Environmental and dietary risk factors for nasopharyngeal carcinoma: a case-control study in Zangwu County, Guangxi, China

A case-control study was conducted on 88 incident cases of histologically confirmed undifferentiated nasopharyngeal carcinoma (NPC) in Zangwu County, China, and 176 age- sex- and neighbourhood-matched controls. The design of this study was defined after an anthropological survey on living habits in regions of high NPC incidence and the evidence of carcinogenic substances in some commonly consumed preserved foods. Subjects were interviewed regarding living conditions and diet in the year preceding the diagnosis of NPC and, with the help of their families, during childhood and weaning. After adjustment for a living conditions score to eliminate a confounding effect, an increased risk associated with consumption of salted fish during weaning and childhood was confirmed, especially for salted fish in rice porridge. The consumption of leafy vegetables was associated with a reduced risk for NPC, and consumption of melon seeds between 2 and 10 years of age with an increased risk. After multivariate analysis and adjustment according to the living conditions score, the consumption of salted fish in rice porridge before age 2 (OR = 3.8, P = 0.005), exposure to domestic woodfire (OR = 5.4, P = 0.01) and consumption of herbal tea (OR = 4.2, P = 0.02) were found to be independently related to the risk of NPC. The excess risk associated with the use of domestic wood fire increased if there were no windows in the house and with poor ventilation and cooking outside the house in a shack. As well as confirming the importance of the consumption of salted fish in childhood, this study has been the first to provide unequivocal evidence for two other factors implicated in increasing the risk of NPC in China, the adult consumption of traditional medicines (herbal tea) and exposure to domestic wood fumes.

[Comparative epidemiology of HTLV and HIV retroviruses]

There are interesting contrasts between the epidemiological characteristics of the two subfamilies of human retroviruses. The oncoretrovirus HTLV-I and II are endemic in Intertropical Africa, North and South Americas and in the South of Japan. The lentiretroviruses HIV 1 and 2 are epidemic in the five continents and are progressing rapidly. The sexual transmission is much more efficient for HIV than for HTLV. The mother-to-child transmission occurs mostly by breast feeding for HTLV, while it is perinatal for HIV. Concerning the cell-virus relationship, while the oncoretroviruses stimulate and eventually immortalize the T4 or T8 target cells, the lentiretroviruses are cytocidal for the T4 cells. The contrast extends to the latent period between primary infection and disease: much longer in a case of HTLV linked to either hematological (ATL) or neurological (TSP/HAM) disorders than HIV linked to AIDS. Finally, prevention by vaccine should be achievable much earlier for HTLVs than for HIVs.

The risk of tropical spastic paraparesis differs according to ethnic group among HTLV-I carriers in Inongo, Zaire

Following the finding in 1990 of six HTLV-I-positive cases of tropical spastic paraparesis (TSP/HAM) is a field survey carried out in the city of Inongo (Bandundu, Zaire), the prevalence of HTLV-I infection has been studied by detection of specific antibodies on a randomized sample of the general population. Among the 1,162 subjects surveyed, 36 (3.1%) were found to be HTLV-I seropositive, giving a seroprevalence of 3.2% (CI: 2.1, 4.3) estimated by direct standardization on age and sex distribution given by the census in the city. Among the five major ethnic groups, the Bolia showed the highest prevalence rate (6.5%) but with no detected TSP/HAM cases, while all six TSP/HAM cases were found among the Ntomba, who showed a prevalence rate of only 2.2%. This finding suggests that besides HTLV-I infection, critical environmental and/or genetic cofactors play a part in the development of TSP/HAM.

Urinary excretion of nitrosamino acids and nitrate by inhabitants of high- and low-risk areas for nasopharyngeal carcinoma in southern China

The hypothesis that endogenous synthesis of nitrosamines from dietary precursors is a risk factor for nasopharyngeal carcinoma (NPC) in China was tested by applying the nitrosoproline (NPRO) test to subjects living in high- and low-risk districts for NPC in Zangwu county, Guangxi region, in southern China. Samples of 12-h urine were collected from 77 subjects: (a) before any treatment; (b) after ingestion of proline; and (c) after ingestion of proline together with vitamin C. NPRO, other nitrosamino acids, and nitrate were measured as indices of exposure to preformed and endogenously formed nitrosamines or their precursors. The NPRO level after proline intake was significantly increased in subjects from the high-risk area (P = 0.012) and markedly reduced after ingestion of ascorbic acid (P = 0.007), but such an effect was not seen in subjects from the low-risk area. Levels of N-nitrosothiazolidine-4-carboxylic acid and the sum of nitrosamino acids in subjects in the high-risk area were significantly reduced by ascorbic acid (P < 0.01) but were not reduced in subjects from the low-risk area. The urinary nitrate level was about twice as high in subjects from the high-risk area. In subjects from high- and low-risk areas combined, NPRO levels in any of the three dose groups were highly correlated with nitrate levels (P = 0.0001). These results demonstrate a higher potential for endogenous nitrosation in subjects living in the high-risk area of NPC and suggest the occurrence of nitrosation inhibitors in the diet consumed in the low-risk area.(ABSTRACT TRUNCATED AT 250 WORDS)

An HTLV-I vaccine: why, how, for whom?

