Meijer, L. | bioRxiv Science

bioRxiv2021

Bronchoalveolar lavage affects thorax computed tomography of healthy and SARS-CoV-2 infected rhesus macaques (Macaca mulatta)

Medical imaging as method to assess the longitudinal process of a SARS-CoV-2 infection in non-human primates is commonly used in research settings. Bronchoalveolar lavage (BAL) is also regularly used to determine the local virus production and immune effects of SARS-CoV-2 in the lower respiratory tract. However, the potential interference of those two diagnostic modalities with each other is unknown in non-human primates. The current study investigated the effect and duration of BAL on computed tomography (CT) in both healthy and experimentally SARS-CoV-2-infected female rhesus macaques (Macaca mulatta). In addition, the effect of subsequent BALs was reviewed. Thorax CTs and BALs were obtained from four healthy animals and 11 experimentally SARS-CoV-2-infected animals. From all animals, CTs were obtained just before BAL, and 24 hours post-BAL. Additionally, from the healthy animals, CTs immediately after and four hours post-BAL were obtained. Thorax CTs were evaluated for alterations in lung density, measured in Hounsfield units, and a visual semi-quantitative scoring system. An increase in the lung density was observed on the immediately post-BAL CT but resolved within 24 hours in the healthy animals. In the infected animals, a significant difference in both the lung density and CT score was still found 24 hours after BAL. Furthermore, the differences between timepoints in CT score were increased for the second BAL. These results indicate that the effect of BAL on infected lungs is not completed within the first 24 hours. Therefore, it is of importance to acknowledge the interference between BAL and CT in rhesus macaques.

biophysics↗

bioRxiv2020

Comparison of SARS-CoV-2 infection in two non-human primate species: rhesus and cynomolgus macaques

The post-acute phase of SARS-CoV-2 infection was investigated in rhesus macaques (Macaca mulatta) and cynomolgus macaques (Macaca fascicularis). During the acute phase of infection, SARS-CoV-2 was shed via nose and throat, and viral RNA was occasionally detected in feces. This phase coincided with a transient change in systemic immune activation. Even after the alleged resolution of the infection, as suggested by the absence of viral RNA in nasal and tracheal swabs, computed tomography (CT) and positron emission tomography (PET)-CT were able to reveal pulmonary lesions and activated tracheobronchial lymph nodes in all animals. Post-mortem histological examination of the lung tissue revealed mostly marginal or resolving minimal lesions that were indicative of SARS-CoV-2 infection. Evidence for SARS-CoV-2-induced histopathology was also found in extrapulmonary tissue samples, like conjunctiva, cervical and mesenteric lymph nodes. However, 5-6 weeks after SARS-CoV-2 exposure, upon necropsy, viral RNA was still detectable in a wide range of tissue samples in 50% of the macaques and included amongst others the heart, the respiratory tract and surrounding lymph nodes, salivary gland, and conjunctiva. Subgenomic messenger RNA was detected in the lungs and tracheobronchial lymph nodes, indicative of ongoing virus replication during the post-acute phase. These results could be relevant for understanding the long-term consequences of COVID-19 in humans. Author summaryMore than a year after the start of the pandemic, the long-term consequences of SARS-CoV-2 infection start to surface. The variety of clinical manifestations associated with post-acute COVID-19 suggests the involvement of multiple biological mechanisms. In this study, we show that rhesus and cynomolgus macaques shed virus from their respiratory tract, generate virus-specific humoral immune responses, and show signs of SARS-CoV-2-induced lung pathology. PET-CT revealed that both species showed ongoing mild to moderate pulmonary disease, even after the virus was no longer detectable in nasal and tracheal swabs. Five to six weeks after infection, necropsy confirmed minimal to mild histopathological manifestations in various tissues, like the lungs, heart, lymph nodes, and conjunctiva. We detected Viral RNA in the heart, respiratory tract, and tracheobronchial lymph nodes, and subgenomic messenger RNA in the lungs and surrounding lymph nodes, indicative of ongoing virus replication. We show widespread tissue dissemination of SARS-CoV-2 in infected macaques and the presence of replicating virus in lungs and surrounding lymph nodes after alleged convalescence of infection. This finding is intriguing in the light of long-COVID disease symptoms seen in humans as it has been hypothesized that persistent infection may contribute to this phenomenon.

microbiology↗