ADJUVANTS IN IMMUNIZATION WITH INFLUENZA VIRUS VACCINES

Considerations for Size, Surface Charge, Polymer Degradation, Co-Delivery, and Manufacturability in the Development of Polymeric Particle Vaccines for Infectious Diseases

Vaccines have advanced human health for centuries. To improve upon the efficacy of subunit vaccines they have been formulated into nano/microparticles for infectious diseases. Much progress in the field of polymeric particles for vaccine formulation has been made since the push for a tetanus vaccine in the 1990s. Modulation of particle properties such as size, surface charge, degradation rate, and the co-delivery of antigen and adjuvant has been used. This review focuses on advances in the understanding of how these properties influence immune responses to injectable polymeric particle vaccines. Consideration is also given to how endotoxin, route of administration, and other factors influence conclusions that can be made. Current manufacturing techniques involved in preserving vaccine efficacy and scale-up are discussed, as well as those for progressing polymeric particle vaccines toward commercialization. Consideration of all these factors should aid the continued development of efficacious and marketable polymeric particle vaccines.

Intranasal immunization of mice with inactivated virus and mast cell activator C48/80 elicits protective immunity against influenza H1 but not H5

Vaccination represents the most economic and effective strategy of preventing influenza pandemics. We previously demonstrated that intranasal immunization of mice with recombinant hemagglutinin and the mast cell activator C48/80 elicited protective immunity against challenge with the 2009 pandemic H1N1 influenza in mice, demonstrating that the novel C48/80 mucosal adjuvant was safe and effective. The present study demonstrated that intranasal immunization with inactivated H1N1 virus and C48/80 elicited protective immunity against lethal challenge with homologous virus, however, when the immunogen was replaced with inactivated H5N1 virus protection was lost. These observations suggested that the adjuvant effects conferred by C48/80 were virus subtype specific and that its use as a broad-spectrum adjuvant for use in immunizations against all influenza viruses needs to be further analyzed.

STUDIES ON THE TOXICITY OF INFLUENZA VIRUSES : II. THE EFFECT OF INTRA-ABDOMINAL AND INTRAVENOUS INJECTION OF INFLUENZA VIRUSES

Upon intra-abdominal or intravenous injection of allantoic fluids infected with influenza viruses, mice frequently died within 8 to 96 hours. Similar results were observed upon injection of rabbits, rats, and guinea pigs. Autopsy of the mice revealed widespread necrosis of liver and spleen, hemorrhages into the intestines, pleural exudation, and other occasional findings. Survivors frequently developed pulmonary consolidation or jaundice. The dominant type of lesion depended on the strain of virus used. All attempts to demonstrate propagation of the influenza viruses outside of the respiratory tract failed. It was concluded that the early lesions were the result of toxic activities of the virus and not of virus multiplication in the affected tissues. Injection into chick embryos of highly diluted inocula produced higher titers of virus, hemagglutmin, and toxicity in the allantoic fluids than the use of more concentrated seed culture. Serial passage of various strains in high dilution frequently increased the toxic activity. The infectivity often reached its peak in 24 hours when tests for toxicity were still negative. Maximal toxicity was usually not attained before 48 hours. The toxic activity could not be separated from the infective property by such means as differential centrifugation and adsorption onto and elution from chicken red cells. However, upon heating, formalinization, and irradiation with ultraviolet light, the ability of the agents to propagate was lost at a faster rate than the toxic property. The toxic property remained stable for 2 to 3 months at 4°C. This stability was comparable to that of the infectivity for chick embryos. Specific immune sera neutralized in high dilution the toxic activity of the homologous virus. Non-specific neutralization occurred in low dilutions of normal and heterologous immune sera. Strain differences were indicated by this method of testing. Vaccination of mice by the subcutaneous or intra-abdominal routes protected mice specifically against the toxic effects of intra-abdominally or intravenously injected preparations of virus.

