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Certain human leukocyte antigens, by presenting conserved immunogenic epitopes for T cell recognition, may, in part, account for the observed differences in human immunodeficiency virus type 1 (HIV-1) susceptibility. To determine whether HLA polymorphism influences HIV-1 susceptibility, a longitudinal cohort of highly HIV-1-exposed female sex workers based in Nairobi, Kenya, was prospectively analyzed. Decreased HIV-1 infection risk was strongly associated with possession of a cluster of closely related HLA alleles (A2/6802 supertype; incidence rate ratio [IRR], 0.45; 95% confidence interval [CI], 0.27-0.72; P=.0003). The alleles in this supertype are known in some cases to present the same peptide epitopes for T cell recognition. In addition, resistance to HIV-1 infection was independently associated with HLA DRB1*01 (IRR, 0.22; 95% CI, 0.06-0.60; P=.0003), which suggests that anti-HIV-1 class II restricted CD4 effector mechanisms may play an important role in protecting against viral challenge. These data provide further evidence that resistance to HIV-1 infection in this cohort of sex workers is immunologically mediated. [ABSTRACT FROM AUTHOR]

A small group of women (n = 80) within the Nairobi-based Pumwani Sex Workers Cohort demonstrates epidemiologic resistance to HIV-1 infection. Chemokine receptor polymorphisms and beta-chemokine overproduction have been among the mechanisms suggested to be responsible for resistance to HIV-1 infection. This study attempts to determine if any of those mechanisms are protecting the HIV-1-resistant women. Genetic analysis of CCR5 and CCR3 from the resistant women demonstrated no polymorphisms associated with resistance. Expression levels of CCR5 among the resistant women were shown to be equivalent to that found in low-risk seronegative (negative) controls, while CXCR4 expression was greater among some of the resistant women. In vitro infection experiments showed that phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMCs) from resistant women were as susceptible to infection to T cell- and macrophage-tropic North American and Kenyan HIV-1 isolates as were the PBMCs from negative controls. No significant difference in circulating plasma levels of MIP-1alpha and MIP-1beta were found between the resistant women and negative or HIV-1-infected controls. In vitro cultures of media and PHA-stimulated PBMCs indicated that the resistant women produced significantly less MIP-1alpha and MIP-1beta than did negative controls and no significant difference in RANTES levels were observed. In contrast to studies in Caucasian cohorts, these data indicate that CCR5 polymorphisms, altered CCR5 and CXCR4 expression levels, cellular resistance to in vitro HIV-1 infection, and increased levels of beta-chemokine production do not account for the resistance to HIV-1 infection observed among the women of the Pumwani Sex Workers Cohort.

Objectives: To evaluate cross-clade recognition of p55 antigen by cytotoxic T lymphocytes (CTL) in persons infected with diverse clades of HIV-1; to facilitate the development of a CTL-inducing vaccine to prevent transmission of multiple clades of HIV-1., Design: Experiments were designed to evaluate whether persons in Uganda and the United Kingdom, infected with diverse clades of HIV-1, have CTL capable of recognizing and killing autologous target cells infected with recombinant vaccinia viruses (rVV) expressing the Gag protein from A, B, C and D clade HIV-1. The extent of cross-reactivity within such individuals, each infected with characterized virus, might reflect the type of cross-reactive immune response inducible by a monovalent vaccine., Methods: Asymptomatic HIV-positive individuals were fully tissue-typed by ARMS (amplification of refractory mutation system) polymerase chain reaction. rVV expressing the Gag protein from identified A, B, C and D viruses were prepared. CTL were cultured and tested for cytolytic activity on autologous rVV-infected or peptide-pulsed B cells., Results: Ugandan patients had inducible CTL responses recognizing A, B, C and D clade HIV-1 Gag. The majority of UK patients had inducible CTL responses that recognized two or more clades. No patient showed any HIV-2 cross-reactivity. Cross-reactive responses were characterized in three Ugandan patients., Conclusions: Most patients tested mounted cross-reactive CTL responses that recognized Gag proteins from clades of HIV-1 other than those with which they were infected.

