Biology subjects

Koehler, J. W.

Publications and source records attributed to Koehler, J. W..

6 recordsLinked to original sources

bioRxiv2025

Stability and characterization of infectious monkeypox virus extracellular virions in vitro2and vivo; implications for transmission, pathogenesis and treatment

Abstract/SummaryPoxviruses exist as multiple infectious morphogenic forms commonly simplified as mature virions (MV) and extracellular virions (EV). The roles of morphogenic subtypes as related to disease and transmission are enigmatic as EVs can exist both as cell associated (CEV) or released particles (rCEV) each with potentially unique biochemical properties impacting stability and infectivity. In vitro analysis of prototypical poxviruses is commonly utilized to infer larger conclusions about the in vivo function of all EV-like particles. Here we show that infectious EV of MPXV and VACV strains are stable for [≥] 14 weeks and are more sensitive to human or non-human primate complement compared to rabbit-derived complement. We also characterize the levels of EV produced during MPXV infection in NHPs and found temporal differences in production that may influence spread. Also, we present data characterizing and contrasting the EV from monkeypox (MPXV) and vaccinia virus (VACV) strains. Specifically, we quantified infectious EV quantities produced by different cultured cell lines and characterized the infectious properties and composition of the released (extracellular) virions. We conclude that A33 neutralizable cell associated-like virions (CEV-like), a form of EV, can significantly increase, depending on the strain of VACV or MPXV and the cell lines from which they were released. Based on the outcomes of our studies, the importance of understanding specific orthopoxvirus EV roles in a host-specific manner, as it relates to pathogenesis, stability, and transmission, is warranted and requires further study.

microbiology↗

bioRxiv2023

Wide distribution of Mediterranean and African Spotted fever agents and the first identification of Israeli Spotted Fever agent in ticks in Uganda

Rickettsia microorganisms are causative agents of several neglected emerging infectious diseases transmitted to humans by ticks among other arthropod vectors. In this study, ticks were collected from four geographical regions of Uganda, pooled in sizes of 1-179 ticks based on location, tick species, life stage, host, and time of collection, and were tested by real time PCR for Rickettsia species harboured. The tick pools were tested with primers targeting gltA, 17kDa and ompA genes, followed by Sanger sequencing of 17kDa and ompA genes. Of the 471 tick pools tested, 116 (24.6%) were positive for Rickettsia spp. by the gltA primers. The prevalence of Rickettsia varied by district with Gulu recording the highest (30.1%) followed by Luwero (28.1%) and Kasese had the lowest (14%). Tick pools with highest positivity rates were from livestock (cattle, goats, sheep, and pigs), 26.9%, followed by vegetation 23.1% and pets (dogs and cats) 19.7%. Of 116 gltA-positive tick pools, 86 pools were positive using 17kDa primers of which 48 purified PCR products were successfully sequenced. The predominant Rickettsia spp. identified was R. africae (n=15) in four tick species, followed by R. conorii (n=5) in three tick species (Haemaphysalis elliptica, Rhipicephalus appendiculatus, and Rh. decoloratus). Rickettsia conorii subsp. israelensis was detected in one tick pool. These findings indicate that multiple Rickettsia spp. capable of causing human illness are circulating in the four diverse geographical regions of Uganda including new strains previously known to occur in the Mediterranean region. Physicians should be informed about Rickettsia spp. infections as potential causes for acute febrile illnesses in these regions. Continued and expanded surveillance is essential to further identify and locate potential hotspots with Rickettsia spp. of concern. Author SummaryTick-borne rickettsioses are emerging infectious diseases of public health importance worldwide. Spotted fever rickettsioses transmitted by ticks can cause mild to severe human illness depending on the Rickettsia spp. and co-morbidities. Their diagnosis is challenging due to non-specific symptoms particularly in limited resource settings. Little is known about their prevalence in Uganda. Using entomological and molecular tools, we surveyed and studied tick-borne spotted fever rickettsioses in five districts from four diverse eco-regions of Uganda. Overall, 24.6% (116/471) tick pools were positive for Rickettsia species. By sequencing the 17kDa and ompA genes of Rickettsia, we identified R. africae as the most common agent, followed by R. conorii and R. conorii subsp. israelensis. The findings indicate multiple Rickettsia spp. that can cause febrile illness in humans are circulating in the four geographically diverse regions of Uganda. Physicians should be aware these agents are potential causes of febrile illness in these areas, particularly in individuals who encounter livestock or their grazing areas.