Endemic infection with the human T cell leukemia/lymphoma viruses I and II (HTLV-I/II) is now recognized to be worldwide, and is becoming epidemic among intravenous drug abusers (IVDAs) in the United States and Europe. The number of people around the world infected with HTLV-I can be estimated as between 10 and 20 million (Table 1). HTLV-I causes a rapidly progressing adult T cell leukemia/lymphoma (ATLL), and an incurable progressive neuromyelopathy named tropical spastic paraparesis/HTLV-I-associated myelopathy (TSP/HAM), as well as a number of less well-studied syndromes. There is evidence that coinfection with HTLV-I or -II accelerates progression to AIDS. The cumulative lifetime risk of developing ATLL or TSP/HAM is around 5%, which, in terms of the induction of serious diseases, places HTLV-I in the same category of viruses for which efficient vaccines are made and used. Furthermore, there are factors favoring the feasibility of a vaccine against HTLV-I, in that the virus displays relatively low antigenic variability, natural immunity occurs in humans, and experimental vaccination with the envelope (Env) antigen is successful in animal models. A vaccine against HTLV-I would be of significant public health value in the fields of oncology, neurology, and AIDS, and it would serve as a pathfinder for a vaccine against HIV.

Retrovirus infections in the south of Cameroon

The results of a national HIV seroprevalence survey carried out in 1986/87 showed a 1% HIV seroprevalence in the South of Cameroon, which is higher than in the other regions of the country. We here demonstrate the presence of HTLV-I infections in the South of Cameroon with possible clustering of infection in some villages. Some evidence suggestive of the presence of HTLV-II was obtained. Sera from patients with onchocerciasis did not react on HTLV testing. No HTLV associated haematological or neurological syndromes were observed during this survey. Regarding the human immunodeficiency viruses, the HIV-1 prevalence varied from 0 to 3% in the different populations studied. None of the subjects was HIV-2 positive.

In vivo genomic variability of human T-cell leukemia virus type I depends more upon geography than upon pathologies

To investigate the geography- and disease-associated genomic variation of human T-cell leukemia virus type I (HTLV-I), we studied ex vivo DNA from peripheral blood lymphocytes from nine patients by polymerase chain reaction and direct DNA sequencing. For each viral strain, 1,917 bp was sequenced, including parts of the long terminal repeat, the env gene, and the px II, px III, and px IV coding frames of the px region. The number of genomic variations observed in the U3 region of the long terminal repeat was higher than that seen in the env and px genes. Very few mutations were present in the px II and px III genes. In contrast, the px IV open reading frame exhibited numerous single point mutations. While no specific mutation could be linked to any pathology (adult T-cell leukemia/lymphoma or tropical spastic paraparesis/HTLV-I-associated myelopathy), variations among HTLV-I isolates from different geographic areas (Ivory Coast, Caribbean, and Japan) existed. The Ivory Coast HTLV-I appeared to represent a group by itself.

[Investigation of a transfusion contaminated by HTLV-I virus]

In front of the successive development of an HTLV-I seroconversion and a neuromyelopathy in a French Caucasian following a cardiac transplantation, an ascendant epidemiologic investigation must be manage to search a risk factor or a possible blood donor contaminated with HTLV-I virus. We selected an HTLV-I seropositive donor whose RBC participated to the patient's transfusion. This woman from Martinique island was a regular donor in our blood center and a second investigation was initiated to examine the patients transfused with the blood products issued from her previous donation. Nine were identified and controlled among them a patient who has received a RBC was found HTLV-I seropositive. An evaluation of the infectivity of the different blood products according to their type and specificity has been done. These data confirm that transmission of the HTLV-I is possible through donation of healthy seropositive donor and can induce the development of associated pathology, and prove the importance of screening blood donors for HTLV-I antibodies.

