Antigenicity of polypeptides (poly alpha amino acids). XVI. Genetic control of immunogenicity of synthetic polypeptides in mice

Stimuli-sensitive synthetic polypeptide-based materials for drug and gene delivery

Stimuli-sensitive synthetic polypeptides are unique biodegradable and biocompatible synthetic polymers with structures mimicking natural proteins. These polymers exhibit reversible secondary conformation transitions and/or hydrophilic-hydrophobic transitions in response to changes in environmental conditions such as pH and temperature. The stimuli-triggered conformation and/or phase transitions lead to unique self-assembly behaviors, making these materials interesting for controlled drug and gene delivery applications. Therefore, stimuli-sensitive synthetic polypeptide-based materials have been extensively investigatid in recent years. Various polypeptide-based materials, including micelles, vesicles, nanogels, and hydrogels, have been developed and tested for drug- and gene-delivery applications. In addition, the presence of reactive side groups in some polypeptides facilitates the incorporation of various functional moieties to the polypeptides. This Review focuses on recent advances in stimuli-sensitive polypeptide-based materials that have been designed and evaluated for drug and gene delivery applications. In addition, recent developments in the preparation of stimuli-sensitive functionalized polypeptides are discussed.

Fetal and Maternal Transforming Growth Factor-β1 May Combine to Maintain Pregnancy in Mice1

One of the mysteries of pregnancy is why a mother does not reject her fetuses. Cytokine-modulation of maternal-fetal interactions is likely to be important. However, mice deficient in transforming growth factor-beta1 (TGF beta 1) and other cytokines are able to breed, bringing this hypothesis into question. The phenotype of TGF beta 1 null-mutant mice varies with genetic background. We report here that, in outbred mice, the loss of TGF beta 1-deficient embryos is influenced by the parity of their mother. This is consistent with the loss of mutants being due to immune rejection. An inbred line of TGF beta 1(+/-) mice that supported TGF beta 1-deficient fetuses had high levels of TGF beta 1 in their plasma. Analysis of the amniotic fluids in this line indicated that biologically relevant levels of maternal TGF beta 1 were present in the TGF beta 1(-/-) fetuses. These data are consistent with maternal and fetal TGF beta 1 interacting to maintain pregnancy, within immune-competent mothers.

Genetic control of the immune response to staphylococcal nuclease. I. Ir-Nase: control of the antibody response to nuclease by the Ir region of the mouse H-2 complex

A number of inbred and congenic resistant strains of mice were immunized with staphylococcal nuclease (Nase). Antibody responses were measured in the sera of the animals by a sensitive method involving inhibition of enzymatic hydrolysis of DNA, High responder strains included A/J, DBA/2, BALB/c, AKR/J, C57BR, and SJL/J. DBA/1 and C57BL/6 mice were low responders. The strain distribution of anti-Nase response potential was compatible with the relevant immune response gene(s) being linked to the murine major histocompatibility complex. Linkage of this response to H-2 was demonstrated by the findings that: (a) the congenic C3H/HeJ and C3H.SW mice were respectively high and low responders; (b) the congenic lines B10.A and B10.D2 were high responders, whereas the C57BL/10 strain was a poor responder; and (c) anti-Nase response potential of F(2) progeny from DBA/1 x SJL/J matings correlated with their H-2 type. Three B10.A recombinant lines were used to map this Ir gene within H-2. B10.A(4R) was a high responder to Nase, whereas B10.A(2R) and B10.A(5R) were both low responders. We wish to propose the name Ir-Nase for the gene(s) controlling antibody responsiveness to this immunogen. Our data indicate that Ir-Nase is located within the same chromosomal segment of the H-2 complex as is Ir-IgG.

