<p>Acute physiological changes caused by complement activators and amphotericin B-containing liposomes in mice</p>

Abstract

Undesirable complement (C) activation by nanomedicines can entail an adverse immune reaction known as C activation-related pseudoallergy (CARPA) in sensitive patients. The syndrome includes cardiopulmonary, hemodynamic, and a variety of other physiological changes that have been well described in man, pigs, dogs, and rats. However, the information on CARPA is scarce and ambiguous in mice, a species widely used in preclinical studies. The present study aimed to fill this gap by exploring signs of CARPA in mice following i.v. administration of AmBisome and Abelcet, which are nano-formulations of Amphotericin B with high risk to cause CARPA. Materials and methods: Anesthetized NMRI mice were intravenously injected with liposomal amphotericin B (Abelcet and AmBisome; 30-300 mg phospholipid/kg), drug-free high cholesterol multilamellar vesicles (HC-MLV), and positive controls, cobra venom factor (CVF) and zymosan, followed by the measurement of blood pressure (BP), heart rate, white blood cell, and platelet counts and plasma thromboxane B2 (TXB2) levels. C activation was assessed by C3a ELISA, a C3 consumption assay (PAN-C3) and a modified sheep red blood cell hemolytic assay. Results: All test agents, except HC-MLV, caused transient hypertension, thrombocytopenia, and elevation of plasma TXB2, which were paralleled by significant rises of plasma C3a in CVF and zymosan-treated animals, wherein the initial hypertension turned into hypotension and shock. Abelcet and AmBisome caused minor, delayed rise of C3a that was not associated with hypertension. The C3a receptor inhibitor SB-290157 attenuated the hypertension caused by Abelcet and decreased the BP thereafter. Conclusion: The parallelism between C3a anaphylatoxin production and severity of physiological changes caused by the different agents is consistent with CARPA underlying these changes. Although the reactive dose of liposomal phospholipids was substantially higher than that in other species (pigs, dogs), the mouse seems suitable for studying the mechanism of hypersensitivity reactions to liposomal formulations of amphotericin B, a frequent side effect of these drugs.

Human Clinical Relevance of the Porcine Model of Pseudoallergic Infusion Reactions

“…As for the concordance of blood cells changes in pigs and man, leukopenia followed by leukocytosis and/or thrombocytopenia were described during drug-induced HSRs in man as Cactivation-related [108][109][110][111], just as in pigs [15], rats [58,112], mice [20], and monkeys [113].…”

“…However, it is critical to emphasize that C activation is not the only mechanism of these reactions. The mechanism of HSRs is complex and varies in different species under different conditions, also involving C-independent pathways, referred to as C-independent pseudoallergy (CIPA) [19,20]. Table 1 lists 30 experimental studies [15, which utilized the pig model to analyze the cardiopulmonary adverse effects of different nanoparticles (NPs) or other agents.…”

“…The vasoactivity of TXA2 is a key contributor to the massive hemodynamic changes following NP injection of pigs and other animals. [15,20,48,[50][51][52][53][54][55][56][57][58] Arguable Claims:…”

The Critical Choice of Animal Models in Nanomedicine Safety Assessment: A Lesson Learned From Hemoglobin-Based Oxygen Carriers

“…Although rodents also react to certain iv. nanomedicines with hemodynamic changes, the effect is seen only at extremely high doses that are clinically not relevant (59)(60)(61). Thus, it does not seem reasonable to replace the pig model with a rat or mouse model to mimic human HSRs, and the idea to use a cirrhotic rat model seems even more far-fetched (6).…”

Complement Activation-Related Pathophysiological Changes in Anesthetized Rats: Activator-Dependent Variations of Symptoms and Mediators of Pseudoallergy

“…Complement (C) activation is one explanation for these reactions, leading to the term C activation-related pseudoallergy (CARPA) [7]. However, recent studies in pigs [8] and mice [9] raised the possibility of C-independent mechanisms as well, referred to as C-independent pseudoallergy (CIPA). At this time, we cannot exclude the possibility that the apparent absence of C activation in these cases was due to assay failure, such as low sensitivity and/or improper test and/or incorrect sampling times, and, in fact, C activation was present, just not detected.…”