Impact of Transplantation Timing on Renal Graft Survival Outcomes and Perioperative Complications

Nighttime organ transplantation aims to decrease cold ischemia duration, yet conflicting data exists on its impact on graft function and perioperative complications. This multicenter TRANSPLANT'AFUF study including 2,854 patients, transplanted between 1 January 2011, and 31 December 2022, investigated nighttime kidney transplantation's impact (8:00 p.m.-8:00 a.m.) versus daytime (8:00 a.m.-8:00 p.m.) on surgical complications and graft survival. Overall, 2043 patients (71.6%) underwent daytime graft, while 811 (28.4%) underwent nighttime graft. No impact was observed of timing of graft surgery on graft survival with a median survival of 98 months and 132 months for daytime and nightime grafting, respectively (p = 0.1749). Moreover, no impact was observed on early surgical complications (Clavien I-II = 20.95% for DG and 20.10% for NG; Clavien III-IV-V = 15.42% for DG and 12.94% for NG; p = 0.0889) and late complications (>30 days) (Clavien I-II = 6.80% for DG and 5.67% for NG; Clavien III-IV-V = 12.78% for DG and 12.82% for NG; p = 0.2444). Noteworthy, we found a significant increase in Maastricht 3 donors' rates in nighttime transplantation (5.53% DG vs. 21.45% NG; p < 0.0001). In conclusion, nighttime kidney transplantation did not impact early/late surgical complications nor graft survival.

An overview of the nutritional status of childbearing age women, children and adolescents living in a rural area of Madagascar: preliminary results of the Tany Vao project

OBJECTIVE

To describe the food consumption, nutrition knowledge and nutritional assessment of childbearing age women and their children, living in rural villages in Madagascar. The results presented are related to the Tany Vao research study.

DESIGN

A cross-sectional pilot study.

SETTING

The study was carried out in Ampanitosoha village on Nosy Mitsio island in Madagascar.

PARTICIPANTS

32 women (14-49 years) and 36 children and adolescents (2-17 years).

RESULTS

70 % of the women lacked nutrition knowledge and did not reach the Minimum Dietary Diversity Index for Women cut-off. The median BMI was 21·1 kg/m2 but 55·2 % of the women exceeded the cut-off for waist-to-hip ratio, 51·7 % for waist-to-height ratio and 81·2 % for mid-upper arm circumference (MUAC). Almost all had adequate intake of energy, protein and carbohydrates, while 27·6 % had excessive fat intake and 75·9 % of added sugars. Over half of the women did not meet the micronutrients Reference Daily Intake (RDI). For children, the MUAC z-score was lower for boys than for girls (P-value = 0·041).

CONCLUSIONS

These results underline the importance of increasing women's nutritional knowledge to promote healthy pregnancy and lactation. Moreover, it is fundamental to provide people living in rural areas with sustainable tools to improve dietary diversity and support long-term health.

Biomass production, metal and nutrient content in sorghum plants grown on soils amended with sewage sludge

Sludge generation from wastewater treatment plants in Uruguay has increased in recent years. Agricultural soils may be a final destination. A greenhouse experiment was conducted to quantify the effect of this sludge on 1) plant biomass production and nutrient concentration of sorghum (Sorghum bicolor var. vulgare); 2) the chemical properties of amended soils; and 3) assess whether heavy metal concentrations in sludge are appropriate according to environmental regulations. Two soils (S1 and S2) were amended with pure sludge (PS) and limed sludge (LS), with low dose (LD) of 16.0 and 17.3 Mg ha⁻¹ and high dose (HD) of 32.0 and 34.6 Mg ha⁻¹, respectively. Sludge treatments increased plants' nutrient absorption and dry matter production. The LS treatments incremented plant biomass production, depending on soil pH and nutrient availability. The effect of sludge treatments on elemental concentration in aboveground biomass depended on the element, treatments, and soil type. Mineralized nitrogen (N) and plant available phosphorus (P-Bray 1) values increased with sludge addition without exceeding Uruguay's critical soil level of P-Bray 1 for the sorghum crop. The PS did not increase metal concentration in soils. The LS slightly decreased soil Pb and slightly increased Cr and Zn soil concentration; levels were according to Uruguayan environmental guidelines. Therefore, agriculture soils are a viable final destination for PS and LS. Land applied sludge has acceptable levels of metals and promotes crop development.

Gaining insight into the kinetics of partial oxidation of light hydrocarbons on Rh, through a multiscale methodology based on advanced experimental and modeling techniques

This chapter updates previous reviews on the catalytic partial oxidation of methane and light hydrocarbons over noble metals; specifically, it focuses on the development of experimental and modeling tools that in recent years allowed to measure with accuracy and formalize the kinetics of the surface process, thus setting the basis for the engineering of short contact time CPO reformers. Such advanced tools include special micro-reactor designs for the kinetic investigation under isothermal conditions, first-principle microkinetic schemes, techniques for the spatially resolved measurement of temperature and concentration profiles inside working adiabatic reactors, detailed reactor models accounting for the role of transport phenomena in structured catalysts as well as that of homogeneous reactions. These contributions pave a multi-scale path, that runs from the fundamentals of surface kinetics to the reactor optimal design.

Granulocyte/monocyte apheresis induces sustained increases in CD4 T cells in HIV-1 infected patients with poor CD4 T cell restoration after suppression of viral replication by HAART

Current antiretroviral regimens (HAART) are generally effective in reducing viral replication to undetectable levels and inducing a raise in CD4 T cells. However, in approximately 5 to 15% of patients suppression of viral replication is not followed by an increase in CD4 T cells. Such patients may be at increased risk for opportunistic infections. Here we report the results from a phase II open label randomised trial on 30 patients classified as poor responders to HAART who were either subjected to eight consecutive cycles of selective monocyte apheresis or maintained under HAART alone. The results show that monocyte apheresis results in increased CD4 T cell counts which are maintained for at least 31 weeks after last apheresis. This effect was observed only on patients with complete suppression of viral replication. Other effects of monocyte apheresis included a strong reduction of TNF-alpha production in patients with high baseline levels of this cytokine and activation of resting T cells during the apheresis cycles. In two patients with high cellular HIV DNA load apheresis was followed by a 98% reduction, suggesting purging of infected cells. There was no evidence of increased viral replication during or after the apheresis cycles. The data show that monocyte apheresis is safe, well tolerated and may be indicated in patients who respond poorly to HAART.

