Humans with OKT4-epitope deficiency have a single nucleotide base change in the CD4 gene, resulting in substitution of TRP240 for ARG240.

The OKT4 epitope of the CD4 cell-surface protein has been shown to be polymorphic in white, black, and Japanese populations. The variable phenotypic expression is due to an alteration of the OKT4 epitope, since those persons lacking reactivity with OKT4 monoclonal antibody (mAb) are reactive with OKT4A-F mAb as well as other mAb specific for CD4. To determine the nature of this polymorphism at the gene level, we sequenced polymerase chain reaction-amplified genomic DNA containing the CD4-V3 and -V4 exons from American black subjects who are OKT4-normal, OKT4-negative heterozygous, or OKT4-negative homozygous. Comparison of the sequences revealed that the two CD4 exons are identical except for a cytosine-to-thymidine transition occurring at nucleotide position 868. This alters the first codon position of mino acid 240 and results in a tryptophan residue replacing an arginine residue. The change was also found in white and Japanese persons who are OKT4-negative.

A novel DRB1 allele in DR2-positive American blacks.

Class II D region antigens of the major histocompatibility complex are naturally occurring dimeric proteins found on the surface of lymphoid cells. In most haplotypes at least two of the polymorphic beta chains are associated with a nonpolymorphic alpha chain. The allelic variation of these proteins lies in the first domain of the expressed protein. At present, there are four known DRB genes. DRB1 encodes for the classical DR 1, 3, 4, 5, etc., specificities. DRB3 and DRB4 encode the four supertypic specificities of DRw52 and the single phenotype of DRw53, respectively. Two DRB genes are expressed in human leukocyte antigen DR2-positive individuals. While DRB1 is the more polymorphic gene in most haplotypes, in DR2 haplotypes it appears that DRB5 encodes the polymorphic DR beta chain and the DRB1 encodes a nonpolymorphic beta chain. We attempted to further define the diversity of this region by direct dideoxynucleotide sequencing of polymerase-chain-reaction-amplified genomic DNA. We identified a novel DRB1 allele in DR2-positive individuals that was only observed in the American blacks sampled. This allele may code for a black specific class II antigen.

Production of a novel viral suppressive activity associated with resistance to infection among female sex workers exposed to HIV type 1.

To investigate mechanisms of natural resistance to human immunodeficiency virus type 1 (HIV-1), we obtained blood samples from eight women who remained HIV-1 negative after > 3 years of high-risk sex work in Chiang Rai, Thailand. CD4+ T lymphocytes from these highly exposed, persistently seronegative (HEPS) women were readily infectable in vitro with HIV-1 subtypes B and E. Autologous CD8+ cell suppression of both HIV-1 subtypes was evident in HEPS infection cultures, but to an extent also observed in cultures from non-HIV-exposed individuals. Furthermore, production of beta-chemokines was not enhanced in HEPS cultures. However, HEPS cultures displayed significantly enhanced production of a soluble activity that suppressed postintegrated HIV-1 replication. This activity was the unique product of CD4+ T cell and monocyte cocultures. Therefore, although HEPS individuals are apparently susceptible to infection, the production of a postintegrated HIV-1 suppressive activity during monocyte-T cell interactions might protect against the establishment of infection by limiting viral dissemination.

An HLA-directed molecular and bioinformatics approach identifies new HLA-A11 HIV-1 subtype E cytotoxic T lymphocyte epitopes in HIV-1-infected Thais.

Only limited cytotoxic T lymphocyte (CTL) epitope mapping has been done in nonsubtype B HIV-infected persons. We used molecular immunogenetic tools to determine HIV-specific CTL responses in HIV-1 Env subtype E-infected female sex workers (FSWs) from northern Thailand, where more than 50% of the population is HLA-A11 positive. EpiMatrix, a computer-based T cell epitope prediction algorithm, and a manual editing approach were used to predict 77 possible HLA-A11 CTL epitopes in HIV-1, some of which were conserved between subtypes B and E. MHC binding of these peptides was determined in an HLA-A11 stabilization assay, and binding peptides were tested for CTL recognition in eight HLA-A11-positive FSWs. Subtype E versions of known HLA-A2 subtype B HIV epitopes were also tested in four HLA-A2 positive FSWs. CTL responses were detected in all HLA-A11-positive and in three of four HLA-A2-positive persons. Among the 12 FSWs responses to peptides were found to Pol in 9 (75%), Env in 7 (58%), Nef in 5 (42%), and Gag in 5 (42%), and to conserved epitopes in 8 (67%). To identify HLA-A11 CTL epitopes in the absence of prediction tools, it would have been necessary to test almost 3000 10-mer peptides. EpiMatrix and manual predictions reduced this number to 77, of which 26 were MHC binding and 12 were CTL epitopes. Six of these HLA-A11 CTL epitopes have not been previously reported and are located in RT, gp120, and gp41. This report of CTL responses in subtype E-infected individuals defines epitopes that may be useful in HIV pathogenesis or vaccine studies.

