Stability of the HTLV-1 glycoprotein 46 (gp46) gene in an endemic region of the Brazilian Amazon and the presence of a significant mutation (N93D) in symptomatic patients.

BACKGROUND: The human T-lymphotropic virus type 1 (HTLV-1) affects 2-5 million people worldwide, and is associated with a number of degenerative and infectious diseases. The Envelope glycoproteins (gp) are highly conserved among the different HTLV-1 isolates, although nucleotide substitutions in the region that codifies these proteins may influence both the infectivity and the replication of the virus. The gp46 gene has functional domains which have been associated with the inhibition of the formation of the syncytium, cell-cell transmission, and the production of antibodies. The present study investigated the genetic stability of the gp46 gene of HTLV-1 in an endemic region of Brazilian Amazonia. METHODS: Index case (IC - a sample of a given family group) carriers of HTLV-1 were investigated in the metropolitan region of Belém (Pará, Brazil) between January 2010 (registered retrospectively) and December 2015. The sequences that codify the gp46 were amplified by PCR, purified and sequenced (MF084788-MF084825). The gene was characterized using bioinformatics and Bayesian Inference. RESULTS: The 40 patients analyzed had a mean age of 45.2 years and 70% presented some type of symptom, with a predominance of pain and sensitivity, dysautonomia, and motor disorders. All patients presented the aA (Transcontinental Cosmopolitan) genotype, with an extremely low mutation rate, which is characteristic of the codifying region (aA - 1.83 × 10-4 mutations per site per year). The gp46 gene had a nucleotide diversity of between 0.00% and 2.0%. Amino acid mutations were present in 66.6% of the samples of individuals with signs/symptoms or diseases associated with HTLV-1 (p = 0.0091). Of the three most frequent mutations, the previously undescribed N93D mutant was invariably associated with symptomatic cases. CONCLUSIONS: The aA HTLV-1 subtype is predominant in the metropolitan region of Belém and presented a high degree of genetic stability in the codifying region. The rare N93D amino acid mutation may be associated with the clinical manifestations of this viral infection. IMPORTANCE: Little is known of the phylogeny of HTLV-1 in the endemic region of Brazilian Amazonia, and few complete gene sequences are available for the gp46 glycoprotein from the local population. The nucleotide sequences of the viral gp46 gene recorded in the present study confirmed the genetic stability of the region, and pointed to a homogeneous viral group, with local geographic characteristics. Further research will be necessary to more fully understand the molecular diversity of this protein, given the potential of this codifying region as a model for an effective HTLV-1 vaccine. The identification of a rare mutation (N93D), present only in symptomatic patients, should also be investigated further as a potential clinical marker. TRIAL REGISTRATION: ISRCTN 12345678, registered 28 September 2014.

Low genetic diversity of the Human T-cell Lymphotropic Virus (HTLV-1) in an endemic area of the Brazilian Amazon basin.

The Human T-cell Lymphotropic Virus (HTLV-1) is a Deltaretrovírus that was first isolated in the 1970s, and associated with Adult T-cell Leucemia-Lymphoma (ATLL), and subsequently to Tropical Spastic Paraparesis-Myelopathy (TSP/HAM). The genetic diversity of the virus varies among geographic regions, although its mutation rate is very low (approximately 1% per thousand years) in comparison with other viruses. The present study determined the genetic diversity of HTLV-1 in the metropolitan region of Belém, in northern Brazil. Blood samples were obtained from patients at the UFPA Tropical Medicine Nucleus between January 2010 and December 2013. The DNA was extracted and the PX region of the HTLV was amplified using nested PCR. The positive samples were then digested using the Taq1 enzyme for the identification and differentiation of the HTLV-1 and HTLV-2. The 5'LTR region of the positive HTLV-1 samples were amplified by nested PCR, and then sequenced genetically. The phylogenetic analysis of the samples was based on the maximum likelihood method and the evolutionary profile was analyzed by the Bayesian approach. Overall, 78 samples tested positive for HTLV-1, and 44 were analyzed here. The aA (cosmopolitan-transcontinental) subtype was recorded in all the samples. The following evolutionary rates were recorded for the different subtypes-a: 2.10-3, b: 2.69. 10-2, c: 6.23. 10-2, d: 3.08. 10-2, e: 6. 10-2, f: 1.78. 10-3, g: 2.2. 10-2 mutations per site per year. The positive HTLV-1 samples tested in the present study were characterized by their low genetic diversity and high degree of stability.

Moderate endemicity of the human T-lymphotropic virus infection in the metropolitan region of Belém, Pará, Brazil. / Moderada endemicidade da infecção pelo vírus linfotrópico-T humano na região metropolitana de Belém, Pará, Brasil.

INTRODUCTION: The spread of the HTLV infection in families living in the metropolitan area of Belém, Pará, Brazil, and the lack of studies in the general population requires studies to better understand its prevalence in the region. METHODS: An anti-HTLV-1/HTLV-2 antibodies test was carried out on random adults in public places in Belém between November 2014 and November 2015. A proviral DNA test detected if the person was infected, and then a clinical evaluation and an intrafamilial investigation were carried out. RESULTS: Of the 1059 individuals being investigated, 21 (2.0%) had seroreagent samples, 15 (1.4%) had HTLV-1, 5 (0.5%) had HTLV-2, and proviral DNA was undetectable in one case. The mean age of the infected people (57.2) was higher than that of those that were uninfected (46.2) (p = 0.0010). The prevalence of infection increased with age, especially in individuals with a family income equal to or less than a minimum wage. Intrafamilial transmission seems to have occurred in all of the families being studied. Among the patients with HTLV-1, 30% (3/10) already had some symptom related to the infection. DISCUSSION: The increase in prevalence rates according to age may be due to late seroconversion of a previously acquired infection, or the cumulative risk of new infections, especially in women. CONCLUSION: There was a moderate prevalence of the HTLV infection among adult individuals from the metropolitan area of Belém, with a predominance of HTLV-1. This infection was associated with low income and increasingly older women. It also presented intrafamily spread and negligence in the diagnosis of associated diseases.

