An augmented hybrid multibaseline and referenceless MR thermometry motion compensation algorithm for MRgHIFU hyperthermia.

PURPOSE: A hybrid principal component analysis and projection onto dipole fields (PCA-PDF) MR thermometry motion compensation algorithm was optimized with atlas image augmentation and validated. METHODS: Experiments were conducted on a 3T Philips MRI and Profound V1 Sonalleve high intensity focused ultrasound (high intensity focused ultrasound system. An MR-compatible robot was configured to induce motion on custom gelatin phantoms. Trials with periodic and sporadic motion were introduced on phantoms while hyperthermia was administered. The PCA-PDF algorithm was augmented with a predictive atlas to better compensate for larger sporadic motion. RESULTS: During periodic motion, the temperature SD in the thermometry was improved from 1 . 1 ± 0 . 1 $$ 1.1\pm 0.1 $$ to 0 . 5 ± 0 . 1 ∘ $$ 0.5\pm 0.{1}^{\circ } $$ C with both the original and augmented PCA-PDF application. For large sporadic motion, the augmented atlas improved the motion compensation from the original PCA-PDF correction from 8 . 8 ± 0 . 5 $$ 8.8\pm 0.5 $$ to 0 . 7 ± 0 . 1 ∘ $$ 0.7\pm 0.{1}^{\circ } $$ C. CONCLUSION: The PCA-PDF algorithm improved temperature accuracy to <1°C during periodic motion, but was not able to adequately address sporadic motion. By augmenting the PCA-PDF algorithm, temperature SD during large sporadic motion was also reduced to <1°C, greatly improving the original PCA-PDF algorithm.

An adaptive targeting algorithm for magnetic resonance-guided high-intensity focused ultrasound controlled hyperthermia.

BACKGROUND: Mild hyperthermia has been demonstrated to improve the efficacy of chemotherapy, radiation, and immunotherapy in various cancer types. One localized, non-invasive method of administering mild hyperthermia is magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU). However, challenges for ultrasound such as beam deflection, refraction and coupling issues may result in a misalignment of the HIFU focus and the tumor during hyperthermia. Currently, the best option is to stop the treatment, wait for the tissue to cool, and redo the treatment planning before restarting the hyperthermia. This current workflow is both time-consuming and unreliable. PURPOSE: An adaptive targeting algorithm was developed for MRgHIFU controlled hyperthermia treatments for cancer therapeutics. This algorithm executes in real time while hyperthermia is being administered to ensure that the focus is within our target region. If a mistarget is detected, the HIFU system will electronically steer the focus of the HIFU beam to the correct target. The goal of this study was to quantify the accuracy and precision of the adaptive targeting algorithm's ability to correct a purposely misplanned hyperthermia treatment in real-time using a clinical MRgHIFU system. METHODS: A gelatin phantom with acoustic properties matched to the average speed of sound in human tissue was used to test the adaptive targeting algorithm's accuracy and precision. The target was purposely offset 10 mm away from the focus at the origin, in four orthogonal directions, allowing the algorithm to correct for this mistarget. In each direction, 10 data sets were collected for a total sample size of 40. Hyperthermia was administered with a target temperature set at 42°C. The adaptive targeting algorithm was run during the hyperthermia treatment and 20 thermometry images were collected after the beam steering occurred. The location of the focus was quantified by calculating the center of heating on the MR thermometry data. RESULTS: The average calculated trajectory passed to the HIFU system was 9.7 mm ± 0.4 mm where the target trajectory was 10 mm. The accuracy of the adaptive targeting algorithm after the beam steering correction was 0.9 mm and the precision was 1.6 mm. CONCLUSION: The adaptive targeting algorithm was implemented successfully and was able to correct the 10 mm mistargets with high accuracy and precision in gelatin phantoms. The results demonstrate the capability to correct the MRgHIFU focus location during controlled hyperthermia.

Enhanced tumor immunogenicity through coupling cytokine expression with antigen presentation.

The density of tumor antigen in conjunction with major histocompatibility complex (MHC) class I molecules on the cell surface affects cytotoxic T cell (CTL) function in an active antitumor immune response. Thus, methods to enhance antigen expression/presentation could augment the effect of cancer immune therapy. In the present study, we investigated the feasibility of modifying a cytokine signal peptide with a tumor antigenic epitope. We inserted the genes encoding the MHC class I-restricted antigenic epitope of chicken ovalbumin and tyrosinase-related protein 2 into the signal sequence of the interleukin-2 gene, replacing part of the signal sequence at different positions. Our results showed that these modified signal peptides still functioned, as indicated by cytokine secretion. The antigenic epitope within the modified signal peptide could be processed properly and presented on tumor cell surface. Tumor cells demonstrated enhanced immunogenicity as indicated by increased susceptibility to CTL lysis in vitro and decreased tumor grow in vivo after gene modification. These data provide potential perspectives in designing therapeutic or vaccine strategies in immuno-gene therapy of cancer.

