TLR8 stimulation enhances cetuximab-mediated natural killer cell lysis of head and neck cancer cells and dendritic cell cross-priming of EGFR-specific CD8+ T cells.

BACKGROUND: Cetuximab is an anti-epidermal growth factor receptor (EGFR) monoclonal antibody that prolongs survival in the treatment for head and neck cancer (HNC), but only in 10-20 % of patients. An immunological mechanism of action such as natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity (ADCC) has been suggested. We investigated the effects of activating toll-like receptor (TLR)-8 to enhance activity of cetuximab-stimulated, FcγR-bearing cells. OBJECTIVE: To determine the capability of TLR8-stimulation to enhance the activation and function of NK cells and dendritic cells (DC) in the presence of cetuximab-coated HNC cells. METHODS: Peripheral blood mononuclear cells (PBMC), NK, DC, and CD8(+) T cells were isolated and analyzed using (51)Cr release ADCC, flow cytometry analysis, cytokine ELISA, and EGFR853-861 tetramer staining. RESULTS: TLR8 stimulation of unfractionated PBMC led to enhanced cetuximab-mediated ADCC in healthy donors (p < 0.01) and HNC patients (p < 0.001), which was dependent on NK cells. Secretion of Th1 cytokines TNFα (p < 0.0001), IFNγ (p < 0.0001), and IL-12p40 (p < 0.005) was increased. TLR8 stimulation of PBMC augmented cetuximab-enhanced NK cell degranulation (p < 0.001). TLR8-stimulated NK cells enhanced DC maturation markers CD80, CD83, and CD86 in co-culture with cetuximab-treated HNC cells. TLR8 stimulation of NK-DC co-cultures significantly increased DC priming of EGFR-specific CD8(+) T cells in the presence of cetuximab. DISCUSSION: VTX-2337 and cetuximab combination therapy can activate innate and adaptive anti-cancer immune responses. Further investigation in human trials will be important for determining the clinical benefit of this combination and for determining biomarkers of response.

Mechanisms of resistance for Streptococcus pyogenes in northern Utah.

OBJECTIVE: The purpose of this study was to (1) determine the rates of penicillin and erythromycin resistance among Streptococcus pyogenes isolates in northern Utah, and (2) determine the genotype of the erythromycin resistant strains, thereby providing information regarding the mechanism of the resistance. DESIGN: Seven hundred thirty-nine isolates of S. pyogenes were identified on 5% Sheep Blood Agar. Susceptibility to erythromycin and penicillin was performed using Muller-Hinton blood agar. All isolates resistant to erythromycin were then genotyped using PCR primers specific to one of the following: mefA gene, indicating the mechanism of resistance was an efflux pump; ermA gene, in which the mechanism was inducible methylation of the ribosomes; and ermB indicating constitutive methylation of the ribosomes. LOCATION: This study was conducted at Weber State University, in the Department of Clinical Laboratory Sciences. PATIENT SAMPLES: Samples were collected from 9 clinics ranging from North Ogden to Taylorsville, Utah. All samples were previously tested positive for S. pyogenes by the clinic from where the samples were collected. RESULTS: Of the 739 S. pyogenes isolates tested, 2.4% were resistant to erythromycin with no resistance observed to penicillin. Of the strains that displayed some degree of resistance, the gene frequencies observed were as follows: 48.1% mefA, 26.0% ermA, 3.7% ermB, and 22.2% multiple genes. CONCLUSION: The most common genotype was mefA, indicating that the efflux pump (M phenotype) is the most common mechanism in the surveyed area, followed by ermA, which produces the inducible methylating enzyme. A significant number of isolates was also observed to express both the efflux pump and the constitutive methylating enzyme.