cOver 200 million people worldwide suffer from malaria every year, a disease that causes 584,000 deaths annually. In recent years, significant improvements have been achieved on the treatment of severe malaria, with intravenous artesunate proving superior to quinine. However, mortality remains high, at 8% in children and 15% in adults in clinical trials, and even worse in the case of cerebral malaria (18% and 30%, respectively). Moreover, some individuals who do not succumb to severe malaria present longterm cognitive deficits. These observations indicate that strategies focused only on parasite killing fail to prevent neurological complications and deaths associated with severe malaria, possibly because clinical complications are associated in part with a cerebrovascular dysfunction. Consequently, different adjunctive therapies aimed at modulating malaria pathophysiological processes are currently being tested. However, none of these therapies has shown unequivocal evidence in improving patient clinical status. Recently, key studies have shown that gaseous therapies based mainly on nitric oxide (NO), carbon monoxide (CO), and hyperbaric (pressurized) oxygen (HBO) alter vascular endothelium dysfunction and modulate the host immune response to infection. Considering gaseous administration as a promising adjunctive treatment against severe malaria cases, we review here the pathophysiological mechanisms and the immunological aspects of such therapies.
Malaria exerts a heavy burden over human populations, with an estimated 124 to 283 million cases and 584,000 deaths in 2013 (1). Currently, intravenous (i.v.) artesunate is the treatment of choice in severe malaria cases in children and adults (2, 3). However, despite the efficacy of intravenous artesunate, mortality from severe malaria in general and from cerebral malaria (CM) in particular remains high, at 18% for African children and 30% for adults in Southeast Asia (2, 3). In addition, 11% of children who survive CM show severe neurological deficits, and up to 25% can maintain long-term cognitive deficits (4-8). Therefore, strategies focusing only on parasite killing may not be sufficient to prevent neurological complications and deaths related to severe malaria. Accordingly, adjunctive therapies-defined as therapies administered in combination with antiparasitic drugs that modify pathophysiological processes caused by malaria-are being sought in order to mitigate complications caused by severe malaria (9). Considering the fact that currently administered antimalarial drugs often take 12 to 18 h to kill parasites, adjunctive therapies could reduce the risk of neurocognitive sequelae and mortality, particularly in patients with CM (10).Different adjunctive therapies have been or are being tested, including treatments aimed at modulation of the immune response to infection (dexamethasone, intravenous immunoglobulin), reduction of iron burden, reduction of oxidative stress, modulation of the prothrombotic state, and reduction of parasitemia (blood transfusion), amon...