Two monoclonal antibodies against glycoprotein Gn protect mice from Rift Valley Fever challenge by cooperative effects.

Rift Valley fever virus (RVFV) is a zoonotic arbovirus that causes severe disease in humans and ruminants. The infection is characterized by abortions in pregnant animals, high mortality in neonates as well as febrile illness in humans that develop in 1% of cases encephalitis or hemorrhagic fever. There is presently no specific antiviral treatment for RVFV infection available. In this study, two monoclonal antibodies (mAbs), raised against glycoprotein Gn, were applied in a therapeutic study. Treatment of RVFV infected mice with neutralizing mAb Gn3 alone at two different time points (30 minutes before or 30 minutes after virus challenge) showed only moderate efficacy of about 58.3% survival in both applications. However, a combination therapy together with non-neutralizing mAb Gn32 demonstrated complete protection (100% survival) when applied 30 minutes after the lethal challenge dose. The increase of mAb efficacy is probably based on cooperative neutralization effects. These data suggest that a combination therapy with mAbs Gn3 and Gn32 could be an effective treatment option against RVFV infection.

Co-infection of pigs with Hepatitis E and porcine circovirus 2, Saxony 2016.

Hepatitis E virus (HEV) is a recognized zoonotic disease; autochthonous infections in Europe are caused to a great extent by HEV genotype 3. Pigs and wild boar are the main reservoirs for this genotype and normally they develop no or only subclinical symptoms with mild histopathological lesions. However, co-infections with other pig pathogens can lead to severe cases in pigs, including liver hemorrhage and necrosis. During a monitoring program 2016 in Saxony, Germany, farmed pigs with various clinical outcomes including fatalities were analysed for HEV and concurrent infections. We could detect eight HEV infected pigs from which six were co-infected with porcine circovirus 2 (PCV2). Phylogenetic analysis revealed HEV sub-genotypes 3e and 3f as well as PCV2 genotypes 2b and 2d. A direct correlation of the co-infection to the course of disease could not be determined, but the results provide hints that the immune modulatory effects of PCV2 combined with HEV influence the disease pattern in pigs.

Generation and application of monoclonal antibodies against Rift Valley fever virus nucleocapsid protein NP and glycoproteins Gn and Gc.

Rift Valley fever virus (RVFV) is a vector-borne virus that causes high neonatal mortality in livestock and deadly haemorrhagic fever in humans. In this paper, we describe the generation of monoclonal antibodies (mabs) against all three structural proteins of RVFV (glycoproteins Gn and Gc and nucleocapsid protein NP). After immunization of BALB/c mice with individual recombinant proteins, a total of 45 clones secreting ELISA-reactive monoclonal antibodies against NP, Gn and Gc epitopes were obtained. Twelve clones were directed to NP, 28 to Gn, and 5 to Gc. Western blot analysis revealed that most of the mabs were reactive to linearized epitopes on recombinant as well as native virus proteins. Six mabs against NP, 21 against Gn and all mabs against Gc also detected conformational epitopes, as shown by indirect immunofluorescence on RVFV-infected cells. All of the mabs were evaluated for their use in a competition enzyme-linked immunosorbent assay (ELISA) for the detection of a RVFV infection. Several mabs were identified that competed with polyclonal rabbit serum, and one of them - mab Gn123, raised against Gn protein - was selected for a proof-of-principle study with field sera from a recent Rift Valley fever outbreak. The novel Gn-based competition ELISA demonstrated high performance, offering a promising alternative and addition to serological assays based on nucleocapsid protein.

European ring trial to evaluate ELISAs for the diagnosis of infection with Rift Valley fever virus.

A ring trial was organized to evaluate Rift Valley fever virus (RVFV) ELISAs by European laboratories. A total of five ELISAs, two of which specific for IgM antibodies, were evaluated by six participants. Sera were derived from cattle or sheep and originated from either a RVFV endemic area, a RVFV-free area or from experimental infection studies. Cohen's kappa analysis showed higher than 90% agreement of two commercially available ELISAs with the virus neutralization test, suggesting that primary screening as well as serological confirmation using these ELISAs is feasible. More extensive validations with sera of known IgM status are, however, required to determine agreement between IgM ELISAs.