Long-term activation of the immune system after mild COVID-19

30 Aug 2021 | Back to News, Publications and Annual Reports



COVID-19 has many faces. While one person just has a runny nose, the other gets really sick. Also, some suffer from the long-term consequences of SARS-CoV-2 infection, such as persistent fatigue and shortness of breath. Even after mild infection.

It has already been assumed that there may be long-lasting effects of SARS-CoV-2. In September 2020, scientists from Amsterdam showed abnormalities in the lungs, heart, kidneys and brain of patients who had died after severe COVID-19. Whether this is also the case after a mild infection is hard to investigate in humans. BPRC therefore studies this so-called post-acute phase of COVID-19 in macaques.

Mild infection in macaques

Experimental exposure of macaques leads to a mild to moderate infection with temporary virus shedding from throat and nose and production of virus-specific antibodies. Monkeys do not develop a fever and show no overt clinical signs of disease.

Moderate lung damage

Medical imaging techniques were used to monitor the development of lung disease over a period of six weeks. Fourteen days after infection, CT was still distorted in all eight infected animals. After six weeks, we still observed moderate lung damage in half of the macaques.

The animals were sacrificed to study tissues and organs. The researchers detected viral RNA in various tissues of the respiratory system, but also in, for example, the heart, kidney, liver and spleen. They also found evidence of active virus replication in the lungs and lymph nodes of the respiratory system in four of the eight monkeys. Histopathological examination indicated the presence of inflammatory cells in the lungs and surrounding lymph nodes.

Indication that even mild infection can lead to long-term complaints

These findings indicate that even after a mild SARS-CoV-2 infection, the virus disseminates to organs outside the respiratory system and can lead to long-term activation of the immune system. This may partly explain the long-term complaints that some COVID-19 patients experience.

The results of the research have been published in the journal Virusses. This article is freely accessible.