Charles E. Larsen

Immunoglobulin deficiencies and susceptibility to infection among homozygotes and heterozygotes for C2 deficiency

About 25% of C2-deficient homozygotes have increased susceptibility to severe bacterial infections. C2-deficient homozygotes had significantly lower serum levels of IgG2, IgG4, IgD, and Factor B, significantly higher levels of IgA and IgG3 and levels of IgG1 and IgM similar to controls. Type I (28 bp deletion in C2 exon 6 on the [HLA-B18, S042, DR2] haplotype or its fragments) and type II (non-type I) C2-deficient patients with increased susceptibility to bacterial infection had significantly lower mean levels of IgG4 (p < 0.04) and IgA (p < 0.01) than those without infections (who had a higher than normal mean IgA level) but similar mean levels of other immunoglobulins and Factor B. Of 13 C2-deficient homozygotes with infections, 85% had IgG4 deficiency, compared with 64% of 25 without infections. IgD deficiency was equally extraordinarily common among infection-prone (50%) and noninfection-prone (70%) homozygous type I C2-deficient patients. IgD deficiency was also common (35%) among 31 type I C2-deficient heterozygotes (with normal or type II haplotypes), but was not found in 5 type II C2-deficient heterozygotes or 1 homozygote. Thus, C2 deficiency itself is associated with many abnormalities in serum immunoglobulin levels, some of which, such as in IgG4 and IgA, may contribute to increased susceptibility to infection. In contrast, IgD deficiency appears not to contribute to increased infections and appears to be a dominant trait determined by a gene or genes on the extended major histocompatibility complex (MHC) haplotype [HLA-B18, S042, DR2] (but probably not on type II C2-deficient haplotypes) similar to those previously identified on [HLA-B8, SC01, DR3] and [HLA-B18, F1C30, DR3].

Complex cytokine responses to hepatitis B surface antigen and tetanus toxoid in responders, nonresponders and subjects naive to hepatitis B surface antigen

Some human subjects vaccinated with hepatitis B surface antigen (HBsAg) do not produce antibodies to the vaccine (nonresponders). The mechanism for nonresponse is unknown. To understand the response and nonresponse to nominal antigens better, we determined the level and kinetics of cytokine secretion in response to HBsAg and tetanus toxoid (TT) by peripheral blood mononuclear cells (PBMC) in vitro from HBsAg vaccine responders and nonresponders and from individuals naive to HBsAg. Proliferating PBMC secreted peak levels of interleukin-2 (IL-2) at 2 days and peak levels of tumor necrosis factor-beta (TNF-beta), interferon-gamma (IFN-gamma), IL-4 and IL-10 at 3-6 days post-stimulation. In contrast, nonproliferating PBMC (whether from nonresponders, naive subjects or weak responders) did not produce detectable levels of TNF-beta or IFN-gamma, nor was IL-4 or IL-10 produced significantly, and that produced had a different kinetic profile from that of proliferating PBMC. HBsAg-specific cytokine production by PBMC from strong responders broadly paralleled their cytokine responses to TT. Cellular cytokine mRNA levels measured by reverse transcriptase-polymerase chain reaction corroborated the secreted cytokine results. The anti-HBsAg- and anti-TT-specific T cell cytokine responses were mixed Th(1/2)-like and donor-specific. An HBsAg-specific cytokine response, but not a TT-specific cytokine response, was completely missing in nonresponders. These data suggest that the T cell defect of HBsAg nonresponse is not due to a skewed cytokine profile.

Genetic fixity in the human major histocompatibility complex and block size diversity in the class I region including HLA-E

BackgroundThe definition of human MHC class I haplotypes through association of HLA-A, HLA-Cw and HLA-B has been used to analyze ethnicity, population migrations and disease association.ResultsHere, we present HLA-E allele haplotype association and population linkage disequilibrium (LD) analysis within the ~1.3 Mb bounded by HLA-B/Cw and HLA-A to increase the resolution of identified class I haplotypes. Through local breakdown of LD, we inferred ancestral recombination points both upstream and downstream of HLA-E contributing to alternative block structures within previously identified haplotypes. Through single nucleotide polymorphism (SNP) analysis of the MHC region, we also confirmed the essential genetic fixity, previously inferred by MHC allele analysis, of three conserved extended haplotypes (CEHs), and we demonstrated that commercially-available SNP analysis can be used in the MHC to help define CEHs and CEH fragments.ConclusionWe conclude that to generate high-resolution maps for relating MHC haplotypes to disease susceptibility, both SNP and MHC allele analysis must be conducted as complementary techniques.

