Regional variation in prevalence of antibody against human T-lymphotropic virus types I and III in Kenya, East Africa

Refining the global spatial limits of dengue virus transmission by evidence-based consensus

BACKGROUND

Dengue is a growing problem both in its geographical spread and in its intensity, and yet current global distribution remains highly uncertain. Challenges in diagnosis and diagnostic methods as well as highly variable national health systems mean no single data source can reliably estimate the distribution of this disease. As such, there is a lack of agreement on national dengue status among international health organisations. Here we bring together all available information on dengue occurrence using a novel approach to produce an evidence consensus map of the disease range that highlights nations with an uncertain dengue status.

METHODS/PRINCIPAL FINDINGS

A baseline methodology was used to assess a range of evidence for each country. In regions where dengue status was uncertain, additional evidence types were included to either clarify dengue status or confirm that it is unknown at this time. An algorithm was developed that assesses evidence quality and consistency, giving each country an evidence consensus score. Using this approach, we were able to generate a contemporary global map of national-level dengue status that assigns a relative measure of certainty and identifies gaps in the available evidence.

CONCLUSION

The map produced here provides a list of 128 countries for which there is good evidence of dengue occurrence, including 36 countries that have previously been classified as dengue-free by the World Health Organization and/or the US Centers for Disease Control. It also identifies disease surveillance needs, which we list in full. The disease extents and limits determined here using evidence consensus, marks the beginning of a five-year study to advance the mapping of dengue virus transmission and disease risk. Completion of this first step has allowed us to produce a preliminary estimate of population at risk with an upper bound of 3.97 billion people. This figure will be refined in future work.

High prevalence of HTLV-I infection in Mashhad, Northeast Iran: a population-based seroepidemiology survey

BACKGROUND

Mashhad, in the northeast of Iran has been suggested as an endemic area for human T cell lymphotropic virus type I (HTLV-I) infection since 1996.

OBJECTIVES

We performed a community-based seroepidemiology study to examine the prevalence and risk factors for HTLV-I infection in the city of Mashhad.

STUDY DESIGN

Between May and September 2009, overall 1678 subjects from all the 12 geographical area of Mashhad were selected randomly by multistage cluster sampling for HTLV antibody. The study population included 763 males and 915 females, with the mean age of 29.1 ± 18.5 years. 1654 serum samples were assessed for HTLV antibody using ELISA and reactive samples were confirmed by Western blot and PCR.

RESULTS

The overall prevalence of HTLV-I infection in whole population was 2.12% (95% CI, 1.48-2.93) with no significant difference between males and females (p = 0.093) and the prevalence of HTLV-II seropositivity was 0.12% (95% CI, 0.02-0.44). The HTLV-I Infection was associated with age (p<0.001), marital status (p<0.001), education (p = 0.047), and history of blood transfusion (p = 0.009), surgery (p<0.001), traditional cupping (p = 0.002), and hospitalization (p = 0.004). In logistic regression analysis, age was the only variable that had a significant relation with the infection (p = 0.006, OR = 4.33).

CONCLUSIONS

Our results demonstrated that Mashhad still remains an endemic area for HTLV-I infection despite routine blood screening. Thus, further strategies are needed for prevention of the virus transmission in whole population.

Human T-lymphocyte transformation with human T-cell lymphotropic virus type 2

Human T-cell lymphotrophic virus type 2 (HTLV-2), a common infection of intravenous drug users and subpopulations of Native Americans, is uncommon in the general population. In contrast with the closely related HTLV-1, which is associated with both leukemia and neurologic disorders, HTLV-2 lacks a strong etiologic association with disease. HTLV-2 does shares many properties with HTLV-1, including in vitro lymphocyte transformation capability. To better assess the ability of HTLV-2 to transform lymphocytes, a limiting dilution assay was used to generate clonal, transformed lymphocyte lines. As with HTLV-1, the transformation efficiency of HTLV-2 producer cells was proportionately related to the number of lethally irradiated input cells and was comparable to HTLV-1-mediated transformation efficiency. HTLV-2-infected cells were reproducibly isolated and had markedly increased growth potential compared to uninfected cells; HTLV-2 transformants required the continued presence of exogenous interleukin 2 for growth for several months and were maintained for over 2 years in culture. All HTLV-2-transformed populations were CD2 and/or CD3 positive and B1 negative and were either CD4+ or CD8+ populations or a mixture of CD4+ and CD8+ lymphocytes. Clonality of the HTLV-2 transformants was confirmed by Southern blot analysis of T-cell receptor beta chain rearrangement. Southern blot analysis revealed a range of integrated full-length genomes from one to multiple. In situ hybridization analysis of HTLV-2 integration revealed no obvious chromosomal integration pattern.

