Viral pathogenesis and central nervous system infection

Cardiorespiratory and skeletal muscle damage due to COVID-19: making the urgent case for rehabilitation

INTRODUCTION

It has become increasingly evident that COVID-19 contributes to multiorgan pathophysiology. The systemic inflammatory response increases both pro-inflammatory cytokine and chemokine levels, leading to immune dysregulation and increasing the likelihood of incurring cardiac and pulmonary injuries.

AREAS COVERED

Longer periods of hospitalization (~20 days) increase susceptibility to ICU-acquired muscle weakness and deconditioning, which decreases muscle function and functional capacity. These conditions affect the quality of life in the post-COVID-19 period and require multi-disciplinary approaches to rehabilitate the cardiopulmonary and musculoskeletal systems of these patients. In this context, this narrative review, which included articles published in the Embase, PEDro and PubMed databases up to December 2020, is focused on discussing the essential role of exercise and rehabilitation health professionals in the COVID-19 recovery process, from hospitalization to hospital discharge, addressing strategies for professionals to mitigate the cardiac and pulmonary impairments associated with hospitalization to home or ambulatory rehabilitation, purposing ways to conduct rehabilitation programs to restore their functional status and quality of life after the infection.

EXPERT OPINION

In the current environment, these findings further point to the vital role of rehabilitation health professionals in the coming years and the urgent need to develop strategies to assist COVID-19 survivors.

Penetration of solutes, viruses, and cells across the blood-brain barrier

The aspects presented here of how solutes, viruses and cells are able to cross the BBB indicate that there must be an active interaction of endothelium with viruses and immune system cells before they can penetrate the brain and spinal cord. The axoplasmic pathway taken by lectin-solute conjugates is similar but not identical to that followed by viral particles during their retrograde or anterograde transit through the axoplasm. Both the conjugates and virus are transferred to other neurons transsynaptically but the receptor mediated transfer utilized by viruses is far more specific. Cranial nerves are involved in both the entry and egress of antigens into and out of the brain. Antigen, generated within the CNS, may be able to escape from the brain to lymphoid tissue by passing into the fluid around a cranial nerve, thence via the lymph into lymph nodes to initiate an immune response involving the CNS.

Antibody-mediated clearance of viruses from the mammalian central nervous system

The novel role of antibody in clearing virus from the central nervous system without the help of other immune effectors is an important phenomenon that has only recently been documented. Possible routes for antibodies across the blood-brain barrier and how they work in the CNS are discussed here.