ENHANCED GENE DELIVERY AND EXPRESSION IN HUMAN HEPATOCELLULAR CARCINOMA CELLS BY CATIONIC IMMUNOLIPOSOMES

AbstractA targeted vector allowing enhanced gene transfer to human hepatocellular carcinoma (HCC1) cells in vitro was developed using cationic liposomes covalently conjugated with the mAb AF-20. This high affinity antibody recognizes a rapidly internalized 180 kDa cell surface glycoprotein which is abundantly expressed on the surface of human HCC and other cancer cells. Quantitative binding analysis of liposomes with target cells by flow cytometry showed specific association of mAb-targeted liposomes with human HCC cells. Using mAb-targeted cationic liposomes containing 20% DOTAP, in the presence or absence of serum, gene expression in HuH-7 cells was enhanced up to 40-fold as compared to liposomes conjugated with an isotype-matched non-relevant control antibody. Transfection specificity was not observed in a control cell line that does not express the antigen recognized by mAb AF-20. This study demonstrates that cationic liposome formulations can be targeted with monoclonal antibodies (mAbs) to enhance s...

HLA-Cw7 zygosity affects the size of a subset of CD158b+ natural killer cells

Individuals with certain HLA class I genotypes are highly susceptible to disease after viral infection. Natural killer (NK) cells kill virus-infected cells through a mechanism involving HLA class I receptors. These facts may be connected if an individuals HLA genotype regulates the number and function of NK cells. We have observed that subjects homozygous for the HLA-B/C region of conserved major histocompatibility complex (MHC) extended haplotypes have lower NK cell activity and a significantly lower frequency of CD16+CD56+ NK cells than heterozygotes. The proportion of CD16−CD56+ NK cells was unaffected by zygosity for the HLA-B/C region. We show here that the frequency of CD16+CD158b+, but not CD16−CD158b+ NK cells, was significantly lower (p <0.026) in homozygotes for HLA-Cw7 (NK1 ligand) haplotypes than in heterozygotes. The frequencies of CD16+CD158a+ and CD16−CD158a+ and CD16−CD158a+ or CD16+NKB1+ and CD16−NKB1+ NK cells were not different in these donor groups. These findings suggest that the proportion of NK cells coexpressing CD16 and CD158b, but not CD158a nor NKB1, is influenced by zygosity for the HLA-Cw7 (NK1 ligand) haplotype. Since NK cells are involved in protection from virus infection, a reduced size of a ligand-specific NK subset in individuals homozygous for some HLA-B/C haplotypes may help explain their increased susceptibility to virus-induced diseases.

Frequent occurrence of conserved extended haplotypes (CEHs) in two Caucasian populations

Conserved extended haplotypes (CEHs) are large (>or=1Mb) regions of identical DNA of the major histocompatibility complex (MHC) region of chromosome 6p in unrelated individuals. They are recognized by family studies and constitute nearly half of MHC haplotypes among European Caucasians. We studied 49 Hungarian Caucasian families in comparison with the previous findings in 2675 normal American Caucasian chromosomes from families in the Boston area. Besides HLA-A, -B and HLA-DRB1/-DQB1 alleles, copy number polymorphism of C4A and C4B genes and several SNPs encoded in the central (class III) MHC region were determined. By comparing 188 Caucasian haplotypes in Hungary to 2675 normal Caucasian chromosomes in Boston, we found that 11 of 12 of the most common CEHs (with a frequency of at least 1%) among the Boston chromosomes also occurred in Hungary. Moreover, there was a significant correlation (R=0.789; p=0.0023) in the frequency order of these haplotypes between the two Caucasian populations. Of 10 haplotypes found in >or=2 copies among the Hungarian chromosomes, all but one occurred in one to 14 copies among the Boston haplotypes. These findings indicate that CEHs are commonly shared by distinct European Caucasian populations; however, lower frequency CEHs may differ.