No relationship between HTLV-1 infection and filariasis--Serological study on patients with filariasis in Recife, Brazil

The seroprevalence of antibodies against human T-cell leukemia virus was determined by ELISA in 68 patients with filarial infestation living in an endemic area. The total seropositivity was 2.9% and the HTLV-1-positive cases were detected in 2 microfilaremic patients 12 and 40 years old. This value is very close to that obtained for healthy individuals in the same region and age groups. This result suggests that there is no relationship between filariasis and HTLV-1 infection as previously proposed.

Human T cell leukemia virus type 1 (HTLV-1) antibodies in healthy populations and renal transplanted patients in the north-east of Brazil

The seroprevalence of human T cell leukemia virus type 1 (HTLV-1) infection was investigated in Brazilians (570): native inhabitants (298) and descendants from Japanese (272) living in Recife and its neighborhoods--North-east of Brazil. Furthermore, polytransfused renal transplanted patients (54) were also examined for the serological status to this virus. The seropositivity to HTLV-1, screened by enzyme-linked immunosorbent assay (ELISA), was low: 1.34% for the local population and 0.73% for the descendants from Japanese. However, the seropositivity for the renal transplanted patients was found to be 11.1%. This higher value suggests that this retrovirus infection seems to be of importance in this clinical condition.

Development of HTLV-I-associated myelopathy after blood transfusion in a patient with aplastic anemia and a recipient of a renal transplant

We report the development of rapid progressive HTLV-I-associated myelopathy (HAM) after blood transfusion in two immunosuppressed patients, one of whom had aplastic anemia and the other was the recipient of a renal transplant receiving immunosuppressive chemotherapy. Spastic paraparesis developed 11 or 16 months after transfusion and rapidly progressed to a wheelchair-bound state. The present 2 cases suggest that the coexistent immunosuppression may play an important role in the rapid development of HAM in transfusion-acquired cases.

Human retroviruses

It was only in 1980 that the first human retrovirus, HTLV-1, was isolated. Since then, HTLV-2, HIV-1 and HIV-2 have been identified. All four viruses are transmitted with varying efficiency sexually, vertically from mother to infant, and through blood by transfusion or contamination. HTLV-1 is endemic in populations in south-west Japan, Taiwan, sub-Saharan Africa, the Caribbean, southern USA, central and south America, Australia, Papua New Guinea, Solomon Islands and western Asia. There is now epidemic spread amongst IVDUs in north and south America and southern Europe. HTLV-1 is the aetiological agent of adult T-cell leukaemia/lymphoma (ATL) and tropical spastic paraparesis/HTLV-1 associated myelopathy (TSP/HAM). Other associations which may be causative are with polymyositis, infective dermatitis, gastrointestinal malignant lymphoma and chronic lymphatic leukaemia. ATL appears to be due to malignant transformation of HTLV-1 infected cells, and TSP/HAM to chronic activation of these cells. The epidemiology of HTLV-2 is being separated only recently from HTLV-1 through the application of PCR. It has a low level of endemicity in populations of central Africa, and central and south America. It is being spread epidemically amongst IVDUs in north America and southern Europe. Its association with any pathology in man remains uncertain. HIV-1 is epidemic and spreading rapidly throughout the world. In areas where homosexual contact was the predominant mode of transmission, heterosexual spread is becoming increasingly important. The areas where heterosexual contact is the predominant mode of transmission include the worst affected populations in the world, for example sub-Saharan Africa and some of the Caribbean. There have been recent and explosive increases of HIV-1 seroprevalence in IVDUs and female prostitutes in Asia, especially Thailand and India. Of the diverse pathology following infection, only the haematological consequences are reviewed in detail: these include anaemia, leucopenia, thrombocytopenia, disorders of coagulation and lymphomas. HIV-2, compared to HIV-1, is less infectious and causes less immunosuppression with more slowly progressive disease. It is prevalent in west Africa, but is spreading, albeit slowly, far beyond.

