Frequency of adult T-cell leukaemia/lymphoma and HTLV-I in Ibadan, Nigeria

Geographic distribution, clinical epidemiology and genetic diversity of the human oncogenic retrovirus HTLV-1 in Africa, the world's largest endemic area

The African continent is considered the largest high endemic area for the oncogenic retrovirus HTLV-1 with an estimated two to five million infected individuals. However, data on epidemiological aspects, in particular prevalence, risk factors and geographical distribution, are still very limited for many regions: on the one hand, few large-scale and representative studies have been performed and, on the other hand, many studies do not include confirmatory tests, resulting in indeterminate serological results, and a likely overestimation of HTLV-1 seroprevalence. For this review, we included the most robust studies published since 1984 on the prevalence of HTLV-1 and the two major diseases associated with this infection in people living in Africa and the Indian Ocean islands: adult T-cell leukemia (ATL) and tropical spastic paraparesis or HTLV-1-associated myelopathy (HAM/TSP). We also considered most of the book chapters and abstracts published at the 20 international conferences on HTLV and related viruses held since 1985, as well as the results of recent meta-analyses regarding the status of HTLV-1 in West and sub-Saharan Africa. Based on this bibliography, it appears that HTLV-1 distribution is very heterogeneous in Africa: The highest prevalences of HTLV-1 are reported in western, central and southern Africa, while eastern and northern Africa show lower prevalences. In highly endemic areas, the HTLV-1 prevalence in the adult population ranges from 0.3 to 3%, increases with age, and is highest among women. In rural areas of Gabon and the Democratic Republic of the Congo (DRC), HTLV-1 prevalence can reach up to 10-25% in elder women. HTLV-1-associated diseases in African patients have rarely been reported in situ on hospital wards, by local physicians. With the exception of the Republic of South Africa, DRC and Senegal, most reports on ATL and HAM/TSP in African patients have been published by European and American clinicians and involve immigrants or medical returnees to Europe (France and the UK) and the United States. There is clearly a huge underreporting of these diseases on the African continent. The genetic diversity of HTLV-1 is greatest in Africa, where six distinct genotypes (a, b, d, e, f, g) have been identified. The most frequent genotype in central Africa is genotype b. The other genotypes found in central Africa (d, e, f and g) are very rare. The vast majority of HTLV-1 strains from West and North Africa belong to genotype a, the so-called 'Cosmopolitan' genotype. These strains form five clades roughly reflecting the geographic origin of the infected individuals. We have recently shown that some of these clades are the result of recombination between a-WA and a-NA strains. Almost all sequences from southern Africa belong to Transcontinental a-genotype subgroup.

Cancer in Africa 2018: The role of infections

We estimate the fractions of cancer attributed to infections in Africa in 2018. The number of new cancer cases occurring was taken from Globocan2018 with some additional estimations based on data from African population-based registries. Population attributable fractions were calculated using prevalence of infection and relative risk in exposed vs. nonexposed. The greatest share of infection-associated cancers is due to the human papillomaviruses (12.1% of all cancers in Africa and 15.4% in sub-Saharan Africa [SSA]); of these, cervical cancer is by far the most common. Kaposi sarcoma-associated herpesvirus is responsible for 3.1% of all cancers in Africa, the hepatitis viruses (B and C) for 2.9% and Helicobacter pylori for 2.7% (non-Cardia Gastric cancer and primary gastric lymphomas). Two percent of cancers are attributable to the Epstein-Barr virus, Schistosoma haematobium increases the risk of bladder cancer resulting in 1.0% of all cancers. HIV-related NHL and squamous cell carcinoma of the conjunctiva account for 0.6% of cancers. Altogether 24.5% of cancers in Africa and 28.7% in SSA are due to infectious agents. Infections are by far the most common cancer risk factor for cancer in Africa-the traditional risk factors (smoking, alcohol and unhealthy diet) probably cause only one in eight cancers in Africa. Prevention should focus on those infectious diseases preventable through vaccination (HPV and hepatitis B) which could reduce two-thirds of the burden. Helicobacter pylori and schistosomiasis are treatable with antibiotics and praziquantel, with a potential reduction of one in eight infection-associated cancers.

Prevalence of human T-lymphotropic virus 1/2 in Nigeria's capital territory and meta-analysis of Nigerian studies

Objectives:

This study was aimed at determining human T-lymphotropic virus 1/2 prevalence among apparently healthy, immunocompromised and haematologic malignant individuals in Nigeria’s capital, as well as meta-analysis of all Nigerian studies until date.

Methods:

A total of 200 participants were recruited into a cross-sectional study. In total, 1 mL each of sera and plasma were obtained from 5 mL blood of each participant and analysed for antibodies to human T-lymphotropic virus 1/2 using enzyme-linked immunosorbent assay; positive samples confirmed with qualitative real-time polymerase chain reaction, followed by statistical and meta-analysis. Sociodemographic characteristics and possible risk factors were assessed via questionnaires.

