Chemical inactivation of recombinant vaccinia viruses and the effects on antigenicity and immunogenicity of recombinant simian immunodeficiency virus envelope glycoproteins

Production and characterization of monoclonal antibodies against binary ethylenimine inactivated Nipah virus

Nipah virus, a zoonotic paramyxovirus which emerged recently was chemically inactivated using binary ethylenimine (BEI). The inactivated virus was concentrated and purified by sucrose gradient centrifugation. The gradient fractions were examined by electron microscopy and Western immunoblot, and gradient fraction containing mainly Nipah matrix (M) and nucleocapsid (N) proteins was used for immunizing BALB/c mice to generate hybridomas. Screening of the resultant hybridoma clones identified five strongly positive clones producing IgG monoclonal antibodies (mAbs) reactive to the Nipah virus antigen. The protein specificity of these mAbs was determined by Western immunoblot using Nipah virus and recombinant Nipah virus proteins expressed in mammalian cells. Four mAbs reacted with Nipah N protein and one reacted with Nipah M protein. None of the mAbs neutralized Nipah virus infectivity in vitro. However, all mAbs recognized Nipah virus in ELISA and immunofluorescence assay. F45G2 mAb was most suitable for immunohistochemistry on long term formalin-fixed Nipah virus infected swine tissues. Three of the anti-nucleocapsid mAbs (F45G2, F45G3 and F45G6) showed cross-reactivity with closely related Hendra virus N protein in both immunofluorescence and Western Immunoblot assays. Two of the mAbs were specific for the Nipah virus only, F45G4 (anti-N) and F45G5 (anti-M), and could be used in the primary identification of Nipah virus. The use of these immunoreagents to develop new diagnostic assays is discussed.

Accelerated viraemia in cats vaccinated with fixed autologous FIV-infected cells

We have vaccinated cats with fixed autologous FIV infected PBMC to determine whether autologous presentation of antigen is capable of inducing a protective immune response against homologous challenge. To this end autologous PBMC were infected with a FIV molecular clone (19k1). When infection was established, cells were inactivated by dialysis against paraformaldehyde. Upon vaccination, cats developed a virus specific immune response as measured by ELISA against the Gag protein of FIV. No antibodies against the envelope protein were detected with a peptide ELISA. Virus neutralizing antibodies however could be detected with a neutralization assay based on infection of CrFK cells, but not in an assay based on infection of primary T-cells. Although vaccination led to the induction of these virus-specific immune responses, vaccinated cats were not protected against homologous challenge but showed an accelerated viraemia upon infection. This was shown both by PCR and cell-associated viral load. The possible mechanisms underlying this observation are discussed in this paper.