The effects of scrambling on Spanish and Korean agrammatic interpretation: why linear models fail and structural models survive

Several models of comprehension deficits in agrammatic aphasia rely heavily on linear considerations in the assignment of thematic roles to structural positions (e.g., the Trace-Deletion Hypothesis, the Mapping Hypothesis, and the Argument-Linking Hypothesis). These accounts predict that constructions in languages with rules that affect syntactic structure but preserve relative linear order should be unimpaired. Other models [e.g., the Double-Dependency Hypothesis, (DDH)] do not resort to linearity but are purely structural in conception and therefore should be immune to word-order effects. We tested linear and nonlinear accounts with scrambling structures in Korean and topicalization structures in Spanish. The results are very clear. The (nonlinear) DDH is entirely compatible with the evidence, but the linear accounts are not.

Role of the kinetochore protein Ndc10 in mitotic checkpoint activation in Saccharomyces cerevisiae

Mitotic checkpoints delay cell cycle progression in response to alterations in the mitotic apparatus, thus ensuring correct chromosome segregation. While improper spindle orientation activates the Bub2/Bfa1-dependent checkpoint in budding yeast, delaying exit from mitosis, lack of bipolar kinetochore-microtubule attachment activates a signal transduction cascade that prevents both anaphase onset and exit from mitosis by inhibiting the Cdc20/APC (Anaphase Promoting Complex)-mediated proteolysis of securin and inactivation of mitotic cyclin-dependent kinases (CDKs), respectively. Proteolysis of the securin Pdsl is necessary to liberate the separase Esp1, which then triggers sister chromatid separation, whereas inactivation of mitotic CDKs is a prerequisite for exit from mitosis and for starting a new round of DNA replication in the next cell cycle. In budding yeast, this latter checkpoint response involves the proteins Mad1, 2, 3, Bub1 and Bub3, whose vertebrate counterparts localize to unattached kinetochores. Mutations that alter other kinetochore proteins result in mitotic checkpoint activation, while the ndc10-1 mutation not only impairs kinetochore function, but also disrupts the checkpoint response, indicating a role for Ndc10 in this process. Here we present evidence that Ndc10 is not part of the Bub2/Bfa1-dependent pathway, and its role in the checkpoint response might also be different from that of the other Mad and Bub proteins. Indeed, Ndc10, unlike other mitotic checkpoint proteins, is not required for the mitotic block induced by overexpression of the Mpsl protein kinase, which is implicated in mitotic checkpoint control. Furthermore, the delay in mitotic exit caused by non-degradable Pds1, which does not require Mad and Bub proteins, depends on Ndc10 function. We propose that a pathway involving Ndc10 might monitor defects in the mitotic apparatus independently of the Mad and Bub proteins. Since the Espl separase is required for exit from mitosis in both ndc10-1 and nocodazole-treated mad2delta cells, the two signal transduction cascades might ultimately converge on the inactivation of Esp1.

Antibodies to C-C chemokine receptor 5 in normal human IgG block infection of macrophages and lymphocytes with primary R5-tropic strains of HIV-1

In the present study, we demonstrate that normal human IgG for therapeutic use (i.v. Ig) contains natural Abs directed against the CCR5 coreceptor for HIV-1. Abs to CCR5 were isolated from i.v. Ig using an affinity matrix consisting of a synthetic peptide corresponding to the N-terminus of CCR5 coupled to Sepharose. Natural anti-CCR5 Abs inhibited the binding of RANTES to macrophages, demonstrating their interaction with the coreceptor of R5-tropic HIV-1. Affinity-purified anti-CCR5 Ig further inhibited infection of lymphocytes and monocytes/macrophages with primary and laboratory-adapted strains of HIV-1, but did not inhibit infection with X4-tropic HIV. Our results suggest that anti-CCR5 Abs from healthy immunocompetent donors may be suitable for development of novel passive immunotherapy regimens in specific clinical settings in HIV infection.

Psychological verbs and the double-dependency hypothesis

The double-dependency hypothesis (DDH, Mauner et al., 1993) holds that where two dependencies of a certain kind are present, comprehension in Broca's aphasia will be random, but that where there is only one dependency, comprehension will be intact. We tested this hypothesis by examining the performance of Broca's aphasics on sentences with psychological verbs of two different classes. One class has an argument structure in which the Experiencer role is assigned to the subject. In the other class, the Experiencer role is assigned to the object. Subject-Experiencer verbs can form verbal passives which have two relevant dependencies, whereas object-Experiencer verbs can form adjectival passives and have only one relevant dependency. Thus these sentence types make contrasting predictions relevant to the DDH. Our results clearly demonstrate that patients understand the adjectival passive psychological verbs, as predicted by the DDH. On the verbal passive psychological verbs, patients perform at chance, again consistent with DDH predictions. These results firmly buttress the DDH account. They also contradict the results of an earlier study (of verbal passive psychological verbs only), a study which we argue is plagued with problems (namely, Grodzinsky, 1995b).

Insulin receptor antibodies inhibit insulin uptake by the liver: in vivo 123I-insulin scintigraphic scanning and in vitro characterization in autoimmune hypoglycemia

BACKGROUND

Insulin receptor antibodies can induce severe hypoglycemia or insulin resistance in rare autoimmune syndromes. In vitro properties of these antibodies occasionally explain the clinical features of the syndrome, but direct evidence of their in vivo activity is poor. We studied a 58-year-old male with rheumatoid arthritis who presented with hypoglycemic coma.

METHODS AND RESULTS

Antibodies were detected by inhibition of 125I-insulin binding to human insulin receptor-3T3 cells by the patient's serum. By immunofluorescence, they were immunoglobulin G of all four subclasses, immunoprecipitated insulin receptors from biotin-labeled cells, and triggered phosphorylation of the beta subunit of the insulin receptor. Insulin binding on the patient's red blood cells was markedly reduced. A biodistribution study after intravenous 123I-Tyr A14 insulin showed a marked inhibition of tracer uptake by the liver, reaching 10% of the injected dose (controls, mean +/- SD, 21.1 +/- 1.7%; n = 10). Time activity curves generated on the liver and on the heart were parallel, with a T1/2 of 11.5 minutes for both, suggesting that no specific uptake occurred in the liver, where tracer activity represented only the blood pool. Clearance of insulin from the blood was indeed slower than in controls and mainly occurred through the kidneys. Analysis of plasma 123I-insulin immunoreactivity and trichloroacetic acid precipitate showed that insulin degradation did not occur as in normal controls.

CONCLUSIONS

In this patient with hypoglycemic syndrome, insulin receptor antibodies with in vitro insulin-like activity are capable of blocking in vivo the access of insulin to the liver receptor compartment, as directly demonstrated by the markedly altered biodistribution of intravenously injected 123I-insulin.

