Tropical Spastic Paraparesis/Human T Leukemia Virus Type 1--Associated Myelopathy in HIV Type 1--Coinfected Patients

Immunological and Neurological Signatures of the Co-Infection of HIV and HTLV: Current Insights and Future Perspectives

The human retroviruses HIV and HTLV-1/HTLV-2 are transmitted through similar pathways but result in markedly different diseases. This review delineates the immune-mediated mechanisms by which HTLVs influence HIV pathology in co-infected individuals. In the context of HIV co-infection, HTLV-1/HTLV-2 alter the cellular microenvironment to enhance their own survival while simultaneously impeding the progression of HIV. Despite the extensive body of literature on the biological and clinical implications of retroviral co-infections, decades of research have been marred by controversy due to several flawed epidemiological studies and anecdotal reports lacking robust statistical and scientific backing. Nevertheless, recent systematic and well-designed research has led to a growing consensus supporting at least three key conclusions: (1) co-infections of HIV-1 and HTLV-1 are frequently observed in patients with elevated CD4+ T-cell counts who present with lymphoma or neurological complications; (2) HIV-1 and HTLV-2 co-infections have been associated in some instances with a "long-term non-progressor" phenotype; (3) the differential function and/or overexpression of the HTLV-1 and HTLV-2 Tax proteins are likely crucial in the clinical and immunologic outcomes of HIV/HTLV-1 and -2 co-infections. The present review will provide a comprehensive account of research on retroviral co-infections, focusing particularly on their clinical manifestations and associated pathological features.

Co-Infections and Superinfections between HIV-1 and Other Human Viruses at the Cellular Level

Co-infection or superinfection of the host by two or more virus species is a common event, potentially leading to viral interference, viral synergy, or neutral interaction. The simultaneous presence of two or more viruses, even distantly related, within the same cell depends upon viral tropism, i.e., the entry of viruses via receptors present on the same cell type. Subsequently, productive infection depends on the ability of these viruses to replicate efficiently in the same cellular environment. HIV-1 initially targets CCR5-expressing tissue memory CD4+ T cells, and in the absence of early cART initiation, a co-receptor switch may occur, leading to the infection of naïve and memory CXCR4-expressing CD4+ T cells. HIV-1 infection of macrophages at the G1 stage of their cell cycle also occurs in vivo, broadening the possible occurrence of co-infections between HIV-1 and other viruses at the cellular level. Moreover, HIV-1-infected DCs can transfer the virus to CD4+ T cells via trans-infection. This review focuses on the description of reported co-infections within the same cell between HIV-1 and other human pathogenic, non-pathogenic, or low-pathogenic viruses, including HIV-2, HTLV, HSV, HHV-6/-7, GBV-C, Dengue, and Ebola viruses, also discussing the possible reciprocal interactions in terms of virus replication and virus pseudotyping.

Socio-Demographic, Clinical, and Mortality Differences between HIV-Infected and HIV/HTLV-1 Co-Infected Patients in Peru

BACKGROUND AND AIMS

In Peru, the estimated prevalence of human immunodeficiency virus (HIV) and human T-lymphotropic virus-1 (HTLV-1) co-infection has been reported to be as high as 18%. Despite the endemicity of HTLV-1 in Peru, few studies have assessed the impact of HIV/HTLV-1 co-infection. Our study compared socio-demographic and clinical characteristics, and mortality rates between HIV-infected and HIV/HTLV-1 co-infected patients.

METHODS

We reviewed the medical records of patients aged 18 years and older belonging to the HIV and HTLV-1 cohorts in Lima during a 30-year period: 1989-2019. Each HIV/HTLV-1 co-infected patient was randomly matched with two HIV-infected patients with similar characteristics (same sex, age ± 5 years, and same year of HIV diagnosis). Allegedly co-infected patients without a confirmatory diagnosis of HIV and HTLV-1 were excluded. Most of the patients in the HIV-infected group did not have a negative test result for HTLV-1 infection, so we used two probabilistic sensitivity analysis models to correct for potential HTLV-1 exposure misclassification bias in the group of HIV-infected patients.

RESULTS

Of 162 patients enrolled, 54 were HIV/HTLV-1 co-infected and 108 were HIV-infected. The median age was 42 years (IQR = 34-51 years) and the majority were male (61.1%), single (44.4%), heterosexual (71%), born in Lima (58%), educated at the secondary school level (55.6%), and receiving antiretroviral treatment (91.4%). HIV/HTLV-1 co-infection was associated with an increased risk of death (HR: 11.8; 95% CI: 1.55-89.00; p = 0.017) while antiretroviral treatment was associated with a decreased risk of death (HR: 0.03; 95% CI: 0.003-0.25; p = 0.001). The overall mortality rate was 13.6 per 100 persons and the survival time for co-infected patients (median = 14.19 years) was significantly shorter than that of HIV-infected patients (median = 23.83 years) (p < 0.001).

