The Post-Acute Phase of SARS-CoV-2 Infection in Two Macaque Species Is Associated with Signs of Ongoing Virus Replication..., 2021,

https://www.mdpi.com/1999-4915/13/8/1673

The Post-Acute Phase of SARS-CoV-2 Infection in Two Macaque Species Is Associated with Signs of Ongoing Virus Replication and Pathology in Pulmonary and Extrapulmonary Tissues

Primarily a Dutch study
Biomedical Primate Research Centre (BPRC), Department of Virology, 2288 GJ Rijswijk, The Netherlands

Abstract
The post-acute phase of SARS-CoV-2 infection was investigated in rhesus (Macaca mulatta) and cynomolgus macaques (Macaca fascicularis). During the acute phase of infection, SARS-CoV-2 was shed via the 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, computed tomography (CT) and positron emission tomography (PET)-CT revealed 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, such as 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.

 

With respect and thanks to the animals that died in this study; it's never nice to read about primate research that ends in the animals being killed. Also thanks to the people who took care of the animals - it must be difficult work.

This seems to be a well-conducted study aiming to infect some macaques with CoV-2 and follow the infection, checking for viral dissemination in body tissues after 6 weeks. While persisting virus had been found in people who have suffered severe Covid-19 infections, less was known about viral persistence in people who have asymptomatic or mild disease. These macaques had mild infections.

 

The macaques had sensors inserted into their abdomen cavity to measure activity. There were two species of macaques - rhesus (shown in warm colours) and cynomolgus (shown in cool colours). Each animal is represented by one colour.



The activity of the cynomolgus macaques didn't change throughout the study, whereas the activity of the rhesus macaques increased 3 weeks after infection. There was a pattern of reduced activity after the third week.
Edit - unfortunately, we don't know what their usual activity levels (under the study conditions) was.

 

Have a look at the places the virus is turning up - it's really variable from animal to animal. No virus at all was found in 4 out of the 8 animals. Virus was found in a calf vein, in lymph nodes, in the heart and in the throat, the spleen, among other places.

They looked for subgenomic messenger RNA (sgmRNA). They say that this is indicative of viral replication.

 

The finding of virus in the eye of an animal reminds me of the finding of Ebola virus persisting in the eye tissue of survivors.


Some other quotes from the Discussion that I found interesting:

Sadly, the comment in this 2021 paper about the vaccination program (potentially eliminating both the acute disease and minimising long-Covid) has not been borne out in reality. I wonder if the people who did this study are continuing their work.

Establishing whether viral persistence is causing ME/CFS-like Long Covid in humans is surely not an impossible task?