A putative gene located at the MHC class I region around the D6S105 marker contributes to the setting of CD8+ T-lymphocyte numbers in humans

Significant associations between human leucocyte antigen (HLA)-A and -B alleles and CD8+ T-lymphocyte numbers have been reported in the literature in both healthy populations and in HFE-haemochromatosis patients. In order to address whether HLA alleles themselves or alleles at linked genes are responsible for these associations, several genetic markers at the MHC class I region were typed on a population of 147 apparently healthy unrelated subjects phenotypically characterized for their CD8+ and CD4+ T-lymphocyte numbers. By using a machine learning approach, a set of rules was generated that predict the number of CD8+ T-lymphocyte numbers on the basis of the information of the D6S105 microsatellite alleles only. We demonstrate that the previously reported associations with HLA-A and -B alleles are due to the presence of common long (up to 4 megabases long) haplotypes that increased in frequency recently due to positive selection and that encompass a region where a putative gene contributing to the setting of CD8+ T lymphocytes is located, in the neighbourhood of microsatellite locus D6S105, in the 6p21.3 region.

Involvement of the major histocompatibility complex region in the genetic regulation of circulating CD8 T-cell numbers in humans

Variability in T-lymphocyte numbers is partially explained by a genetic regulation. From studies in animal models, it is known that the Major Histocompatibility Complex (MHC) is involved in this regulation. In humans, this has not been shown yet. The objective of the present study was to test the hypothesis that genes in the MHC region influence the regulation of T-lymphocyte numbers. Two approaches were used. Association studies between T-cell counts (CD4(+) and CD8(+)) or total lymphocyte counts and HLA class I alleles (A and B) or mutations in the HFE (C282Y and H63D), the hemochromatosis gene, in an unrelated population (n = 264). A second approach was a sibpair correlation analysis of the same T-cell counts in relation to HLA-HFE haplotypes in subjects belonging to 48 hemochromatosis families (n = 456 sibpairs). In the normal population, results showed a strong statistically significant association of the HLA-A*01 with high numbers of CD8(+) T cells and a less powerful association with the HLA-A*24 with low numbers of CD8(+) T cells. Sibpair correlations revealed the most significant correlation for CD8(+) T-cell numbers for sibpairs with HLA-HFE-identical haplotypes. This was not observed for CD4(+) T cells. These results show that the MHC region is involved in the genetic regulation of CD8(+) T-cell numbers in humans. Identification of genes responsible for this control may have important biological and clinical implications.

[Control of malaria transmission in a gold-mining area in Amapá State, Brazil, with participation by private enterprise]

This paper reports on the epidemiological characterization of malaria following implementation of a program to control the endemic in a gold-mining area in northern Amapá State. The study focuses on total malaria cases in Amapá and the impact of the disease on the population, as represented by the Mineração Novo Astro S/A company and its employees as well as the community of Vila de Lourenço in the municipality of Calçoene, and adjacent gold miners. The effect of control measures in the program area is indicated by a significant reduction in malaria incidence and malaria-related morbidity and mortality. The importance of participation by private enterprise is emphasized, particularly in large projects for the control of endemic diseases (notably malaria) in the Amazon Region.

T-cell receptor repertoire in hereditary hemochromatosis: a study of 32 hemochromatosis patients and 274 healthy subjects

Low CD8(+) T lymphocyte numbers have contributed to deciphering the genotype/phenotype discrepancies found in hereditary hemochromatosis (HH) patients genotyped for the Hfe mutations, C282Y and H63D. In this study, we extend the analysis of T lymphocytes in HH to the T cell receptor (TcR) repertoire. Thirty-two HH patients (C282Y homozygous) and 274 Hfe genotyped healthy subjects were studied. The following TcR chains were analyzed: Valpha2.3, Vbeta5.1, Vbeta5.2, Vbeta5.3, Vbeta6.7, Vbeta8, and Vbeta12 among the CD4(+) and CD8(+) populations. Lymphopenias and absence of expansions of the Vbeta5.2 and Vbeta12 chains in the CD8(+) pool were seen in controls heterozygous for the C282Y mutation. Expansions in the control group were seen within the CD8(+) pool and were rare/absent within the CD4(+) pool. TcR expansions were found more frequent in patients with iron overload related pathology than in patients without pathology. 9/16 of the patients with pathology have at least one expansion among the CD8(+) pool a number significantly higher compared with patients without pathology (1/16). These findings suggest that Hfe has an effect in the shaping of T-cell populations either directly, as indicated by the lymphopenia seen in the two chains in C282Y heterozygous without iron overload, or indirectly by contributing to iron overload pathology.