Volatile nitrosamine levels and genotoxicity of food samples from high-risk areas for nasopharyngeal carcinoma before and after nitrosation

Traditional life-style, especially food habits, infection by Epstein-Barr virus (EBV) and genetic factors, have been associated with an increased risk of nasopharyngeal carcinoma (NPC). N-Nitroso compounds and other carcinogens either present in food or formed endogenously, as well as food constituents that activate EBV, have been suspected as etiological factors in NPC pathogenesis. For their characterization preserved food items, frequently consumed in NPC endemic areas in Tunisia, South China and Greenland, were sampled and screened for the presence of mutagens and volatile nitrosamines before and after nitrosation. Aqueous extracts as well as 2 organic extracts of the samples were assayed for genotoxicity in 2 Salmonella typhimurium strains and the SOS chromotest. The same extracts had previously been analyzed for volatile nitrosamines and for EBV-activating substances in Raji cells. In our study, 13 out of 16 food samples showed a weak, directly-acting genotoxicity in the SOS chromotest in at least one of the extracts, but only one sample from Greenland was found to be weakly mutagenic in Salmonella TA 98. Chemical nitrosation for 9 out of 15 samples of aqueous food extracts increased the genotoxic effect in the SOS chromotest. Levels of volatile nitrosamines were also elevated for 12 out of 15 samples; highest levels of N-nitrosodimethylamine were found in hard salted and dried fish from China (1,200 micrograms/kg) and highest N-nitrosopyrrolidine levels in a Tunisian spice (3,840 micrograms/kg). In non-nitrosated aqueous food extracts, the level of volatile nitrosamines and genotoxic activities were not correlated with the EBV-inducing activity of the same samples. After chemical nitrosation, EBV-inducing activity was decreased or showed no change and was not correlated with increases in either the genotoxicity or the nitrosamine levels. Our results suggest that EBV-activating compounds belong to a different class of substances. However, there was an association between the changes in genotoxicity and nitrosamine levels due to nitrosation.

Chronic progressive myelopathy associated with HTLV-I: oligoclonal IgG and anti-HTLV-I IgG antibodies in cerebrospinal fluid and serum

Among 22 patients with human T-lymphotropic virus type I (HTLV-I)-associated chronic progressive myelopathy, agarose isoelectric focusing (AIF) revealed oligoclonal IgG bands in 21: in 3 in CSF only; in 11 in CSF and to some extent in serum; and in 7, identical patterns in CSF and serum. By immunoblot after AIF of CSF and serum, we observed bands of anti-HTLV-I IgG antibodies in 19 patients: in 5 in CSF only; in 9 in CSF and partly in serum; and in 5, identical in CSF and serum. Oligoclonal anti-HTLV-I IgG antibody bands could only partly be traced to oligoclonal IgG bands. If, prior to AIF, serum and CSF were absorbed with HTLV-I antigen, practically all oligoclonal HTLV-I-specific IgG antibody activity was abolished, while the oligoclonal pattern of total IgG was affected only to a minor extent. Alongside with HTLV-I-specific oligoclonal B cell response, HTLV-I myelopathy is regularly accompanied by production of oligoclonal IgG of unknown antibody specificities.

Characterization of HTLV-I isolates and T lymphoid cell lines derived from French West Indian patients with tropical spastic paraparesis

Lymphoid cell lines derived from the peripheral blood of French West Indian patients with HTLV-I sero-positive Tropical Spastic Paraparesis and HTLV-I isolates were characterized. While patients' peripheral blood lymphocytes did not express detectable HTLV-I antigens when uncultured, they did so after short-term culture. Established cell lines were of T-cell lineage: CD2+, CD3+, CD4+, CD7+, WT31+ with activated T-cell markers CD25+, DR+ and a clonal rearrangement of the beta and gamma genes of the T-cell receptor. HTLV-I antigens were detected in cell lines by indirect immunofluorescence, Western blot and radio-immunoprecipitation assays. After 4 months in culture, low levels of Mg2+ dependent reverse transcriptase activity were detected and electron microscopy revealed numerous type-C retroviral particles similar to HTLV-I virions. Western blot and radio-immunoprecipitation analysis of purified viruses revealed gp46, p24, p19 and Pr53gag proteins similar to those detected in HUT 102 and MT2 cell lines. Deep analysis of env-coded precursor of one TSP versus ATL isolates revealed minor differences in their molecular weights. Southern blot analysis using 32P HTLV-I env gene as a probe showed the presence of HTLV-I proviral fragments clonally integrated into the genome of the cell lines. Our data suggest that HTLV-I isolated from Tropical Spastic Paraparesis does not differ significantly from the leukemogenic prototypes. Does HTLV-I induce either acute lymphoproliferative diseases or chronic neuromyelopathies depending upon as yet unknown co-factors? This question remains to be determined.