Specific immune response genes of the guinea pig. I. Dominant genetic control of immune responsiveness to copolymers of L-glutamic acid and L-alanine and L-glutamic acid and L-tyrosine

The immunogenicity of three random copolymers of amino acids with L-glutamic acid and L-alanine (GA), L-glutamic acid and L-tyrosine (GT), or L-glutamic acid, L-alanine, and L-tyrosine (GAT), administered in complete Freund's adjuvant, was studied in several inbred and random-bred guinea pig strains. The animals were tested for delayed sensitivity and their sera were assayed for the presence of antibody directed against the immunizing polymer. All of the guinea pigs developing delayed hypersensitivity also had significant antibody levels in their sera. Inbred strain 2 guinea pigs responded to immunization with GA, but failed to form detectable responses to GT. Inbred strain 13 animals, on the other hand, responded to GT, but not to GA. The (2 x 13)F(1) hybrids responded to both GA and GT with both delayed hypersensitivity and circulating antibody. Thus, the ability of these inbred guinea pigs to respond immunologically to GA or GT is controlled by distinct autosomal dominant genes. A variable percentage of random-bred guinea pigs, depending on their source as well as their strain, responded to immunization with GA and with GT. All guinea pigs, both inbred and random bred, responded to immunization with GAT. The ability to respond immunologically to GAT, therefore, does not seem to be under simple genetic control. However, the levels of anti-GAT antibody found in the sera of animals lacking the ability to respond to GA were much lower than those detected in GA responder animals.

Specific immune response genes of the guinea pig. II. Relationship between the poly-L-lysine gene and the genes controlling immune responsiveness to copolymers of L-glutamic acid and L-alanine and L-glutamic acid and L-tyrosine in random-bred Hartley guinea pigs

The ability of guinea pigs to make immune responses to GA, a linear random copolymer of L-glutamic acid and L-alanine, GT, a random linear copolymer of L-glutamic acid and L-tyrosine, and PLL, a linear homopolymer of L-lysine, is controlled by different autosomal dominant genes specific for each of those polymers. We have investigated the relationship between the PLL gene and the GA and GT immune response genes by simultaneously immunizing random-bred Hartley strain guinea pigs with GA and PLL, GT and PLL, or GA and GT. In most Hartley guinea pigs the ability to respond immunologically to GA and to PLL is inherited together; that is, most animals responding to GA respond to PLL and vice versa. However, a few animals respond to either GA or to PLL but not both, demonstrating that the GA and PLL immune response genes are not identical but linked in most Hartley animals. Conversely, when simultaneously immunized with GT and PLL, most Hartley guinea pigs respond to either PLL or GT but not both, indicating that GT and PLL responsiveness tends to segregate away from each other. Thus, the GT and PLL immune response genes also are not inherited independently but, rather, behave as alleles or pseudoalleles. Similar results are observed when Hartley guinea pigs are simultaneously immunized with GA and GT. The ability to respond to GA segregates away from the ability to respond to GT. Our studies demonstrated that the specific immune response genes thus far identified in guinea pigs controlling the ability to respond to GA, GT, and PLL, respectively, are found on the same chromosome. In most Hartley animals, the GA and PLL immune response genes are often linked, i.e. occur on the same chromosome strand, and tend to behave as alleles or pseudoalleles to the GT immune response gene.

Immunological reactivity to sheep red blood cells in three congenic resistant strains of mice

(1) Immunological reactivity to sheep red blood cells was tested in three congenic resistant strains of mice and was found to vary according to the H-2 locus and its alleles. The reactivity of the strains in decreasing order is: A. CA, A/Sn, A. BY.

(2) Non-specific immunostimulation with Brucella increases the immune response to sheep red blood cells in the A. CA and A/Sn strains but not in strain A. BY. This immunostimulation with Brucella is H-2 dependent.

(3) Methylcholanthrene has an immunodepressive effect on the immunological reactivity to sheep red blood cell antigens in the three strains of mice, each strain being equally affected.

Genetic control of the immune response of guinea pigs to limiting doses of bovine serum albumin: relationship to the poly-L-lysine gene

The response of strain 2 guinea pigs to limiting doses of bovine serum albumin is under dominant genetic control linked with the poly-L-lysine gene. Inbred strains 2 and 13 guinea pigs make similar antibody responses to 10 mug bovine serum albumin, whereas strain 2 but not strain 13 animals produce significant amounts of antibodies in response to 0.1 mug. The relationship between the presence of the poly-L-lysine gene and the ability to respond to limiting doses of bovine serum albumin has also been investigated in random-bred Hartley strain guinea pigs.

