The discovery of CD16+ monocytes containing persistent S1 proteins from PASC patients may help further understand its pathophysiology and identify targets for therapy (4). Both CD16+ monocytes subsets, intermediate (CD14+CD16+) and nonclassical (CD14- CD16+), respectively, are known to interact significantly with the endothelium and platelets via the fractalkine pathway (26). This suggests that the pathophysiology of PASC may lie with the monocytic-endothelial-platelet axis. Fractalkine, which mediates cell adhesion and leucocyte recruitment, is a transmembrane protein expressed in the brain, colon, heart, and lung, along with endothelial cells and astrocytes. Intermediate monocytes express high levels of both CCR5 and fractalkine receptors, whereas nonclassical monocytes express high levels of fractalkine receptors (6, 7). This interaction between fractalkine and fractalkine receptors have been involved in the pathogenesis of atherosclerosis, vasculitis, vasculopathies, and inflammatory brain disorders (27) and could also be contributing to vascular endothelialitis in PASC. Vascular endothelialitis leads to collagen exposure along with platelet activation and adherence via glycoprotein 1b-IX-V-receptor (GPIb-IX-V) with collagen-bound von Willebrand factor (vWF) (28). Activated platelets release soluble CD40 ligand (sCD40L) to recruit both neutrophils and monocytes to the vascular lesions (29), thus activating the coagulation cascade. Stimulated platelets also release RANTES which binds to endothelial cells and encourages monocyte adhesion to inflamed endothelial tissues (30) and acts as a chemotactic agent for inflammatory cells. Activated platelets and endothelial cells can also secrete VEGF which induces angiogenesis and microvascular hyperpermeability. VEGF is a diagnostic marker for vasculitic neuropathy and also contributes to a pro-inflammatory-prothrombotic environment (31). While the vascular effects of statins have been well documented (32), the protective role of maraviroc on the endothelium has also been similarly published (33). Hence, we targeted CCR5 and fractalkine receptors on the S1 protein expressing CD16+ monocytes using maraviroc and pravastatin, respectively, hypothesizing that this combination could be therapeutically effective in treating vascular endothelialitis and resolving symptoms associated with PASC.
Neurological symptoms associated with PASC include severe headaches and cognitive impairment (brain fog), along with neuropathy and weakness, necessitating the need for assistance in performing daily tasks. CD14+CD16+ monocytes are known to transmigrate across the blood brain barrier and play an important role in central nervous system (CNS) immune surveillance. These monocytes were implicated as HIV reservoirs in the CNS causing neuroinflammation, neuronal damage, and cognitive defects (34). We hypothesize that the S1 protein containing CD14+CD16+ monocytes in PASC patients are also crossing the blood brain barrier and triggering neuroinflammation and inducing neurological symptoms. Both maraviroc and statins are known to cross the blood-brain-barrier, and more specifically, maraviroc has been suggested as treatment for Parkinson’s, neurocognitive impairment, and strokes (35). Interestingly, after the introduction of maraviroc and pravastatin, participants showed a decrease in modified Rankin scale scores (p=0.0002) (Figure 2) and reported improvement in neurological function and ability. These findings were correlated with a statistically significant decrease in VEGF (r= 0.4, p=0.02) and sCD40L (r= 0.42, p=0.01), suggesting treatment targeting cytokines associated with vascular endothelialitis correlated with improvement in neurological symptoms.
Autonomic dysfunction such as postural orthostatic tachycardia syndrome (POTS) and light sensitivity has also been associated with PASC. POTS is a syndrome consisting of unexplained tachycardia, dizziness, light-headedness, fainting, and abdominal pain. While the true etiology of POTS has yet to be defined, endothelial dysfunction has been suggested as the pathophysiology (36). There is also evidence that POTS maybe be associated with G-protein-coupled receptor autoantibodies (37). Interestingly, since CCR5 and fractalkine receptor are also G-protein-coupled receptors (9, 38), it is possible that antagonism of these receptors could also inhibit the autonomic effects of these autoantibodies. We observed a statistically significant decrease in COMPASS-31 (p=0.0001) (Figure 3) scores correlating with statistically significant decreases in VEGF (r=0.6, p=0.0005), sCD40L (r=0.6, p=0.0001), and TNF-alpha (r=0.5, p=0.0026), suggesting that pro-inflammatory macrophage activation may be triggering vascular endothelialitis. Interestingly, elevations in sCD40L have also been associated with sympathoadrenal activation and targeting these vascular markers may address PASC associated dysautonomia (39).
