Antibody response elicited by T-dependent and T-independent antigens in gene targeted kappa-deficient mice

A recombinant protein containing influenza viral conserved epitopes and superantigen induces broad-spectrum protection

Influenza pandemics pose public health threats annually for lacking vaccine that provides cross-protection against novel and emerging influenza viruses. Combining conserved antigens that induce cross-protective antibody responses with epitopes that activate cross-protective T cell responses might be an attractive strategy for developing a universal vaccine. In this study, we constructed a recombinant protein named NMHC that consists of influenza viral conserved epitopes and a superantigen fragment. NMHC promoted the maturation of bone marrow-derived dendritic cells and induced CD4+ T cells to differentiate into Th1, Th2, and Th17 subtypes. Mice vaccinated with NMHC produced high levels of immunoglobulins that cross-bound to HA fragments from six influenza virus subtypes with high antibody titers. Anti-NMHC serum showed potent hemagglutinin inhibition effects to highly divergent group 1 (H1 subtype) and group 2 (H3 subtype) influenza virus strains. Furthermore, purified anti-NMHC antibodies bound to multiple HAs with high affinities. NMHC vaccination effectively protected mice from infection and lung damage when exposed to two subtypes of H1N1 influenza virus. Moreover, NMHC vaccination elicited CD4+ and CD8+ T cell responses that cleared the virus from infected tissues and prevented virus spread. In conclusion, this study provides proof of concept that NMHC vaccination triggers B and T cell immune responses against multiple influenza virus infections. Therefore, NMHC might be a candidate universal broad-spectrum vaccine for the prevention and treatment of multiple influenza viruses.

Receptor editing in lymphocyte development and central tolerance

The specificities of lymphocytes for antigen are generated by a quasi-random process of gene rearrangement that often results in non-functional or autoreactive antigen receptors. Regulation of lymphocyte specificities involves not only the elimination of cells that display 'unsuitable' receptors for antigen but also the active genetic correction of these receptors by secondary recombination of the DNA. As I discuss here, an important mechanism for the genetic correction of antigen receptors is ongoing recombination, which leads to receptor editing. Receptor editing is probably an adaptation that is necessitated by the high probability of receptor autoreactivity. In both B cells and T cells, the genes that encode the two chains of the antigen receptor seem to be specialized to promote, on the one hand, the generation of diverse specificities and, on the other hand, the regulation of these specificities through efficient editing.

The primary antibody repertoire of kappa-deficient mice is characterized by non-stochastic Vlamda1 + V(H) gene family pairings and a higher degree of self-reactivity

We have investigated the primary antibody repertoire of genetically manipulated 129/Sv kappa-deficient (JCkappaD) mice, in order to understand the contributions of the lambda-light chain, in the absence of an otherwise predominant kappa-light chain, to the development of humoral immunity. The expression of Vlambda1 gene (lambda1 and lambda3 subtypes) and the Vlambda1 + V(H) (J558, 36-60, V(H)11 and S107) gene family associations were studied in 7.43 x 10(3) mitogen-activated splenic B-lymphocyte clones of JCkappaD origin. Furthermore, the functional significance of the exclusive expression of the lambda-light chain, in the peripheral B-cell repertoire of JCkappaD mice, was analysed by determining natural autoantibody specificities in the circulating serum immunoglobulin and the frequency of autoreactive B-lymphocyte clones in the peripheral B-lymphocyte repertoire. These experiments revealed that: first, of the three available Vlambda genes at the lambda locus, the Vlambda1 gene is the one that is expressed most frequently (59.9%); second, non-random Vlambda1 + V(H) (J558, 36-60) gene family pairings occur in kappa-deficient mice; and third, a higher degree of self-reactivity is generated as a result of exclusive use of the lambda-light chain, as evidenced by higher levels of serum natural autoantibodies as well as a high frequency of autoreactive B-lymphocyte clones in kappa-deficient (129/Sv JCkappaD) mice. These observations suggest that the high murine kappa/lambda ratio in mice may, apart from high sequence diversity at the kappa-locus, be a result of endogenous selection against the lambda-light chain to restrict self-reactivity within the homeostatic threshold.

V lambda-light chain genes reconstitute immune responses to defined carbohydrate antigens or haptens by utilizing different VH genes

The contribution of the lambda-light chain to the development of peripheral B cell repertoire and generation of specific antibodies to haptens and polysaccharide antigens was studied in genetically manipulated kappa-deficient and lambda 2-transgenic mice. The results clearly demonstrate a non-stoichiometric VH gene family expression in the absence of k-light chain and suggest a non-stochastic pairing between VH and V lambda genes, expressed in the peripheral B cell repertoire. A shift in VH gene utilization in the case of VI lambda + antibodies was evident in response to beta 2-6 fructosan and TNP hapten. These observations demonstrate the availability of compensatory mechanisms in the absence of VK genes and are consistent with the hypothesis that VH gene family expression is controlled by genetic factors from inside the VH locus. Furthermore, genetic factors from outside the VH locus, namely restricted available light chain diversity, may lead to a shift in VH gene utilization in the peripheral B cell repertoire.