HTLV-1 envelope sequences from Brazil, the Caribbean, and Romania: clustering of sequences according to geographic origin and variability in an antibody epitope

We sequenced the envelope genes of Human T-cell leukemia type I viruses (HTLV-I) derived from five Brazilian, two Caribbean, and one Romanian case of adult T-cell leukemia after amplification of the complete env gene by PCR. A comparison with previously reported HTLV-I sequences revealed that, although highly homologous, no two env sequences were identical. All envelope sequences differed from each other by 0.3-2.1% nucleotide differences. The five Brazilian sequences clustered together and were about as different from each other (0.5-0.75% nucleotide difference) as were three previously reported Japanese sequences (0.7-0.95%). In contrast, sequences of Caribbean origin were less homogeneous (0.5-1.9% nucleotide differences within this group). The Romanian sequence was not significantly more divergent than any of the others and was closest to our two Caribbean sequences. We observed two changes in a region (aa 176-209) which has previously been shown to contain a linear antibody epitope recognized by most human sera from seropositive individuals. One of these changes affects the binding of monoclonal antibodies to this epitope demonstrating the variability of an antibody epitope in the HTLV-I envelope.

Relative prevalence and risk factors of HTLV-I and HTLV-II infection in US blood donors

The clinical significance of human T-cell lymphotropic virus type II (HTLV-II) infection, unlike that of HTLV-I, is unknown, and the major known association of HTLV-II seropositivity is with intravenous drug abuse. Screening of blood donors for HTLV-I, now routine in North America, does not distinguish this retrovirus from HTLV-II. To find out more about the seroepidemiology of and risk factors for HTLV I and II, blood from 480,000 volunteer donors in five geographically separate US urban centres was tested for antibodies to HTLV-I/II and HIV-1. Confirmed HTLV-I/II seropositive donors were then followed up by DNA amplification to distinguish type I from type II and by interviews focusing on possible risk factors. HTLV seroprevalence was 3.3 times greater than that for HIV-1 (0.043% vs 0.013%). DNA amplification on 65 of the 207 HTLV-I/II seropositive donors revealed that 34 (52%) had HTLV-II infection and 28 (43% had HTLV-I; 3 samples were uninformative. Interviews of 49 donors showed that whereas HTLV-I was principally associated with donor origin from endemic regions, the major risk factor for HTLV-II infection was intravenous drug use. The surprisingly high rate of HTLV-II infection in US blood donors raises important public health and donor counselling issues since HTLV-I infection is associated with adult T-cell leukaemia and a neurological disorder while the pathogenicity of HTLV-II is as yet unclear.

Seroepidemiology of human T-cell lymphotropic virus type I/II in Benin (West Africa)

In 1988-1989, a national survey was conducted in Benin to determine the distribution of HTLV-I infection in a representative sample of adult individuals. This study comprised 2625 healthy subjects recruited in the six provinces of Benin and 1300 blood donors from Cotonou and from the other five provinces. Sera were screened for HTLV-I antibody by both immunofluorescence (IF) and enzyme immunoassay (EIA). Sera positive or doubtful by at least one technique were further analyzed by Western blot and radioimmunoprecipitation assay (RIPA) when indeterminate. Samples were considered as positive if they reacted with two gene products. No blood donor was positive. Over the 2625 subjects, 39 (1.5%) were positive. We observed a statistical difference between male and female (1%, 2%, p less than 0.05). A difference was also observed according to the areas studied: the HTLV-I antibody rate increased from coastal (0.3%) to northern (5.4%) provinces. HTLV-I seroprevalence increased significantly with age. This survey shows that HTLV-I infection exists in Benin but varies according to regions.

