Paulo Ricardo da Silva Sanches

Chikungunya virus (CHIKV) infection presents a wide spectrum of clinical outcomes, ranging from mild self-limiting disease to severe and fatal manifestations, which are influenced by both host and viral factors. Animal models are essential for elucidating CHIKV pathogenesis and for preclinical evaluation of antiviral strategies; however, a well-characterized model evaluating the effect of different viral doses in AG129 mice remains limited. In this study, we investigated the clinical, virological, and pathological outcomes of CHIKV infection in male AG129 mice inoculated intraperitoneally with different viral doses (10, 100, and 1000 PFU/mL) of a Brazilian strain belonging to the East/Central/South African (ECSA) lineage. Lower-dose inoculation (10 PFU/mL) resulted in a milder disease course, characterized by transient viremia, limited tissue viral dissemination, minimal histopathological alterations, partial survival, and viral clearance. In contrast, higher doses (≥100 PFU/mL) led to rapid systemic viral dissemination, severe histopathological damage in the spleen, liver, and kidneys, and uniform lethality. Viral RNA was detected in serum and multiple organs in a time-dependent manner, with limited differences among inoculum doses in most tissues. Notably, dose-related differences were observed in specific compartments and time points, particularly in hind-limb muscles at early time points and in serum at later stages.

Chikungunya virus (CHIKV) belongs to the Alphavirus genus and is responsible for significant outbreaks worldwide. Currently, there is no approved antiviral therapy against CHIKV. Bioactive peptides have great potential for new drug development. Here, we evaluated the antiviral activity of the synthetic peptide GA-Hecate and its analogs PSSct1905 and PSSct1910 against CHIKV infection. Initial screening showed that all three peptides inhibited the CHIKV replication cycle in baby hamster kidney fibroblast cells (BHK-21) and human hepatocarcinoma epithelial cells (Huh-7). GA-Hecate and its analog PSSct1905 were the most active, demonstrating suppression of viral infection by more than 91%. The analog PSSct1905 exhibited a protective effect in cells against CHIKV infection. We also observed that the analogs PSSct1905 and PSSct1910 affected CHIKV entry into both cell lines, inhibiting viral attachment and internalization. Finally, all tested compounds presented antiviral activity on the post-entry steps of CHIKV infection in all cells evaluated. In conclusion, this study highlights the potential of the peptide GA-Hecate and its analogs as novel anti-CHIKV compounds targeting different stages of the viral replication cycle, warranting the development of GA-Hecate-based compounds with broad antiviral activity.

Re-emerging arboviruses represent a serious health problem due to their rapid vector-mediated spread, mainly in urban tropical areas. The 2013–2015 Zika virus (ZIKV) outbreak in South and Central America has been associated with cases of microcephaly in newborns and Guillain–Barret syndrome. We previously showed that the conjugate gallic acid—Hecate (GA-FALALKALKKALKKLKKALKKAL-CONH₂)—is an efficient inhibitor of the hepatitis C virus. Here, we show that the Hecate peptide is degraded in human blood serum into three major metabolites. These metabolites conjugated with gallic acid were synthesized and their effect on ZIKV replication in cultured cells was evaluated. The GA-metabolite 5 (GA-FALALKALKKALKKL-COOH) was the most efficient in inhibiting two ZIKV strains of African and Asian lineage at the stage of both virus entry (virucidal and protective) and replication (post-entry). We also demonstrate that GA-metabolite 5 does not affect cell growth after 7 days of continuous treatment. Thus, this study identifies a new synthetic antiviral compound targeting different steps of ZIKV replication in vitro and with the potential for broad reactivity against other flaviviruses. Our work highlights a promising strategy for the development of new antivirals based on peptide metabolism and bioconjugation.

Chikungunya virus (CHIKV) and Zika virus (ZIKV) are important disease-causing agents worldwide. Currently, there are no antiviral drugs or vaccines approved to treat these viruses. However, peptides have shown great potential for new drug development. A recent study described (p-BthTX-I)₂K [(KKYRYHLKPF)₂K], a peptide derived from the Bothropstoxin-I toxin in the venom of the Bothrops jararacussu snake, showed antiviral activity against SARS-CoV-2. In this study, we assessed the activity of this peptide against CHIKV and ZIKV and its antiviral action in the different stages of the viral replication cycle in vitro. We observed that (p-BthTX-I)₂K impaired CHIKV infection by interfering with the early steps of the viral replication cycle, reducing CHIKV entry into BHK-21 cells specifically by reducing both the attachment and internalization steps. (p-BthTX-I)₂K also inhibited the ZIKV replicative cycle in Vero cells. The peptide protected the cells against ZIKV infection and decreased the levels of the viral RNA and the NS3 protein of this virus at viral post-entry steps. In conclusion, this study highlights the potential of the (p-BthTX-I)₂K peptide to be a novel broad-spectrum antiviral candidate that targets different steps of the replication cycle of both CHIKV and ZIKV.

