H-2 linked genetic control of immune responsiveness to hepatitis B surface antigen (HBsAg) in mice

Hock immunization: a humane alternative to mouse footpad injections

Footpad injection is a commonly used immunization method in mice. Being relatively easy to do with well-characterized lymphatic drainage, it has become a very useful immunization protocol to study local immune responses in draining lymph nodes. However, its disadvantages include use of only hind feet as a routine site of immunization since mice use their fore feet for food handling, and exacerbation of inflammation and swelling at the injection site leading to unrelieved pain and distress since feet are weight-bearing structures. With increasingly stringent Institutional guidelines for animal manipulations, there is increasing need for more humane protocols. A novel immunization protocol involving injection into the hock, the lateral tarsal region just above the ankle, a non-weight bearing structure draining to the same lymph node as the footpad, retains the advantages of footpad immunization without its drawbacks. This study, comparing immune responses between footpad and hock immunization in six different inbred mouse strains to two different protein antigens and a heat-killed bacterium, shows that hock immunization is a better alternative to footpad immunization, inducing comparable immune responses and being considerably more humane.

Ultraviolet radiation, resistance to infectious diseases, and vaccination responses

Exposure to ultraviolet (UV) radiation, as in sunlight, can modulate immune responses in animals and humans. This immunomodulation can lead to positive health effects especially with respect to certain autoimmune diseases and allergies. However, UV-induced immunomodulation has also been shown to be deleterious. Experimental animal studies have revealed that UV exposure can impair resistance to many infectious agents, such as bacteria, parasites, viruses, and fungi. Importantly, these effects are not restricted to skin-associated infections, but also concern systemic infections. The real consequences of UV-induced immunomodulation on resistance to infectious diseases are not known for humans. Risk estimations have been performed through extrapolation of animal data, obtained from infection models, to the human situation. This estimation indicated that UV doses relevant to outdoor exposure can impair the human immune system sufficiently to have effects on resistance to infections. To further quantify and validate this risk estimation, data, e.g., from human volunteer studies, are necessary. Infection models in humans are not allowed for ethical reasons. However, vaccination against an infectious disease evokes a similar immune response as the pathogen and thereby provides an opportunity to measure the effect of UV radiation on the immune system and an estimate of the possible consequences of altered resistance to infectious agents. Effects of controlled UVB exposure on immune responses after hepatitis B vaccination have been established in mice and human volunteers. In mice, cellular and Th1-associated humoral immune responses to hepatitis B were significantly impaired, whereas in human volunteers no significant effect of UVB on these responses could be found. Preliminary data indicate that cytokine polymorphisms might be, at least in part, responsible for interindividual differences in immune responses and in susceptibility to UVB-induced immunomodulation. In addition, adaptation to UV exposure needs to be considered as a possible explanation for the difference between mice and humans that was observed in the hepatitis B vaccination model.

A collaborative study to establish the International Reference Reagent for hepatitis B vaccine containing plasma-derived hepatitis B surface antigen

A collaborative study was conducted to establish a suitable international reference reagent for hepatitis B vaccine for use in immunogenicity assays. The limiting dilution required to induce antibodies in 50% of the test animals was determined for the proposed international reference reagent and three other plasma-derived hepatitis B vaccines. The minimum antigenic dose of these preparations varied widely (100-fold range) between laboratories. However, the expression of potencies of vaccines relative to the proposed International Reference Reagent reduced the variation between laboratories to within a 10-fold range. The reference reagent is intended for use in assays of hepatitis B vaccines in mouse (or guinea-pig) immunogenicity studies. For products made by different procedures, clinical trials in humans are necessary to establish a correlation between the immunogenic potency in animals and man.

Hepatitis B virus surface antigen (HBsAg) as carrier for synthetic peptides having an attached hydrophobic tail

B- and T-cell epitopes from three distinct regions of the hepatitis B virus (HBV) envelope (env) protein (preS1, preS2 and S) are involved in eliciting protective immunity. Since preS1 sequences inhibit the secretion of HBV env proteins from eukaryotic cells, it is difficult to prepare immunogens rich in preS1 sequences. This problem can be overcome by linking synthetic peptides from the preS1 region to particles containing both S and preS2 sequences. We describe here a novel approach for binding of synthetic peptides to exposed hydrophobic domains on HBV env proteins. Long chain fatty acids or mercaptans are covalently linked to synthetic peptides. Peptides with the attached hydrophobic tails interact strongly with HBV env proteins (S + preS2), whereby hybrid immunogens are generated. Such immunogens can be used in combination with alum, the only adjuvant approved for human use. The combination of the preS1 peptide [preS(12-47)] with particles containing the S and preS2 regions resulted in an immunogen which: (1) elicits a broad spectrum of protective antibodies; (2) circumvents the nonresponsiveness to: (a) preS1 epitopes in preS1-nonresponder strains of mice; and (b) S-protein in S-protein-nonresponder strains of mice; and (3) augments the immune response to S-protein. The combination of HBV env proteins with a synthetic peptide from the envelope of the human immunodeficiency virus (HIV-1) resulted in an immunogen eliciting anti-HIV-1. Hybrid immunogens consisting of viral proteins and of synthetic peptides represent a feasible approach for the design of future vaccines.

Genetic restriction of immune responsiveness to synthetic peptides corresponding to sequences in the pre-S region of the hepatitis B virus (HBV) envelope gene

Proteins of the HBV envelope (env) are coded for by two adjacent regions of the HBV env gene: the pre-S and S regions. Antigenic determinants corresponding to amino acid sequences of both regions are recognized by human antibodies and are important in virus-neutralizing responses. Protective immune responses to HBV appear to be linked to the major HLA histocompatibility complex. Inbred and congenic strains of mice represent a model system relevant for studies on the genetic control of immune responsiveness of humans to HBV envelope proteins. Such mouse strains were ranked according to their antibody response to the S protein and divided into high [d,q], intermediate [a,k,b], and low [s] responders (letters in brackets indicate H-2 haplotype.) Selected pre-S antigenic determinants can be mimicked with high fidelity by synthetic peptide analogues that are immunogenic without any carriers. Thus it is possible to study directly the genetic control of immune responsiveness to pre-S epitopes mimicked by these peptides without having to consider the influence of carriers or of S protein. The results presented here show that inbred mouse strains can be ranked according to their antibody responses to the synthetic peptide pre-S(120-145) as follows: A/J[a] approximately equal to SWR/J[q] greater than C57BL/6J[b] approximately equal to AKR/J[k] approximately equal to SJL/J[s] much greater than DBA/2J[d] greater than BALB/cJ[d]. Only SJL/J[s] mice responded well to another synthetic peptide pre-S (12-32). Thus, H-2-linked genes regulating the immune response to S protein and to epitopes on pre-S-coded sequences are distinct. Anti-pre-S(120-145) responses in S protein-nonresponders circumvent this nonresponsiveness. This should be considered in the design of hepatitis B vaccines.