Infective dermatitis of Jamaican children: a marker for HTLV-I infection

In Jamaican children infective dermatitis is a chronic eczema associated with refractory nonvirulent Staphylococcus aureus or beta-haemolytic streptococcus infection of the skin and nasal vestibule. 14 children between the ages of 2 and 17 years with typical infective dermatitis, attending the dermatology clinic at the University Hospital of the West Indies in Jamaica, were tested for antibody to human T-lymphotropic virus type 1 (HTLV-1). All were seropositive, whereas 11 children of similar age with atopic eczema were all negative. In 2 of 2 cases of infective dermatitis, the biological mother was HTLV-1 seropositive. None of the 14 patients showed signs of adult T-cell leukaemia/lymphoma, though experience with previous cases of infective dermatitis indicates the possibility of such progression.

Immunological crossreactivity between the human immunodeficiency virus type 1 virion infectivity factor and a 170-kD surface antigen of Schistosoma mansoni

A monoclonal antibody (mAb) directed against a synthetic peptide derived from the sequence of the human immunodeficiency virus type 1 (HIV-1) regulatory protein virion infectivity factor (vif) labeled the surface of Schistosoma mansoni schistosomula by indirect immunofluorescence. Western blotting showed that two S. mansoni proteins of 170 and 65 kD were recognized by the mAb. Sera from 20% of S. mansoni-infected HIV-seronegative individuals tested recognized the PS4 peptide in an ELISA as did sera from S. mansoni-infected rats. Sera from individuals seropositive for HIV-1, but without schistosomiasis, that reacted with the vif peptide also recognized a 170-kD S. mansoni protein. This crossreactive S. mansoni antigen appears to be a target of immunity in vivo since passive transfer of the mAb VIF-CD3 to naive rats had a protective effect against a challenge infection with S. mansoni cercariae.

A cluster of HTLV-1 associated tropical spastic paraparesis in Equateur (Zaire): ethnic and familial distribution

In Lisala, Equateur province, Zaire, 25 patients from 21 pedigrees were identified with human T-lymphotropic virus type 1 (HTLV-1) associated tropical spastic paraparesis (TSP). In the 10 (48%) pedigrees with additional genuine TSP cases established mainly by history, seven of 10 patients' mothers, no fathers or spouses, one of 59 surviving offspring, five of 105 siblings, and six other close blood relatives had TSP. A child may develop TSP before its mother. Three familial cases were in paternal relatives only. In total, 39 cases (11 men, 28 women) were identified in this population of about 50,000. Half were in the Mundunga minority of less than or equal to 10% (p less than 0.001). The data suggest maternal transmission of HTLV-1 and enhanced TSP susceptibility in those infected due to familial, probably genetic factors.

Patterns of migration indicate sexual transmission of HTLV-I infection in non-pregnant women in Papua New Guinea

The prevalence of infection with human T-cell leukaemia virus (HTLV-I) was studied in Madang Province on the north coast of Papua New Guinea. Serum specimens collected from non-pregnant women in 17 villages were tested for anti-HTLV-I by gelatin particle agglutination screening and confirmed by immunofluorescence and Western blotting. Overall, 13.9% of subjects were antibody-positive, with the prevalence of antibodies varying from less than 10% to 30% in villages situated less than 10 km apart. Two groups of migrant women were identified, and in both a parity-related increase in antibody prevalence which occurred only after marriage suggested that the predominant mode of transmission in migrant women was sexual. There was no parity-associated increase in anti-HTLV-I in indigenous women, and in contrast to migrant women, nulliparous indigenous women had a high prevalence of antibody (16.8% vs. 0%; p = 0.005). Vertical transmission cannot be excluded in indigenous women. No correlation was detected between the prevalence of anti-HTLV-I and a variety of indices of malarial infection.