HIV-specific cytotoxic T lymphocytes (CTL) are believed to play a major role in controlling virus levels through the asymptomatic period of HIV infection. For the rational design of an HIV vaccine, we need to know whether protective immunity can ever develop following HIV exposure in people who remain uninfected. We have detected HIV-specific CTL in 5/6 repeatedly exposed, persistently seronegative female sex-workers in The Gambia. Their CTL, repeatedly detected over two years, recognise epitopes presented by HLA-B35 which are cross-reactive between HIV-1 & HIV-2, suggesting they could have been primed first by HIV-2 exposure and subsequently boosted by exposure to HIV-1. Using previously identified clade B HIV-1 epitope peptides, we have now detected HIV-specific CTL in 6/15 highly exposed and apparently HIV-resistant Kenyan prostitutes, predominantly towards epitopes highly conserved between B and the Kenyan A & D clades of HIV-1. This CTL activity towards conserved virus epitopes may represent protective immunity to HIV generated in response to repeated exposure, and prophylactic HIV vaccines should aim to generate similar CTL responses.

We describe the case of a patient with chronic myeloid leukemia who rejected a bone marrow (BM) graft from a sibling donor believed to be HLA identical. Sequencing of the HLA genes showed the mother to be heterozygous for two closely related HLA haplotypes that could not be resolved by serological typing. The donor and the recipient had each inherited a different maternal haplotype resulting in allelic mismatches for the HLA-B35 and the HLA-DR11 genes. T cell cytotoxicity directed towards the donor's B35 allele was detected in the patient, in addition to CTL specificity for an HLA-B7-restricted minor histocompatibility antigen carried by the donor, resulting in three histocompatibility mismatches between the BM donor and the recipient.

HIV-specific cytotoxic T lymphocytes (CTLs) play an important role in the immune response to HIV infection. Long-term nonprogressors (LTNPs) or slow progressors (SPs) in HIV infection may make qualitatively different CTL responses compared to those generated by seropositive individuals who progress to disease at a faster rate. The class I molecule HLA-B*57 has been identified as one restriction element overrepresented in SP groups studied, and, together with the closely related molecule HLA-B*58, occurs commonly in ethnic groups where HIV is most prevalent. In this study, we have identified five new HLA-B*57-restricted CTL epitopes recognized by SP donors, one of which is also HLA-B*5801 restricted. These HLA-B*57-restricted responses represent the dominant HIV-specific CTL response in each of the SP donors tested. These and other such epitopes may be an important component in future vaccine design.

Primary infection with Epstein-Barr virus often results in the clinical syndrome of acute infectious mononucleosis (glandular fever). This illness is characterized by a striking lymphocytosis, the nature of which has been controversial. We show that large monoclonal or oligoclonal populations of CD8+ T cells account for a significant proportion of the lymphocytosis and provide molecular evidence that these populations have been driven by antigen. The results suggest that the selective and massive expansion of a few dominant clones of CD8+ T cells is an important feature of the primary response to this virus.

Burkitt lymphomas (BL) that arise in HLA-AII-positive individuals are characterized by selective loss/down-regulation of the HLA AII polypeptide. We have investigated the molecular basis of such down-regulation by comparing 5 pairs of BL lines and Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCL) derived from the normal B cells of the same individuals. The presence of apparently intact HLA AII genes was confirmed in all 5 BL/LCL pairs by polymerase chain reaction (PCR) typing and by Southern-blot hybridization with HLA A locus-specific probes. Northern-blot analysis with locus- and allele-specific probes revealed a significantly lower expression or absence of AII-specific mRNA in all 5 BL lines compared to the corresponding LCLs. Up-regulation of AII-specific mRNA was achieved by IFN alpha treatment of 2 BL lines with low HLA AII expression (BL-28 and BL-72) while the treatment had no effect in 3 BL lines (WWI-BL, WW2-BL and BL41) that did not express the endogenous gene. HLA AII expression was restored by transfection of the gene in WWI-BL whereas transfectants of BL-41 remained AII-negative. An HLA-AII-promoter-driven chloramphenicol acetyl transferase reporter gene (pAIICAT) was active in WWI-BL but not in BL-41. HLA-AII was expressed in hybrids of BL-41 with an AII-positive LCL, while expression of the endogenous HLA AII gene could not be restored by fusion of BL-41 with an AII-negative LCL, although an adequate set of transcription factors was present in the hybrid. Our results suggest that genetic defects and lack of transcription factors may contribute to the selective down-regulation of HLA AII in BL cells.

