Stability and Perpetuation of Human T-Lymphotropic Virus 1 (HTLV-1) in Intrafamilial Transmissions of Infection in an Endemic Region of the Brazilian Amazon: A Pilot Study.

[INTRODUCTION] Human T-lymphotropic virus 1 (HTLV-1) is related to several clinical diseases, including adult T-cell leukemia/lymphoma and HTLV-1-associated myelopathy. Intrafamilial transmission of HTLV-1 is rarely reported in Brazil and worldwide.

[OBJECTIVE] To identify HTLV-1 family transmissions in Belem, Para, the Amazon region of Brazil.

[METHODS] Nested PCR of the pX gene, followed by restrict fragment length polymorphism (RFLP) to identify HTLV-1. Nested PCR of the 5'LTR region was used for nucleotide sequencing. Nucleotide sequences were analyzed using GENEIOUS 4.8.5 and MAFFT V.7.

[RESULTS] The study investigated 72 individuals (14 index cases and 58 relatives) from 14 families, identifying HTLV-1 infection in 47% (27/58) of the relatives. Vertical transmission occurred in 14 (39%) of the 36 mother/child relationships investigated, and sexual transmission was observed in 14 (74%) of the 19 marital relationships ( = 0.0299). Both transmission routes were identified only in families with the highest average number of relatives investigated. Nucleotide analysis demonstrated HTLV-1 stability in intrafamilial transmission.

[CONCLUSION] High rate of HTLV-1 intrafamilial transmission was identified in this study. Sexual and vertical transmission are important to familiar dissemination and perpetuation of the virus in this endemic area of the Brazilian Amazon.