High rate of HTLV-II infection in seropositive i.v. drug abusers in New Orleans

Confirmed infection with HTLV-II (human T cell leukemia virus type II) has been described only in rare cases. The major limitation to serological diagnosis of HTLV-II has been the difficulty of distinguishing HTLV-II from HTLV-I (human T cell leukemia virus type I) infection, because of substantial cross-reactivity between the viruses. A sensitive modification of the polymerase chain reaction method was used to provide unambiguous molecular evidence that a significant proportion of intravenous drug abusers are infected with HTLV, and the majority of these individuals are infected with HTLV-II rather than HTLV-I. Of 23 individuals confirmed by polymerase chain reaction analysis to be infected with HTLV, 21 were identified to be infected with HTLV-II, and 2 were infected with HTLV-I. Molecular identification of an HTLV-II--infected population provides an opportunity to investigate the pathogenicity of HTLV-II in humans.

[Retrospective seroepidemiology of HIV-1]

Serum samples collected between 1974 and 1980 out of populations from the States of Pará and Goiás, Brazil, were tested for antibodies against HIV-1 through ELISA, immunofluorescence, and immunoblot. The aim was to describe the possibility of the virus presence in this country before the present epidemic. Four samples from an epidemiologically closed community, the Xicrin indians, gave positive reaction in the ELISA test, but were negative in the confirmatory tests. The negative results suggest the absence of HIV-1, in the groups tested, prior to the 1980's.

AIDS as a moral metaphor: an analysis of the politics of the 'third epidemic'

This paper examines some of the moral meanings of aids, and argues that in addition to understanding aids in the context of the sexual counter-revolution, it also needs to be placed in the wider context of global economic and ideological crises, and the ‘New Right's’ struggle for hegemony. Denis Altman refers to aids as ‘the most political of diseases’ (Altman 1986, p. 11). A few years ago, Evans Stark pointed out that all epidemics are ‘social events’, even though they may appear as natural, random phenomena. This is because they have become the focus of struggles for control over resources (principally housing, medicines, and sanitation) (Stark 1977). Epidemics further tend to throw into relief deeply held social tensions and anxieties, which can become triggers for social reorganisation around traditional values. It is not difficult to see how this is the case with aids, which is infused in particular with tensions over sexuality and desire. In relation to this it is important to emphasize first, that sexual contact is estimated to be responsible for around two-thirds of reported aids cases amongst adults in the U.S.A. (Gracie et al. 1986), but it is not actually an exclusively sexually transmitted disease; and secondly that compared with other major causes of morbidity and mortality, aids remains a relatively rare condition in many parts of the world. It is sociologically significant though, that the two major routes of transmission, IV use and penetrative sexual intercourse, involve issues of control over body boundaries.

HIV infection in developing countries

Shortly after the first reports on the acquired immunodeficiency syndrome (AIDS) in the United States, it became clear that the disease was also particularly frequent in Haitians living in North America (Pitcheniket at., 1983; Curranet al., 1985) and in Africans seen in Europe for medical care (Katlamaet al., 1984; Clumecket al., 1984). Subsequently, surveys in Haiti and in Central Africa confirmed the occurrence of epidemic foci of AIDS in these areas (Papeet al., 1983; Malebrancheet al., 1983; Piotet al., 1984; Van de Perreet al., 1984).

Epidemiology of HTLV-I in Gabon (Western Equatorial Africa)

In 1986 a survey to determine the distribution of HTLV-I infection was conducted in Gabon in a representative sample of adults and children. Five samples were taken in adults and 2 samples in children living in urban and rural areas. Samples were taken by the cluster sampling technique, i.e., clusters of randomly selected households. Sera were tested for IgG antibodies to HTLV-I by ELISA. ELISA-positive sera were retested by Western blot. The study comprised 1,874 adults and 684 children, all apparently healthy. In the adults the crude prevalence rates of anti-HTLV-I antibodies ranged from 5.0% in urban areas to 10.5% in the southern province. In rural areas, the age-adjusted prevalence rate (9.1%) was significantly higher than in urban areas (5.0%) (p less than 0.01). In children there was no significant difference between urban (2.4%) and rural (2.0%) prevalence rates. Prevalence increased with age but was not related to sex. This survey shows that HTLV-I infection is common in Gabon but varies considerably by region.