Hepatic amyloidosis with light chain deposition disease. A rare association

Monoclonal immunoglobulin deposition diseases are due to pathological protein deposition in various tissues and organs. Protein deposits may be found in a single tissue or systemically and the organs most frequently involved are kidney, heart, peripheral nerves and the liver. Depending on the pattern of the deposits and the type of immunoglobulin, these diseases are distinguished as primary amyloidosis, light chain deposition disease. Differential diagnosis is made in tissue specimens: microscopically by the identification of positive Congo red staining of the deposits, by immunohistochemical demonstration of proteins reacting with light chain (lambda or kappa) antisera or by recognition of fibrillar structures on electron microscopy. We report an unusual case of light chain deposition disease associated with amyloidosis, where hepatomegaly was the presenting manifestation and liver failure the cause of death, without any kidney involvement.

Genetic aspects in sarcoidosis

Sarcoidosis is an immune-mediated, multiorgan, granulomatous disorder thought to be triggered by an intricate combination of environmental and genetic factors. Two robust lines of evidence support the hypothesis of a genetic component in the pathogenesis of sarcoidosis: racial variation in its epidemiology and familial clustering of cases. The relationship between epidemiology and environmental factors affecting variations in sarcoidosis incidence/prevalence and presentation are reviewed, as well as strategies to be pursued in the search for susceptibility genes for the disorder. Pathogenic processes leading to sarcoid granuloma formation and maintenance have prompted investigators interested in the genetics of sarcoidosis to focus mainly on major histocompatibility complex genes, and indeed a remarkable amount of data has been accumulated during the last two decades. Whilst in contrast with some autoimmune disorders a clear association between human leukocyte antigen (HLA) and sarcoidosis is still a controversial issue, there is, however, a general agreement that some HLA genes are related to phenotypic variations of the disease. Some genetic investigators have focused on T-cell receptor genes, immunoglobulin genes, angiotensin converting enzyme gene, chemokine genes and others. From a review of studies performed in different racial and ethnic groups, a reasonable suggestion arises that genetic factors are the major determinant in the racial variations in the epidemiology of the disorder. This assumption is, however, so far limited by lack of studies considering both genetic and environmental factors simultaneously.

Increased frequency of CFTR gene mutations in sarcoidosis: a case/control association study

A complete screening of the CFTR gene by DGGE and DNA sequencing was performed in patients with sarcoidosis. In 8/26 cases, missense and splicing CFTR gene mutations were found, a significant difference over controls (9/89) from the same population (P = 0.014). The odds ratio for a person with a CFTR gene mutation to develop the disease is 3.95 (1.18 < OR < 13.26). Seven different CFTR gene mutations were observed: R75Q, R347P, 621 + 3 A/G, 1898 + 3 A/G, L997F, G1069R, and a novel mutation which was detected in this study, I991V. R75Q mutation was present in 3/26 patients, a significant increase (P = 0. 01) in cases over controls, indicating its preferential association with sarcoidosis. A trend towards disease progression was observed in patients with CFTR gene mutations compared to patients without mutations. These data suggest that CFTR gene mutations predispose to the development of sarcoidosis.

Anti-cell antibodies in exposed seronegative individuals with HIV type 1-neutralizing activity

Despite repeated exposures to HIV-1, some individuals remain seronegative. This study reports that sera from a fraction of exposed seronegative (ESN) subjects showed HIV-neutralizing activity; 5 of 17 ESN sera and none of 17 controls neutralized two different HIV-1 primary isolates (range of neutralizing titers: 1/20 to 1/60). The neutralizing activity was associated with the IgG fraction of 4 of 4 neutralizing ESN sera. Moreover, in 11 of 17 and 9 of 17 ESN sera (but none of the control sera) we found antibodies against HLA class I and CD4, respectively. One of the ESN sera (EU22) neutralized efficiently the primary virus derived from the seropositive partner and showed a good broadly cross-reactive neutralization. Immunoadsorption of two IgG fractions from EU19 and EU22 on peripheral blood mononuclear cells (PBMC) removed virus-neutralizing antibodies. The correlations between the ESN status and neutralizing activity (p<0.05), anti-HLA antibodies (p<0.0002), and anti-CD4 antibodies (p<0.001) were statistically significant. However, there was no statistically significant correlation between neutralizing activity and either anti-HLA or anti-CD4 antibodies. It can therefore be said that exposure to HIV-1 without seroconversion is, in some individuals, associated with HIV-neutralizing antibodies (not directed against viral antigens) and/or with anti-cell autoantibodies, which are possibly specific for cellular antigens involved in the infection/entry process.

Ex-vivo purging of circulating monocytes results in immunovirologic improvement in partially HAART responder HIV-infected patients

AIDS pathogenesis results from a complex array of immune alterations which include, among others, changes in the pattern of cytokine production. Some monocyte-derived cytokines, like TNFalpha play a major role in HIV pathogenesis. TNFalpha transactivates HIV NF-kB thereby inducing viral replication, potentiates HIV replication in lymphomonocytes TNFalpha is one of the main factors of HIV-induced cachexia and might be involved in HAART-associated lipodystrophy. In addition, monocytes are infectable by HIV in vitro and infected monocytes can be recovered from the blood of HIV infected patients. For these reasons, we tested whether renewal of the pool of circulating monocytes by selective monocyte apheresis may improve the immune reconstitution which follows treatment with highly active anti-retrovirals (HAART). HIV-infected HAART receiving (> 1 year) patients who were either virologically non-responders (HIV-1 RNA >50,000 copies/ml) or immunologically non-responders (CD4 counts < 200) were treated with a novel monocyte apheresis device (G-1 Adacolumn). Plasma HIV viral load, proviral DNA and phenotypic and functional immunological analyses were performed. G-1 apheresis was well tolerated, not accompanied by adverse responses, and followed by clinical improvement. TNFalpha production was suppressed and CD4 T cell counts increased. In one G-1 patient with elevated HIV-1 proviral DNA a significant reduction (from 1,500 to 40 copies/10(5) cells) was observed. Neither immunologic nor virologic parameters were modified in the control patients who received HAART alone. Thus, purging of circulating monocytes by G-1 apheresis has a dramatic suppressive effect on TNFalpha production and is followed by both clinical and immunovirological improvement. G-1 apheresis should be considered in patients in whom HAART is only partially effective.

Enhanced HIV infectivity and changes in GP120 conformation associated with viral incorporation of human leucocyte antigen class I molecules

BACKGROUND

Assembly of human immunodeficiency virus type 1 (HIV-1) occurs at the level of the plasma membrane of the host cell. During this process HIV incorporates significant quantities of cell surface-derived molecules into its lipid bilayer including human leucocyte antigen (HLA) class I and II, intercellular adhesion molecule-1 and lymphocyte function antigen-1. Several studies indicate that virion-bound host-cell-derived molecules are functional and affect the biological properties of HIV-1. Virion-associated HLA class II and intercellular adhesion molecule-1 enhance the infectivity of T-cell line-adapted (TCLA) viruses. No role for virion-associated HLA class I molecules has yet been identified.

