Coevolutionary networks: a novel approach to understanding the relationships of humans with the infectious agents

The adaptation of SARS-CoV-2 to humans

The process of adaptation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to humans probably had started decades ago, when its ancestor diverged from the bat coronavirus. The adaptive process comprises strategies the virus uses to overcome the respiratory tract defense barriers and replicate and shed in the host cells. These strategies include the impairment of interferon production, hiding immunogenic motifs, avoiding viral RNA detection, manipulating cell autophagy, triggering host cell death, inducing lymphocyte exhaustion and depletion, and finally, mutation and escape from immunity. In addition, SARS-CoV-2 employs strategies to take advantage of host cell resources for its benefits, such as inhibiting the ubiquitin-proteasome system, hijacking mitochondria functions, and usage of enhancing antibodies. It may be anticipated that as the tradeoffs of adaptation progress, the virus destructive burden will gradually subside. Some evidence suggests that SARS-CoV-2 will become part of the human respiratory virome, as had occurred with other coronaviruses, and coevolve with its host.

The importance of multiparasitism: examining the consequences of co-infections for human and animal health

Most parasites co-occur with other parasites, although the importance of such multiparasitism has only recently been recognised. Co-infections may result when hosts are independently infected by different parasites at the same time or when interactions among parasite species facilitate co-occurrence. Such interactions can have important repercussions on human or animal health because they can alter host susceptibility, infection duration, transmission risks, and clinical symptoms. These interactions may be synergistic or antagonistic and thus produce diverse effects in infected humans and animals. Interactions among parasites strongly influence parasite dynamics and therefore play a major role in structuring parasite populations (both within and among hosts) as well as host populations. However, several methodological challenges remain when it comes to detecting parasite interactions. The goal of this review is to summarise current knowledge on the causes and consequences of multiparasitism and to discuss the different methods and tools that researchers have developed to study the factors that lead to multiparasitism. It also identifies new research directions to pursue.

Effects of temperature and incubation time on the in vitro expression of proteases, phospholipases, lipases and DNases by different species of Trichosporon

Fungi produce a broad spectrum of enzymes capable of degrading different substrates in nature. When the substrate is the tissue of a vertebrate host, these enzymes acts as a fungal virulence factor that increases the pathogenicity of the fungus. Trichosporon yeasts are emerging pathogens that infect immunocompromised patients. Little is known about the virulence characteristics of these fungi. The aim of this research was to characterize the behavior of protease, phospholipase, lipase and DNase production in different species of Trichosporon, with a focus on the influence of incubation temperature on the expression of these enzymes. Classical methodologies were used in all of the experiments, and the results were statistically analyzed. The proportions of the samples that produced each type of enzyme were as follows: lipases (95.5%), phospholipases (56.8%), proteases (50,0%) and DNases (38.6%). The incubation temperature was an important factor in the expression of enzymatic activity, and it influenced the incubation period of each species. Although these data concerning the enzymatic activity expressed by isolates of Trichosporon are valuable, further research is warranted to completely characterize this new pathogen, as well as in vivo studies to determine the roles of these enzymes in the pathogenesis of trichosporonosis.

Parasites or cohabitants: cruel omnipresent usurpers or creative "éminences grises"?

This paper presents many types of interplays between parasites and the host, showing the history of parasites, the effects of parasites on the outcome of wars, invasions, migrations, and on the development of numerous regions of the globe, and the impact of parasitic diseases on the society and on the course of human evolution. It also emphasizes the pressing need to change the look at the parasitism phenomenon, proposing that the term “cohabitant” is more accurate than parasite, because every living being, from bacteria to mammals, is a consortium of living beings in the pangenome. Even the term parasitology should be replaced by cohabitology because there is no parasite alone and host alone: both together compose a new adaptive system: the parasitized-host or the cohabitant-cohabited being. It also suggests switching the old paradigm based on attrition and destruction, to a new one founded on adaptation and living together.

