Comparative analysis of the immunostimulatory properties of different adjuvants on the immunogenicity of a prototype parainfluenza virus type 3 subunit vaccine

Viral infections of the respiratory tract: prevention and treatment

The rapid discovery of specific viral agents as the cause of many acute respiratory diseases was accompanied by considerable optimism that vaccines or other control measures could be developed quickly. Subsequent experience has demonstrated that effective control of these important public health problems has been an elusive goal. However, recent exciting developments in our understanding of the molecular biology and immunology of these viruses may provide the basis for more effective strategies in the future.

Adjuvants for porcine reproductive and respiratory syndrome virus vaccines

This review deals with present and past efforts in utilization of vaccine adjuvants for porcine reproductive and respiratory syndrome virus (PRRSV) vaccines. PRRSV vaccines elicit delayed and weak cell-mediated immune (CMI) and antibody responses after vaccination. Several kinds of vaccine adjuvants have been utilized to accelerate and magnify immune responses to PRRSV vaccines. These adjuvants include cytokines, chemical reagents, and bacterial products. Of 11 vaccine adjuvants tested, five (i.e. interleukin-2 (IL-2), IL-12, interferon alpha (IFNalpha), polyinosinic and polycytidylic acid, and cytidine-phosphate-guanosine oligodeoxynucleotides (CpG ODN)) significantly enhance CMI response to PRRSV vaccines. The response is characterized by proliferation, cytotoxicity, and IFNgamma secretion of peripheral blood mononuclear cells or T cells in response to recall PRRSV antigens in vitro. Two (i.e. CpG ODN and cholera toxin) significantly enhance PRRSV-specific antibody response after vaccination. Two (i.e. IL-2 and CpG ODN) significantly enhance protective efficacy of PRRSV vaccines in challenge models. Improvement of immune responses to PRRSV vaccines should focus in future studies on assessing more vaccine adjuvants for their efficiency in enhancing both CMI and antibody responses and on identifying PRRSV components and strategies that down-modulate pig immune responses in order to devise vaccine adjuvants that can regulate such strategies of the virus.

Viral pneumonia in children

Viral pneumonia causes a heavy burden on our society. In the United States, more than one million cases of pneumonias afflict children under the age of 5 years, costing hundreds of millions of dollars annually. The majority of these infections are caused by a handful of common viruses. Knowledge of the epidemiology of these viruses combined with new rapid diagnostic techniques will provide faster and more, reliable diagnoses in the future. Although the basic clinical epidemiology of these viruses has been carefully investigated over the last 30 years, new molecular techniques are greatly expanding our understanding of these agents and the diseases they cause. Antigenic and genetic variations are being discovered in many viruses previously thought to be homogeneous. The exact roles and the biological significance of these variations are just beginning to be explored, but already evidence of differences in pathogenicity and immunogenicity has been found in many of these substrains. All of this information clearly will impact the development of future vaccines and antiviral drugs. Effective drugs exist for prophylaxis against influenza A and respiratory syncytial virus, and specific therapy exists for influenza A. Ribarivin is approved for use in respiratory synctial virus infections, and it alone or in combination with other agents (eg, IGIV) may be effective in immunocompromised patients, either in preventing the development of pneumonia or in decreasing morbidity and mortality. Many new antiviral agents are being tested and developed, and several are in clinical trials.

ESAT-6 subunit vaccination against Mycobacterium tuberculosis

The ESAT-6 antigen from Mycobacterium tuberculosis is a dominant target for cell-mediated immunity in the early phase of tuberculosis (TB) in TB patients as well as in various animal models. The purpose of our study was to evaluate the potential of ESAT-6 in an experimental TB vaccine. We started out using dimethyl dioctadecylammonium bromide (DDA), an adjuvant which has been demonstrated to be efficient for the induction of cellular immune responses and has been used successfully before as a delivery system for TB vaccines. Here we demonstrate that, whereas immune responses to both short-term-culture filtrate and Ag85B are efficiently induced with DDA, this adjuvant was inefficient for the induction of immune responses to ESAT-6. Therefore, we investigated the modulatory effect of monophosphoryl lipid A (MPL), an immunomodulator which in different combinations has demonstrated strong adjuvant activity for both cellular and humoral immune responses. We show in the present study that vaccination with ESAT-6 delivered in a combination of MPL and DDA elicited a strong ESAT-6-specific T-cell response and protective immunity comparable to that achieved with Mycobacterium bovis BCG.

Vaccine delivery to animals

For many years vaccination of animals has been practiced to prevent infectious diseases using inactivated organisms or modified live organisms. The live vaccines were effective but lacked safety. The vaccines made with inactivated organisms required an adjuvant to induce an immune response that was not as effective as either the clinical disease or live vaccines. An 'ideal' vaccine would induce effective immunity specific for the type of infection, have long duration, require minimal or no boosters, have impeccable safety, would not induce adverse reactions, and be easy to administer. The desire to meet these criteria, and especially safety, has resulted in the development of vaccines that do not depend on the use of the viable disease agent. The emphasis on subunit or inactivated vaccines that meet the desired criteria of a perfect vaccine has resulted in a critical need for better adjuvants and delivery systems. This has resulted in a technological innovation revolution with development of a wide array of different technologies to generate effective vaccines. This review will describe the historical relevance of adjuvants used for parenterally administered inactivated/subunit vaccines as well as describe some of the exciting technological advances including adjuvants (ISCOMS), delivery systems (recombinant vectors, microparticles), and novel approaches (transgenic plants, naked DNA) that are currently being, or will be used in the future, in the search for better, more effective vaccines that meet the current and future needs of veterinary medicine.