OBJECTIVE

To investigate the role of HLA class I molecules in HIV replication and infectivity.

METHODS

HLA class I negative human cells lines transfected with the HLA Cw4 gene were infected with different TCLA viruses as well as primary X4 isolates. The infectivity of HLA Cw4 positive and negative viruses was determined on indicator cell lines and on phytohaemagglutinin-activated peripheral blood mononuclear cells. An entry polymerase chain reaction assay was used to determine differences in entry-competence of Cw4 positive and negative viruses. The expression of selected gp120 epitopes on native Env molecules derived from Cw4 positive and negative viruses was determined by a monoclonal antibody-based enzyme-linked immunosorbent assay. Immunoprecipitation experiments were performed to investigate the presence of gp120/HLA Cw4 complexes. Neutralization assays determined the differences in susceptibility to neutralization between HLA Cw4 negative and positive viruses.

RESULTS AND CONCLUSIONS

The infectivity of primary HIV-1 X4 isolates and of TCLA viruses is increased upon viral incorporation of HLA Cw4 molecules. This effect is associated with changes in viral envelope proteins conformation including an enhanced expression of the V3 loop of gp120, and of epitopes that are exposed upon CD4 binding. The gp120 conformational changes are consistent with the formation of a multimolecular complex between HLA class I and gp120/160. HLA Cw4 incorporation is also associated to a lower susceptibility to antibody neutralization. These findings have important implications for understanding the immune response to cryptic and conformational epitopes of the viral envelope.

Recruiting comparative crosslinguistic evidence to address competing accounts of agrammatic aphasia

Several hypotheses have been advanced whose aim has been to provide a descriptive generalization of comprehension patterns in agrammatic aphasia in terms of current linguistic theory, most notably, the Trace-Deletion Hypothesis. The basic insight of these syntactic accounts of aphasia is that chains are disrupted. In this paper, we seek to confront the Trace-Deletion Hypothesis (TDH) and one of its variants, the Double-Dependency Hypothesis (DDH), with discriminating, crosslinguistic data. We adduce evidence that on raising constructions both hypotheses are able to derive Spanish agrammatic data correctly. However, neither the TDH nor the DDH are able to account for above-chance performance on SV or VS truncated passives. Finally, only the DDH explains the observed data on passive constructions in which a postverbal subject follows the by phrase (V-by phrase-S). The VS word order data are the critical cases because focusing simply on English would not allow these structures to be tested and, in the case of the V-by phrase-S passive, both hypotheses make different predictions. While the data on raising constructions extend the range of both the TDH and the DDH, the VS data suggest that modifications are required.

Double-agents and trace-deletion in agrammatism

The Trace-Deletion Hypothesis (henceforth TDH; Grodzinsky 1986, 1995) states that syntactic traces are deleted in agrammatism and that whenever a trace is deleted, a default strategy is activated. The default strategy assigns the role of Agent to the first NP. In structures where a second NP receives the Agent role syntactically, the consequence is that the agrammatic representation contains two conflicting Agents for the same action. This is the mechanism that induces guessing and the random performance on comprehension tests that has often been observed for passives and certain other structures. In this paper, we isolate the default strategy of the TDH, using a sentence-picture matching task in which one of the pictures matches the meaning arrived at by the default strategy. Our results show that an agrammatic representation does not involve double-Agents, and thus the default strategy (and therefore the TDH) is refuted.

Pathogenetic and clinical aspects of C1 inhibitor deficiency

People deficient in C1-INH present recurrent angioedema localized to subcutaneous or mucous tissues. The defect can be caused by impaired synthesis, due to a genetic defect (hereditary angioedema), or by increased catabolism (acquired angioedema). In our experience the majority of patients with acquired angioedema (16 of 18) have autoantibodies to C1-INH in their serum. These autoantibodies bind to C1-INH with different and generally low affinity. The vasopermeability mediator responsible for attacks is still undefined: bradykinin (derived from cleavage of high molecular weight kininogen) and a kinin-like peptide (derived from the second component of complement) still remain the two primary candidates. We examined the systems controlled by C1-INH (complement, contact system, fibrinolysis and coagulation) and found that all of them are activated during angioedema attacks. Activation of the coagulation leads to generation of thrombin whose vasoactive effect can thus influence edema formation. Treatment of severe angioedema attacks is satisfactorily performed with C1-INH plasma concentrate although patients with an acquired defect frequently need very high doses. Attenuated androgens effectively prevent attacks in hereditary angioedema, but their safety, on the very long-term, needs to be further assessed. Acquired angioedema generally fail to respond to these drugs, but can be treated prophylactically with antifibrinolytic agents.

Imaging of the buffering effect of insulin antibodies in the autoimmune hypoglycemic syndrome

Insulin autoimmune hypoglycemia is characterized by recurrent hypoglycemia and high levels of immunoreactive insulin in the presence of insulin autoantibodies. The mechanisms inducing hypoglycemia are largely unknown. An [123I]insulin scintigraphic scanning was performed to directly demonstrate the effect of antibodies on insulin biodistribution in one patient with this syndrome both before and after treatment. The patient had insulin autoantibodies IgG3 lambda, which had a single site dissociation constant (Kd = 10(-7) mol/L, by Scatchard analysis), a very fast dissociation rate of immune complexes, and a very rapid association of [125I]insulin. Insulin receptors on red blood cells were down-regulated. The [123I]insulin scintigraphic study imaged the buffering effect of antibodies on insulin bioavailability. [123I]Insulin was not removed from the blood, and no liver or kidney uptake of the hormone occurred. The frequency and severity of hypoglycemic episodes required treatment. Insulin antibody levels decreased and [123I]insulin biodistribution improved after treatment with plasmapheresis and prednisone. Improved hormone bioavailability was further evidenced by the reduction in the hypoglycemic delay after i.v. insulin from 90 min before any treatment to 60 min after plasmapheresis and 30 min after steroid administration. Glucose tolerance was normal after treatment. Plasmapheresis followed by steroid treatment can lower the insulin antibody concentration, abolish severe hypoglycemia, and improve insulin biodistribution and glucose tolerance in insulin autoimmune hypoglycemia.

HIV-1-resistance phenotype conferred by combination of two separate inherited mutations of CCR5 gene

BACKGROUND

Despite multiple exposures to HIV-1, some individuals remain uninfected, and their peripheral-blood mononuclear cells (PBMC) are resistant to in-vitro infection by primary HIV-1 isolates. Such resistance has been associated with a homozygous 32-base-pair deletion (delta 32) in the C-C chemokine receptor gene CCR5. We examined other mutations of the CCR5 gene that could be associated with resistance to HIV-1 infection.

