Respiratory

Opioids and cannabinoids are a group of endogenous and exogenous compounds that function through activation of their respective receptors (opioid receptors: µ, δ, and κ, cannabinoid receptors: CB1 and CB2) [1,2]. Besides their analgesia and psychoactive functions, opioid/cannabinoids systems have received remarkable attention since they can modulate the immune response, which affects immune-associated disease progression [3,4]. Modulation of the immune response by opioids/cannabinoids may be achieved through induction of apoptosis, suppression of cell proliferation, inhibition of pro-inflammatory and inflammatory cytokines/chemokines production, increase in anti-inflammatory cytokines, and induction of regulatory T cells [5,6]. In vitro and in vivo studies as well as findings in humans indicate that these systems positively or negatively affect viral replication and virus-mediated pathology.