AIDS and cancer in Nigerians

HIV-associated lymphoma in Africa: an autopsy study in Cote d'Ivoire

HIV infection predisposes to the development of non-Hodgkin lymphoma (NHL). The frequency of NHL among HIV-positive adults and children in sub-Saharan Africa is not known. In 1991-1992, a representative autopsy study of HIV infection was performed in Abidjan, Côte d'Ivoire. Of 247 HIV-positive adult (> 14 years) medical patients dying in hospital, 2.8% had NHL, 1.6% with visceral NHL and 1.2% with primary cerebral lymphoma. The estimated crude incidence of NHL among HIV-positive adults in Abidjan was 84/100,000 per year, 10-fold greater than the expected pre-AIDS incidence of NHL but less than the incidence observed among HIV-positive adults in industrialised countries. None of 78 autopsied HIV-positive children (median age = 17 months) had NHL. HIV infection augments the incidence of NHL among adults in Africa, but short survival with advanced HIV disease probably prevents the major increase in HIV-associated NHL seen in industrialised countries. Survival of HIV-positive children in Africa appears too short to permit the significant development of additional NHL; classic Burkitt lymphoma is not an AIDS-associated tumour in Africa.

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.

Human immunodeficiency virus infection in childhood

Acquired immunodeficiency syndrome is associated with considerable morbidity in infants and children. It is caused by human immunodeficiency virus (HIV) which can be transmitted vertically from mother to infant early in pregnancy. Transmission might also occur via breast milk. Although the exact transmission rate of HIV from mother to infant is not known, HIV can become a major threat to child survival. This threat is already present in Africa where high seroprevalences have been reported among infants and young children. Transmission via blood products is decreasing due to reliable methods of screening donors for HIV antibody. Where these tests are not available, parenteral transmission will increase the incidence of HIV infection. The clinical picture of HIV infection in children presents with failure to thrive, pulmonary interstitial pneumonitis, hepatosplenomegaly and recurrent bacterial infections. These are common manifestations of diseases prevalent in children in Africa where malnutrition and recurrent parasitic infections already cause immunosuppression. Recognition of the syndrome is therefore difficult. There is no available cure for HIV infection. Supportive treatment and relief of pain and suffering are the only means of management at present. Prevention of spread of the illness to infants and young children is therefore of paramount importance.

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.

Human immunodeficiency virus antibody screening in blood donors from India, Nigeria and Thailand

Screening for human immunodeficiency virus (HIV) (LAV/HTLV-III) antibodies in 3 blood donor populations from India (n = 1,000), Nigeria (n = 500) and Thailand (n = 650; sampling in 1982) with a sensitive enzyme immunoassay (EIA; Abbott) yielded seropositivity rates of 0.5, 2.2 and 1.7%, respectively. Two EIAs with control antigens prepared from uninfected cell cultures ('ELAVIA', VIRGO'), a recombinant Escherichia coli DNA EIA ('ENV/CORE'), Western blot, an immunofluorescence assay and a radio-immunoprecipitation assay confirmed none of the EIA-reactive specimens as truly positive. The lack of specificity of the screening test was also attributable to monochromatic evaluation of the test trays at 492 nm only, and to reactivities against determinants of H9 cells used to grow HIV (HLA antibodies).

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.

No evidence of LAV infection in the Republic of Liberia, West Africa, in the year 1973

Sera collected 13 years ago from 592 residents of the Republic of Liberia have been tested for antibodies to LAV polypeptides. 7 sera were positive by ELISA using two commercially available test kits whereas immunoblotting did not confirm antibodies specific for LAV.