Dominant Sequences of Human Major Histocompatibility Complex Conserved Extended Haplotypes from HLA-DQA2 to DAXX

We resequenced and phased 27 kb of DNA within 580 kb of the MHC class II region in 158 population chromosomes, most of which were conserved extended haplotypes (CEHs) of European descent or contained their centromeric fragments. We determined the single nucleotide polymorphism and deletion-insertion polymorphism alleles of the dominant sequences from HLA-DQA2 to DAXX for these CEHs. Nine of 13 CEHs remained sufficiently intact to possess a dominant sequence extending at least to DAXX, 230 kb centromeric to HLA-DPB1. We identified the regions centromeric to HLA-DQB1 within which single instances of eight “common” European MHC haplotypes previously sequenced by the MHC Haplotype Project (MHP) were representative of those dominant CEH sequences. Only two MHP haplotypes had a dominant CEH sequence throughout the centromeric and extended class II region and one MHP haplotype did not represent a known European CEH anywhere in the region. We identified the centromeric recombination transition points of other MHP sequences from CEH representation to non-representation. Several CEH pairs or groups shared sequence identity in small blocks but had significantly different (although still conserved for each separate CEH) sequences in surrounding regions. These patterns partly explain strong calculated linkage disequilibrium over only short (tens to hundreds of kilobases) distances in the context of a finite number of observed megabase-length CEHs comprising half a populations haplotypes. Our results provide a clearer picture of European CEH class II allelic structure and population haplotype architecture, improved regional CEH markers, and raise questions concerning regional recombination hotspots.

Hepatitis B surface antigen- and tetanus toxoid-specific clonal expansion of CD4+ cells in vitro determined by TCRBV CDR3 length and nucleotide sequence.

We demonstrate activation of primary human TCRBV-specific CD4+ cells in vitro towards hepatitis B surface antigen (HBsAg) and tetanus toxoid (TT) without the use of cell lines, clones or added cytokines. By multiplex PCR analysis and spectratyping, antigen-activated cells exhibited clonal T cell receptor expansion within specific and limited TCRBV families. The expanded CD4+ T cells were CD45RO+. Three of four unrelated HBsAg responders showed CD4+ expansion within the TCRBV16 family. The response comprised predominantly single CDR3 sequences in all three donors and was completely monoclonal in one of them. However, the CDR3 lengths and sequences differed among the responders. Clonality induced by HBsAg in TCRBV16 was specific, reproducible and distinct from that induced by TT in terms of sequence, nucleotide addition and diversity (BD) or junctional (BJ) element usage. Thus, for the first time, we show monoclonal or oligoclonal expansion of primary human CD4+ peripheral blood mononuclear cells (PBMC) in vitro in response to nominal protein antigen without manipulations utilizing exogenous IL-2. The ability to induce monoclonal/ oligoclonal responses to HBsAg now permits motif identification studies for determining the T cell role in non-responsiveness to the HBsAg vaccine.

Interaction between immunoglobulin allotypes and NK receptor genes in diabetes post-hepatitis C virus infection

Genetic interactions between natural killer (NK) cells immunoglobulin-like receptor (KIR) genes and immunoglobulin allotypes have been previously reported in type 2 diabetes mellitus (DM) patients. Puerto Rican Americans with a history of intravenous drug use who developed DM following HCV infection (n=32) were compared to individuals infected with HCV without diabetes (n=121) and to DM non-infected individuals (n=95). Subjects were genotyped for KIRs and immunoglobulin allotypes. We found interactions of immunoglobulin allotypes KM3/KM3 with NK inhibitory receptors 2DL3/2DL3, 2DL1 in the absence of 2DS4 associated with susceptibility to DM in HCV infected individuals. These data suggest the possibility that a subset of patients with HCV could have an immune-mediated component contributing to the development of DM.