Results:

Enzyme-linked immunosorbent assay yielded 1% prevalence which was confirmed to be zero via polymerase chain reaction. A total of 119 (59.5%) of the participants were male, while the mean age was 35.28 ± 13.61 years. Apart from sex and blood reception/donation, there was generally a low rate of exposure to human T-lymphotropic virus–associated risk factors. Meta-analysis revealed pooled prevalence of human T-lymphotropic virus 1 and 2 to be 3% and 0%, respectively, from Nigerian studies.

Conclusion:

This study discovered zero prevalence of human T-lymphotropic virus 1/2 from five major hospitals in Nigeria’s capital, exposing the importance of confirmatory assays after positive antibody detection assay results. Meta-analysis highlighted the existence of very few reliable Nigerian studies compared to the demography of the nation. Large-scale epidemiological studies and routine screening of risk populations are therefore needed since Nigeria lies in the region of endemicity.

Early Onset of HTLV-1 Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP) and Adult T-cell Leukemia/Lymphoma (ATL): Systematic Search and Review

Human T-cell lymphotropic virus type 1 (HTLV-1) is endemic in some regions and its vertical transmission occurs mainly through breastfeeding. About 10% of carriers develop associated diseases including HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP), adult T-cell leukemia/lymphoma (ATL) and infectious dermatitis associated with HTLV-1 (IDH). We searched for available case reports of early-onset HAM/TSP and ATL to evaluate demographic and disease aspects in infantile-juvenile patients. In the reviewed literature, 27 HAM/TSP and 31 ATL cases were found. In almost all of them, the most likely route of transmission was through breastfeeding. ATL is rarely reported, notwithstanding it may be underestimated because T-cell lymphomas are not investigated for HTLV-1 infection in this age group. IDH was frequently associated with HAM/TSP. The investigation of HTLV-1 infection in pregnant women is an important matter of public health and should be mandatory in endemic countries.

Hematology in Africa

This review of hematology in Africa highlights areas of current practice and the immediate needs for development and clinical research. Acute hematological practice is dominated by anemia, sickle cell disease, and the need to provide a safe and rapidly available supply of blood. There is a growing need for specialist services for bleeding and coagulation, hematological malignancy, and palliative care. There are many areas of practice where straightforward measures could yield large gains in patient care. There is an urgent need for good clinical research to describe the epidemiology, natural history, and management of hematological diseases in Africa.

Seroprevalence of HTLV-1 and HTLV-2 amongst mothers and children in Malawi within the context of a systematic review and meta-analysis of HTLV seroprevalence in Africa

OBJECTIVES

Human T-lymphotropic virus (HTLV)-1 causes T-cell leukaemia and myelopathy. Together with HTLV-2, it is endemic in some African nations. Seroprevalence data from Malawi are scarce, with no reports on associated disease incidence. HTLV seroprevalence and type were tested in 418 healthy mothers from Malawi. In addition, we tested the sera of 534 children to investigate mother-to-child transmission. To provide context, we conducted a systematic review and meta-analysis of HTLV seroprevalence in African women and children.

METHODS

Stored samples from a previous childhood cancer and BBV study were analysed. ELISA was used for HTLV screening followed by immunoblot for confirmation and typing. Standard methods were used for the systematic review.

RESULTS

HTLV seroprevalence was 2.6% (11/418) in mothers and 2.2% (12/534) in children. Three mothers carried HTLV-1 alone, seven had HTLV-2 and one was dually infected. Three children carried HTLV-1 alone, seven had HTLV-2 and two were dually infected. Only two corresponding mothers of the 12 HTLV-positive children were HTLV positive. The systematic review included 66 studies of women and 13 of children conducted in 25 African countries. Seroprevalence of HTLV-1 varied from 0 to 17% and of HTLV-2 from 0 to 4%.

CONCLUSIONS

In contrast to findings from other studies in Africa, the seroprevalence of HTLV-2 was higher than that of HTLV-1 in Malawi and one of the highest for the African region. The lack of mother-child concordance suggests alternative sources of infection among children. Our data and analyses contribute to HTLV prevalence mapping in Africa.

