Gene therapy has continuously evolved throughout the years since its first proposal to develop more specific and effective transfection, capable of treating a myriad of health conditions. Viral vectors are some of the most common and most efficient vehicles for gene transfer. However, the safe and effective delivery of gene therapy remains a major obstacle. Ultrasound contrast agents in the form of microbubbles have provided a unique solution to fulfill the need to shield the vectors from the host immune system and the need for site specific targeted therapy. Since the discovery of the biophysical and biological effects of microbubble sonification, multiple developments have been made to enhance its applicability in targeted drug delivery. The concurrent development of viral vectors and recent research on dual vector strategies have shown promising results. This review will explore the mechanisms and recent advancements in the knowledge of ultrasound-mediated microbubbles in targeting gene and drug therapy.

Currently, the response to cancer treatments is highly variable, and severe side effects and toxicity are experienced by patients receiving high doses of chemotherapy, such as those diagnosed with triple-negative breast cancer. The main goal of researchers and clinicians is to develop new effective treatments that will be able to specifically target and kill tumor cells by employing the minimum doses of drugs exerting a therapeutic effect. Despite the development of new formulations that overall can increase the drugs’ pharmacokinetics, and that are specifically designed to bind overexpressed molecules on cancer cells and achieve active targeting of the tumor, the desired clinical outcome has not been reached yet. In this review, we will discuss the current classification and standard of care for breast cancer, the application of nanomedicine, and ultrasound-responsive biocompatible carriers (micro/nanobubbles, liposomes, micelles, polymeric nanoparticles, and nanodroplets/nanoemulsions) employed in preclinical studies to target and enhance the delivery of drugs and genes to breast cancer.

Oncolytic virotherapy has shown great promise in mediating targeted tumor destruction through tumor-selective replication and induction of anti-tumor immunity; however, obstacles remain for virus candidates to reach the clinic. These include avoiding neutralizing antibodies, preventing stimulation of the adaptive immune response during intravenous administration, and inducing sufficient apoptosis and immune activation so that the body’s defense can work to eradicate systemic disease. We have developed a co-formulation of oncolytic viruses (OVs) with Imagent^® lipid-encapsulated, perfluorocarbon microbubbles (MBs) to protect the OVs from the innate and adaptive immune system. Once inside the MB, the viral particles become acoustically active such that external ultrasound can target the delivery of the virus locally within the tumor. Humanized NSG female mice (Hu-CD34⁺ NSG-SGM3) engrafted in their flanks with MDA-MB-231-Luc triple-negative breast cancer (TNBC) cells were transduced with MB/OVs, with or without adjuvant Pembrolizumab treatment, and tumor sizes and tumor necrosis were assessed. The presence of CD8⁺ (cytotoxic T-cells), CD4⁺ (helper T-cells), and CD25⁺ (Tregs) tumor-infiltrating lymphocytes (TILs) was quantified in the tumor samples by immunohistochemistry. In an in vivo model of humanized mice engrafted with a human immune system, we observed significantly greater tumor necrosis and smaller tumor mass in human TNBC xenografts systemically treated with MB/OV complexes in the presence or absence of pembrolizumab adjuvant treatment, compared to controls. Additionally, we observed a low ratio of CD4⁺/CD8⁺ TILs and a high ratio of CD8⁺/CD25⁺ TILs in the MDA-MB-231 xenografts treated with MB/OVs complexes with or without pembrolizumab adjuvant treatment, compared to controls. Our study demonstrated the feasibility of using MBs to target OVs to TNBC through diagnostic ultrasound, which decreased tumor mass by increasing tumor necrosis and stimulated a local and systemic antitumoral immune response by increasing intratumoral CD8⁺ T-cytotoxic lymphocyte infiltration and decreasing CD25⁺ Treg cells.

Immunotherapy has been extensively explored in recent years with encouraging results in selected types of cancer. Such success aroused interest in the expansion of such indications, requiring a deep understanding of the complex role of the immune system in carcinogenesis. The definition of hot vs. cold tumors and the role of the tumor microenvironment enlightened the once obscure understanding of low response rates of solid tumors to immune check point inhibitors. Although the major scope found in the literature focuses on the T cell modulation, the innate immune system is also a promising oncolytic tool. The unveiling of the tumor immunosuppressive pathways, lead to the development of combined targeted therapies in an attempt to increase immune infiltration capability. Oncolytic viruses have been explored in different scenarios, in combination with various chemotherapeutic drugs and, more recently, with immune check point inhibitors. Moreover, oncolytic viruses may be engineered to express tumor specific pro-inflammatory cytokines, antibodies, and antigens to enhance immunologic response or block immunosuppressive mechanisms. Development of preclinical models capable to replicate the human immunologic response is one of the major challenges faced by these studies. A thorough understanding of immunotherapy and oncolytic viruses’ mechanics is paramount to develop reliable preclinical models with higher chances of successful clinical therapy application. Thus, in this article, we review current concepts in cancer immunotherapy including the inherent and synthetic mechanisms of immunologic enhancement utilizing oncolytic viruses, immune targeting, and available preclinical animal models, their advantages, and limitations.

A left ventricle pseudoaneurysm (LV PSA) is defined as a free wall rupture of the left ventricle contained by the adjacent pericardial tissue. This rare complication is most commonly encountered following myocardial infarction, trauma, or infection. Surgery is typically warranted to avoid progression to spontaneous rupture, which may potentially lead to cardiac tamponade and death. Cardiac magnetic resonance imaging is the modality of choice to characterize left ventricle morphology and function. Accurate distinction between a pseudoaneurysm and a true aneurysm is crucial, since management and prognosis are significantly different between these 2 entities. We present a case of a 63-year-old male heart transplant recipient, admitted for suspicion of acute cellular rejection, with an unexpected finding of a LV PSA.

Immunoglobulin G4-related aortitis (IgG4-RA) is histologically characterized by the infiltration of IgG4 positive plasma cells and fibrosis in systemic organs and the elevation of serum IgG4 levels. The cardiovascular system is commonly involved with various possible presentations such as aortitis, arteritis, periaortitis, periarteritis, and inflammatory aneurysm. We present a case of a 48-year-old male without known previous medical history, admitted for further workup of long-standing chest pain and shortness of breath with suspected aortic dissection on initial assessment. Investigation with computed tomography angiography (CTA) and magnetic resonance angiography (MRA) indicated severe thoracic and abdominal aortoarteritis associated with an ascending thoracic aortic aneurysm, which was confirmed to be IgG4-RA on histopathologic analysis. Thoracic and abdominal IgG4-RA clinical and radiological presentation may simulate other causes of acute aortic syndrome such as aortic dissection, atherosclerotic aneurysm and inflammatory conditions. Accurate recognition of IgG4-RA diagnostic imaging features are essential for early diagnosis and treatment surveillance.