METHODS

We assessed the susceptibility of PBMC to in-vitro infection by HIV-1 isolates that use the CCR5 as the major coreceptor for viral entry in 18 men who had frequent unprotected sexual intercourse with a seropositive partner. We also did genotypic analysis of CCR5 alleles. One of the 18 exposed but uninfected men (who we refer to as ExU2) showed total resistance to in-vitro infection by CCR5-dependent viruses, and was found to carry a CCR5 delta 32 allele and a single point mutation (T-->A) at position 303 on the other allele. To find out whether the CCR5 mutation was restricted to ExU2's family or existed in the general population, we did genetic analyses of the CCR5 genotype in ExU2's father and sister and also in 209 healthy blood donors who were not exposed to HIV-1.

FINDINGS

The m303 mutation found in ExU2 introduced a premature stop codon and prevented the expression of a functional coreceptor. The family studies revealed that the m303 mutant allele was inherited as a single mendelian trait. Genotype analysis showed that three of the 209 healthy blood donors were heterozygous for the mutant allele.

INTERPRETATION

We characterise a new CCR5 gene mutation, present in the general population, that prevents expression of functional coreceptors from the abnormal allele and confers resistance to HIV-1 infection when associated to the delta 32 CCR5 mutant gene.

HLA-C heavy chains free of beta2-microglobulin: distribution in normal tissues and neoplastic lesions of non-lymphoid origin and interferon-gamma responsiveness

Lacking monospecific antibodies to HLA-C, the expression and synthesis of these molecules have been difficult to evaluate. Using biochemical and flow cytometry approaches, the present report demonstrates that the reactivity of the murine monoclonal antibody L31 is restricted to naturally occurring HLA-C (HLA-Cw1 through -Cw8), HLA-B8 and HLA-B51 heavy chains not associated with beta2-microglobin (beta2m). This is due to two properties of HLA-C heavy chains: (a) they share the L31 epitope which distinguishes them from all the HLA-A and most HLA-B molecules; (b) they accumulate intracellularly, in a beta2m-free form, in much greater amounts than most L31-reacting HLA-B heavy chains. On the basis of this restricted reactivity, a representative panel of normal and neoplastic human tissues and cells derived from HLA-B8- B51- individuals was selected and employed to assess the tissue distribution, surface expression and IFN-gamma responsiveness of beta2m-free HLA-C heavy chains. At variance from antibody W6/32 to beta2m-associated heavy chains, L31 stains normal and neoplastic tissues with a ground-glass pattern and weakly binds to the surface of viable cells, even after treatment with interferon gamma (IFN-gamma). Thus, beta2m-free HLA-C heavy chains are, for the most part, located intracellularly. In spite of their distinct cellular localization, L31- and W6/32-reacting molecules have an overlapping tissue distribution, undergo concordant changes upon transformation and are upregulated in their synthesis by IFN-gamma to a similar extent. These observations demonstrate a coordinate regulation of HLA-C with HLA-A and -B molecules. In addition, they indicate that the assembly of HLA-C is impaired in most body districts and IFN-gamma is unable to completely reverse this impairment. The present results are consistent with a low surface expression of HLA-C and with a privileged role of these molecules in signaling class I loss to cytotoxic effectors in pathological conditions.

Human immunodeficiency virus type 1 glycoprotein 120-specific T lymphocytes provide intermolecular help for anti-CD4 autoantibody production in exposed uninfected subjects

Anti-CD4 antibodies have been documented in about 10-20% of HIV-infected patients. This autoimmune response could be triggered by increased CD4 processing and unveiling of hidden (cryptic) epitopes. Multiple markers of exposure to HIV have been described in exposed uninfected individuals. Here, we investigated the mechanisms underlying the generation of anti-CD4 antibodies in a cohort of 54 seronegative exposed uninfected individuals. We identified anti-CD4 antibodies above normal levels in 16 of 47 (34%) exposed uninfected subjects. The fine specificity of these antibodies was different in this cohort when compared with those found in HIV+ patients. This suggested the possibility of different mechanisms underlying the generation of anti-CD4 antibodies in these two groups. Indeed, in exposed uninfected subjects, we found circulating CD4 T cells specific for gp120, but not for CD4. In contrast, HIV-1-seropositive patients had peripheral blood T cells specific for both molecules. Noncovalent binding of gp120 to soluble CD4 enhanced activation of gp120-specific T lymphocytes in exposed uninfected subjects, but not in HIV+ subjects. Moreover, gp120-specific T cells isolated from exposed uninfected, but not from HIV+, subjects provided help for anti-CD4 antibody production by B cells pulsed with CD4-gp120 complex. We conclude that gp120-specific T cells are present in exposed uninfected individuals, and can provide intermolecular help for anti-CD4 antibody production. This mechanism is distinct from that found in HIV-1-seropositive patients and may play a protective role against HIV-1 infection in vivo.

Antigen-driven C-C chemokine-mediated HIV-1 suppression by CD4(+) T cells from exposed uninfected individuals expressing the wild-type CCR-5 allele

Despite repeated exposure to HIV-1, certain individuals remain persistently uninfected. Such exposed uninfected (EU) people show evidence of HIV-1-specific T cell immunity and, in rare cases, selective resistance to infection by macrophage-tropic strains of HIV-1. The latter has been associated with a 32-base pair deletion in the C-C chemokine receptor gene CCR-5, the major coreceptor of macrophage-tropic strains of HIV-1. We have undertaken an analysis of the HIV-specific T cell responses in 12 EU individuals who were either homozygous for the wild-type CCR-5 allele or heterozygous for the deletion allele (CCR-5Delta32). We have found evidence of an oligoclonal T cell response mediated by helper T cells specific for a conserved region of the HIV-1 envelope. These cells produce very high levels of C-C chemokines when stimulated by the specific antigen and suppress selectively the replication of macrophage-tropic, but not T cell-tropic, strains of HIV-1. These chemokine-producing helper cells may be part of a protective immune response that could be potentially exploited for vaccine development.

Nuclear levels of NF-kappaB correlate with syncytium-forming capacity of 8e51 cells, expressing a defective HIV virus

The double NF-kappaB site identified in the LTR of the human immunodeficiency virus-1 (HIV-1) has been demonstrated to be necessary for efficient viral transcription. In this report we present the characterisation of NF-kappaB subunits engaged in complexes binding to the HIV-1 NF-kappaB site in human 8e51 T-cells, that harbour a defective HIV-1. At least four different specific NF-kappaB complexes are present in the nucleus of these cells. With the use of specific antibodies we have determined the composition of each complex using electrophoretic mobility shift assays. The results show the presence of several NF-kappaB family members, with the transactivating RelA being engaged in multiple complexes. The importance of NF-kappaB complexes in viral functions has been established comparing the level of NF-kappaB DNA-binding complexes with syncytia-forming activity of 8e51 cells. In fact, 8e51 cells that had almost lost their syncytia-forming capacity were found to contain at least 10 times less active NF-kappaB DNA-binding complex than the actively fusing cells. The correlation is specific as the level of at least three other transcription factors did not change.