The lambda B cell repertoire of kappa-deficient mice

Analysis of the B cell repertoire is complicated by the huge diversity inherent in the germ line determined combinatory. Making use of knockout technology, kappa-deficient mice have been obtained. They constitute a shrewd model to follow the expression of an Ig minilocus, such as the lambda one, in the normal condition compared with classical transgenic models. Indeed, in contrast to wild type mice, in which only 5% of lambda B cells are produced, these mutant mice exclusively produce lambda positive B cells. Although, the lambda locus is well characterized and has a relatively simple organization, the mechanistic and selective pressures that govern its utilization are still poorly understood. The analysis of the lambda B cell repertoire in kappa-deficient mice, should therefore bring more conclusive informations. Here we present the lambda subtype distribution in the various cellular compartments of the kappa-deficient mice, and discuss the rules that can be responsible for this distribution. Our recent data indicate that the lambda subtype proportions in the bone marrow and the spleen result, for the major part, from mechanistic processes (i.e., recombinase accessibility, production of V-J functional joint and H/L pairings) while the lambda proportions found in the peritoneal cavity ensue from selective processes. Finally, the capacity to respond to various antigens is discussed from such a generated lambda B cell repertoire.

Subtle differences in antibody responses and hypermutation of lambda light chains in mice with a disrupted chi constant region

Analysis of lambda light chain use in normal mice is made difficult by the dominant chi light chain repertoire. We produced mice rendered deficient in chi light chain expression by gene targeting and focused on questions concerned with the generation of lambda light chain diversity. Whilst these mice compensate the chi deficiency with increased lambda liters, and their Ig level is therefore not significantly reduced, they show major differences in immunization titers, germinal center (GC) development and somatic hypermutation. After immunization, using antigens that elicit a restricted IgL response in normal mice, we obtained in the chi-/- mice elevated primary antibody titers but a subsequent lack in titer increase after repeated antigen challenge. Analysis of the Peyer's patches (PP) revealed a dramatically reduced cell content with rather small but highly active GC. Flow cytometric analysis showed different cell populations in the PP with enriched peanut agglutinin (PNA)hi/CD45R(B220)+ B cells, implying that the apparent compensation for the lack of lambda light chain expression involves the GC microenvironment in cell selection, the initiation of hypermutation and high affinity expansion. The three V lambda genes, V1, V2 and Vx, are mutated in the GC B cells, but show no junctional diversity. In contrast, a reduced rate of V lambda hypermutation is found in the hybridoma antibodies, which appears to reflect a selection bias rather than structural constraints. However, mechanisms of somatic mutation and specificity selection can operate with equal efficiency on the few V lambda genes.

Antibody response against poly (Glu60Ala30Tyr10) terpolymer and bacterial levan in kappa-deficient mice

In murine species, the kappa (+)-bearing immunoglobulins dominate the antibody (Ab) repertoire with a kappa/lambda ratio of 95:5. The aim of the present study is to investigate the characteristics of the antibody response in kappa-deficient (K-/-) mice immunized with a T-dependent synthetic antigen, poly(Glu60Ala30Tyr10) (GAT) and a T-independent antigen, bacterial levan (BL). K-/- mice were obtained by targeted deletion of the J kappa C kappa gene segments. In response to GAT, K-/- mice respond by producing increasing amounts of anti-GAT Ig lambda 1 and Ig lambda 2 in the primary as well as secondary response, although anti-GAT specific monoclonal antibodies (mAb) raised in K-/- mice are mostly of IgM isotype. The GAT public idiotype, GATIdX, present on all GAT-specific Ab bearing kappa light chain, is not detected in the sera of K-/- mice or on any of the anti-GAT lambda 1 mAb. In response to BL, the amount of Ig lambda 1+ Ab in K-/- mice is comparable to the amount of Ig kappa + Ab in normal mice. However, lambda 2+ Ab are detected neither in wild-type nor in K-/- mice. Like kappa + Ab, the majority of lambda 1+ mAb are specific for beta 2-6 fructosan present in BL and rye levan and, to some extent, express the BL-specific idiotype, A48ld. Our results show that important compensatory mechanisms occur in kappa-deficient mice, restoring their ability to mount immune responses against a variety of T-dependent and T-independent antigens by the alternative usage of the clonally restricted lambda repertoire.

Human antibodies from transgenic mice

We have used homologous recombination in ES cells to engineer B cell-deficient mice that are incapable of expressing endogenous immunoglobulin heavy and kappa light chain genes. We find that B cell development in these mutant mice can be rescued by the introduction of human germline-configuration heavy- and kappa light-chain minilocus transgenes. The transgenes rearrange during B cell differentiation, and subsequently undergo class switching and somatic mutation in response to antigen stimulation; thus recapitulating both stages of the humoral immune response using human, rather than mouse, sequences. The mice can be immunized; and human sequence, antigen specific, monoclonal antibodies can be obtained using conventional rodent hybridoma technology. These animals are also of interest for studying the normal processes of immunoglobulin gene expression. We discuss the example of heavy chain class switching, which has not been previously observed within an autonomous transgene.