MECHANISM OF THE AUGMENTING ACTION OF MINERAL OIL ON ANTIBODY PRODUCTION : TISSUE REACTIONS AND ANTIBODY RESPONSE TO DYSENTERY VACCINE IN SALINE, AND IN SALINE-LANOLIN-MINERAL OIL EMULSION

A comparative study was made in rabbits of antibody production and tissue changes following the injection into the foot pads, of saline in Falba and mineral oil emulsion, of killed cells of Shigella paradysenteriae Flexner in saline, and of killed cells of Shigella paradysenteriae in saline in Falba-mineral oil emulsion. It was found that antibody production was greatly prolonged by the emulsification in oil. While with antigen in saline the serum titers began to fall 9 days after injection and disappeared somewhere between the 3rd and 6th months, with antigen in paraffin oil they began to drop only after 14 days, and were still high after 10 months, when the experiment was ended. The toxic effects of the antigen were greatly reduced by the emulsification in oil. A subcutaneous dose of 1.5 mg. of antigen in saline caused mesenchymal reactions in lung, liver, and spleen as well as toxic degeneration and sometimes necrosis of the liver whereas eight times as much of the antigen in oil produced no systemic lesions. Oil drops remained detectable in the foot pad until the end of the experiment. Bacteria remained visible in the oil for 1 week or more, but with saline they disappeared within 1 day. The latter observation shows that retention of antigen at the site of injection is at least one of the mechanisms of prolongation of antibody formation by paraffin oil. The tissue reaction in the foot pad to antigen in oil was largely one of suppuration with the production of persisting mononuclear granulomata whereas after antigen in saline it was chiefly one of catarrhal inflammation, subsiding within a month. The changes in the regional lymph nodes were essentially those of lymphatic hyperplasia with the production of numerous lymphocytes and large active secondary nodules, the macrophages remaining subsidiary. The lymphocytic reaction in the lymph nodes closely paralleled the antibody response but the monocytic reaction at the site of injection was not correlated with this response; in fact, in the antigen in oil experiments the monocytic reaction reached its height after the peak of antibody production. The tissue changes observed in the various experiments were consistent with the finding previously reported from this laboratory, that the lymphocyte is concerned in antibody formation.

ALLERGIC ENCEPHALOMYELITIS IN MONKEYS IN RESPONSE TO INJECTION OF NORMAL MONKEY NERVOUS TISSUE

By subcutaneous injection of central nervous tissue emulsified with adjuvants according to Freund's technique it has been possible to induce in the majority of monkeys an acute disseminated encephalomyelitis which is interpreted as an isoimmunization to CNS tissue. Positive reactions occurred only in response to CNS tissue containing white matter; i.e., cerebral white matter, spinal cord (whether normal or poliomyelitis-infected), and cortical "gray" matter (with an estimated 10 per cent contamination with white matter). No reaction occurred when peripheral nerve or kidney suspension or saline alone was injected with adjuvants. The perivascular and extravascular infiltration induced was confined to the CNS.

THE RAPID PRODUCTION OF ACUTE DISSEMINATED ENCEPHALOMYELITIS IN RHESUS MONKEYS BY INJECTION OF HETEROLOGOUS AND HOMOLOGOUS BRAIN TISSUE WITH ADJUVANTS

1. A picture resembling acute disseminated encephalomyelitis in the human being has been regularly and rapidly produced in rhesus monkeys by injection of emulsions of adult rabbit and monkey brain administered with adjuvants. 2. No lesions of the central nervous system resulted from injection of similar emulsions of fetal rabbit brain or adult rabbit lung. 3. A description of the gross and histological findings in the central nervous system is given and compared with features of human demyelinating disease. 4. The experimental findings are in accord with the hypothesis that antibody to the injected brain emulsion reacts with the tissues of the nervous system of the animal to produce the pathological changes.