Analysis of false positive HIV-1 serologic testing in Kenya

Sera of 95 mothers and 129 children from Nairobi, Kenya, collected in 1976, and of 466 adults and 193 children of Embu District, Kenya, collected in 1984 and 1985, were analyzed for the presence of human immunodeficiency virus type 1 (HIV-1) antibodies. Although no HIV-1 seropositivity was demonstrated by western blot analysis in both study groups, 7% of Nairobi mothers and 10% of adult females from Embu District had false positive results by enzyme immunoassay (EIA) compared with less than 1% seroreactivity rates observed in adult males and children. False positive results were not due to simian T lymphotropic virus type III (STLV-IIIAGM)/human T lymphotropic virus type IV (HTLV-IV) seropositivity. Sixty-one percent of the HIV-1 EIA reactive sera could not be explained by cytotoxic activity to lymphocytes bearing the HLA-DR4 or HLA-DQw3 phenotype. We conclude that false positive HIV EIA tests are frequently encountered in East Africa. Seroprevalence rates in rural Africa must be interpreted with caution due to the decreased specificity of HIV EIAs.

HTLV-I, adult T-cell leukemia, and tropical spastic paraparesis

Human lymphotropic retroviruses have been identified as the etiological agents of adult T-cell leukemia and acquired immunodeficiency syndrome (AIDS). Human T-lymphotropic virus type I (HTLV-I) has been linked to the etiology of ATL, and human immunodeficiency virus type I (HIV-1) has been identified as the cause of AIDS. Both retroviruses are T-cell tropic. HTLV-I is a transforming virus, whereas HIV-1 is a cytopathic virus and kills the cells it infects. HTLV-I has recently been identified from some patients with tropical spastic paraparesis, and it appears that HTLV-I infection alone or in the presence of other cofactors may be important in the development of this neurological dysfunction.

Possible aetiological factors in leukaemias in Africa

The hypothesis that the true incidence of c-ALL is relatively uniform throughout the world is not supported by experience in tropical Africa, where ALL is uncommon under five years of age. A high rate of spontaneous somatic mutation in pre-B cells may initiate the development of c-ALL, but its progress could be determined by (i) a leukaemogenic agent causing a second genetic event, (ii) the effects of intense antigenic barrage, either stimulating or suppressing pre-B-cell mitosis, or (iii) genetic determinants. Epidemiological patterns in populations of low, intermediate and high socio-economic status may be classified I-III with increasing incidence of diagnosed T-ALL in children over five years and c-ALL in younger children, and subclassified A and B with decreasing incidence of BL. There may be two forms of AML, one similar to that seen in industrialized countries, the other occurring at high prevalence in African children of low socio-economic status, often presenting with chloroma, and perhaps associated with immune suppression secondary to malnutrition, malaria and other intercurrent infections. Uncontrolled exposure to petroleum and other chemicals, and the use of alkylating agents in treatment of neoplasms in young patients could emerge as important causes of ANLL in Africa. There are two varieties of CLL also, one similar to that seen in the western world, the other prevalent in adults below 45 years of age, especially women: transmission of a leukaemogenic agent is postulated, to which women are more susceptible due to immunosuppression during normal pregnancy. The human population and some subhuman primates of subSaharan Africa are the largest reservoir of HTLV-1, which shows association with B-CLL over 50 years of age and ATL.

Acquired immunodeficiency syndrome after travelling in Africa: an epidemiological study in seventeen Caucasian patients

Seventeen Caucasian patients with acquired immunodeficiency syndrome (AIDS) contracted after long stays in Africa are reported. Central Africa was concerned in all cases. Men are particularly exposed to AIDS whatever their occupation. This study suggests that the risk of contracting AIDS in Africa is high; the transmission of the virus was related to sexual contact, particularly with prostitutes, in Africa in most of the cases. It suggests also that Caucasians who travel in Africa spread the virus throughout the world by means of their heterosexual relations.