Cardiorespiratory complaints such as chest pain, shortness of breath, and symptoms resembling POTS are very commonly reported by PASC patients. Many PASC patients with cardiac and pulmonary symptoms have undergone extensive workup (EKG, echocardiogram, stress test, pulmonary function testing, etc.) which have not detected any abnormalities or pathologies. Subsequently, current clinical approaches have only been used to treat symptoms with antiarrhythmics, bronchodilators or alpha-adrenergics, instead of addressing the underlying pathophysiology. We observed an improvement in cardiac symptoms evidenced by a decrease in NYHA functional classification (p=0.002) (Figure 4). This improvement was associated with statistically significant decreases in IL-8 (r=0.4, p=0.03) and GM-CSF (r=0.4, p=0.01). Interestingly, endothelial cells are main producers of IL-8 (40) and statins are known to decrease IL-8 (41). Additionally, maraviroc has been suggested as reducing the cardiovascular risk for acute coronary disease by protecting the endothelium from pro-inflammatory macrophage infiltration (42). These mechanisms potentially support their use in addressing PASC associated cardiac symptoms. We also observed improvement in respiratory symptoms after initiating maraviroc and pravastatin therapy. Participants reported improvements as reflected by a statistically significant decrease in the MRC Dyspnea scale (p=0.0153) (Figure 5). These responses and improvements correlated with statistically significant decreases in IL-2 (r=0.4, p=0.05), GM-CSF (r=0.6, p=0.0002), sCD40L (r=0.4, p=0.04), and TNF-alpha (r=0.4, p=0.01). Intriguingly, CD16+ monocytes are known to produce large quantities of TNF-alpha and could be activated by the retained S1 proteins (43), causing vascular endothelialitis via the fractalkine-fractalkine receptor interaction in pulmonary vasculature. Elevations in sCD40L have been associated with pulmonary arterial hypertension (PAH) (44), while IL-2 can induce pulmonary microvasculature injury and generate an asthma-like bronchoconstriction (45). We previously published a multi-class model score that described an increase IL-2 as a characteristic specific to PASC (8), thus confirming the clinical significance of IL-2 in PASC. Both maraviroc and statins can decrease IL-2 and TNF-alpha (41, 46), which may explain the observed improvements in PASC associated respiratory symptoms. The patient Fatigue Severity Score (FSS) also significantly decreased (p<0.0001) (Figure 6) after maraviroc and pravastatin which correlated with decrease in sCD40L (r=0.5, p=0.001), VEGF (r=0.5, p=0.001), TNF-alpha (r=0.7, p=4e-5 ), IL-2 (r=0.6, p=0.0005), and GM-CSF (r=0.5, p=0.004), again suggesting that targeting the monocytic-platelet-endothelial axis can alleviate PASC associated fatigue.
Despite a black box warning for hepatoxicity, maraviroc has demonstrated a strong safety profile in adult, pediatric, and neonatal populations (47, 48). Analysis of the MOTIVATE study demonstrated a low incidence of hepatoxicity with maraviroc even after 96 weeks of treatment at the FDA approved dose of 300mg B.I.D (49). This influenced our decision to treat with this dose. Hepatic safety was monitored in all the participants by measuring and evaluating AST, ALT, and total bilirubin (LFTs) prior to commencing treatment with maraviroc and every two weeks while on treatment. None of participants presented here experienced any clinical signs of hepatotoxicity or elevated liver function serologies while on, or after, treatment. Maraviroc is metabolized by CYP3A4, and we chose to avoid any CYP3A4 metabolizing statins to mitigate any potential drug interactions. This approach guided our decision to treat with pravastatin 10mg PO daily over the other statins since it is metabolized via glucuronidation. However, the therapeutic benefits with other statins have also been observed and could be considered.
Since some of the participants were already on other therapeutics including ivermectin, fluvoxamine, and prednisone, all the biomarker data and subjective responses were documented from the initiation of maraviroc and pravastatin. Some participants saw symptom relief after six weeks and were ready to stop all medications, while others needed treatment up to twelve weeks before discontinuing medications. Further studies will need to be conducted to understand this variation in length of treatment between participants. The results we present in this case series do not replace the need for a double-blinded placebo controlled randomized trial to understand drug efficacy. However, we do believe this case series sets the framework for such future clinical trial designs to further investigate the efficacy and usefulness of maraviroc and pravastatin to treat PASC.