Adjuvants and Antibody Production: Dispelling the Myths Associated with Freund's Complete and Other Adjuvants

Adjuvants have been used for more than 70 yr to enhance the immune response of the host animal to an antigen. Among the mechanisms that adjuvants use to enhance the immune response are the "depot" effect, antigen presentation, antigen targeting, immune activation/modulation, and cytotoxic lymphocyte induction. The immunostimulatory properties of adjuvants result in inflammation, tissue destruction, and the potential for resulting pain and distress in the host animal. The inflammatory lesions produced by adjuvants such as Freund's complete adjuvant (FCA) have led some to conclude that pain and distress are present, even in cases where the scientific evidence fails to support this conclusion. Recommendations and regulations in the literature, based on available scientific evidence, provide guidance on total adjuvant volumes, volumes per site, routes of injection, booster injections, and adjuvants used for antibody production. Among the numerous adjuvants that are used for experimental antibody production reviewed in this article, many claim to be less inflammatory, tissue destructive, and painful than FCA while producing equal or superior antibody responses. Although no adjuvant surpasses FCA for experimental antibody production against a wide range of antigenic molecules, many produce excellent antibody responses with less inflammation and tissue destruction. Balancing the requisite degree of immuno-stimulation and the extent of inflammation, necrosis, and potential pain and distress requires consideration of the nature of the antigen, the host immune responsiveness, the adjuvant's mechanisms of action, and the desired end-product. In cases where the antigen is a weak immunogen or has a very limited availability, the type and role of adjuvant becomes a critical component in producing an acceptable immune response and humoral antibody response.

Studies on host-virus interactions in the chick embryo-influenza virus system. V. Simultaneous serial passage of the agents of influenza A and B in relation to variations in the growth cycle of influenza B virus

The combined passage of influenza A and B viruses in series, as reported by Sugg and Magill, has been confirmed. When the mixed passage materials were not too highly diluted both agents could be traced through 10 transfers. Growth curve experiments revealed that both agents developed independently, as measured by hemagglutination-inhibition tests in the presence of specific immune sera against one or the other type. However, the hemagglutinin titers of the 2 viruses in the mixed series were always substantially lower than those recorded when the strains were used individually as seed in the same concentrations as were employed in the mixed series. Assay of the infectivity titers of the individual strains in the presence of appropriate immune sera led to the demonstration that the time required for the growth cycle of influenza B virus varied with the dose of seed virus. With undiluted infected allantoic fluid as seed only 4 to 5 hours elapsed before new generations of virus were liberated. With increasing 10-fold dilution of the seed the constant period became increasingly longer until it stabilized at 8 to 10 hours. This finding offers an explanation for the seeming discrepancy between the observations on interference between the 2 viruses and the difference reported previously in the extent of their growth periods, on the one hand, and the fact that the 2 agents could be carried simultaneously in series through numerous passages in the chick embryo.

The use of adjuvants in studies on influenza immunization. I. Measurements in monkeys of the dimensions of antigenicity of virus-mineral oil emulsions

Untoward reactions at the site of inoculation were not observed in monkeys vaccinated with influenza virus incorporated in a water-in-oil emulsion without acid-fast bacilli. Studies were then made to measure some of the dimensions of antigenicity of these emulsions to evaluate the extent of the immunologic adjuvant effect. This included measurements of height and persistence of the antibody response to inoculation and measurements of the extent to which the vaccine could be diluted and still induce antibody formation; i.e., antigenic extinction. In addition, comparisons were made of the rates of development of hemagglutination-inhibiting, virus-neutralizing, and complement-fixing antibody activities to determine the relationship among these three properties of the serum of immunized animals. It was found that levels of antibody many fold higher were induced by the virus-adjuvant mixtures as compared with virus in an aqueous menstruum, and that the level of antibody induced was related to the quantity of antigen incorporated in the emulsion. The stock vaccine when emulsified could be diluted 100,000-fold and was still active in antibody formation whereas a 100-fold dilution of the antigen without emulsification was essentially ineffective. Equivalent quantities of virus in 0.1 ml. or 1.0 ml. of emulsion induced antibody responses that were indistinguishable with respect to level or persistence. In comparing the course of antibody development it was found that hemagglutination-inhibiting, virus-neutralizing, and complement-fixing antibodies develop at different rates; careful analysis of the data derived from the present study together with other observations warrant the conclusion that these antibody activities are not present in constant proportion and are independent of one another. The implications of this observation and of the others mentioned above are discussed.