A prevalence study of HIV antibodies in rural Kenya

In order to describe the prevalence of HIV antibodies and AIDS in West Kenya, serological tests, including ELISA, and in some cases immunoblotting, were performed on whole blood collected on filter paper from 603 Kenyans. Serum samples from 55 of these persons underwent the same examinations, and 45 were further examined by immunofluorescence and a commercial ELISA. The majority of the Kenyans examined were residents of a province in West Kenya, while the others were students from other parts of Kenya, predominantly rural areas. Male/female ratio was 62/38. Median age was 18 years (range 0-70). Five Danes with previously demonstrated HIV antibodies, and 10 Danish controls were examined for HIV antibodies in filter paper whole blood, and in serum by ELISA and immunoblotting. The tests carried out on the filter paper blood were found to be reliable. Only one of the examined Kenyans had antibodies to HIV by both ELISA and immunoblotting, representing a prevalence of 0.17% (95% confidence limits: 0.00-0.93%). This low prevalence is not in accord with results previously presented from rural districts in Kenya.

Ethnic composition, age and sex, together with location and standard of housing as determinants of HLTV-I infection in an urban Trinidadian community

The presence of antibody to human T-cell leukaemia virus (HLTV-I) has been assessed in 2,143 men and women who represent 83% of all adults aged 35 to 69 years resident in a defined urban community in Trinidad. Individuals of African descent had a higher sero-positivity rate (7.0%) than those originating from India (1.4%), Europe (0%) or of mixed descent (2.7%). Women were infected more frequently than men, and the prevalence of infection increased with age in both sexes. Sero-positivity rates were significantly increased in adults who lived in housing of poor quality (p less than 0.001) or close to water courses (p less than 0.025). These data and others raise the possibility that one route of HLTV-I transmission may be via insect vectors under particular domestic circumstances.

Antibodies to HTLV-I in Nigerian blood-donors, their relatives and patients with leukaemias, lymphomas and other diseases

Antibodies to HTLV-I have been detected in sera from 15 (2.0%) of 736 adult blood-donors in Nigeria, in 4 (20.0%) of 20 patients with chronic lymphatic leukaemia, 3 (10.0%) of 30 with non-Hodgkin's lymphoma, one of 12 with Burkitt's lymphoma and one of 7 with acute lymphoblastic leukaemia. The frequency of positivity was higher (3.6%) in the blood-donors from the guinea and wooded savanna of northern Nigeria than in those from the rain-forest and mangrove swamps of southern Nigeria (1.8% in Lagos and 0.7% in Calabar). Two of the 3 seropositive patients with lymphoma had clinical presentation and courses similar to those of Japanese and Caribbean patients with adult T-cell leukaemia/lymphoma.

Seroepidemiology of human immunodeficiency virus in Africa

Serum samples from 6015 African subjects without symptoms of the acquired immune deficiency syndrome (AIDS) or contact with the disease were examined for antibodies to the human immunodeficiency virus by a combination of an enzyme linked immunosorbent assay and radioimmunoprecipitation (2567 samples) or by immunofluorescence (3448 samples). Serum samples had been collected between 1976 and 1984 in Senegal (n = 789), Liberia (935), Ivory Coast (1195), Burkina Faso (299), Nigeria (536), Gabon (1649), Zaire (15), Uganda (164), and Kenya (433). Only four samples contained antibodies. Three of these were from attenders at the Lambarene clinic in Gabon and one from a villager in Senegal. By contrast, two out of six AIDS suspects from Guinea-Bissau, all 13 patients with AIDS from Kinshasa (Zaire), and two out of three of their contacts were seropositive, all these specimens having been collected in 1985. These data show that fewer than one in a 1000 subjects were seropositive for AIDS at the time of sampling before 1985 and do not support the hypothesis of the disease originating in Africa.

Serial transmission of human T-cell leukemia virus type I by blood transfusion in rabbits and its prevention by use of X-irradiated stored blood

Human T-cell leukemia virus type I (HTLV-I) was serially transmitted for 5 passages from rabbit to rabbit by blood transfusion. The virus could be transmitted with 20 ml of whole blood or washed blood cell suspension (fresh or stored for 1-2 weeks at 4 degrees C) but not with cell-free plasma from seroconverted rabbits. Seroconversion occurred 2-4 weeks after blood transfusion and serum anti-HTLV-I titers ranged from 1:20 to 1:640 with the immunofluorescence assay. From transfusion recipients of the 1st to 4th passages, virus-producing cell lines were established by culturing lymphocytes in the presence of T-cell growth factor (TCGF). Three of the 4 cell lines became TCGF-independent after 2-12 months of continuous culture. Blood was transfused between rabbits of opposite sexes and the recipient origin of each cell line was determined by chromosome analysis. We also investigated the effect of X-irradiation (6,000 rad) on blood from seropositive rabbits. Seroconversion likewise occurred in rabbits transfused with blood that had been irradiated immediately before transfusion but not in rabbits transfused with blood that had been irradiated and stored for 1-2 weeks at 4 degrees C. Thus, our rabbit model shows that HTLV-I is serially transmissible by blood transfusion and that this can be prevented by irradiation of blood. The same procedure, therefore, may be useful for the prevention of transfusion-related transmission of HTLV-I in humans.