Conformation and surface expression of free HLA-CW1 heavy chains in the absence of beta 2-microglobulin

A beta 2-microglobulin (beta 2m)-deficient kidney carcinoma cell line and three monoclonal antibodies to the alpha 1 (L31), alpha 2 (W6/32), and alpha 3 (Q1/28) domain of class I HLA molecules were selected to assess the role of beta 2m in regulating the conformation and surface expression of HLA-C molecules. HLA-A2, -B27, and -CW1 molecules synthesized by beta 2m-deficient cells were compared to heavy chains synthesized in transfectants expressing a large excess of beta 2m. As assessed by differential binding with monoclonal antibodies and partitioning studies in the detergent TX-114, no HLA-A2, -B27, or -CW1 molecules can be expressed, in a correct conformation, by beta 2m-deficient cells. These cells, however, do express low but significant amounts of free HLA-CW1 heavy chains at the cell surface. Transfection with beta 2m causes a coordinate change in the antibody reactivity of the three domains of HLA-CW1 molecules, thereby providing the first experimental demonstration that assembly with beta 2m affects the folding of not only the alpha 1 and alpha 2, but also of the alpha 3 domain. HLA-CW1 heavy chains, when free of beta 2m, are less soluble in the detergent TX-114 than free HLA-B27 heavy chains, and when associated with beta 2m share an alpha 3 domain epitope with free HLA-A2 and -B27 heavy chains. Moreover, their assembly with beta 2m is largely incomplete. Those data additionally demonstrate an impaired ability of HLA-CW1 to properly fold and establish a close similarity of HLA-CW1 to murine Db and Ld molecules. Although the functional role, if any, of free HLA-CW1 heavy chains remains to be determined, the present study demonstrates that the absence of beta 2m does not completely ablate class I expression in neoplastic cells of human origin.

Low prevalence of islet autoantibodies in patients with gestational diabetes mellitus

OBJECTIVE

To determine the proportion of patients with gestational diabetes mellitus (GDM) who have serological characteristics typical of IDDM.

RESEARCH DESIGN AND METHODS

Islet cell antibodies (ICAs), insulin autoantibodies (IAAs), GAD65, and IA-2 antibodies were measured in 145 pregnant women with GDM, 33 with impaired glucose tolerance (IGT), and in 73 with normal glucose tolerance (NGT). ICAs were measured by indirect immunofluorescence; GAD65 and IA-2 antibodies, by a radio-ligand immunoassay incorporating 35S-labeled recombinant antigen; and IAAs, by a liquid-phase radiobinding assay.

RESULTS

The prevalences of islet autoantibodies were low and not significantly different between groups. ICAs were detected at levels ranging from 5 to 45 Juvenile Diabetes Foundation U in 14 (10%) women with GDM, 2 (6%) women with (GT, and in 4 (5%) women with NGT. IAAs were detected at levels between 3 and 4 SD above the mean in 4 (3%) women with GDM, 0 women with IGT, and in 1 (1%) woman with NGT. None had both ICAs and IAAs. Neither GAD65 nor IA-2 antibodies, which have been detected in the majority of pre-IDDM and IDDM patients, were found in NGT, IGT, or GDM patients.

CONCLUSIONS

Low-titer ICAs and IAAs are not infrequent in pregnant women, but multiple islet autoantibodies and antibodies to GAD65 or IA-2 were not found in GDM. These findings suggest that the serological characteristics of IDDM are rare in GDM.

Heterogeneity in exposed uninfected individuals

In spite of repeated exposures to HIV, some individuals remain seronegative and apparently uninfected. A variety of mechanisms potentially able to confer resistance to HIV infection, including cell-mediated and (unconventional) humoral immune responses, as well as mutations affecting receptors for virus entry have been considered and analysed. In this article, we want to discuss recent reports on specific immune responses and genetic factors potentially involved in mechanisms of protection, and to present some of our data relative to a cohort of people sexually exposed to HIV-1, but persistently seronegative. These EU (exposed uninfected) individuals can be distinguished from "normal" unexposed controls on the basis of significantly increased frequencies of a number of immunological parameters that might be considered "unconventional" correlates of HIV infection/protection. However, EU individuals are highly heterogeneous since the various unconventional immune responses considered can be present in all possible combinations. Aim of future research will be to ascertain the role of such immune responses in the maintenance of the protection state, or their secondary nature as signals of a particular kind of infection.

Relevance of lymphoproliferative disorders and of anti-C1 inhibitor autoantibodies in acquired angio-oedema

We looked for autoantibodies to C1 inhibitor (C1-INH) and evaluated the relationship of their presence to the associated lymphoproliferative diseases and to the cleaved form of C1-INH in 13 patients with acquired C1-INH deficiency (acquired angio-oedema (AAE)). At the time of manifestation of angio-oedema symptoms or within a few years the following diseases were diagnosed: liver angioma (n = 1), M-components (n = 7, one of whom also had echinococcal liver cysts), breast cancer (n = 1), chronic lymphocytic leukaemia (CLL; n = 1); three patients had no associated disease. Anti-C1-INH autoantibodies, measured both as immunoglobulin binding to C1-INH immobilized onto microtitre plates (ELISA) and as plasma inhibitory activity of C1-INH function, were found in 12 patients. Binding of C1-INH to paraproteins, transferred to Immobilon after agarose gel electrophoresis, was detectable in five of seven M-components associated with AAE. Immunoblotting analysis of SDS-PAGE-separated plasma demonstrated that C1-INH circulated in the cleaved 96-kD form in the 12 patients with autoantibodies, but not in the one without. In conclusion, the large majority of our patients have autoantibodies to C1-INH. Circulating autoantibodies are necessary for the generation of cleaved C1-INH. The paraproteins associated with AAE are frequently autoantibodies to C1-INH and thus account for its consumption.

Insulin antibodies do not preclude optimization of metabolic control in women with IDDM during pregnancy

OBJECTIVE

To evaluate whether the presence of insulin antibodies (IAs) may preclude the optimization of metabolic control during pregnancy and affect outcome in women with IDDM.

RESEARCH DESIGN AND METHODS

IAs were measured by radiobinding assay in 44 women with IDDM referred to the Diabetes and Pregnancy Outpatients' Clinic during 46 pregnancies. Age, duration of IDDM, metabolic control (HbA1c, mean pre- and postprandial capillary blood glucose, frequency of hypo- or hyperglycemia), insulin requirement at 1st and 3rd trimester of pregnancy, BM1, and weight gain were recorded. Neonatal variables such as gestational age, weight, length, and the presence at birth of either hypoglycemia, hypocalcemia, or jaundice requiring phototherapy were also considered.