Although the exact mechanism of the pathogenesis of coronavirus SARS-CoV-2 (COVID-19) is not fully understood, oxidative stress and the release of pro-inflammatory cytokines have been highlighted as playing a vital role in the pathogenesis of the disease. In this sense, alternative treatments are needed to reduce the level of inflammation caused by COVID-19. Therefore, this study aimed to investigate the potential effect of red photobiomodulation (PBM) as an attractive therapy to downregulate the cytokine storm caused by COVID-19 in a zebrafish model. RT-qPCR analyses and protein–protein interaction prediction among SARS-CoV-2 and Danio rerio proteins showed that recombinant Spike protein (rSpike) was responsible for generating systemic inflammatory processes with significantly increased levels of pro-inflammatory (il1b, il6, tnfa, and nfkbiab), oxidative stress (romo1) and energy metabolism (slc2a1a and coa1) mRNA markers, with a pattern similar to those observed in COVID-19 cases in humans. On the other hand, PBM treatment was able to decrease the mRNA levels of these pro-inflammatory and oxidative stress markers compared with rSpike in various tissues, promoting an anti-inflammatory response. Conversely, PBM promotes cellular and tissue repair of injured tissues and significantly increases the survival rate of rSpike-inoculated individuals. Additionally, metabolomics analysis showed that the most-impacted metabolic pathways between PBM and the rSpike treated groups were related to steroid metabolism, immune system, and lipid metabolism. Together, our findings suggest that the inflammatory process is an incisive feature of COVID-19 and red PBM can be used as a novel therapeutic agent for COVID-19 by regulating the inflammatory response. Nevertheless, the need for more clinical trials remains, and there is a significant gap to overcome before clinical trials can commence.

Non-SARS-CoV-2 respiratory viral infections, such as influenza virus (FluV) and human respiratory syncytial virus (RSV), have contributed considerably to the burden of infectious diseases in the non-COVID-19 era. While the rates of co-infection in SARS-CoV-2-positive group (SCPG) patients have been determined, the burden of other respiratory viruses in the SARS-CoV-2-negative group (SCNG) remains unclear. Here, we conducted a cross-sectional study (São José do Rio Preto county, Brazil), and we collected our data using a meta-analysis to evaluate the pooled prevalence of FluV and RSV among SCNG patients. Out of the 901 patients suspected of COVID-19, our molecular results showed positivity of FluV and RSV in the SCNG was 2% (15/733) and 0.27% (2/733), respectively. Co-infection with SARS-CoV-2 and FluV, or RSV, was identified in 1.7% of the patients (3/168). Following our meta-analysis, 28 studies were selected (n = 114,318 suspected COVID-19 patients), with a pooled prevalence of 4% (95% CI: 3–6) for FluV and 2% (95% CI: 1–3) for RSV among SCNG patients were observed. Interestingly, FluV positivity in the SCNG was four times higher (OR = 4, 95% CI: 3.6–5.4, p < 0.01) than in the SCPG. Similarly, RSV positivity was significantly associated with SCNG patients (OR = 2.9, 95% CI: 2–4, p < 0.01). For subgroup analysis, cold-like symptoms, including fever, cough, sore throat, headache, myalgia, diarrhea, and nausea/vomiting, were positively associated (p < 0.05) with the SCPG. In conclusion, these results show that the pooled prevalence of FluV and RSV were significantly higher in the SCNG than in the SCPG during the early phase of the COVID-19 pandemic.

The COVID-19 outbreak has rapidly spread on a global scale, affecting the economy and public health systems throughout the world. In recent years, peptide-based therapeutics have been widely studied and developed to treat infectious diseases, including viral infections. Herein, the antiviral effects of the lysine linked dimer des-Cys¹¹, Lys¹²,Lys¹³-(pBthTX-I)₂K ((pBthTX-I)₂K)) and derivatives against SARS-CoV-2 are reported. The lead peptide (pBthTX-I)₂K and derivatives showed attractive inhibitory activities against SARS-CoV-2 (EC₅₀ = 28–65 µM) and mostly low cytotoxic effect (CC₅₀ > 100 µM). To shed light on the mechanism of action underlying the peptides’ antiviral activity, the Main Protease (M^pro) and Papain-Like protease (PL^pro) inhibitory activities of the peptides were assessed. The synthetic peptides showed PL^pro inhibition potencies (IC₅₀s = 1.0–3.5 µM) and binding affinities (K_d = 0.9–7 µM) at the low micromolar range but poor inhibitory activity against M^pro (IC₅₀ > 10 µM). The modeled binding mode of a representative peptide of the series indicated that the compound blocked the entry of the PL^pro substrate toward the protease catalytic cleft. Our findings indicated that non-toxic dimeric peptides derived from the Bothropstoxin-I have attractive cellular and enzymatic inhibitory activities, thereby suggesting that they are promising prototypes for the discovery and development of new drugs against SARS-CoV-2 infection.

In recent years, synthetic peptides have been considered promising targets for drug development that possess low side-effects, are cost-effective and are susceptible to rational design. Hecate was initially described as a potent bacterial inhibitor and subsequently as an anticancer drug with functions related to its lipid interaction property. Viruses, such as hepatitis C virus (HCV), have a lipid-dependent life cycle and could be affected by Hecate in many ways. Here, we assessed modifications on Hecate’s N-terminus region and its effects on HCV and hepatotoxicity. Gallic acid-conjugated Hecate was the most efficient Hecate-derivative, presenting high potential as an antiviral and inhibiting between 50 to 99% of all major steps within the HCV infectious cycle. However, the most promising aspect was GA-Hecate’s mechanism of action, which was associated with a balanced lipid interaction with the viral envelope and lipid droplets, as well as dsRNA intercalation, allowing for the possibility to affect other ssRNA viruses and those with a lipid-dependent cycle.