A novel inducible amplifier expression vector for high and controlled gene expression.

Safety and efficacy are both required for successful gene therapy. In this regard, our laboratory has created a novel expression system, pHi-Hot that combines inducible and amplifier strategies in one construct. In pHi-Hot, the first transcriptional unit contains an inducible heat shock protein (hsp70B) promoter controlling the expression of a transcriptional factor, Tat, which transactivates a second promoter, the HIV2 LTR, located downstream on the same construct. The second promoter drives the gene of interest. The magnitude of the amplified second gene expression can be regulated through manipulating the activity of the hsp promoter driving the Tat gene. Using the human interleukin-2 (IL-2) cytokine gene as the reporter gene, we demonstrated that moderate heat shock at 42 degrees C for 30 min, the pHi-Hot vector could achieve high gene expression levels while maintaining its inducibility. The induced IL-2 levels were 35- to 70-fold higher than achieved by using the hsp promoter alone, and 10- to 35-fold higher than achieved by using the CMV promoter. Using inducible and amplifier strategies, we can achieve high and controlled gene expression levels from a single construct. Finally, we discuss the advantages of using these strategies in developing new targeting and inducible vectors for genetic research and gene therapy.

A differential role for BB0365 in the persistence of Borrelia burgdorferi in mice and ticks.

Borrelia burgdorferi, the etiologic agent of Lyme disease, persists in both an arthropod vector and vertebrate hosts, usually wild rodents. Analysis of the B. burgdorferi transcriptome in vivo indicates that the bb0365 gene is markedly induced as spirochetes enter the feeding ticks from infected mice. To understand the importance of the bb0365 gene product in the spirochete life cycle, we inactivated this gene in an infectious isolate of B. burgdorferi B31. BB0365-deficient spirochetes were fully pathogenic in mice and survived in diverse murine tissues. When naive ticks engorged on spirochete-infected mice, the B. burgdorferi bb0365 mutant entered ticks but had a markedly decreased survival rate compared with wild type B. burgdorferi. BB0365 therefore is not necessary for B. burgdorferi persistence in the vertebrate host but is required for survival of the Lyme disease agent within the feeding arthropod vector, and strategies for interfering with this gene may potentially interrupt the B. burgdorferi life cycle.

Immuno-gene therapy of melanoma by tumor antigen epitope modified IFN-gamma.

Cytokine-based vaccines play a major part in tumor immuno-gene therapy. However, down-regulated antigen expression on tumor cells may diminish the immuno-potentiating aspects of cellular vaccines. In this study, we coexpressed a tumor antigen epitope with IFN-gamma in the same gene by replacing the IFN-gamma signal peptide with an antigen epitope-expressing signal peptide. We then investigated the effect of the antigen epitope-incorporated IFN-gamma on the immunotherapy of murine melanoma B16 tumors. Results showed that TRP-2 epitope-expressing IFN-gamma decreased B16 tumorigenicity and enhanced its immunogenicity after gene transfer. Protective immunity against wild type B16 tumors was induced by vaccination with IFN-gamma transiently gene-modified tumor cells. These data suggest that cellular vaccines engineered to express an antigen epitope within an immunostimulatory cytokine could potentiate the immunization effect.

Antigen epitope-expressing cytokines for DNA immunization.

Strategies to enhance the efficacy of DNA vaccination against malignancy remain to be established. In this study, a plasmid expressing a tumor antigen incorporated into the signal peptide of human IL-2 was tested as a DNA vaccine in a murine model system. Results showed that antigen-specific CTL responses were elicited by intramuscular injection of these plasmids. Importantly, compared with a minigene vector expressing the same epitope, the OVA epitope-incorporated, IL-2 expression plasmid vaccination was more effective in protecting mice from OVA-expressing tumor challenge. The improved efficacy appears to result from enhanced antigen presentation as well as the immunostimulatory activity of IL-2. This approach may provide new perspectives in designing cytokine-adjuvant DNA vaccines for clinical applications.