RESULTS

IAs correlated positively with insulin requirement (P < 0.05) and negatively with HbA1c at term (P < 0.01). Patients with IA levels > or = 40% insulin binding (8 of 46) had a higher insulin requirement and lower preprandial capillary blood glucose at the beginning of pregnancy but not at term (P < 0.005), whereas they had lower HbA1c at term than did patients with low IA levels (P < 0.01). IA levels decreased slightly at term (P = 0.007). IA levels > or = 40% were not associated with a higher rate of hypo- or hyperglycemic episodes or with diabetic complications or thyreopathy. No correlation was found between 1A levels and any of the neonatal variables considered.

CONCLUSIONS

The presence of IAs does not preclude optimization of metabolic control during pregnancy and is compatible with a favourable outcome.

Role of HLA class I in HIV type 1-induced syncytium formation

Neutralization of HIV-1 in vitro by anti-HLA class I antibodies suggests that class I molecules are involved in HIV-1 infection. HIV-infected cells can fuse with uninfected cells in a process that leads to the formation of multinucleated syncytia, involving an interaction between host and viral antigens expressed at the cell surfaces. We used a syncytium assay between the 8E5 cell line chronically infected with a pol-defective variant of LAV IIIb, and the CD4-positive cell line MOLT3, to study the role of HLA class I in HIV-1-induced cell fusion. By probing cells with a panel of anti-HLA monoclonal antibodies (MABs) we demonstrated that the fusion process is modulated specifically by C alleles of HLA class I expressed on uninfected cells but not by that on already infected cells. Addition of beta 2-microglobulin to the cocultures resulted in a dose-dependent enhancement in both the number and size of syncytia, whereas exogenous HLA-C-restricted peptides inhibited syncytium formation, implying that only certain conformational states of HLA class I are permissive for syncytium formation. Treatment of cocultures with HLA-Cw4-restricted peptides containing amino acid substitutions in the anchor residues showed that syncytium inhibition was dependent on conventional binding of the peptide inside the groove. The data indicate that HLA class I, in a conformation free of peptide but associated with beta 2-microglobulin, can directly influence virus-induced cell fusion.

HIV-1-specific immunity in persistently seronegative individuals at high risk for HIV infection

A growing number of reports indicates that certain groups of individuals who almost certainly have been exposed to human immunodeficiency virus (HIV), yet continue to exhibit no signs or symptoms of infection, often have subtle evidence of specific immunity. We studied such a high-risk (HR) cohort of persistently seronegative individuals with histories of long-term sexual exposure to an HIV-infected partner to look for evidence of both humoral and cellular immunity that might have been induced by exposure to the virus. Twenty-three heterosexual and four homosexual monogamous couples with discordant HIV status were included in the study. Twelve of the HR partners were studied for in vitro stimulation of peripheral blood mononuclear cells (PBMC) by HIV envelope-derived peptides. All 12 responded overwhelmingly to a peptide containing the fifth conserved region of gp120. By generating and cloning T cell lines specific for this peptide, we concluded that in these individuals the T cell response to the envelope is mainly focused on the carboxy-terminus region of gp120 and is characterized by an oligoclonal expansion of CD4+ T cells expressing the same TCR Eighteen HR partners and 37 HIV-1 seropositive subjects were tested for the presence of anti-CD4 antibodies (anti-CD4 Abs) using a recombinant CD4-based enzyme-linked immunosorbent assay (ELISA). Anti-CD4 Abs were detected in eight of the HR partners (six confirmed by Western blot) and in nine of the HIV-1 seropositive subjects (eight confirmed by Western blot). Results from binding competition assays with a panel of monoclonal anti-CD4 Abs suggested that the anti-CD4 Abs detected in the HR partners are directed toward epitopes that are induced by gp120 binding. Twenty-seven of the HR partners were tested for the presence of antibodies that cross-react with HLA class I and gp120 (anti-HLA Abs). Anti-HLA Abs were detected in 16 of the HR partner sera and in 4/94 sera from a control population of normal healthy blood donors. Taken together, the results suggest that in some individuals with a history of long-term exposure to HIV, specific immunity may develop in the absence of overt infection. The common trigger for these responses is gp120.

Distinctive features of the alpha 1-domain alpha helix of HLA-C heavy chains free of beta 2-microglobulin

Only a few monoclonal antibodies are available with a restricted specificity to HLA-C products. In the present report, we demonstrate that antibody L31, previously shown to react with beta 2m-less (free) class I MHC heavy chains, binds to an epitope (residues 66-68 of the alpha 1 domain alpha helix) present on all the HLA-C alleles corresponding to the accepted (CW1 through CW8) serologic specificities, and on a few HLA-B heavy chains sharing with HLA-C an aromatic residue at position 67. Extensive IEF blot testing of HLA homozygous, EBV-transformed B-lymphoid cells indicates that HLA-C molecules are present at significantly lower levels than HLA-B polypeptides not only at cell surface, as previously demonstrated, but also in total cellular extracts. Testing of metabolically labeled HLA-CW1, -CW5, and -CW6 transfectants and HLA homozygous lymphoid cells, particularly HLA-CW1-expressing cells, demonstrates that the L31 epitope is present on a subpopulation of naturally occurring HLA-C molecules distinct from that identified by antibody W6/32 to beta 2m-associated heavy chains. Pulse-chase experiments demonstrate that this epitope is transiently made available to antibody binding at early biosynthetic stages, but becomes hidden upon assembly with beta 2m. Thus, free HLA-C and other Y/F67+ heavy chains are characterized by distinctive antibody binding features in a region (residues 66-68) included in a previously identified HLA-C restricted motif, which has been suggested to be the primary cause of distinctive features of the antigen-binding groove, low affinity for endogenous peptide antigens and beta 2m, and preferential uptake of exogenous peptides, possibly of viral origin. We also show that HLA-CW1 heavy chains, both free and beta 2m associated, acquire sialilation. Free HLA-CW1 heavy chains are expressed at the cell surface even when unsialilated, albeit at low levels.