Coadaptation and malaria control

Malaria emerges from a disequilibrium of the system 'human-plasmodium-mosquito' (HPM). If the equilibrium is maintained, malaria does not ensue and the result is asymptomatic plasmodium infection. The relationships among the components of the system involve coadaptive linkages that lead to equilibrium. A vast body of evidence supports this assumption, including the strategies involved in the relationships between plasmodium and human and mosquito immune systems, and the emergence of resistance of plasmodia to antimalarial drugs and of mosquitoes to insecticides. Coadaptive strategies for malaria control are based on the following principles: (1) the system HPM is composed of three highly complex and dynamic components, whose interplay involves coadaptive linkages that tend to maintain the equilibrium of the system; (2) human and mosquito immune systems play a central role in the coadaptive interplay with plasmodium, and hence, in the maintenance of the system's equilibrium; the under- or overfunction of human immune system may result in malaria and influence its severity; (3) coadaptation depends on genetic and epigenetic phenomena occurring at the interfaces of the components of the system, and may involve exchange of infectrons (genes or gene fragments) between the partners; (4) plasmodia and mosquitoes have been submitted to selective pressures, leading to adaptation, for an extremely long while and are, therefore, endowed with the capacity to circumvent both natural (immunity) and artificial (drugs, insecticides, vaccines) measures aiming at destroying them; (5) since malaria represents disequilibrium of the system HPM, its control should aim at maintaining or restoring this equilibrium; (6) the disequilibrium of integrated systems involves the disequilibrium of their components, therefore the maintenance or restoration of the system's equilibrium depend on the adoption of integrated and coordinated measures acting on all components, that means, panadaptive strategies. Coadaptive strategies for malaria control should consider that: (1) host immune response has to be induced, since without it, no coadaptation is attained; (2) the immune response has to be sustained and efficient enough to avoid plasmodium overgrowth; (3) the immune response should not destroy all parasites; (4) the immune response has to be well controlled in order to not harm the host. These conditions are mostly influenced by antimalarial drugs, and should also be taken into account for the development of coadaptive malaria vaccines.

Interfaces do corpo: integração da alteridade no conceito de doença

A cultura ocidental fragmentou o corpo em redutoras perspectivas teóricas que fizeram aparecer diferentes ordens de realidade: biológica, psíquica e social. Este artigo identifica o limite da biomedicina em integrar a alteridade no conceito de doença, como uma das lacunas importantes para a aproximação entre os conceitos de psiquismo e corpo biológico. Apresenta a proposição de que as interfaces do corpo são centrais para a compreensão da constituição do corpo biológico em seus processos de individuação. Levanta a possibilidade de ocorrer uma transformação epistemológica na medicina, a partir da valorização dos estudos sobre fenômenos biológicos que ocorrem nestas interfaces. Ressalta, mediante análise da literatura médica recente, indícios de uma possível integração da alteridade no conceito de doença. Esta análise se detém na crescente elaboração de um discurso sobre a relação com os microorganismos e sua importância na constituição ontogênica do organismo humano e, por conseqüência, na etiologia das doenças.

Transcession of DNA from Bacteria to Human Cells in Culture: A Possible Role in Oncogenesis

The human organism is continuously in close contact with microorganisms, especially bacteria. In the present work, by means of a real-time polymerase chain reaction (PCR) technique, we looked for the presence of a distinct bacterial gene in human cells. To this end, we cultured a human cell line, HL60, in a supernatant in which bacteria (Bacillus subtilis) had been grown. A transient transcession of bacterial DNA into the human cells was observed.

[Evolutionary epidemiological thought on infections]

The objective of the study is to analyse the main aspects of current epidemiological knowledge on the evolutionary status of infections. Living organisms in the biosphere are part of dynamic systems of variable intensities. Some of these systems are on the surface while others take place inside the genome core. Parasitism is a phenomenon commonly seen in nature. Infective parasites relate to each other through several mechanisms, such as genetic DNA exchange, and because of the connections established communities of infectious agents are not isolated. The internalization process allows the parasites to get into their hosts' cells, which is accomplished through the phagocytosis of infectious agents or other more sophisticated mechanisms such as pill production. To leave the intracellular medium, some organisms make use of apoptosis, a highly specialized genetic mechanism that makes possible to destroy macrophages. It is currently accepted that molecular DNA can flow into the blood stream as the so-called infectrons. Thus it is hypothesized the existence of infection networks that allows the coadaptability of parasites and their hosts, and creates coevolutionary forces between hosts and their parasites facilitating the emergence of new pathogens.