Linkage between the poly-L-lysine gene and the locus controlling the major histocompatibility antigens in strain 2 guinea pigs

The data presented demonstrate linkage between the major histocompatibility locus of inbred strain 2 guinea pigs and a "specific immune response gene," the PLL gene, which controls responsiveness to poly-L-lysine and hapten conjugates of this polypeptide in these animals. This finding extends to another species and to a different immune system the linkage observed in mice between the H(2) locus and specific immune response genes at the Ir-1 locus. The general significance of the linkage of specific immune response genes to histocompatibility loci is discussed.

Transfer of responsiveness to hapten conjugates of poly-L-lysine and of a copolymer of L-glutamic acid and L-lysine to lethally irradiated nonresponder guinea pigs by bone marrow or lymph node and spleen cells from responder guinea pigs

Hartley guinea pigs genetically unresponsive to hapten-PLL (poly-L-lysine) conjugates were lethally irradiated and given allogeneic bone marrow from Hartley responder animals. Many of the animals died of graft versus host disease before their response to 2,4-dinitrophenyl-PLL (DNP-PLL) could be measured. The immune response of the surviving recipient animals was evaluated by anti-DNP antibody production, development of delayed hypersensitivity to DNP-poly-L-lysine, as well as by lymph node cell stimulation in vitro by this antigen. 12 of 14 recipient animals thus treated made an immune response as measured by 2 of the 3 parameters. Strain 13 guinea pigs, genetically unable to respond immunologically to DNP-PLL and to DNP-GL (2,4-dinitrophenyl-L-glutamic acid L-lysine copolymer) were lethally irradiated and given bone marrow from (2 x 13) F(1) responder animals or strain 13 bone marrow and (2 x 13) F(1) lymph node and spleen cells. A high proportion of the animals survived this procedure; no evidence of graft versus host disease was observed. Three of three strain 13 animals irradiated and, given strain 13 bone marrow and (2 x 13) F(1) lymph node and spleen, and then immunized with DNP-PL, made a specific immune response. 7 of 10 irradiated strain 13 animals given strain 13 bone marrow and (2 x 13) F(1) lymph node and spleen made an immune response to DNP-GL. However, only one of six irradiated strain 13 animals made a vigorous immune response to DNP-GL after reconstitution with (2 x 13) F(1) bone marrow alone. The ability to transfer the immune response to PLL antigens from responder to nonresponder animals demonstrates unequivocally that the defect in the non-responder animals is immunological rather than due to some other type of non-immunological mechanism. The bone marrow contains all the immunological cells necessary for the expression of the PLL gene. However, the finding that (2 x 13) F(1) lymph node and spleen cells were more effective than (2 x 13)F(1) bone marrow cell populations (known to be a rich source of monocyte precursors) suggests that the cells in which the PLL gene function is expressed may be lymphocytes rather than monocytes and macrophages.

The requirement of more than one antigenic determinant for immunogenicity

Rabbits primarily stimulated with a BSA (bovine serum albumin)-sulfanilic acid complex will produce a good secondary response to the sulfanilic acid hapten if the carrier used in the secondary stimulus is again BSA, and not if the secondary carrier is HGG (human gamma globulin). In the latter situation, a good secondary response is obtained, however, if the rabbits are pretreated a few weeks earlier with free HGG. We conclude that the immune stimulus involves the recognition of carrier determinants unrelated to the hapten. As the receptors for recognition of unrelated determinants are probably situated on different cells, we suggest that the immune stimulus leading to antibody formation requires the interaction of two antigen-bridged cells.

Rabbit antibodies to streptococcal carbohydrates. Influence of primary and secondary immunization and of possible genetic factors on the antibody response

In a search for possible genetic factors which may influence the immune response to the streptococcal carbohydrates, over 100 rabbits have been immunized with streptococcal vaccines, and representative examples of high and low response pairs mated. The concentration of precipitins to the group-specific carbohydrates has been measured in the antisera following primary intravenous immunization with heat-killed streptococcal vaccines, Group A, Group A-variant, and Group C. For the majority of rabbits, the concentration of precipitins varied between 1 and 10 mg/ml of antiserum; while in the minority, it was between 11 and 32 mg/ml. The offspring of rabbits with high antibody levels had a significantly higher concentration of antibody than was seen in the offspring of rabbits of low response parents. Such data suggest that the magnitude of the immune response to these carbohydrate antigens is under some form of genetic control. Not uncommonly in rabbits with hyper-gamma-globulinemia following primary immunization, the group-specific precipitins are the predominant component of the gamma-globulin. An unusual feature of such components is that they are electrophoretically monodisperse, and possess individual antigenic specificity. In this respect they resemble the myeloma proteins. When a response of this sort is not seen after primary immunization, it may occur after secondary immunization. Therefore, prior exposure to the same or closely related antigen may also have an influence on the occurrence of high concentrations of such uniform antibodies.

