HTLV-1c associated bronchiolitis in an Aboriginal man from central Australia

High level of genomic divergence in orf-I p12 and hbz genes of HTLV-1 subtype-C in Central Australia

BACKGROUND

Human T cell lymphotropic virus type 1 (HTLV-1) infection remains a largely neglected public health problem, particularly in resource-poor areas with high burden of communicable and non-communicable diseases, such as some remote populations in Central Australia where an estimated 37% of adults are infected with HTLV-1. Most of our understanding of HTLV-1 infection comes from studies of the globally spread subtype-A (HTLV-1a), with few molecular studies reported with the Austral-Melanesian subtype-C (HTLV-1c) predominant in the Indo-Pacific and Oceania regions.

RESULTS

Using a primer walking strategy and direct sequencing, we constructed HTLV-1c genomic consensus sequences from 22 First Nations participants living with HTLV-1c in Central Australia. Phylogenetic and pairwise analysis of this subtype-C proviral gDNA showed higher levels of genomic divergence in comparison to previously published HTLV-1a genomes. While the overall genomic homology between subtypes was 92.5%, the lowest nucleotide and amino acid sequence identity occurred near the 3' end of the proviral genome coding regulatory genes, especially overlapping hbz (85.37%, 77.46%, respectively) and orf-I product p12 (82.00%, 70.30%, respectively). Strikingly, the HTLV-1c genomic consensus sequences uniformly showed a defective translation start codon for the immune regulatory proteins p12/p8 encoded by the HTLV-1A orf-I. Deletions in the proviral genome were detected in many subjects, particularly in the structural gag, pol and env genes. Similarly, using a droplet digital PCR assay measuring the copies of gag and tax per reference host genome, we quantitatively confirmed that provirus retains the tax gene region at higher levels than gag.

CONCLUSIONS

Our genomic analysis of HTLV-1c in Central Australia in conjunction with earlier Melanesian HTLV-1c sequences, elucidate substantial differences with respect to the globally spread HTLV-1a. Future studies should address the impact these genomic differences have on infection and the regionally distinctive frequency of associated pulmonary disease. Understanding the host and virus subtype factors which contribute to the differential morbidity observed, is crucial for the development of much needed therapeutics and vaccine strategies against this highly endemic infection in remote First Nations communities in Central Australia.

Human T-cell Lymphotropic Virus Type-1-associated Bronchioloalveolar Disorder with Non-necrotizing Granulomas: A Case Report and Literature Review

Human T-cell lymphotropic virus type-1 (HTLV-1)-associated bronchioloalveolar disorder (HABA) is a pulmonary disorder characterized by lymphocytic infiltration of the peribronchiolar space and interstitium in HTLV-1 carriers and in adult T-cell leukemia/lymphoma (ATLL). We herein report an 85-year-old woman carrying HTLV-1 with HABA who presented with a miliary pattern of micronodules in both lungs on high-resolution computed tomography and a lymphocytic infiltrate with non-necrotizing granulomas on pathology. This rare case of HABA should be differentiated from sarcoidosis, hypersensitivity pneumonitis, or miliary tuberculosis.

HTLV-I associated bronchioloalveolar disorder (HABA): disease concept and differential diagnosis of an unsolved disease entity

INTRODUCTION

Human T-cell leukemia virus type 1 (HTLV-I) associated bronchioloalveolar disorder (HABA) is a chronic and progressive bronchiolar/alveolar disorder related to HTLV-1 infection. Clinical knowledge and guidance are lacking for the diagnosis and management of this condition.

AREAS COVERED

This work aimed to review the latest information and challenges regarding HABA diagnosis and treatment.

EXPERT OPINION

HABA is an immune-mediated state induced by HTLV-1. For diagnosis of HABA, other infectious diseases and pulmonary infiltration of adult T-cell leukemia should be excluded by investigations such as computed tomography (CT), transbronchial biopsy, and bronchoalveolar lavage fluid (BALF) analysis. Typical CT findings in HABA include diffuse panbronchiolitis-like or bronchiectasis patterns, whereas cases with other abnormalities, including interstitial pneumonia, have also been reported. A high rate of polyclonal CD4+ and CD25+ lymphocytes is detected in BALF of patients with HABA, reflecting the infiltration of HTLV-1 infected T-cells in the lung. Current treatment options are not HABA specific, and include corticosteroids, macrolide antibiotics, and pirfenidone. Mitigation of the adverse effects of HTLV-1 infection requires the establishment of diagnostic criteria for the disease, screening programs for HABA in HTLV-1 infected individuals, and the development of effective disease treatment strategies.

Human T-cell leukaemia virus type 1 associated pulmonary disease: clinical and pathological features of an under-recognised complication of HTLV-1 infection

The lung is one of several organs that can be affected by HTLV-1 mediated inflammation. Pulmonary inflammation associated with HTLV-1 infection involves the interstitium, airways and alveoli, resulting in several clinical entities including interstitial pneumonias, bronchiolitis and alveolitis, depending on which structures are most affected. Augmentation of the inflammatory effects of HTLV-1 infected lymphocytes by recruitment of other inflammatory cells in a positive feedback loop is likely to underlie the pathogenesis of HTLV-1 associated pulmonary disease, as has been proposed for HTLV-1 associated myelopathy. In contrast to the conclusions of early case series, HTLV-1 associated pulmonary disease can be associated with significant parenchymal damage, which may progress to bronchiectasis where this involves the airways. Based on our current understanding of HTLV-1 associated pulmonary disease, diagnostic criteria are proposed.

Neurological Aspects of HIV-1/HTLV-1 and HIV-1/HTLV-2 Coinfection

Simultaneous infection by human immunodeficiency viruses (HIV) and human T-lymphotropic viruses (HTLV) are not uncommon since they have similar means of transmission and are simultaneously endemic in many populations. Besides causing severe immune dysfunction, these viruses are neuropathogenic and can cause neurological diseases through direct and indirect mechanisms. Many pieces of evidence at present show that coinfection may alter the natural history of general and, more specifically, neurological disorders through different mechanisms. In this review, we summarize the current evidence on the influence of coinfection on the progression and outcome of neurological complications of HTLV-1/2 and HIV-1.