Malaria vectors in the municipality of Serra do Navio, State of Amapá, Amazon Region, Brazil

We conducted a survey to determine the vectors of malaria in six localities of Serra do Navio municipality, State of Amapá, from 1990 to 1991. Malaria infection rates of 29.3%, 6.2% and 20.4% were detected by human blood smears in Colônia Agua Branca, Porto Terezinha and Arrependido, respectively. There was no malaria infection detected in Serra do Navio. Fifteen species were identified among 3,053 anopheline mosquitoes collected by human bait and 64.4% were identified as Anopheles albitarsis s.l., 16.7% An. braziliensis, 9.5% An. nuneztovari and 5.8% An. triannulatus. An. darlingi, the main vector of malaria in the Amazon region of Brazil, was scare. Using enzyme-linked immunosorbent assay (ELISA), a total positive rate of 0.8% (23/2876) was found for six species: fifteen An. albitarsis s.l., four An. nuneztovari, and one of each: An. braziliensis, An. triannulatus, An. oswaldoi and An. rangeli. Nine of 23 positive mosquitoes were infected with Plasmodium malariae, eight with P. vivax VK210, three with P. vivax VK247 and three with P. falciparum. Since An. albitarsis s.l. was collected feeding on humans, was present in the highest density and was positive by ELISA for malaria sporozoites, it probably plays an important role in malaria transmission in this area.

Expansions of CD8+CD28- and CD8+TcRVbeta5.2+ T cells in peripheral blood of heavy alcohol drinkers

BACKGROUND

Despite heavy alcohol consumption, only a low percentage of heavy drinkers develop liver disease. Imbalances in T-cell subsets and iron metabolism parameters are common findings in heavy drinkers, yet the possible role played by discrete T-lymphocyte subsets under heavy alcohol consumption remains unclear.

METHODS

To gain new insights into the possible role played by T lymphocytes during alcohol consumption, characterization of CD28 expression and TcR repertoire in peripheral blood CD4+ and CD8+ T cells by two and three-color flow cytometry was performed. A group of heavy alcohol drinkers (AHD, n = 71) and a group of age-matched controls (n = 81), both HLA-phenotyped and HFE-genotyped, constituted the groups under study.

RESULTS

Marked expansions of CD28- T cells within the CD8+ but not the CD4+ T-cell pool were observed in AHD compared with controls. These CD8+CD28- expansions were paralleled by expansions of CD8+ T cells bearing specific TcR Valpha/beta chains, namely VP5.2. Moreover, AHD, but not controls, carrying the H63D mutation in the HFE gene showed significantly higher percentages of CD28- T cells within the CD8+ T-cell pool than AHD carrying the normal HFE gene. Finally, high numbers of CD8+CD28- T cells in AHD were associated with lower levels of the liver-related enzymes ALT and GGT.

CONCLUSIONS

This study showed that under active ethanol consumption, expansions of discrete CD8+ T-cell subsets occur within the CD8+ T-cell pool, that molecules of the MHC-class I locus seem to influence the extent of the expansions, and that high numbers of CD8+CD28- T cells are associated with low levels of liver enzymes in AHD.

T cell numbers relate to bone involvement in Gaucher disease

The major elements of bone pathology in Gaucher disease are a failure of osteoclast and osteoblast function, resulting in osteopenia and also osteonecrosis. T lymphocytes have recently been found to be involved in the regulation of osteoblast/osteoclast activity in vitro. In the present report the peripheral blood T major lymphocyte subsets were investigated in a group of genotyped type 1 Gaucher disease patients. A total of 31 patients were studied: 21 non-splenectomized (5 N370S homozygotes) and 10 splenectomized (of whom 1 was a N370S homozygote). The results show that non-splenectomized patients present a decrease in absolute numbers of peripheral blood T lymphocytes, specially the CD4+ T subset. However, when patients were analyzed with respect to the presence of bone disease, the number of CD8+ T lymphocytes was found to be statistically significantly lower in patients presenting bone involvement. Furthermore, lower numbers of CD8+ T lymphocytes were significantly correlated with higher levels of plasma tartrate resistant acid phosphatase (TRAP) activity, a putative marker of osteoclast cell activity. These in vivo findings are in agreement with the results reached in vitro by others. They provide an additional marker of disease severity in Gaucher disease. In the group of genotyped Gaucher disease patients, the majority of the N370S homozygous patients presented a clinically milder phenotype, including the absence of bone involvement, confirming earlier reports predicting that a number of these patients may remain undiagnosed. Collectively the homozygosity for the N370S mutation and normal T cell numbers may provide additional markers for the clinical heterogeneity of Gaucher disease.

