Immunoblot analysis of natural and vaccine-induced IgG responses to rubella virus proteins expressed in insect cells

Background: The three structural proteins of rubella virus (RV), the capsid protein C and the envelope glycoproteins E1 and E2, were produced individu ally in soluble form in Sf9 insect cells using the baculovirus system. All proteins were equipped with a polyhistidine tag at their C-terminal ends to enable gentle purification by metal ion affinity chromatography. In additi on, the E2 and E2 proteins were engineered to display the FLAG epitope tag at their N-terminal ends. Study design: The diagnostic potential of the rec ombinant purified proteins was evaluated by immunoblot and enzyme immune as says (EIA) using a total of 57 well-characterised serum samples obtained at various time points after natural RV infection, congenital rubella syndrom e (C:RS), MMR vaccination or from controls with past RV immunity. In additi on, acute and convalescent phase serum pools from a total of 20 patients we re evaluated. Authentic RV proteins were used as a reference. Results: The recombinant E1 and C proteins were predominant in eliciting the immune resp once in both postnatal and vaccinal RV infections, being much weaker in the vaccinal ones. The IgG responce to the recombinant C protein was very stro ng after the first month post infection and decreased with time. The immune responce against the recombinant E2 protein, however, was generally poor, but notably stronger after congenital infection. Together, the results show ed that the individual recombinant protein antigens could be suitable for d iagnosis of RV infection and for study of the immune response to rubella va ccination. (C) 1999 Elsevier Science B.V. All rights reserved.