Evidence for the expression of HLAA-C class I mRNA and protein by human first trimester trophoblast

In this study, evidence is provided that normal human first trimester extravillous trophoblast expresses class I HLA-C molecules in addition to HLA-G. cDNA from highly purified trophoblast cells obtained by flow cytometric sorting was amplified by reverse-transcriptase PCR using HLA locus-specific primers. The identity of the product was confirmed by Southern blotting and hybridization by a second HLA-C-specific oligonucleotide. HLA-C mRNA was clearly demonstrated in all trophoblast samples as well as in JEG-3 and BeWo choriocarcinoma cells. JAR choriocarcinoma cells did not express HLA-C. The presence of HLA-C protein in extravillous trophoblast was investigated using a panel of Abs: L31 is specific for heavy chains of all HLA-C alleles; Q1/28 reacts with all HLA class I products except HLA-G; HC-10 has preferential reactivity with HLA-B and HLA-C heavy chains. We performed 35S metabolic and 125I surface labeling of normal first trimester trophoblast and found abundant HLA-C intracellularly together with low levels of expression of both the beta 2m-associated forms and free heavy chains on the surface. Flow cytometric analysis of normal trophoblast confirmed the expression of a class I HLA molecule distinct from HLA-G by positive reactivity with Q1/28. Immunohistologic studies of first trimester placenta and the implantation site clearly showed expression of HLA-C in all extravillous trophoblast populations. Our results demonstrate the presence of two HLA class I molecules, HLA-G and HLA-C, on the surface of extravillous trophoblast. These results have implications in understanding how maternal uterine lymphocytes, notably the abundant NK-like cells, might recognize the implanting placenta.

Evidence for the expression of HLAA-C class I mRNA and protein by human first trimester trophoblast

In this study, evidence is provided that normal human first trimester extravillous trophoblast expresses class I HLA-C molecules in addition to HLA-G. cDNA from highly purified trophoblast cells obtained by flow cytometric sorting was amplified by reverse-transcriptase PCR using HLA locus-specific primers. The identity of the product was confirmed by Southern blotting and hybridization by a second HLA-C-specific oligonucleotide. HLA-C mRNA was clearly demonstrated in all trophoblast samples as well as in JEG-3 and BeWo choriocarcinoma cells. JAR choriocarcinoma cells did not express HLA-C. The presence of HLA-C protein in extravillous trophoblast was investigated using a panel of Abs: L31 is specific for heavy chains of all HLA-C alleles; Q1/28 reacts with all HLA class I products except HLA-G; HC-10 has preferential reactivity with HLA-B and HLA-C heavy chains. We performed 35S metabolic and 125I surface labeling of normal first trimester trophoblast and found abundant HLA-C intracellularly together with low levels of expression of both the beta 2m-associated forms and free heavy chains on the surface. Flow cytometric analysis of normal trophoblast confirmed the expression of a class I HLA molecule distinct from HLA-G by positive reactivity with Q1/28. Immunohistologic studies of first trimester placenta and the implantation site clearly showed expression of HLA-C in all extravillous trophoblast populations. Our results demonstrate the presence of two HLA class I molecules, HLA-G and HLA-C, on the surface of extravillous trophoblast. These results have implications in understanding how maternal uterine lymphocytes, notably the abundant NK-like cells, might recognize the implanting placenta.

Autoantibodies to CD4 in HIV type 1-exposed seronegative individuals

The aim of this study was to investigate the presence and the fine specificity of anti-CD4 autoantibodies in seronegative subjects sexually exposed to HIV-1. Anti-CD4 autoantibodies were previously detected in a fraction of HIV-1-seropositive individuals. Whole sera, purified IgG fractions, and supernatants of EBV-transformed lymphoblastoid cell lines were analyzed by means of ELISA, Western blot, and by competition assays using monoclonal antibodies with known fine specificities. Anti-CD4 antibodies were found in 6 of 18 individuals exposed to HIV-1 infection and who have been persistently seronegative. These antibodies inhibited HIV-1-driven syncytium formation, did not interfere with the CD4-gp120 interaction, and competed for CD4 binding with two of three anti-CD4 monoclonals with known fine specificities. Moreover, autoantibodies with the same fine specificities were found in the supernatants of oligoclonal EBV-transformed B cell lines derived from these individuals. At variance, in the HIV-1-positive patients included in our study, the anti-CD4 antibody response was directed to a broader panel of epitopes, including those involved in CD4-gp120 interactions. In conclusion, anti-CD4 antibodies specific for defined epitopes of the CD4 molecule are generated in the course of an early immune response to HIV-1 antigens in the absence of other signs of infection, as they can be detected by conventional methods. These autoantibodies may play a protective role either alone or in association with other cellular and humoral factors.

Human immunodeficiency virus type 1 (HIV-1)-seronegative injection drug users at risk for HIV exposure have antibodies to HLA class I antigens and T cells specific for HIV envelope

The question of whether persistently seronegative persons at high risk for human immunodeficiency virus type 1 (HIV-1) infection exhibit HIV-1-specific T cell responses and antibodies to HIV-1 envelope epitopes shared with selected HLAs was assessed. These antibodies are not detectable by conventional serologic methods. Envelope-specific helper T (Env-Th) cell responses and antibodies specific for the HIV/HLA epitopes were studied in 21 HIV-1-negative injection drug users (IDUs). HIV/HLA antibodies were detected in 7 (33.3%) of 21 IDUs and 4 (4.3%) of 94 low-risk controls. Env-Th cell responses were detected in 16 (76.2%) of 21 IDUs and in 2 (3.1%) of 65 low-risk controls. All HIV/HLA antibody-positive IDUs also had Env-Th cell responses. These findings confirm the presence of HIV-1-specific immunity in conventionally seronegative individuals. Further characterization of these responses could provide the basis for new preventive strategies.

Expression of distinct conformations of free HLA-Cw4 heavy chains in transfected neuroblastoma cells

Epitope mapping of HLA-Cw4 indicates that the two monoclonal antibodies (mAbs) L31 and M38, specific for beta 2-microglobulin (beta2m)-free HLA-C heavy chains, react preferentially with the KYK motif, located in the binding groove (alpha1 domain). Transfection of HLA-Cw4 cDNA into a neuroblastoma cell line, which normally expresses negligible HLA class I, resulted in the constitutive surface expression of molecules displaying different reactivities with the two mAbs. This cellular system was used to determine whether L31 and M38 recognize distinct conformations of beta2m-free HLA-C proteins, and to investigate their mechanism of expression. Interferon-gamma greatly enhanced the expression of L31-reactive free chains, while abolishing that of M38-reactive molecules. The cytokine-induced expression of L31-reactive molecules was inhibited by anti-sense oligonucleotides specific for beta2m mRNA, while constitutive expression of L31-reactive molecules was only partially affected. Exogenous beta2m resulted in a reduction of constitutive L31 reactivity, and in a concomitant increase of M38 reactivity. These results indicate that: 1) at the cell surface, L31 and M38 react with two distinct conformations of HLA-Cw4 beta2m-free heavy chains, of which the L31-reactive conformation is the least folded; 2) the expression of both conformers can be modulated by endogenous or exogenous beta2m; and (3) L31-reactive molecules exposed at the cell surface are likely to derive from the dissociation of empty HLA-Cw4/beta2m complexes.