molecular biology↗

bioRxiv2022

Detection of Dugbe virus from ticks in Ghana

Vector-borne pathogens historically have impacted U.S. warfighters and active-duty personnel stationed both domestically and globally during deployments or forward operations. Tick-borne diseases continue to spread to new geographical regions affecting both animal and human health. In Ghana, there is limited information on the circulating tick-borne pathogens and their risk of infections. This military-to-military vector surveillance study focused on seven sites in Ghana: Navrongo, Airforce Base, 6th Battalion Infantry, Air Borne Force, Army Recruit Training School, 1st Battalion Infantry and 5th Battalion Infantry for detection of tick-borne pathogens. Ticks from these sites were collected by hand-picking with a pair of forceps from domesticated animals including cattle, sheep, goats and dogs. A total of 2,016 ticks were collected from two main ecological zones; the northern Sahel savannah and the coastal savannah. Amblyomma variegatum was the predominant species, accounting for 59.5% of the collected ticks. Next-generation sequencing allowed for Dugbe virus whole genome detection. This study reports the second detection of Dugbe virus in Ghana, which is closely related to Dugbe virus strains from Kenya and Nigeria. This study (sponsored by the Armed Forces Health Surveillance Branch-Global Emerg-ing Infections Surveillance Section) aimed to better inform Force Health Protection (FHP) decisions within the U.S. AFRICOM area of responsibility, the Ghana Armed Forces, and enhance global health security countermeasures. Further surveillance needs to be conducted within the country to determine the distribution of tick-borne pathogens to formulate effective control measures. Author summaryThe prevalence of Dugbe virus in tick species within Ghana was investigated. This study involved seven sampling sites that covered two ecological zones, the northern Sahel savannah and the coastal savannah. About 2,000 ticks were collected from cattle, sheep, goats and dogs and identified using a dissecting microscope. The most predominant tick species was Amblyomma variegatum (59.5%) also known as the tropical bont tick. Using Next-generation sequencing, the full genome of Dugbe virus was for the first time in Ghana identified in A. variegatum. This positive Amblyomma variegatum was collected from the Greater Accra region of Ghana within a military site. The virus was found to be related to Dugbe virus strains from Kenya and Nigeria. Findings from this study show that the trade of livestock across borders facilitates the spread of tick-borne pathogens hence there is a need to enforce measures that prevent the importation of potentially harmful ticks and tick-borne pathogens.

scientific communication and education↗

bioRxiv2021

Aerosol Exposure of Cynomolgus Macaques to SARS-CoV-2 Results in More Severe Pathology than Existing Models

The emergence of SARS-CoV-2 pandemic has highlighted the need for animal models that faithfully recapitulate the salient features of COVID-19 disease in humans; these models are necessary for the rapid down-selection, testing, and evaluation of medical countermeasures. Here we performed a direct comparison of two distinct routes of SARS-CoV-2 exposure, combined intratracheal/intranasal and small particle aerosol, in two nonhuman primate species: rhesus and cynomolgus macaques. While all four experimental groups displayed very few outward clinical signs, evidence of mild to moderate respiratory disease was present on radiographs and at the time of necropsy. Cynomolgus macaques exposed via the aerosol route also developed the most consistent fever responses and had the most severe respiratory disease and pathology. This study demonstrates that while all four models were suitable representations of mild COVID-like illness, aerosol exposure of cynomolgus macaques to SARS-CoV-2 produced the most severe disease, which may provide additional clinical endpoints for evaluating therapeutics and vaccines.

microbiology↗

bioRxiv2020

Animal Model Prescreening: Pre-exposure to SARS-CoV-2 impacts responses in the NHP model

COVID-19 presents herculean challenges to research and scientific communities for producing diagnostic and treatment solutions. Any return to normalcy requires rapid development of countermeasures, with animal models serving as a critical tool in testing vaccines and therapeutics. Animal disease status and potential COVID-19 exposure prior to study execution may severely bias efficacy testing. We developed a toolbox of immunological and molecular tests to monitor countermeasure impact on disease outcome and evaluate pre-challenge COVID-19 status. Assay application showed critical necessity for animal pre-screening. Specifically, real-time PCR results documented pre-exposure of an African Green Monkey prior to SARS-CoV-2 challenge with sequence confirmation as a community-acquired exposure. Longitudinal monitoring of nasopharyngeal swabs and serum showed pre-exposure impacted both viral disease course and resulting immunological response. This study demonstrates utility in a comprehensive pre-screening strategy for animal models, which captured the first documented case of community-acquired, non-human primate infection. One Sentence SummaryPre-exposure to SARS-CoV-2 affects biomarker responses in animal models, highlighting a need for robust pre-screening protocols prior to medical countermeasure studies.

immunology↗

bioRxiv2019

Comparative molecular life history of spontaneous canine and human gliomas

Sporadic gliomas in companion dogs provide a window on the interaction between tumorigenic mechanisms and host environment. We compared the molecular profiles of canine gliomas with those of human pediatric and adult gliomas to characterize evolutionarily conserved mammalian mutational processes in gliomagenesis. Employing whole genome-, exome-, transcriptome-and methylation-sequencing of 81 canine gliomas, we found alterations shared between canine and human gliomas such as the receptor tyrosine kinases, p53 and cell cycle pathways, and IDH1 R132. Canine gliomas showed high similarity with human pediatric gliomas per robust aneuploidy, mutational rates, relative timing of mutations, and DNA methylation patterns. Our cross-species comparative genomic analysis provides unique insights into glioma etiology and the chronology of glioma-causing somatic alterations.\n\nSignificanceDiffuse gliomas are the most common malignant brain tumors, with high-grade tumors carrying a dismal prognosis. Preclinical models have proven themselves as poor predictors of clinical efficacy. Spontaneous glioma in dogs provides an attractive alternative model, because of their comparable tumor microenvironment and tumor life history. We determined the similarities and differences between human and canine gliomas through genomic profiling, and leveraged our datasets to identify conserved somatic drivers, mutational processes and temporal ordering of somatic glioma events across species. We show that canine gliomas resemble human gliomas at (epi-)genetic levels and are more reminiscent of pediatric than adult disease, thus rationalizing sporadic canine glioma as a preclinical model tailored to measuring treatment efficacies in patients with canine or human glioma.

cancer biology↗