Early interactions of human herpesvirus 6 with lymphoid cells: role of membrane protein components and glycosaminoglycans in virus binding

Myocardial Oedema as a Consequence of Viral Infection and Persistence-A Narrative Review with Focus on COVID-19 and Post COVID Sequelae

Microvascular integrity is a critical factor in myocardial fluid homeostasis. The subtle equilibrium between capillary filtration and lymphatic fluid removal is disturbed during pathological processes leading to inflammation, but also in hypoxia or due to alterations in vascular perfusion and coagulability. The degradation of the glycocalyx as the main component of the endothelial filtration barrier as well as pericyte disintegration results in the accumulation of interstitial and intracellular water. Moreover, lymphatic dysfunction evokes an increase in metabolic waste products, cytokines and inflammatory cells in the interstitial space contributing to myocardial oedema formation. This leads to myocardial stiffness and impaired contractility, eventually resulting in cardiomyocyte apoptosis, myocardial remodelling and fibrosis. The following article reviews pathophysiological inflammatory processes leading to myocardial oedema including myocarditis, ischaemia-reperfusion injury and viral infections with a special focus on the pathomechanisms evoked by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In addition, clinical implications including potential long-term effects due to viral persistence (long COVID), as well as treatment options, are discussed.

Glycoproteins of HHV-6A and HHV-6B

Recently, human herpesvirus 6A and 6B (HHV-6A and HHV-6B) were classified into distinct species. Although these two viruses share many similarities, cell tropism is one of their striking differences, which is partially because of the difference in their entry machinery. Many glycoproteins of HHV-6A/B have been identified and analyzed in detail, especially in their functions during entry process into host cells. Some of these glycoproteins were unique to HHV-6A/B. The cellular factors associated with these viral glycoproteins (or glycoprotein complex) were also identified in recent years. Detailed interaction analyses were also conducted, which could partially prove the difference of entry machinery in these two viruses. Although there are still issues that should be addressed, all the knowledges that have been earned in recent years could not only help us to understand these viruses' entry mechanism well but also would contribute to the development of the therapy and/or prophylaxis methods for HHV-6A/B-associated diseases.

Role of heparan sulfate in human parainfluenza virus type 3 infection

Our current studies have demonstrated that human parainfluenza virus type 3 (HPIV-3) utilizes heparan sulfate (HS) for its efficient cellular entry. HPIV-3 interacted with HS-agarose in vitro and the cellular entry and infection of HPIV-3 were reduced following (a) infection of human epithelial lung A549 cells with HPIV-3 pre-incubated with soluble HS; (b) treatment of A549 cells with heparinase to remove cell surface HS and sodium chlorate (NaClO(3)), a potent inhibitor of proteoglycan sulfation; and (c) infection of HS-deficient mutant CHO cell lines. However, in each instance, complete inhibition of HPIV-3 entry did not occur, suggesting the presence of additional nonproteoglycan cell surface molecule(s) that is required for HPIV-3 entry. Thus the cell surface HS appears to play an important role in efficient cellular entry of HPIV-3.

Heparan sulfate: anchor for viral intruders?

Heparan sulfates (HS) are ubiquitous, polyanionic carbohydrate chains linked to core proteins in cell membranes and extracellular matrices of all eukaryotes. Due to the complex nature of the HS-biosynthesis, a wealth of different structures are produced. These seem to have a well defined distribution in different tissues and cells throughout development. Binding of endogenous proteins with different functional properties such as growth factors, adhesion molecules or enzymes, is one of the functions of HS. Besides interaction with endogenous factors, glycosaminoglycans (GAG) and especially HS have also been demonstrated to function as receptors for a number of different pathogens. What roles may HS play in the pathogenesis and tropism of different intruders like parasites or viruses? What implications does binding of viruses to HS have for the development of drugs or the application of viral vectors for gene targeting? In this review an attempt is made to collect our present knowledge on viral usage of HS and the implications that follow.