A live attenuated chimeric recombinant parainfluenza virus (PIV) encoding the internal proteins of PIV type 3 and the surface glycoproteins of PIV type 1 induces complete resistance to PIV1 challenge and partial resistance to PIV3 challenge

The recovery of wild type and attenuated human parainfluenza type 3 (PIV3) recombinant viruses has made possible a new strategy to rapidly generate a live-attenuated vaccine virus fof PIV1. We previously replaced the coding sequences for the hemagglutinin-neuraminidase (HN) and fusion (F) proteins of PIV3 with those of PIV1 in the PIV3 antigenomic cDNA. This was used to recover a fully-viable, recombinant chimeric PIV3-PIV1 virus, termed rPIV3-1, which bears the major protective antigens of PIV1 and is wild type-like with regard to growth in cell culture and in hamsters [Tao T, Durbin AP, Whitehead SS, Davoodi F, Collins PL, Murphy BR. Recovery of a fully viable chimeric human parainfluenza virus (PIV) type 3 in which the hemagglutinin-neuraminidase and fusion glycoprotein have been replaced by those of PIV type 1. J Virol 1998;72:2955-2961]. Here we report the recovery of a derivative of rPIV3-1 carrying the three temperature-sensitive and attenuating amino acid coding changes found in the L gene of the live-attenuated cp45 PIV3 candidate vaccine virus. This virus, termed rPIV3-1.cp45L, is temperature-sensitive with a shut-off temperature of 38 degrees C, which is similar to that of the recombinant rPIV3cp45L, which possesses the same three mutations. rPIV3-1.cp45L is attenuated in the respiratory tract of hamsters to the same extent as rPIV3cp45L. Infection of hamsters with rPIV3-1.cp45L generated a moderate level of hemagglutination-inhibiting antibodies against wild type PIV1 and induced complete resistance to challenge with wild type PIV1. This demonstrates that this novel attenuated chimeric virus is capable of inducing a highly effective immune response against PIV1. It confirms previous observations that the surface glycoproteins of parainfluenza viruses are sufficient to induce a high level of resistance to homologous virus challenge. Unexpectedly, infection with recombinant chimeric virus rPIV3-1.cp45L or rPIV3-1, each bearing the surface glycoprotein genes of PIV1 and the internal genes of PIV3, also induced a moderate level of resistance to replication of wild type PIV3 challenge virus. This indicates that the internal genes of PIV3 can independently induce protective immunity against PIV3 in rodents, albeit a lower level of resistance than that induced by the surface glycoproteins. Thus, a reverse genetics system for PIV3 has been used successfully to produce a live attenuated PIV1 vaccine candidate that is attenuated and protective in experimental infection in hamsters.

A prototype recombinant vaccine against respiratory syncytial virus and parainfluenza virus type 3

We have produced a genetically-engineered chimeric protein composed of the external domains of the respiratory syncytial virus (RSV) fusion (F) protein and the parainfluenza virus type 3 (PIV-3) hemagglutinin-neuraminidase (HN) protein in insect cells using the baculovirus expression system. The yield of the soluble chimeric FRSV-HNPIV-3 protein could be increased approximately 2-fold by using Trichoplasia ni (High Five) insect cells in place of Spodoptera frugiperda (Sf9) for expression. The chimeric protein, purified from the supernatant of baculovirus-infected High Five cells by immunoaffinity chromatography was correctly processed at the F2-F1 proteolytic cleavage site. Immunochemical analysis of the chimera with a panel of anti-F and anti-HN monoclonal antibodies suggested that the antigenicity of the major F and HN neutralization epitopes of the chimeric protein was preserved. Immunization of cotton rats with two 1 or 10 micrograms doses of the chimeric protein adsorbed to aluminum phosphate elicited strong PIV-3 specific HAI responses as well as PIV-3 and RSV specific neutralizing antibodies, and at either dose completely protected against challenge with live RSV and PIV-3.

An update on approaches to the development of respiratory syncytial virus (RSV) and parainfluenza virus type 3 (PIV3) vaccines

RSV and PIV3 are responsible for about 30% of severe viral respiratory tract disease leading to hospitalization of infants and children. For this reason, there is a need to develop vaccines effective against these viruses. Since these viruses cause severe disease in early infancy, vaccines must be effective in the presence of maternal antibody. Currently, several strategies for immunization against these viruses are being explored including peptide vaccines, subunit vaccines, vectored vaccines (e.g., vaccinia-RSV or adenovirus-RSV recombinants), and live attenuated virus vaccines. The current status of these approaches is reviewed. In addition, the immunologic basis for the disease potentiation seen in vaccinees immunized with formalin-inactivated RSV during subsequent RSV infection is reviewed. The efficacy of immunization in the presence of maternal antibody is discussed. Much progress for a RSV and PIV3 vaccine has been made and successful immunization against each of these pathogens should be achieved within this decade.