BACKGROUND Although early reperfusion is the most desirable intervention after ischemic myocardial insult, it may add to damage through oxidative stress. OBJECTIVES We investigated the cardioprotective effects of a single intravenous dose of heat shock protein (HSP72) coupled to a single-chain variable fragment (Fv) of monoclonal antibody 3E10 (3E10Fv) in a rabbit ischemia-reperfusion model. The Fv facilitates rapid transport of HSP72 into cells, even with intact membranes. METHODS A left coronary artery occlusion (40 min), reperfusion (3 h) model was employed in 31 rabbits. Of these, 12 rabbits received the fusion protein (Fv-HSP72) intravenously. The remaining 19 control rabbits received a molar equivalent of 3E10Fv alone (n = 6), HSP72 alone (n = 6), or phosphate buffered saline (n = 7). Serial echocardiographic examinations were performed to assess left ventricular (LV) function before and after reperfusion. Micro-single photon emission computed tomography imaging of 99mTc-labeled annexin-V was performed with micro-computed tomography to characterize apoptotic damage in vivo, followed by gamma counting of the excised myocardial specimens to quantify cell death. Histopathological characterization of the myocardial tissue, and sequential cardiac troponin I measurements were also undertaken. RESULTS Myocardial annexin-V uptake was 43% lower in the area at risk (p = 0.0003) in Fv-HSP72-treated rabbits compared to controls receiving HSP72 or 3E10Fv alone. During reperfusion, troponin I release was 42% lower and the echocardiographic LV ejection fraction 27% higher in the Fv-HSP72-treated group compared to controls. Histopathological analyses confirmed penetration of 3E10Fv-containing molecules into cardiomyocytes in vivo, and treatment with Fv-HSP72 showed fewer apoptotic nuclei compared to control rabbits. CONCLUSIONS A single-dose administration of Fv-HSP72 fusion protein at the time of reperfusion reduced myocardial apoptosis almost by half, and improved LV functional recovery following myocardial ischemia-reperfusion injury in rabbits. It might have a potential to serve as an adjunct to early reperfusion in the management of myocardial infarction.

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The cell cycle kinetics of F3(B6) mouse hybridoma was examined by immunocytochemical staining of bromodeoxyuridine incorporated into the DNA of exponentially growing cells in three different cultures: one supplemented with 10% fetal bovine serum and two adapted to serum-free media, TABIES and BITES. The serum-free cultures, particularly the BITES, had longer cycling times and higher specific antibody production rate. Both observations were correlated to the prolongation of the G1 phase traverse time and substantiated with a starvation blocking experiment.

Heat shock protein 72 (HSP72) is perhaps the most important member of the HSP70 family of proteins, given that it is induced in a wide variety of tissues and cells to combat stress, particularly oxidative stress. Here we review independent observations of the critical role this protein plays as a pulmonary cytoprotectant and discuss the merits of developing HSP72 as a therapeutic for rapid delivery to cells and tissues after a traumatic event. We also discuss the fusion of HSP72 to a cell-penetrating single-chain Fv (scFv) antibody fragment derived from mAb 3E10, referred to as Fv-HSP70. This fusion construct has been validated in vivo in a cerebral infarction model and is currently in testing as a clinical therapeutic to treat ischemic events and as a fieldable medical countermeasure to treat inhalation of toxicants caused by terrorist actions or industrial accidents.

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