Calpeptin is a potent cathepsin inhibitor and drug candidate for SARS-CoV-2 infections.

Several drug screening campaigns identified Calpeptin as a drug candidate against SARS-CoV-2. Initially reported to target the viral main protease (Mpro), its moderate activity in Mpro inhibition assays hints at a second target. Indeed, we show that Calpeptin is an extremely potent cysteine cathepsin inhibitor, a finding additionally supported by X-ray crystallography. Cell infection assays proved Calpeptin's efficacy against SARS-CoV-2. Treatment of SARS-CoV-2-infected Golden Syrian hamsters with sulfonated Calpeptin at a dose of 1 mg/kg body weight reduces the viral load in the trachea. Despite a higher risk of side effects, an intrinsic advantage in targeting host proteins is their mutational stability in contrast to highly mutable viral targets. Here we show that the inhibition of cathepsins, a protein family of the host organism, by calpeptin is a promising approach for the treatment of SARS-CoV-2 and potentially other viral infections.

Impact of an autophagy-inducing peptide on immunogenicity and protection efficacy of an adenovirus-vectored SARS-CoV-2 vaccine.

Because of continual generation of new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), it is critical to design the next generation of vaccines to combat the threat posed by SARS-CoV-2 variants. We developed human adenovirus (HAd) vector-based vaccines (HAd-Spike/C5 and HAd-Spike) that express the whole Spike (S) protein of SARS-CoV-2 with or without autophagy-inducing peptide C5 (AIP-C5), respectively. Mice or golden Syrian hamsters immunized intranasally (i.n.) with HAd-Spike/C5 induced similar levels of S-specific humoral immune responses and significantly higher levels of S-specific cell-mediated immune (CMI) responses compared with HAd-Spike vaccinated groups. These results indicated that inclusion of AIP-C5 induced enhanced S-specific CMI responses and similar levels of virus-neutralizing titers against SARS-CoV-2 variants. To investigate the protection efficacy, golden Syrian hamsters immunized i.n. either with HAd-Spike/C5 or HAd-Spike were challenged with SARS-CoV-2. The lungs and nasal turbinates were collected 3, 5, 7, and 14 days post challenge. Significant reductions in morbidity, virus titers, and lung histopathological scores were observed in immunized groups compared with the mock- or empty vector-inoculated groups. Overall, slightly better protection was seen in the HAd-Spike/C5 group compared with the HAd-Spike group.

SARS-CoV-2 infection impacts carbon metabolism and depends on glutamine for replication in Syrian hamster astrocytes.

COVID-19 causes more than million deaths worldwide. Although much is understood about the immunopathogenesis of the lung disease, a lot remains to be known on the neurological impact of COVID-19. Here, we evaluated immunometabolic changes using astrocytes in vitro and dissected brain areas of SARS-CoV-2 infected Syrian hamsters. We show that SARS-CoV-2 alters proteins of carbon metabolism, glycolysis, and synaptic transmission, many of which are altered in neurological diseases. Real-time respirometry evidenced hyperactivation of glycolysis, further confirmed by metabolomics, with intense consumption of glucose, pyruvate, glutamine, and alpha ketoglutarate. Consistent with glutamine reduction, the blockade of glutaminolysis impaired viral replication and inflammatory response in vitro. SARS-CoV-2 was detected in vivo in hippocampus, cortex, and olfactory bulb of intranasally infected animals. Our data evidence an imbalance in important metabolic molecules and neurotransmitters in infected astrocytes. We suggest this may correlate with the neurological impairment observed during COVID-19, as memory loss, confusion, and cognitive impairment.

Therapeutic Vaccination with Cationic Liposomes Formulated with Dioctadecyldimethylammonium and Trehalose Dibehenate (CAF01) and Peptide P10 Is Protective in Mice Infected with Paracoccidioides brasiliensis.

The peptide P10 is a vaccine candidate for Paracoccidioidomycosis, a systemic mycosis caused by fungal species of the genus Paracoccidioides spp. We have previously shown that peptide P10 vaccination, in the presence of several different adjuvants, induced a protective cellular immune response mediated by CD4+ Th1 lymphocytes that was associated with the increased production of IFN-γ in mice challenged with a virulent isolate of Paracoccidoides brasiliensis. Cationic liposomes formulated with dioctadecyldimethylammonium and trehalose dibehenate (DDA/TDB, termed also CAF01-cationic adjuvant formulation) have been developed for safe administration in humans and CAF01 liposomes are utilized as an adjuvant for modulating a robust Th1/Th17 cellular response. We evaluated the efficacy of the adsorption of peptide P10 to CAF01 cationic liposomes and used the generated liposomes to vaccinate C57Bl/6 mice infected with P. brasiliensis. Our results showed that P10 was efficiently adsorbed onto CAF01 liposomes. The vaccination of infected mice with cationic liposomes formulated with DDA/TDB 250/50 µg/mL and 20 µg of P10 induced an effective cellular immune response with increased levels of Th17 cytokines, which correlated with significant decreases in the fungal burdens in lungs and protective granulomatous tissue responses. Hence, cationic liposomes of DDA/TDB 250/50 µg/mL with 20 µg of P10 are a promising therapeutic for safely and effectively improving the treatment of paracoccidioidomycosis.