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The guinea pig model of recurrent genital herpes simplex virus type 2 (HSV-2) infection was used to test the immunotherapeutic activity of a glycoprotein subunit vaccine. Vaccine formulation consisted of three recombinant herpes simplex virus (HSV) glycoproteins, namely gB1s, gD2t and gE1t, plus aluminium hydroxide [Al(OH)3)] adjuvant. One month after viral challenge, infected animals were therapeutically immunised by seven subcutaneous injections of a low dose of antigens with a weekly interval for the first five and a fortnightly interval for the last two administrations. Results showed that the treatment was highly effective in ameliorating the recidivist pathology of animals, suggesting that this kind of vaccine formulation and administration may be helpful for therapeutic intervention in humans affected by recurrent herpes infections.

A nucleic acid vaccine candidate against dengue-2 virus was constructed to express a truncated dengue-2 E glycoprotein without concomitant expression of prM. The truncated E protein was properly expressed even in the absence of prM. Mice inoculated intramuscularly with the recombinant plasmid containing 94% of the E gene did not respond with anti-dengue antibodies, cellular proliferation, or synthesis of cytokines by their lymphoid cells when stimulated with purified dengue-2 virus. However, protection was observed in 20% of the challenged mice immunized with this recombinant plasmid and the mice survived longer than the control group. The low percentage of protection might be explained by a weak activation of the immune system resulting from an imperfect secretion of E due to lack of the prM protein. This study corroborates with the hypothesis that prM is important for the processing of the E glycoprotein and should be incorporated on candidate vaccines engineered by recombinant DNA technology.

Classical swine fever virus causes significant mortality and morbidity in commercial piggeries in many countries in Europe and Asia. The protective antigen, gp55, is highly conformation-dependent and thus killed virus or bacterially produced proteins are not protective. This report demonstrates that DNA vaccination with the gene encoding gp55 can provide protective immunity with inoculation of two doses of 25 microg DNA or a single shot of 200 microg. Furthermore, the DNA can be delivered intramuscularly or by a simple spring-loaded needleless inoculator. In addition it is shown that inoculation of the DNA at a single site conveys the same level of immunity as division of the dose between two sites.

The ability of a genetically detoxified mutant of heat labile enterotoxin (LTK63) to act as a mucosal adjuvant following intranasal immunization with recombinant gD2 has previously been reported in mice [Ugozzoli M, O'Hagan DT, Ott GS. Intranasal immunization of mice with herpes simplex virus type 2 recombinant gD2: the effect of adjuvants on mucosal and serum antibody responses. Immunol 1998;93:563-571.]. In the current studies, these observations were extended to the guinea pig model. Immunized guinea pigs were subsequently challenged intravaginally with HSV-2. Intranasal immunization with gD2 and LTK63 induced a significant reduction in disease severity and a reduction in mortality. However, only intramuscular immunization with a potent adjuvant (MF59) induced protection against the incidence of disease.

We constructed a recombinant baculovirus which produces a dengue (DEN)-2 virus envelope (E) protein containing a six-histidine (H6) tag in place of the last 100 amino acids at its C-terminus. The recombinant protein was purified from the supernatant of baculovirus-infected Spodoptera frugiperda insect cell cultures to apparent homogeneity by cation-chelation chromatography (TALON) in which the H6-tagged E-protein was eluted under non-denaturing conditions with 100 mM imidazole at pH 8.0. Mice vaccinated with the purified E mixed with aluminium hydroxide adjuvant showed an immune response of IgM and IgG1, IgG2a and IgG2b isotypes, and neutralizing antibodies, similar to that following immunization with purified inactivated DEN-2 virus. Moreover, mice that received the purified recombinant protein were significantly protected against 200 50% lethal dose of DEN-2 virus. This combination of affinity purified H6-tagged protein and adsorption onto a cationic carrier seems promising for the production of immunogenic particulate proteins, especially DEN protein for the four serotypes, and the development of a new generation of vaccines.

Immunological analyses in this laboratory and others have suggested that a nonrecurrent HSV seropositive immune status is more closely correlated with a type 1 T helper cell (Th1) response characterized by elevated levels of interferon-gamma and IL2 rather than high titers of virus-specific antibodies. Effective intervention with an immunotherapeutic vaccine may require modulation of the regulatory network of T helper cells such that there is selective restimulation and expansion of the Th1 response. We have established a murine model for assessing the immunomodulatory capacity of an HSV glycoprotein subunit vaccine in animals with pre-existing herpes immunity. Animals were infected with varying doses of HSV1 and then administered glycoprotein D (gD) vaccine adjuvanted with aluminum phosphate at 3-week intervals. Observed changes in serological and cellular responses indicated that administration of subunit vaccine adjuvanted with aluminum phosphate could shift a dominant Th1 response, induced by sensitization with live HSV, towards a Th2 profile of activity. These data suggest that use of aluminum based adjuvants will not selectively stimulate Th1-associated responses and alternative adjuvants may be required for effective use of subunit vaccine in an immunotherapeutic indication in humans.