NOD/SCID/gamma(c)(null) mouse: an excellent recipient mouse model for engraftment of human cells

To establish a more appropriate animal recipient for xenotransplantation, NOD/SCID/gamma(c)(null) mice double homozygous for the severe combined immunodeficiency (SCID) mutation and interleukin-2Rgamma (IL-2Rgamma) allelic mutation (gamma(c)(null)) were generated by 8 backcross matings of C57BL/6J-gamma(c)(null) mice and NOD/Shi-scid mice. When human CD34+ cells from umbilical cord blood were transplanted into this strain, the engraftment rate in the peripheral circulation, spleen, and bone marrow were significantly higher than that in NOD/Shi-scid mice treated with anti-asialo GM1 antibody or in the beta2-microglobulin-deficient NOD/LtSz-scid (NOD/SCID/beta2m(null)) mice, which were as completely defective in NK cell activity as NOD/SCID/gamma(c)(null) mice. The same high engraftment rate of human mature cells was observed in ascites when peripheral blood mononuclear cells were intraperitoneally transferred. In addition to the high engraftment rate, multilineage cell differentiation was also observed. Further, even 1 x 10(2) CD34+ cells could grow and differentiate in this strain. These results suggest that NOD/SCID/gamma(c)(null) mice were superior animal recipients for xenotransplantation and were especially valuable for human stem cell assay. To elucidate the mechanisms involved in the superior engraftment rate in NOD/SCID/gamma(c)(null) mice, cytokine production of spleen cells stimulated with Listeria monocytogenes antigens was compared among these 3 strains of mice. The interferon-gamma production from dendritic cells from the NOD/SCID/gamma(c)(null) mouse spleen was significantly suppressed in comparison with findings in 2 other strains of mice. It is suggested that multiple immunological dysfunctions, including cytokine production capability, in addition to functional incompetence of T, B, and NK cells, may lead to the high engraftment levels of xenograft in NOD/SCID/gamma(c)(null) mice.     

Drug-resistant tuberculosis: pediatric guidelines

Drug-resistant Mycobacterium tuberculosis (TB) infection represents a serious and growing problem. For patients infected or suspected of being infected with multidrug or extensively drug-resistant TB, several medications have to be given simultaneously for prolonged periods. Here, we review the literature on treatment and monitoring of adverse effects of pediatric drug-resistant TB therapy in a high resource, low TB burden setting.     

Utilization of complement-dependent cytotoxicity to measure low levels of antibodies: application to nonstructural protein 1 in a model of Japanese encephalitis virus

Enzyme-linked immunosorbent assay (ELISA) and related assays are representative of methods currently used for antibody tests. However, they occasionally produce nonspecific reactions, thus making it difficult to reliably measure low levels of specific antibodies. To find a test method that minimizes nonspecific reactions, we introduced the principle of antibody-mediated complement-dependent cytotoxicity (CDC) into an antibody assay. The procedure has three steps: (i) the mixing of test samples with a suspension of cells expressing the antigen of interest on their surfaces, (ii) the addition of rabbit complement, and (iii) the measurement of lactose dehydrogenase (LDH) activities by adding a chromogenic substrate to the reaction mixture. When the specific antibodies exist in the sample, complement activation triggered by antibody binding on the surface of the antigen-expressing cells may lyse the cells, releasing LDH into the medium. Mouse and rabbit sera hyperimmune to nonstructural protein 1 (NS1) of Japanese encephalitis virus (JEV) lysed NS1-expressing cells in a dose-dependent manner. Evaluations using sera from horses naturally infected with JEV showed that the CDC assay had quantitative correlation and qualitative agreement with previously established NS1 antibody-detecting immunostaining and ELISA methods. The assay method also detected NS1 antibodies in sera of mice 2 days after experimental infection with JEV; specific, but not natural, immunoglobulin M antibodies were detected. Since almost all sera examined in this study showed no nonspecific reactions, the CDC assay was shown to be a reliable method for measuring low levels of specific antibodies.     

Wire ThRoUgh Snare Twice (Wire TRUST) technique: A novel method to grasp a lead with inaccessible ends as a supportive femoral approach for transvenous lead extraction

Introduction

Transvenous lead extraction (TLE) is a crucial procedure for managing cardiac implantable electronic devices. The use of a combined superior and femoral approach has been found to enhance the success rate of TLE. This report introduces a novel technique, named “Wire ThRoUgh Snare Twice” (Wire TRUST), for effectively grasping a lead without a free end during TLE.

Method

The Wire TRUST technique was applied in a case involving a 49-year-old male patient requiring TLE due to electrical artifact on the right ventricular (RV) lead, replacement of the RV lead, and pacemaker generator exchange. The Wire TRUST technique involved the insertion of a 4-Fr pigtail catheter and a 6-Fr snare catheter through the 14-Fr sheath inserted from the right common femoral vein. The 4-Fr pigtail catheter was hooked to the RV lead under multidirectional fluoroscopic guidance in the right atrium. The 0.014-in. guidewire was advanced through the pigtail catheter, crossing the RV lead until reaching the inferior vena cava. Subsequently, the distal end of the 0.014-in. guidewire was captured using a snare and pulled, facilitating externalization of the guidewire. After externalization, both ends of the 0.014-in. guidewire were passed through the snare outside the body and reinserted into the 14-Fr sheath. By simultaneously advancing and closing the snare while applying tension to the 0.014-in. guidewire, a secure grip on the lead without free ends was achieved.

Results

The Wire TRUST technique enabled successful lead extraction and replacement without any complications. The technique facilitated the co-axial alignment of the powered sheath with the RV lead, ensuring safe and efficient extraction.

Conclusion

The Wire TRUST technique presents a novel and effective approach for grasping leads with inaccessible ends during TLE.