Immunochemical studies on the cross-reactivity between streptococcal and staphylococcal mucopeptide

Particulate mucopeptides of Group A-variant streptococci and Staphylococcus aureus, solubilized by ultrasonic treatment, give a precipitin reaction with the sera of rabbits immunized with Group A-variant streptococci. gamma-G globulin antibodies have been recovered from these sera which react with the mucopeptides but not with the Group A-variant carbohydrate. The immunochemical basis for the cross-reactivity between the streptococcal and staphylococcal mucopeptides was investigated in detail. Three chemically different fractions have been isolated from enzymatic digests of staphylococcal mucopeptide and were employed as haptenic inhibitors of the precipitin reaction. A fraction consisting of the peptide moiety of mucopeptide was the strongest inhibitor, whereas the hexosamine-rich fraction was less effective. The third fraction, rich in glycine, was least effective. It is suggested that the immunologic cross-reactivity between streptococcal and staphylococcal mucopeptide is due to the fact that these two substances contain chemically similar tetrapeptides. The hexosamine polymer which is identical for both mucopeptides may also contribute to their cross-reactivity.

Antibody formation: initiation in "nonresponder" mice by macrophage synthetic polypeptide RNA

The RNA extracted from normal peritoneal macrophages exposed to a linear, random synthetic polypeptide, Glu(60)Ala(30)Tyr(10), initiated an immune response in C57B1/6J mice, although this strain responds very poorly to the antigen itself. From 10 to 150 micrograms of RNA obtained from mouse, rat, or rabbit macrophages was injected intraperitoneally into recipient mice, and specific antibody was detectable by passive hemagglutination 3 to 4 weeks later. Treatment of the RNA with ribonuclease destroyed its ability to initiate a specific immune response. The RNA contained by weight 0.02 percent of the (specific) antigen. The RNA obtained from cells incubated with a second polypeptide, Glu(36)Lys(24)Ala(40), initiated a response specific for this polymer. This RNA even when incubated in vitro with Glu(60)Ala(30)Tyr(10) failed to initiate antibody formation specific for Glu(60)Ala(30)Tyr(10).

Studies on the relation of a prior immune response to immunogenicity

(1) Two polymers of D-glutamic acid, one synthetic (poly-α-D-glutamic) and the other the capsular polypeptide of Bacillus anthracis (poly-γ-D-glutamic), which did not induce detectable antibody when injected in saline, elicited precipitating antibody in rabbits when complexed with methylated bovine serum albumin (MBSA).

(2) Animals that had made an immune response to either of the polypeptides did not produce detectable anti-hapten antibodies when subsequently immunized with the homologus polypeptide conjugated with p-amino-ṕ-dimethylaminoazobenzene (PDA) groups. Neither was there an observable response to the polypeptide carrier.

(3) Hapten-specific antibody was elicited with an immunogenic carrier, hen egg albumin, and with the polypeptide—PDA conjugates complexed with MBSA, demonstrating that PDA could act as a determinant under the appropriate conditions.

(4) Rabbits that had made PDA-specific antibody were entirely refractory to polypeptide—PDA conjugate, inasmuch as their levels of anti-PDA antibody remained unchanged.

(5) It is concluded that the formation of antibody against a weakly immunogenic molecule does not alter the state of responsiveness of the animal upon subsequent contact with that molecule. Such a molecule cannot serve as a carrier for another structural determinant, either in animals that have made a prior immune response to the carrier or to the determinant.

