Middle East respiratory syndrome coronavirus (MERS-CoV) has continued spreading since its emergence in 2012 with a mortality rate of 35.6%, and is a potential pandemic threat. Prophylactics and therapies are urgently needed to address this public health problem. We report here the efficacy of a vaccine consisting of chimeric virus-like particles (VLP) expressing the receptor binding domain (RBD) of MERS-CoV. In this study, a fusion of the canine parvovirus (CPV) VP2 structural protein gene with the RBD of MERS-CoV can self-assemble into chimeric, spherical VLP (sVLP). sVLP retained certain parvovirus characteristics, such as the ability to agglutinate pig erythrocytes, and structural morphology similar to CPV virions. Immunization with sVLP induced RBD-specific humoral and cellular immune responses in mice. sVLP-specific antisera from these animals were able to prevent pseudotyped MERS-CoV entry into susceptible cells, with neutralizing antibody titers reaching 1: 320. IFN-γ, IL-4 and IL-2 secreting cells induced by the RBD were detected in the splenocytes of vaccinated mice by ELISpot. Furthermore, mice inoculated with sVLP or an adjuvanted sVLP vaccine elicited T-helper 1 (Th1) and T-helper 2 (Th2) cell-mediated immunity. Our study demonstrates that sVLP displaying the RBD of MERS-CoV are promising prophylactic candidates against MERS-CoV in a potential outbreak situation.

Porcine circovirus type 3 (PCV3) is a novel circovirus that was firstly detected in the USA. PCV3 is associated with porcine dermatitis and nephropathy syndrome (PDNS), reproductive failure and cardiac and multisystemic inflammation. Latterly, PCV3 was detected in Guangxi, China. Forty-one of 108 (37.96%) samples and nine of 47 (19.14%) samples were PCV3 positive in pig farms and pig slaughter houses, respectively. Three PCV3 strains were sequenced and designated PCV3-China/GX2016-1, PCV3-China/GX2016-2 and PCV3-China/GX2016-3. The complete genome of PCV3-China/GX2016-2 and PCV3-China/GX2016-3 is both 2,000 bp in length, while PCV3-China/GX2016-1 is of 1,999 bp and has a G deletion at position of 1,155 in its genome. The complete genome and capsid nucleotide of the three PCV3 strains identified in this study shared 97.5%-99.4% and 96.7%-99.1% identities with that of the other PCV3 strains available in NCBI, respectively. Phylogenetic analysis based on complete genome and capsid gene of 35 PCV3 strains showed that the three PCV3 sequences from Guangxi Province were divided into two clusters. The results of this study contribute to the understanding of PCV3 molecular epidemiology.

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Low m.w. hyaluronan (LMW HA) has been shown to elicit the expression of proinflammatory cytokines and chemokines in various cells in vitro. However, the effects of this molecule in vivo are unknown. In this study, we report that intratracheal administration of LMW HA (200 kDa) causes inflammation in mouse lung. A lack of TLR4 is associated with even stronger inflammatory response in the lung as shown by increased neutrophil counts and elevated cytokine and chemokine concentrations. We also demonstrate that TLR4 anti-inflammatory signaling is dependent upon a MyD88-independent pathway. TLR4-mediated IL-1R antagonist production plays a negative regulatory role in LMW HA (200 kDa) induced lung inflammation. These data provide a molecular level explanation for the function of TLR4 in LMW HA (200 kDa)-induced lung inflammation, as inhibition of the β form of pro–IL-1 promotes an anti-inflammatory response.