INTRODUÇÃO: A disseminação da infecção pelo vírus linfotrópico-T humano (HTLV) em famílias da área metropolitana de Belém, Pará, Brasil, e a ausência de estudos na população em geral requisitam investigações que esclareçam melhor a sua prevalência na região. METODOLOGIA: Foi realizada pesquisa de anticorpos anti-HTLV-1/HTLV-2 em indivíduos adultos transeuntes de logradouros públicos de Belém, entre novembro de 2014 e novembro de 2015. A infecção foi confirmada por pesquisa de DNA proviral e foi realizada avaliação clínica e investigação intrafamiliar dos infectados. RESULTADOS: Dos 1.059 indivíduos investigados, 21 (2,0%) apresentaram amostras sororeagentes, 15 (1,4%) confirmados para HTLV-1, 5 (0,5%) para HTLV-2 e o DNA proviral foi indetectável em 1 caso. A média de idade dos infectados (57,2) foi maior que a dos não infectados (46,2) (p = 0,0010). A infecção aumentou com a idade e se destacou nos indivíduos com renda familiar menor ou igual a um salário mínimo. A transmissão intrafamiliar parece ter ocorrido em todas as famílias investigadas. Dentre os portadores de HTLV-1, 30% (3/10) já apresentavam algum sintoma relacionado à infecção. DISCUSSÃO: O aumento da infecção de acordo com a idade pode ocorrer por soroconversão tardia de infecção pré-adquirida ou pelo risco cumulativo de novas infecções, sobretudo em mulheres. CONCLUSÃO: A infecção por HTLV demonstrou moderada prevalência na população estudada, com predomínio do HTLV-1. Essa mostrou-se associada à baixa renda e ao aumento da idade das mulheres. Também apresentou disseminação intrafamiliar e negligência no diagnóstico das doenças associadas.

Moderada endemicidade da infecção pelo vírus linfotrópico-T humano na região metropolitana de Belém, Pará, Brasil / Moderate endemicity of the human T-lymphotropic virus infection in the metropolitan region of Belém, Pará, Brazil

RESUMO: Introdução: A disseminação da infecção pelo vírus linfotrópico-T humano (HTLV) em famílias da área metropolitana de Belém, Pará, Brasil, e a ausência de estudos na população em geral requisitam investigações que esclareçam melhor a sua prevalência na região. Metodologia: Foi realizada pesquisa de anticorpos anti-HTLV-1/HTLV-2 em indivíduos adultos transeuntes de logradouros públicos de Belém, entre novembro de 2014 e novembro de 2015. A infecção foi confirmada por pesquisa de DNA proviral e foi realizada avaliação clínica e investigação intrafamiliar dos infectados. Resultados: Dos 1.059 indivíduos investigados, 21 (2,0%) apresentaram amostras sororeagentes, 15 (1,4%) confirmados para HTLV-1, 5 (0,5%) para HTLV-2 e o DNA proviral foi indetectável em 1 caso. A média de idade dos infectados (57,2) foi maior que a dos não infectados (46,2) (p = 0,0010). A infecção aumentou com a idade e se destacou nos indivíduos com renda familiar menor ou igual a um salário mínimo. A transmissão intrafamiliar parece ter ocorrido em todas as famílias investigadas. Dentre os portadores de HTLV-1, 30% (3/10) já apresentavam algum sintoma relacionado à infecção. Discussão: O aumento da infecção de acordo com a idade pode ocorrer por soroconversão tardia de infecção pré-adquirida ou pelo risco cumulativo de novas infecções, sobretudo em mulheres. Conclusão: A infecção por HTLV demonstrou moderada prevalência na população estudada, com predomínio do HTLV-1. Essa mostrou-se associada à baixa renda e ao aumento da idade das mulheres. Também apresentou disseminação intrafamiliar e negligência no diagnóstico das doenças associadas.

ABSTRACT: Introduction: The spread of the HTLV infection in families living in the metropolitan area of Belém, Pará, Brazil, and the lack of studies in the general population requires studies to better understand its prevalence in the region. Methods: An anti-HTLV-1/HTLV-2 antibodies test was carried out on random adults in public places in Belém between November 2014 and November 2015. A proviral DNA test detected if the person was infected, and then a clinical evaluation and an intrafamilial investigation were carried out. Results: Of the 1059 individuals being investigated, 21 (2.0%) had seroreagent samples, 15 (1.4%) had HTLV-1, 5 (0.5%) had HTLV-2, and proviral DNA was undetectable in one case. The mean age of the infected people (57.2) was higher than that of those that were uninfected (46.2) (p = 0.0010). The prevalence of infection increased with age, especially in individuals with a family income equal to or less than a minimum wage. Intrafamilial transmission seems to have occurred in all of the families being studied. Among the patients with HTLV-1, 30% (3/10) already had some symptom related to the infection. Discussion: The increase in prevalence rates according to age may be due to late seroconversion of a previously acquired infection, or the cumulative risk of new infections, especially in women. Conclusion: There was a moderate prevalence of the HTLV infection among adult individuals from the metropolitan area of Belém, with a predominance of HTLV-1. This infection was associated with low income and increasingly older women. It also presented intrafamily spread and negligence in the diagnosis of associated diseases.