A harmonized balance between positive and negative regulation of pattern recognition receptor (PRR)-initiated immune responses is required to achieve the most favorable outcome for the host. This balance is crucial because it must not only ensure activation of the first line of defense against viral infection but also prevent inappropriate immune activation, which results in autoimmune diseases. Recent studies have shown how signal transduction pathways initiated by PRRs are positively and negatively regulated by diverse modulators to maintain host immune homeostasis. However, viruses have developed strategies to subvert the host antiviral response and establish infection. Viruses have evolved numerous genes encoding immunomodulatory proteins that antagonize the host immune system. This review focuses on the current state of knowledge regarding key host factors that regulate innate immune signaling molecules upon viral infection and discusses evidence showing how specific viral proteins counteract antiviral responses via immunomodulatory strategies.

African swine fever (ASF) is a highly contagious hemorrhagic disease in domestic pigs and wild boars caused by African swine fever virus (ASFV). ASF is a deadly epidemic disease in the global pig industry, but no drugs or vaccines are available.

The Greater Flamingo (Phoenicopterus roseus) is an uncommon migrant bird species found in Sri Lanka, and is a major attraction among avitourists. Jaffna Peninsula, Mannar Island, and the southeastern coastal areas are the known strongholds of this species in Sri Lanka. Previous studies on this species in the Jaffna Peninsula are limited, most probably due to the inaccessibility of the area during the three-decade long civil war. Hence, the objectives of the present study were to determine the population size and movements of the Greater Flamingo in major flocking areas in the Jaffna Peninsula. The study used point counts to determine population size. Binoculars and spotting scopes were used for observations. Counts were taken monthly for five years from April, 2013 to April, 2018 to cover both migratory and nonmigratory seasons. To determine their movements, we mapped the location of flocks using a GPS throughout the study period. The estimated total population size for Greater Flamingo in the Jaffna Peninsula is 6245±300. The highest average count (1081) was recorded from Nagar Kovil area with mean flock size of 367±73. Flamingos were recorded during both migratory and non-migratory seasons. The highest number of birds was observed from June-August. During the height of the dry season, flamingos moved away from western parts of the Jaffna Peninsula and concentrate on eastern parts possibly due to the higher abundance of food. The wetlands are the highly preferred habitats of the flamingos. The year-round presence of flamingos indicates that they remain in Sri Lanka beyond the migratory season as summer loiterers. The present study shows that the Jaffna Peninsula is an important area for the Greater Flamingo, thus protecting their preferred habitats is critical for their survival.

Sargassum fusiforme, a plant used as a medicine and food, is regarded as a marine vegetable and health supplement to improve life expectancy. Here, we demonstrate that S. fusiforme extract (SFE) has antiviral effects against respiratory syncytial virus (RSV) in vitro and in vivo mouse model. Treatment of HEp2 cells with a non-cytotoxic concentration of SFE significantly reduced RSV replication, RSV-induced cell death, RSV gene transcription, RSV protein synthesis, and syncytium formation. Moreover, oral inoculation of SFE significantly improved RSV clearance from the lungs of BALB/c mice. Interestingly, the phenolic compounds eicosane, docosane, and tetracosane were identified as active components of SFE. Treatment with a non-cytotoxic concentration of these three components elicited similar antiviral effects against RSV infection as SFE in vitro. Together, these results suggest that SFE and its potential components are a promising natural antiviral agent candidate against RSV infection.

As a structural protein of the Foot-and-mouth disease virus (FMDV), VP3 plays a vital role in virus assembly and inhibiting the interferon (IFN) signal transduction to promote FMDV replication. Previous studies demonstrated that FMDV VP3 blocks the type-I IFN response by inhibiting the mRNA expression of the mitochondrial antiviral-signaling protein (MAVS); however, the underlying mechanism is poorly understood. Here, we describe the specificity of FMDV VP3 interaction with the transmembrane (TM) domain of MAVS as FMDV driven type-I IFN inhibitory mechanism for its effective replication. The TM domain of MAVS governs the mitochondria localization of MAVS, and it is a key factor in type-I IFN signaling transduction via MAVS aggregation. Thereby, the interaction of FMDV VP3 with the TM domain of MAVS leads to the inhibition of MAVS mitochondria localization, self-association, and aggregation, resulting in the suppression of type-I IFN response. Collectively, these results provide a clear understanding of a key molecular mechanism used by the FMDV VP3 for the suppression of IFN responses via targeting MAVS.