Armead H. Johnson

B-lymphocyte alloantigens associated with systemic lupus erythematosus.

We examined B-lymphocyte alloantigens in 41 patients with systemic lupus erythematosus and 184 controls, using a panel of 47 pregnancy serums, and compared reaction frequencies of individual serums. One serum, la-715, reacted with B lymphocytes from 75.6 per cent of patients and 14.1 per cent of controls (Pc less than 0.005, relative risk 18.8). Twenty-eight of the patients were also typed with a panel of HLA-D-related serums from the Seventh International Histocompatibility Workshop, HLA-DRw types assigned, and compared to 490 Workshop controls. Both HLA-DRw2 (57.1 per cent vs. 26.4 per cent, Pc less than 0.004) and HLA-DRw3 (46.4 per cent vs. 22.2 per cent, Pc less than 0.03) were increased in systemic lupus erythematosus. This study demonstrates that select B-lymphocyte alloantigens, which are controlled by genes in the major histocompatibility complex, are present in increased frequency in systemic lupus erythematosus.

Genetic differences between primary and secondary sicca syndrome.

SICCA syndrome occurs alone or in association with another autoimmune disease, frequently rheumatoid arthritis. We recently proposed that sicca syndrome be termed primary when it occurs alone and s...

Multiplex Assay for Simultaneous Measurement of Antibodies to Multiple Plasmodium falciparum Antigens

ABSTRACT Antibodies to Plasmodium falciparum are classically measured using the enzyme-linked immunosorbent assay (ELISA). Although highly sensitive, this technique is labor-intensive when large numbers of samples must be screened against multiple antigens. The suspension array technology (SAT) might be an alterative to ELISA, as it allows measurement of antibodies against multiple antigens simultaneously with a small volume of sample. This study sought to adapt the new SAT multiplex system for measuring antibodies against nine malarial vaccine candidate antigens, including recombinant proteins from two variants of merozoite surface protein 1, two variants of apical merozoite antigen 1, erythrocyte binding antigen 175, merozoite surface protein 3, and peptides from the circumsporozoite protein, ring erythrocyte surface antigen, and liver-stage antigen 1. Various concentrations of the antigens were coupled to microspheres with different spectral addresses, and plasma samples from Cameroonian adults were screened by SAT in mono- and multiplex formats and by ELISA. Optimal amounts of protein required to perform the SAT assay were 10- to 100-fold less than that needed for ELISA. Excellent agreement was found between the single and multiplex formats (R ≥ 0.96), even when two variants of the same antigen were used. The multiplex assay was rapid, reproducible, required less than 1 μl of plasma, and had a good correlation with ELISA. Thus, SAT provides an important new tool for studying the immune response to malaria rapidly and efficiently in large populations, even when the amount of plasma available is limited, e.g., in studies of neonates or finger-prick blood.

Antigen-specific human T-lymphocyte clones Genetic restriction of influenza virus-specific responses to HLA-D region genes

Human T lymphocytes, primed in vitro to influenza virus, were cloned by limiting dilution and expanded using medium containing interleukin 2 and feeder cells. A detailed analysis of the genetic requirements for induction of T-cell proliferation was conducted using a panel of cells from unrelated donors and two families who had previously been extensively phenotyped for HLA region antigens. Clones obtained from a Dw1, Dw3 individual required Dw1,DR1 histocompatibility for successful presentation of viral antigens by antigen-presenting cells. The antigen-presenting ability segregated with HLA-B,D,DR in an informative HLA-A/B recombinant individual. In contrast, some TLCs responded to antigen presented by cells that did not share known HLA antigens, and in one informative family, reactivity did not segregate with HLA. None of the T-cell clones reacted to allogeneic cells in the absence of antigen, suggesting that the TLCs do not bear receptors that recognize both influenza virus and alloantigen. In antibody-blocking studies, Dw1, DR1-restricted clones were blocked by all monoclonal anti-DR framework antibodies. The non-HLA-restricted TLCs were blocked by some, but not all, of the anti-DR framework monoclonal antibodies. These results confirm and extend the role of HLA-D region gene products in antigen presentation and also provide evidence that yet undefined cell interaction products, which may include hybrid structure, are able to participate in antigen-specific proliferative responses by human T cells.

The DR3(w18),DQw4 haplotype differs from DR3(w17),DQw2 haplotypes at multiple class II loci

The polymorphism of HLA class II molecules in man is particularly evident when comparisons between population groups are made. This study describes a DR3 haplotype commonly present in the American black population. Unlike the Northern European population, in which almost all DR3 individuals are DQw2, approximately 50% of DR3-positive American blacks express a DQw4 allelic product. This study characterizes the DR subregion of that haplotype. cDNA sequence analysis has revealed a DR beta gene which differs at several positions from previously described DR3 beta 1 genes. It is postulated that a gene-conversion-like event with a DRw52 beta gene as donor has generated some of these differences. The haplotype carries a DRw52a allele as defined by oligonucleotide hybridization studies. DNA restriction fragment analysis using a family and several unrelated individuals has allowed us to identify DR alpha and beta fragments associated with the DR3(w18),DQw4 haplotype. The most striking observation is that the DR3(w18),DQw4 haplotype differs from DR3(w17),DQw2 haplotypes at multiple class II loci. Several genetic mechanisms including reciprocal recombination, gene conversion, and point mutation were involved in generating the differences between these haplotypes. Once established, the DR3(w18),DQw4 haplotype appears to be relatively stable in the population.

Antigen, allele, and haplotype frequencies report of the ASHI minority antigens workshops: part 1, African-Americans.