A bibliography of the leukaemias in Africa, 1904-1985

A bibliography of leukaemias in Africa is presented from 1904 to 1985. The literature is listed chronologically and is classified geographically (north, south, east and west Africa) and by leukaemia type. The epidemiology of leukaemias in Africa is discussed briefly, especially as to the rarity of acute lymphoblastic leukaemia under the age of four years, the frequency of chloroma, the young age of presentation of chronic granulocytic leukaemia, the frequency of chronic lymphatic leukaemia in adults, especially women, under 45 years in tropical Africa, and the frequency of infection by the human T-cell leukaemia-lymphoma (or lymphotropic) virus type I and of adult T-cell leukaemia-lymphoma.

Antibodies to acquired immune deficiency syndrome (AIDS)-associated virus (HTLV-III/LAV) in Venezuelan populations

Serum samples from 850 individuals from Venezuela were tested for the presence of antibodies to HTLV-III/LAV virus, the probable etiological agent of acquired immune deficiency syndrome (AIDS). At the time of the study, none of the individuals tested had symptoms indicative of AIDS or related disorders. Viral antibodies were assayed by indirect immunofluorescence (IF) assay, using a chronically infected, HTLV-III/LAV producer cell line CEM/LAV-NIT established in our laboratory. Twenty individuals (2.5%), 8 of them (40%) female, were seropositive by IF and by confirmatory Western blotting and radioimmunoprecipitation assays. The seropositivity rate ranged from 2.4% (11 of 465) in the general healthy population, 4% (2 of 50) among patients with Chagas' disease, and up to 29.2% (7 of 24) among patients with acute malaria infection. The titers of HTLV-III/LAV antibodies ranged from 1:40 to 1:640. In addition, 2 of 36 patients with hemophilia A (5.5%) also had antibodies to HTLV-III/LAV. Two of 7 patients with acute malaria had specific antibodies both to HTLV-III/LAV and HTLV-I, as determined by IF and Western blotting. None of over 169 randomly chosen, healthy blood donors from seven major Venezuelan cities, as well as none of 99 patients with leukemia/lymphoma, had antibodies to HTLV-III/LAV. The presence of specific antibodies among various Venezuelan populations indicates that HTLV-III/LAV, or a closely related cross-reactive virus, is indigenous in Latin American subjects as was previously indicated for tropical populations of central Africa. Isolation and characterization of this virus will help to understand the origin and etiology of AIDS.

Antibodies to HTLV-III/LAV among aboriginal Amazonian Indians in Venezuela

Serum samples from 224 aboriginal Amazonian Indians were tested for antibodies to HTLV-III/LAV by an indirect immunofluorescence (IF) assay. 9 individuals (4%), 5 of them female, were seropositive by IF and by confirmatory western blotting and radioimmunoprecipitation tests. 3 of the positive sera were collected in 1968. HTLV-III/LAV seropositivity rates varied among the ethnic groups and ranged from 13.3% among the Pemon Indians to 3.3% among the Yanoama tribe. The titres of HTLV-III/LAV antibodies ranged from 1/40 to 1/320. All individuals tested were apparently healthy at the time of the study. None of 211 randomly chosen, healthy blood donors from Venezuelan cities had antibodies to HTLV-III/LAV. The prevalence of specific antibodies among Amazonian Indians suggests the HTLV-III/LAV or a closely related cross-reactive virus may be endemic in this area. The findings also indicate that this virus is indigenous in non-negroid Latin American and negroid tropical populations.