability, toxicity, unfavorable pharmacokinetic/biodistribution characteristics, lack of specificity for target cells and the requirement for intracellular uptake. To overcome these challenges, optimized lipid-based delivery systems have been developed to protect the CpG ODN payload, modify their circulation/distribution so as to enhance immune cell targeting and facilitate intracellular uptake. Ultimately, lipid-mediated delivery has the capacity to increase the immunopotency of CpG ODN and enhance their prophylactic or therapeutic efficacy in a range of diseases. Lipid-encapsulation provides a feasible strategy to optimize the immunostimulatory activity and immunotherapeutic efficacy of CpG ODN, thereby allowing their full clinical potential to be realized.

Cytolytic activity of NK cell clones against acute childhood precursor-B-cell leukaemia is influenced by HLA class I expression on blasts and the differential KIR phenotype of NK clones

Relapse after allo-SCT in patients with acute leukaemia remains a major problem. A beneficial impact of alloreactive natural killer (NK) cells has been reported for myeloid malignancies, but has been questionable for B-lineage ALL. We analysed lysis of primary paediatric precursor-B-ALL blasts by 285 NK cell clones to investigate whether HLA class I expression on the blasts and phenotypic killer cell Ig-like receptor (KIR) expression on NK cells affect the lytic activity against ALL blasts. Precursor-B-ALL blasts with low HLA-I expression were lysed by a majority (79%) of NK cell clones, whereas those with high HLA-I expression showed low susceptibility to NK clones independent of their KIR expression patterns. NK cell activity against susceptible blasts was regulated by differential surface expression of the three major KIRs (CD158a, CD158b, CD158e). NK clones with none of these three KIRs or a single KIR that recognized no ligand, were not inhibited by the targets and exerted higher lysis (P = <0.0005) in comparison to NK clones expressing KIRs with a ligand on the ALL blasts. In conclusion, the quantity of HLA-I expression on precursor-B-ALL blast regulates overall NK cell susceptibility; in case of reduced HLA expression, differential surface expression of KIRs affects NK cell alloreactivity against those blasts.