Relationship between nasopharyngeal carcinoma and high antibody titers to Epstein-Barr virus-specific thymidine kinase

Epstein-Barr virus (EBV) has long been implicated in nasopharyngeal carcinoma (NPC). Recent studies in our and other laboratories have shown a correlation between the disease and high antibody titers to EBV-specific DNase. These data led us to also examine serial sera from healthy adults and patients with infectious mononucleosis or NPC, for their capacity to neutralize the EBV-specific thymidine kinase (TK) activity from chemically induced EBV-carrying human lymphoblastoid cells. Our results were the following: (i) sera were found that efficiently blocked the EBV-specific TK activity of induced-Raji TK- cell extracts, but not the host-cell TK activity from EBV-negative BJAB cells; (ii) a relationship appeared between high levels of EBV-specific TK-neutralizing activity in sera and NPC pathology, even though in this preliminary study the degrees of EBV-induced TK-blocking activity detected in sera were not significantly correlated with EBV-specific antibody titers; (iii) the EBV-induced TK-neutralizing activity was found in the main IgG fraction derived from NPC sera. These data must be compared with other known antibody responses to EBV for their clinical interest in NPC control.

Clinical experience of AIDS in relation to HIV-1 and HIV-2 infection in a rural hospital in Ivory Coast, West Africa

A dramatic rise in AIDS cases in a rural hospital 60 km west of Abidjan is described. Out of 212 adult cases diagnosed between January and November 1987 as having AIDS, using the World Health Organization (WHO) criteria defined in Bangui, 128 (60%) had antibodies to HIV-1 only, 61 (29%) had antibodies to both HIV-1 and HIV-2, 15 (7%) had antibodies to HIV-2 only and eight (4%) had no detectable antibodies to HIVs. These results, taken together with those of Ouattara et al. showing that both retroviruses have a similar seroprevalence in the general rural and urban populations, suggest that HIV-2 may have a lower physiopathological potential than HIV-1. This suggestion is supported by a 6-month follow-up of 60 AIDS cases, but only longer follow-up of cohorts of patients and healthy subjects with antibodies to one of the two viruses will allow definitive conclusions.

Glomerulonephritis in common marmosets infected with Plasmodium brasilianum and Epstein-Barr virus

Plasmodium brasilianum causes chronic quartan malaria in the common marmoset Callithrix jacchus, whereas Epstein-Barr virus (EBV) infection is followed by an infectious mononucleosis-like syndrome that resolves. We infected weanling marmosets with one or both of these pathogens. Timing of the infections influenced outcome. Six animals were simultaneously infected with both agents; four became seriously ill (with accompanying proteinuria and edema) and either died or were killed. Histopathology indicated that glomerulonephritis had developed. The two survivors had more-prolonged parasitemia than did animals infected with P. brasilianum alone, as did animals infected with EBV before P. brasilianum. Five of the six simultaneously infected animals had absent or low titers of antibody to Epstein-Barr viral capsid antigens when compared with the other EBV-infected animals. Our results suggest that combined infection may be part of the etiology of quartan malarial nephropathy.

Epstein-Barr virus activation in Raji cells by extracts of preserved food from high risk areas for nasopharyngeal carcinoma

Epstein-Barr virus (EBV) activation of latent infection and traditional life styles, especially food habits, have been strongly associated with an increased risk of nasopharyngeal carcinoma (NPC) in humans. On the basis of anthropological studies in Tunisia, southern China and Greenland, extracts of representative preserved food items consumed frequently by the high-risk populations for NPC were assayed for the presence of EBV activators in Raji cells. A strong EBV activation activity was observed in aqueous extracts of some Cantonese salted dried fish from China, harissa (a spice mixture) and to a lesser extent qaddid (dry mutton preserved in olive oil) from Tunisia. These new data may support epidemiological evidence for the importance of Cantonese salted and dried fish and other food items in the etiology of NPC.

HTLV-I antibody and cell-mediated immunity status in sickle cell anemia

Patients with sickle cell anemia (SCA) had an abnormal susceptibility to infections. In Martinique (French West Indies), a human T-cell leukemia/lymphoma virus type I (HTLV-I) endemic area, we found that 17 (10%) of 173 SCA patients had antibodies to HTLV-I. The possible relationship between HTLV-I seropositivity and altered immunity was studied in 13 SCA patients with HTLV-I antibodies compared with 13 matched SCA patients without HTLV-I antibodies. The immunological results, as evaluated by the T-cell subsets analysis, the lymphocyte proliferation responses analyzed after activation with concanavalin A, phytohemagglutinin, or pokeweed mitogen, and the natural killer activity were not statistically different in these two groups of patients (SCA HTLV-I positive vs SCA HTLV-I negative). These data suggest that HTLV-I infection did not result in a major alteration of cellular immunity in this population.