Reducing AIDS risk among port workers in Santos, Brazil

OBJECTIVES

This study examined the impact of worksite-based AIDS prevention program among port workers in Santos, Brazil, on sexual risk behavior for HIV infection.

METHODS

Male port workers (n = 226) were followed in a 3-wave prospective cohort study. A multifaceted intervention costing US $90,000 for 20,000 workers was conducted between waves 2 and 3.

RESULTS

Heterosexual risk behavior showed no decline between waves 1 and 2 (before the intervention) but decreased substantially between waves 2 and 3 (after the intervention). This decrease resulted from both a decrease in nonprimary partners and an increase in condom use.

CONCLUSIONS

This worksite-based AIDS program produced marked behavior change at modest cost.

Truck drivers in Brazil: prevalence of HIV and other sexually transmitted diseases, risk behavior and potential for spread of infection

OBJECTIVES

To determine the prevalence of HIV and syphilis and related risk behavior in a sample of truck drivers in Santos, Brazil.

SUBJECTS AND METHODS

A cross-sectional study was performed of 300 male truck drivers recruited in the port of Santos, Brazil, including a face-to-face interview and blood sampling for HIV and syphilis serology.

RESULTS

Of 300 subjects, 4 (1.3%) were positive for HIV, 25 (8.3%) for syphilis by the Venereal Disease Research Laboratory (VDRL) test and 38 (13%) were positive for syphilis by the fluorescent treponemal antibody (absorbed) test (FTA-Abs). Seventy-one per cent had been employed as truck drivers for more than 10 years and 93% lived outside of Santos. Most participants were married (72%); 40% reported having more than one sex partner; 21% reported sex with commercial sex workers; 14% reported sex with girls that they met on the road; 16% had sex with other men's wives; and 3.3% reported sex with men during the past year. The use of rebite, an oral stimulant, was reported by 43% and was associated with being FTA-Abs-positive (P = 0.04). Being HIV-positive was associated with having sex with friends (P = 0.04), partners usually considered 'safe' by truck drivers. Being syphilis-positive (VDRL) was significantly associated with sex with partners also considered as 'safe', namely primary sex partners, steady partners and other men's wives.

DISCUSSION

This is the first study to determine HIV and syphilis seroprevalence among truck drivers in South America. Findings confirm that this group has a high potential risk for HIV infection and other sexually transmitted diseases, and thus currently presents an opportunity for prevention.

Relative impact of HLA phenotype and CD4-CD8 ratios on the clinical expression of hemochromatosis

Hemochromatosis is a hereditary iron-overload disease linked to HLA. The clinical expression of hemochromatosis is influenced by sex and age. However, other factors must account for the notorious heterogeneity of expression of the disease independent of sex, age, and HLA phenotype. The present study attempts to clarify some of these additional factors based on exhaustive statistical analysis of data collected from 43 selected patients with hemochromatosis. The statistical analysis focused on three groups of variables: the first group included variables reflecting the clinical expression of the disease; the second group represented the biochemical and hematological values at the time of diagnosis; and the third group consisted of the independent variables sex, age, HLA phenotype, and T-cell subset profile, i.e., the percentages and total numbers of CD4+ and CD8+ cells and the CD4-CD8 ratios. The results show that the relative expansion of the two main T-cell subsets, in the context of the HLA phenotype, correlates significantly with the clinical expression of hemochromatosis and the severity of iron overload. The present findings substantiate further the postulate that T cells have a role in the regulation of iron metabolism.

Iron overload in beta 2-microglobulin-deficient mice

The present paper describes the results of a comparative histological and quantitative analysis of iron distribution in tissues of beta 2m-/- and beta 2m+/- mice of different ages. Progressive hepatic iron overload, indistinguishable from that observed in human hemochromatosis, was found only in mice homozygous for the mutated beta 2m gene. Total iron measurements done by flame atomic absorption showed statistically significant differences between liver samples from 5 beta 2m+/- heterozygotes (468 +/- 174 micrograms/g of dry weight) and 9 mice homozygous for the mutated beta 2m gene with average total hepatic iron levels of 1583 +/- 423 micrograms/g of dry weight.