HLA typing was performed on 977 African Americans residing throughout most of the United States. Class I and class II antigens and class II alleles were defined for all individuals and class I alleles were determined for a subset of individuals. The occurrence of 854 of the individuals in family groups permitted direct counting of allele and haplotype frequencies. The data were analyzed for antigen, allele, and haplotype frequencies; recombination frequencies; segregation distortion; distribution of haplotype frequencies; linkage disequilibria; and geographic distribution of DR antigens. Tables of the antigen, allele, the most common two and three point haplotypes, and 88 extended haplotypes that include class I and class II alleles are presented. Notable findings include a lower than expected frequency of recombination between the B and DR loci (theta= 0.0013), lower than expected frequency of inheritance (44.5% vs 54.5%) of the DRB1*1503; DQB1*0602 haplotype, lower than anticipated linkage disequilibrium values for DR; DQ haplotypes, and a skewed geographic distribution of DR antigens.

DRW8 MICROVARIATION : A NEW DRB1 ALLELE IDENTIFIED IN ASSOCIATION WITH DQW7 IN AMERICAN BLACKS

In the American black population, DRw8 is commonly found in association with DQw7 and an undefined HLA-D specificity. Polymerase chain reaction amplification was used to obtain DRB1 cDNA clones from two unrelated individuals expressing this haplotype. The DRB1 sequence is most similar to a sequence found in cells expressing DRw8, DQw4, Dw8.2 differing at the protein level by a single amino acid substitution at position 86.

Characterization of Conserved T- and B-Cell Epitopes in Plasmodium falciparum Major Merozoite Surface Protein 1

ABSTRACT Vaccines for P. falciparum will need to contain both T- and B-cell epitopes. Conserved epitopes are the most desirable, but they are often poorly immunogenic. The major merozoite surface protein 1 (MSP-1) is currently a leading vaccine candidate antigen. In this study, six peptides from conserved or partly conserved regions of MSP-1 were evaluated for immunogenicity in B10 congenic mice. Following immunization with the peptides, murine T cells were tested for the ability to proliferate in vitro and antibody responses to MSP-1 were evaluated in vivo. The results showed that one highly conserved sequence (MSP-1#1, VTHESYQELVKKLEALEDAV; located at amino acid positions 20 to 39) and one partly conserved sequence (MSP-1#23, GLFHKEKMILNEEEITTKGA; located at positions 44 to 63) contained both T- and B-cell epitopes. Immunization of mice with these peptides resulted in T-cell proliferation and enhanced production of antibody to MSP-1 upon exposure to merozoites. MSP-1#1 stimulated T-cell responses in three of the six strains of mice evaluated, whereas MSP-1#23 was immunogenic in only one strain. Immunization with the other four peptides resulted in T-cell responses to the peptides, but none of the resulting peptide-specific T cells recognized native MSP-1. These results demonstrate that two sequences located in the N terminus of MSP-1 can induce T- and B-cell responses following immunization in a murine model. Clearly, these sequences merit further consideration for inclusion in a vaccine for malaria.

Interaction of HLA and age on levels of antibody to Plasmodium falciparum rhoptry-associated proteins 1 and 2.

ABSTRACT The Plasmodium falciparum rhoptry-associated proteins 1 and 2 (RAP1 and RAP2) are candidate antigens for a subunit malaria vaccine. The design of the study, which looks at the acquisition of immunity to malaria from childhood to old age, has allowed us to document the interaction of HLA and age on levels of antibody to specific malarial antigens. Antibodies reach maximum levels to RAP1 after the age of 15 but to RAP2 only after the age of 30. The effect of HLA-DRB1 and -DQB1 and age on levels of antibody to rRAP1 and rRAP2 was analyzed with a multiple regression model in which all HLA alleles and age were independent variables. DQB1*0301 and -*03032 showed an age-dependent association with levels of antibody to rRAP1, being significant in children 5 to 15 years (P < 0.001) but not in individuals over 15 years of age. DRB1*03011 showed an age-dependent association with antibody levels to rRAP2; however, this association was in adults over the age of 30 years (P< 0.01) but not in individuals under the age of 30 years. No associations were detected between DRB1 alleles and RAP1 antibody levels or between DQB1 alleles and RAP2 antibody levels. Thus, not only the HLA allele but also the age at which an interaction is manifested varies for different malarial antigens. The interaction may influence either the rate of acquisition of antibody or the final level of antibody acquired by adults.

DRw11 haplotypes: continuum of DRB1 diversity augmented by unique DQ/DRw52 associations.

cDNA sequencing of the first domains of DRB1, DRB3, DQA1, and DQB1 alleles was used to examine the extent of diversity in American black individuals expressing several DRw11 haplotypes. In addition to previously described DRw11 alleles, DRB1*1102 and DRB1*1103, two new DRB1 alleles, DRB1*11012 and DRB1*11042, were identified which differ from previously described alleles at the nucleic acid but not at the protein level. Gene conversion-like events have likely generated the DRw11 microvariation resulting in the merging of DRw11 with the DRw13 allele family. The DRw11 alleles are associated with various DQ alleles: DQw1 (DQw5 and DQw6), DQw7, and a serologically undefined DQ allele. This undefined DQ molecule, comprised of a DQ alpha/beta combination encoded by a DQw7 alpha gene (DQA1*0301) and a DQw2 beta gene (DQB1*0201), was previously observed in some DR7 and DR9 haplotypes. DRw11 haplotype diversity is augmented by the association of one of the DRw11 alleles with the DRw52c allele in contrast to the more common DRw11, DRw52b association. The extensive diversity exhibited by the DRw11 and DRw13 family of haplotypes coupled with their high frequency in populations of African ancestry suggest that the DRw11/w13 allele family may be very old and/or that these haplotypes carry some selective advantage.