Chung-Ho Hung

Genetically-engineered subunit vaccine against feline leukaemia virus: protective immune response in cats

A recombinant retroviral subunit vaccine has been developed that successfully protects cats from infectious feline leukaemia virus (FeLV) challenge. The antigen used is a non-glycosylated protein derived from the envelope glycoprotein of FeLV subgroup A, expressed in Escherichia coli. This recombinant protein, rgp70D, includes the entire exterior envelope protein gp70, plus the first 34 amino acids from the transmembrane protein p15E. The vaccine consists of purified rgp70D absorbed on to aluminium hydroxide and used in conjunction with a novel saponin adjuvant. Cats immunized with this formulation developed a strong humoral immune response, including neutralizing and feline oncornavirus-associated cell membrane antigen antibodies. Vaccinated animals showed an anamnestic response upon intraperitoneal challenge with FeLV-A, and were protected from viral infection. In contrast, the control animals developed viraemia shortly after the challenge, which in most cases became chronic. Formulation of the same antigen with other widely used adjuvants elicited poor protective immune responses in cats.

Impact of the saponin adjuvant QS-21 and aluminium hydroxide on the immunogenicity of recombinant OspA and OspB of Borrelia burgdorferi

The impact of the adjuvants QS-21 and aluminium hydroxide (alum) on the immunogenicity of recombinant outer surface proteins A (OspA) and B (OspB) of Borrelia burgdorferi was investigated. Both non-acylated OspA and OspB derived from strain B31 were expressed in Escherichia coli and purified by reversible citraconylation and anion-exchange chromatography. Antisera to OspA or OspB were prepared in mice with antigens formulated with QS-21 or alum, and evaluated for specific immunoglobulin G isotypes, agglutination and borreliacidal activity. QS-21 significantly enhanced IgG2a and IgG2b antibody responses to OspA and OspB, and IgG1 response to OspA when compared with the formulation containing antigen alone. In contrast, alum significantly inhibited the induction of IgG2a and IgG2b responses to OspA. Alum had no significant effect on IgG1 response to OspA, or IgG2a and IgG2b responses to OspB, but significantly enhanced IgG1 antibody response to OspB. Antisera to OspA or OspB formulated by QS-21 possessed higher titres of agglutinating antibody than antisera to OspA or OspB alone. Borreliacidal activity was eight- to 64-fold higher in antisera to OspA formulated with QS-21 than in antisera to OspA formulated with or without alum. These antisera were highly borreliacidal to New York strain B31, a California isolate CA-2-87, German isolate Fr, and Swedish isolate G25. Antisera to OspB formulated with QS-21 were highly borreliacidal to strains B31 and Fr, but not to CA-2-87 and G25. Antisera to OspB formulated with alum were borreliacidal only to B31. Thus, OspA was superior to OspB and QS-21 superior to alum at eliciting functional antibody responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis of Human Immunodeficiency Virus Infection by Immunoassay Using a Molecularly Cloned and Expressed Virus Envelope Polypeptide: Comparison to Western Blot on 2707 Consecutive Serum Samples

To detect human immunodeficiency virus (HIV) antibodies in a simple enzyme-linked immunoassay (CBre3-EIA), we used an Escherichia coli-expressed polypeptide antigen, representing the carboxy-terminal third of the external membrane glycoprotein gene fused with the amino-terminal half of the transmembrane glycoprotein gene. Over a 3-month period, 2707 consecutive serum samples referred for confirmatory testing for human T-lymphotrophic virus type III (HTLV-III) antibodies were evaluated by both Western blot and CBre3-EIA. On a single determination for each sample, the CBre3-EIA was found to have an estimated sensitivity (99.9%) and specificity (99.1%) similar or superior to the more cumbersome Western blot method. This study shows that all HIV-seropositive subjects have antibodies to the virus envelope protein; no other virus antigens are required for construction of highly sensitive immunoassays.