DR beta Taq I restriction fragment length polymorphism (RFLP) associated with insulin dependent diabetes mellitus (IDDM).

DNA from insulin-dependent diabetes mellitus patients (IDDM) and healthy control individuals was evaluated using Southern blotting to determine if a disease-associated restriction fragment length polymorphism could be found. Using a DR beta-cDNA probe hybridized to Taq I digested genomic DNA, a 3.7 kb fragment was found in all IDDM patients examined (n = 33). Although a high percentage (47 per cent) of the control population also carried the fragment, nearly one-third of those persons were serotyped as DR2. The possible role of gene regulation in the development of IDDM is discussed.

The effect of phenazine methosulfate-ascorbate on bacterial active transport and adenosine triphosphate formation: inhibition of Pseudomonas aeruginosa and stimulation of Escherichia coli.

The artificial electron-donor system, phenazine methosulfate (PMS) ascorbate, inhibited active transport of glucose by Pseudomonas aeruginosa irrespective of whether the incubation systems were in air, flushed with oxygen, or gassed with nitrogen under anaerobic denitrifying conditions. Active transport of glucose by P. aeruginosa was also inhibited by reduced 5-N-methyl-phenazonium-3-sulfonate, a membrane-impermeable electron donor. PMS-ascorbate caused rapid depletion of intracellular adenosine triphosphate (ATP) when added to respiring cell suspensions of P. aeruginosa either in the presence or absence of glucose or succinate as oxidizable energy sources. In contrast, under identical conditions, Escherichia coli formed ATP with PMS-ascorbate as the sole oxidizable energy source and ATP formation continued when glucose or succinate was present in addition to PMS-ascorbate in the incubation system.

Cystic fibrosis DNA markers in Alabama blacks.

DNA samples from unrelated Alabama blacks with no family history of cystic fibrosis (CF) were analyzed with DNA markers linked to cf. Allelic frequencies of genetic markers detected by probes pmetH, pmetD, XV2c, KM19, and pJ3.11 were compared to those of other populations. Allelic frequencies for pJ3.11, XV2c, and KM19 in Alabama blacks and previously studied Caucasian populations were similar. In contrast, the met locus allelic frequencies in Alabama blacks were markedly different from those in Caucasian populations.

Maternal exposure to benzo[a]pyrene alters development of T lymphocytes in offspring.

Childhood cancer has been increasing significantly over the past two decades in the United States, suggesting that environmental exposures may be playing a causative role. One such cause may be maternal smoking during pregnancy. Suspected carcinogens in cigarette smoke and environmental pollution include N-nitrosamines and polycyclic aromatic hydrocarbons, which may be several micrograms per exposure. Previously, we have shown that mouse progeny of mothers exposed to benzo[a]pyrene (B[a]P) during midpregnancy had abnormalities in their humoral and cell-mediated immune response. Immunodeficiency was detectable during gestation, at one week after birth and persisted for 18 months. Tumor incidences in progeny were eight to 10-fold higher than in controls. The present study compared frequencies of CD4+, CD8+, V gamma 2+, and V beta 8+ T cells in progeny following in utero exposure to B[a]P. The significant reduction in newborn CD4+CD8+, CD4+CD8+V beta 8+ thymocytes and CD4+ splenocytes from 1-week-old progeny, suggests that B[a]P induces abnormal changes in developing T cells. These early alterations may lead to postnatal T cell suppression, thus providing a more suitable environment for the growth of tumors later in life. These results suggest that developmental immunosuppression mediated by B[a]P may play a critical role in the relationship between maternal exposures and childhood carcinogenesis.