Studies on antibody production. IV. The role of a wax fraction of Mycobacterium tuberculosis in adjuvant emulsions on the production of antibody to egg albumin

After injection of ovalbumin as a water-in-oil emulsion a pronounced adjuvant effect is demonstrable following the incorporation of tubercle bacillary wax into the oily phase of the mixture. With single doses of antigen (10 mg. ovalbumin) there is a 4- to 5-fold increase in the amount of antibody at the median of 3 week serum levels in animals receiving a small dose of wax (40 µg.). With a 5 mg. dose of wax there is an 8-fold increase in serum antibody levels at the median. A striking feature of the action of wax is the stimulation of a macrophage proliferation locally at the site of injection, and the production of morphological abnormalities in these cells. As judged by staining techniques for antibody content, these locally assembled cells are not active in the formation of antibody. Wax injected in mineral oil results in a remarkable systematized stimulation of the reticulo-endothelial system. The greatly increased serum antibody levels demonstrated after the use of tubercle bacillary wax in antigen mixtures is attributed to a widespread proliferation of plasma cell elements in the lymphatic glands, spleen and liver.

Comparative studies on effects of incomplete oil adjuvants with different physical properties

The author investigated the effects of Freund's incomplete adjuvant (FIA) with different physical properties on precipitin formation and skin hyperreactivity in rabbits and mice following intramuscular injection of ovalbumin (OA) with the adjuvant. Histopathological changes in the injection site and in some visceral organs were also examined. The observation periods after the injection for mice and rabbits were 20 and 28 weeks, respectively. In contrast to the most reports, FIA of both imperfectly emulsified-water-in-oil (W/O II) and oil-in-water (O/W) types were sometimes equivalent or superior to perfectly emulsified water-in-oil (W/O 1) type FIA in the enhancing effects in precipitin formation both in rabbits and mice. The skin displayed the immediate type hypersensitivity reaction to OA throughout the observation period irrespective of the type of adjuvant. The O/W type often caused significantly stronger skin hyperreactivity than the other types. Histopathological findings in the injection site indicated that the abscess formation in rabbits was severer than that in mice, and that the O/W type induced the severest abscess. No relation was found between free fatty/acid contents of adjuvant emulsion and abscess formation in either animal species. Granuloma formation in mice was always severer than that in rabbits. The O/W type caused extremely weak granuloma in mice, and none in rabbits. Histopathological changes in main visceral organs, being dependent on the emulsion type, were also discussed.

Control of influenza and poliomyelitis with killed virus vaccines

The requirements for inducing immunity against an infectious disease are outlined, and the application of these requirements to the development of effective vaccines (vaccinology) is discussed. Influenza and poliomyelitis are examined from this viewpoint, and data are presented that demonstrate the effectiveness of killed virus vaccines against these diseases. A comparison between live and killed poliovirus vaccines suggests the desirability of returning to the use of a killed virus vaccine for the eradication of polio. The natural history of influenza and experience with vaccination suggest that influenza might be brought under effective control by routine immunization in childhood with a polyvalent killed virus vaccine potentiated by an immunologic adjuvant.

Rapid Production of Acute Disseminated Encephalomyelitis in Rhesus Monkeys by Injection of Brain Tissue With Adjuvants

Rapid production in the monkey of a pathological condition resembling acute disseminated encephalomyelitis, marked by demyelination, can be achieved by the use of adjuvants added to rabbit brain emulsions.