The immune response to a hybrid protein molecule; specificity of secondary stimulation and of tolerance induction

Upon immunization with LDH-III (subunit composition AABB) rabbits produce anti-A and anti-B antibodies in comparable amounts. These antibodies fit equally well to the hybrid enzyme and to LDH-V (AAAA) or LDH-I (BBBB) respectively, as tested by passive hemagglutination inhibition. No antibodies reacting with both LDH-I and LDH-V were detected. A minority of hybrid-specific antibodies was, however, present in the sera. Animals primed with LDH-III respond regularly to a boosting injection of LDH-V with the production of large amounts of anti-A (but not anti-B) antibodies. A similar injection of LDH-I stimulates (if it has any effect at all) the production of anti-B antibodies only. Stimulation with one of the pure types does not impair a subsequent response to the other. The majority of the animals primed with LDH-III responded not at all or weakly to a boosting injection of LDH-I, though antibodies to LDH-I were present in the sera at the time of stimulation. This effect can hardly be explained on the basis of serological sepcificity. Hyporesponsiveness to LDH-III can be induced by injection of LDH-V into the newborn. Both anti-A and anti-B titers are equally depressed. Within the dose range tested, LDH-I does not exert any tolerogenic action with respect to LDH-III. The carrier property of subunit A is evident in the induction of both immunity and tolerance to LDH-III. The early phase of the immune response to the hybrid enzyme may be carrier-specific, and receptors for the haptenic subunit B may not exist at that stage.

The effect of tolerance on the specificity of the antibody response and on immunogenicity. Antibody response to conformationally and chemically altered antigens

Animals were rendered tolerant to human albumin and were then immunized with azo derivatives of human albumin which differed in the number of hapten groups per molecule and in the extent of conformational change. The incidence and specificity of the resulting antibody response was studied and the presence of antibody to azo groups and to conformationally altered protein determinants was demonstrated. Reactivity with the tolerance-inducing antigen was shown to be due to antibodies directed against conformationally altered protein determinants. The difference in the response of tolerant animals to hapten-poor and hapten-rich derivatives was attributed to the extent of conformational alteration. A genetic factor appeared to be implicated in the capacity of tolerant animals to respond to an antigen which cross-reacts with tolerance-inducing macromolecules.

Differences in immune response to synthetic antigens in two inbred strains of guinea-pigs

The study of the immunogenicity of some linear and multichain synthetic polypetides in guinea-pigs, of inbred strains 2 and 13 led to their division into three categories: (a) immunogenic in both inbred strains: linear copolymer of tyrosine, glutamic acid and alanine; (b) immunogenic in strain 13 and negative in strain 2: linear copolymer of tyrosine and glutamic acid; and (c) immunogenic in strain 2 and negative in strain 13: linear and branched copolymers containing lysine. No immune response was detected in strain 2 guinea-pigs to the copolymer of tyrosine, glutamic acid and lysine, composed only of the D-optical isomers.

The immune response, or lack of response, in F₁ hybrids of the inbred strains was identical with that of inbred strain 2 suggesting that the genetic determinants of this strain are dominant.

No cross-reactions were observed at the delayed stage in inbred strain 2 between linear and multichain copolymers of similar composition.

Genetically controlled specific immunological unresponsiveness

Evidence is presented that in rabbits and mice a relatively simple genetic mechanism exists which controls the animals' ability to produce antibody against bovine serum albumin.

The behavior of hapten-poly-L-lysine conjugates as complete antigens in genetic responder and as haptens in nonresponder guinea pigs

30 to 40% of Hartley strain guinea pigs have previously been demonstrated to possess a dominant autosomal gene which enables them to recognize the antigenicity of hapten-poly-L-lysine conjugates as expressed by the development of both antihapten antibodies and delayed hypersensitivity to the immunizing antigen. In the present study, it was shown that PLL alone was weakly antigenic in such genetic responder animals. Immunization with DNP-PLL electrostatically combined with foreign albumins elicits the production of anti-DNP antibodies in all Hartley strain guinea pigs, although the percentage of animals demonstrating a delayed response to DNP-PLL and therefore considered genetic responders remains 30 to 40%. Immunization with nonantigenic polyanions combined with DNP-PLL does not produce such an effect. Some degree of PLL specificity of purified anti-DNP antibodies produced by genetic nonresponder animals by immunization with DNP-PLL combined with foreign albumins was demonstrated by means of fluorescence quenching.