As part of the Fourth Asia-Oceania Histocompatibility (4AOH) Workshop, the authors have demonstrated a method of DNA-based tissue typing of the HLA-A locus using ARMS-designed primers in a panel of specific PCR reactions. The study was carried out blind under Workshop conditions and the results confirm the method as an accurate means of determining HLA-A locus tissue types.

We describe sequence-specific primer (SSP) combinations for use in a one-step polymerase chain reaction (PCR) typing system to determine HLA-A locus subtypes of A9 (A23, A24), A10 (A25, A26, A43), A28 (A*6801, A*6802, A*6901) and A19 (A*2901, A*2902, A*3001, A*3002, A31, A32, A33) from genomic DNA. SSP's were designed on the basis of the amplification refractory mutation system (ARMS) in which a mismatch at the 3' residue inhibits non-specific amplification. The SSP combinations described extend our low-resolution typing system, to provide a high-definition typing of the HLA-A locus.

Using immunohistochemical methods, we have analysed colorectal biopsies of normal mucosa, metaplastic polyps (5 cases), adenomas (15 cases) and adenocarcinomas (70 cases) with 13 monoclonal antibodies (MAbs) to allelic products of the HLA-A, B, C loci. Nine of the 70 carcinomas showed total loss of HLA Class-I molecules due to an underlying defect regarding not only the expression of beta 2-microglobulin (beta 2-m), but also the heavy chains of HLA A, B and C loci, or both. Much commoner was a loss of one or more Class-I alleles as follows: A1/Aw36 (completely lost in 4 of 29 cases and focally lost in another 2), A2 (in 1 of 37 cases), A3 (in 2 of 14 cases), A1 1/28/31/33 (in 3 of 11 cases), B7 (in 3 of 13 and focally in 1 other case), B17 (in 1 case), Bw4 (in 8 of 45 and focally in another 6), Bw6 (in 9 of 62 and focally in another 3). Focal selective loss (Bw6 and a combined A1-Bw6), was observed in 2 adenomas. Normal colonic mucosa, as well as stromal and lymphoid cells present between the neoplastic glands, were studied in each case as a control. A particular allele was only considered to be lost by the malignant cells if it was still expressed on these adjacent tissues.

In the 11th International Histocompatibility Workshop prescreening study, HLA Class I and Class II monoclonal antibodies (mAb) were tested on panels of peripheral T and B cells and homozygous typing cell (HTC) lymphoblastoid lines. The 102 Class I mAb, of which 64 were new, were screened on 63 HTC lines and 20 peripheral T cells. The 144 Class II mAb were tested on 63 HTC lines, 20 peripheral B and 10 peripheral T cells. For Class I, 45 of the 102 mAbs tested proved to have clear and identifiable reaction patterns on both PBL and HTC lines and included several interesting new HLA-A and -C locus antibodies. Of the 144 Class II mAb, of which 99 were new, 18 DR, 22 DQ and 7 DP antibodies were judged excellent. The DR antibodies included some which were antigen-specific but the majority were complex antibodies, while the DQ antibodies, as previously, identified the majority of DQ antigens both singly and in combinations. The encouraging number of DP antibodies was interesting in the limited range of sites they appear to detect.

Modifications of the standard microcytotoxicity assay make it possible to use this technique to screen both alloantisera and monoclonal antibodies with mouse L cells transfected with Class II genes. It is necessary to maintain a protein-rich environment in order to prevent nonspecific complement lysis. Selection of the complement itself is also an important factor, the best results being achieved using a commercially available complement that had previously been absorbed with mouse cells and used at a dilution of 1/8. Using this modified method with transfectants of DW2 origin we could show that alloantisera against DRw15 recognize the DRB1*1501 gene product, whereas broad DR2 sera react only with the DRB5*0101 product. This technique can be applied successfully to study the fine specificity of polymorphic monoclonal antibodies, as shown by the reactivity of HU-30 which binds to the LDR2b transfectant and not to the LDR2a, indicating that the antibody recognizes an epitope present on the DRB1 chain and not the DRB5 chain of DR2 cell lines.