Epidemiological Aspects and World Distribution of HTLV-1 Infection

The human T-cell leukemia virus type 1 (HTLV-1), identified as the first human oncogenic retrovirus 30 years ago, is not an ubiquitous virus. HTLV-1 is present throughout the world, with clusters of high endemicity located often nearby areas where the virus is nearly absent. The main HTLV-1 highly endemic regions are the Southwestern part of Japan, sub-Saharan Africa and South America, the Caribbean area, and foci in Middle East and Australo-Melanesia. The origin of this puzzling geographical or rather ethnic repartition is probably linked to a founder effect in some groups with the persistence of a high viral transmission rate. Despite different socio-economic and cultural environments, the HTLV-1 prevalence increases gradually with age, especially among women in all highly endemic areas. The three modes of HTLV-1 transmission are mother to child, sexual transmission, and transmission with contaminated blood products. Twenty years ago, de Thé and Bomford estimated the total number of HTLV-1 carriers to be 10-20 millions people. At that time, large regions had not been investigated, few population-based studies were available and the assays used for HTLV-1 serology were not enough specific. Despite the fact that there is still a lot of data lacking in large areas of the world and that most of the HTLV-1 studies concern only blood donors, pregnant women, or different selected patients or high-risk groups, we shall try based on the most recent data, to revisit the world distribution and the estimates of the number of HTLV-1 infected persons. Our best estimates range from 5-10 millions HTLV-1 infected individuals. However, these results were based on only approximately 1.5 billion of individuals originating from known HTLV-1 endemic areas with reliable available epidemiological data. Correct estimates in other highly populated regions, such as China, India, the Maghreb, and East Africa, is currently not possible, thus, the current number of HTLV-1 carriers is very probably much higher.

Genetic mutation and early onset of T-cell leukemia in pediatric patients infected at birth with HTLV-I

T-cell leukemia/lymphoma (T-c LL) associated with prior infection with HTLV-I is rarely described in children. We present herein, the clinical, morphological, and virologic features of T-c LL, which occurred in eight pediatric cases with similar features of ATLL described in adults. There were three girls and five boys with age ranging from 2 to 18 years. Lymphoadenopathy, hepatosplenomegaly and marked skin lesions were presented in all cases. Five patients had hypercalcemia. The diagnostic criteria of T-c LL were based on both morphological and immunophenotypical analyses characterized by T-cell markers positively. Seven cases were cCD3+, CD4/CD25+, whereas CD1a and TdT were negative in all cases tested. HTLV-I antibodies were detected in all cases. HTLV-I provirus integration of at least one provirus was seen in all cases tested by molecular analysis. Mother-to-child transmission of HTLV-I was demonstrated in six cases. Interestingly, a homozygous deletion in p16 gene locus was observed in all four cases studied, while exons 7 and 8 of p53 were deleted in one child. The deletion of the p16(INK4A)/p14(ARF) or mutation of p53, key regulatory protein of cell cycle checkpoint in G1/S progression, found in five of the eight pediatric patients suggests that in these cases genetic lesions associated with HTLV-I infection may predispose for an early onset of leukemia.

Adult T-cell leukemia/lymphoma associated with HTLV-1 infection in a Brazilian adolescent

We present the case of a 15-year-old patient infected with HTLV-1 who developed a cutaneous T-cell lymphoma, confirmed by histopathological and immunohistochemical examination, as well as clinically and hematologically confirmed leukemia. The patient died 3 months after initial presentation of the disease. The rarity of the disease in this age group justifies the present report.

HTLV-I-associated granulomatous T-cell lymphoma in a child

Adult T-cell leukemia/lymphoma (ATLL) is a T-cell malignancy closely associated with human T-cell lymphotropic virus-1 (HTLV-I). Because of its long latency period, ATLL occurs almost exclusively in adults. We report a case of a 13-year-old boy with an 8-year history of skin eruptions. After complete evaluation, a diagnosis of HTLV-I-associated lymphoma/leukemia was made. The T-cell lymphoma exhibited a granulomatous histomorphology. There have been very few reports of ATLL presenting in childhood and none, to our knowledge, demonstrating granulomatous histology. We conclude that ATLL may rarely present as a chronic granulomatous eruption in a child.

Adult T-cell leukemia/lymphoma in northeastern Brazil: a clinical, histopathologic, and molecular study

The state of Bahia in the northeastern coast of Brazil is a region in which HTLV-I infection is endemic. This study investigated the characteristics of 28 HTLV-I-associated lymphomas/leukemias in this region. HTLV-I-infection diagnosis was based on serologic study, Southern blot analysis, and polymerase chain reaction (PCR) in neoplastic tissue. The main clinical differences between these lymphomas and adult T-cell leukemia (ATL) cases from other endemic areas were as follows. The mean age was 47 years; 20% of the cases occurred in young adults; and a predominance was found among male subjects (2:1), blacks, and of those of mixed race (96%). Histologically, 20 cases were T-cell pleomorphic leukemia/lymphoma, 5 were Mycosis fungoides-like cutaneous lymphoma, and 3 were CD30+ large-cell anaplastic lymphoma. Immunohistochemistry demonstrated 4 cases of CD8+ lymphoma. Proviral genomic sequences were demonstrated by PCR in 9 lymph node biopsy specimens and in 3 skin biopsy specimens. Southern blot was performed and was positive in 8 cases.