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Immunotoxicity studies on the insecticide 2-((1-(4-Phenoxyphenoxy)propan-2yl)oxy)pyridine (MPEP) in Hsd:Harlan Sprague Dawley SD rats

Victor J. Johnson1,*, Stefanie C.M. Burleson1, Michael I. Luster1, Gary R. Burleson1, Barry McIntyre2,Veronica G. Robinson2, Reshan A. Fernando3, James Blake3, Donna Browning3, Stephen Cooper3, Shawn Harris4,Dori Germolec2

1Burleson Research Technologies, Inc., Morrisville, NC 27560, USA
2Division of Translational Toxicology, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27560, USA
3RTI International, Research Triangle Park, NC 27713, USA
4DLH, LLC, Bethesda, MD 20817, USA
*Author to whom correspondence should be addressed.

Toxics (2025) DOI: https://doi.org/10.3390/toxics13070600 PMID: 40711044 PMCID: PMC12300427

DOI: https://doi.org/10.22427/DATA-500-005-002-000-2

Publication

Abstract

To address public health programs for vector control, initiated by the recent spread of Zika virus, 2-((1-(4-Phenoxyphenoxy)propan-2-yl)oxy)pyridine (MPEP), a broad-spectrum insect growth regulator (IGR) with insecticidal activity, is increasingly being used. While considered relatively safe for humans under normal conditions, limited toxicology data are available. Current studies were undertaken to address the data gap regarding potential immunotoxicity of MPEP, with particular emphasis on host resistance to viral infection. Hsd:Harlan Sprague Dawley SD® rats were treated for 28 days by oral gavage with doses of 0, 62.5, 125, 250 or 500 mg/kg/day of MPEP in corn oil. There was a dose-dependent increase in liver weights which is consistent with the liver playing a dominant role in MPEP metabolism. However, no histological correlates were observed. Following treatment, rats were subjected to a battery of immune tests as well as influenza virus infection to provide a comprehensive assessment of immune function and host resistance. While several of the immune tests showed minor exposure-related changes, evidenced by negative dose-response trends, most did not show significant differences in any of the MPEP treatment groups relative to the vehicle control. Most notable was a negative trend in pulmonary mononuclear cell phagocytosis with increasing dose of MPEP. Furthermore, MPEP treatment had no effect on the ability of rats to clear the influenza virus nor the T-dependent IgM and IgG antibody response to the virus. Overall, under the conditions of the current studies, the lack of findings in the disease resistance studies and minimal effects in the immunotoxicity studies suggest that there was little impact on immune function in HSD rats following MPEP exposure.

Study Data

Study Tables - 28-day Rat Immunotox Study

Study Tables - Rat Influenza Host Resistance Study

Individual Animal Data - 28-day Rat Immunotox Study

Individual Animal Data - Rat Influenza Host Resistance Study