Suppression of dengue virus replication by the French maritime pine extract Pycnogenol®.

Dengue virus (DENV) is mainly found in the tropics and infects approximately 400 million people annually. However, no clinically available therapeutic agents specific to dengue have been developed. Here, we examined the potential antiviral effects of the French maritime pine extract Pycnogenol® (PYC) against DENV because we previously found that the extract exerts antiviral effects on hepatitis C virus, which belongs to the Flavivirus family. First, we examined the efficacy of PYC against DENV1, 2, 3, and 4 serotypes and determined that it had a dose-dependent suppressive effect on the viral load, especially in the supernatant. This inhibitory effect of PYC may target the late stages of infection such as maturation and secretion, but not replication. Next, we examined the efficacy of PYC against DENV infection in type I interferon (IFN) receptor knockout mice (A129). As the propagation of DENV2 was the highest among the four serotypes, we used this serotype in our murine model experiments. We found that PYC significantly inhibited DENV2 replication in mice on day 4 without significantly decreasing body weight or survival ratio. We further examined the mechanism of action of PYC in DENV2 infection by characterizing the main PYC targets among the host (viral) factors and silencing them using siRNA. Silencing long noncoding-interferon-induced protein (lnc-IFI)-44, polycystic kidney disease 1-like 3 (Pkd1l3), and ubiquitin-specific peptidase 31 (Usp31) inhibited the replication of DENV2. Thus, the results of this study shed light on the inhibitory effects of PYC on DENV replication and its underlying mechanisms.

Investigation of koala retrovirus in captive koalas with pneumonia and comparative analysis of subtype distribution.

This study focused on the involvement of koala retrovirus (KoRV) in pneumonia in koalas. Three deceased pneumonic koalas from a Japanese zoo were examined in this study. Hematological and histopathological findings were assessed, and KoRV proviral DNA loads in the blood and tissues were compared with those of eight other KoRV-infected koalas from different zoos. Demographic data and routine blood profiles were collected, and blood and tissue samples were analyzed to rule out concurrent infections in pneumonic koalas. KoRV subtyping and measurement of the KoRV proviral DNA load were performed by polymerase chain reaction (PCR) using specific primers targeting the pol and env genes. The results showed that the koalas had histopathologically suppurative and fibrinous pneumonia. Chlamydiosis was not detected in any of the animals. PCR analysis revealed KoRV-A, -B, and -C infections in all koalas, except for animals K10-11, which lacked KoRV-B. Significant variations in the proviral DNA loads of these KoRV subtypes were observed in all tissues and disease groups. Most tissues showed reduced KoRV loads in koalas with pneumonia, except in the spleen, which had significantly higher loads of total KoRV (2.54 × 107/µg DNA) and KoRV-A (4.74 × 107/µg DNA), suggesting potential immunosuppression. This study revealed the intricate dynamics of KoRV in various tissues, indicating its potential role in koala pneumonia via immunosuppression and opportunistic infections. Analysis of the levels of KoRV proviral DNA in different tissues will shed light on viral replication and the resulting pathogenesis in future studies.