CONCLUSIONS

HIV/HTLV-1 co-infected patients had a significantly shorter survival time compared to HIV-infected patients, suggesting that the immune alterations caused by HTLV-1 in CD4 cell count may have contributed to late initiation of antiretroviral treatment and prophylaxis against opportunistic infections over the decades, and thus reducing their benefits in these patients.

Human T-Lymphotropic virus type 1 and human immunodeficiency virus co-infection in rural Gabon

Introduction

Human T-cell lymphotrophic virus type-1 (HTLV-1) and human immunodeficiency virus (HIV-1) co-infection occur in many populations. People living with HIV-1 and infected with HTLV-1 seem more likely to progress rapidly towards AIDS. Both HTLV-1 and HIV-1 are endemic in Gabon (Central Africa). We investigated HTLV-1 and HIV-1 co-infection in the Haut-Ogooué province, and assessed factors that may favor the rapid evolution and progression to AIDS in co-infected patients.

Methods

Plasma samples from HTLV-1 patients were tested using ELISA, and positive samples were then tested by western blot assay (WB). We used the polymerase chain reaction to detect HTLV-1 Tax/Rex genes using DNA extracted from the buffy coat of ELISA-positives samples.

Results

We recruited 299 individuals (mean age 46 years) including 90 (30%) men and 209 (70%) women, all of whom are under treatment at the Ambulatory Treatment Centre of the province. Of these, 45 were ELISA HTLV-1/2 seropositive. According to WB criteria, 21 of 45 were confirmed positive: 20 were HTLV-1 (44%), 1 was HTLV-1/2 (2%), 2 were indeterminate (4%) and 22 were seronegative (49%). PCR results showed that 23 individuals were positive for the Tax/Rex region. Considering both serological and molecular assays, the prevalence of HTLV-1 infection was estimated at 7.7%. Being a woman and increasing age were found to be independent risk factors for co-infection. Mean CD4+ cell counts were higher in HTLV-1/HIV-1 co-infected (578.1 (± 340.8) cells/mm³) than in HIV-1 mono-infected (481.0 (± 299.0) cells/mm³) Individuals. Similarly, the mean HIV-1 viral load was Log 3.0 (± 1.6) copies/ml in mono-infected and Log 2.3 (± 0.7) copies/ml in coinfected individuals.

Conclusion

We described an overall high prevalence of HTLV-1/HIV-1 co-infection in Gabon. Our findings stress the need of strategies to prevent and manage these co-infections.

Clonality of HIV-1- and HTLV-1-Infected Cells in Naturally Coinfected Individuals

BACKGROUND

Coinfection with human immunodeficiency virus type 1 (HIV-1) and human T-cell leukemia virus type 1 (HTLV-1) diminishes the value of the CD4+ T-cell count in diagnosing AIDS, and increases the rate of HTLV-1-associated myelopathy. It remains elusive how HIV-1/HTLV-1 coinfection is related to such characteristics. We investigated the mutual effect of HIV-1/HTLV-1 coinfection on their integration sites (ISs) and clonal expansion.

METHODS

We extracted DNA from longitudinal peripheral blood samples from 7 HIV-1/HTLV-1 coinfected, and 12 HIV-1 and 13 HTLV-1 monoinfected individuals. Proviral loads (PVL) were quantified using real-time polymerase chain reaction (PCR). Viral ISs and clonality were quantified by ligation-mediated PCR followed by high-throughput sequencing.

RESULTS

PVL of both HIV-1 and HTLV-1 in coinfected individuals was significantly higher than that of the respective virus in monoinfected individuals. The degree of oligoclonality of both HIV-1- and HTLV-1-infected cells in coinfected individuals was also greater than in monoinfected subjects. ISs of HIV-1 in cases of coinfection were more frequently located in intergenic regions and transcriptionally silent regions, compared with HIV-1 monoinfected individuals.

CONCLUSIONS

HIV-1/HTLV-1 coinfection makes an impact on the distribution of viral ISs and clonality of virus-infected cells and thus may alter the risks of both HTLV-1- and HIV-1-associated disease.

Impact of HIV co-infection on immunological biomarker profile of HTLV-1 infected patients

The impact of HIV co-infection on the plasma immunological biomarker profile of HTLV-1 infected patients was evaluated. The plasma levels of leukotrienes and chemokines/cytokines were quantified by ELISA and Cytometric Bead Array. A total of 138 volunteers were enrolled and divided into two subgroups ("HTLV-1(+)HIV(-)" and "HTLV-1(+)(HIV(+)"), which were categorized according to the HTLV-1-associated neurological disease (AS, pHAM and HAM). Reference controls were BD and HIV mono-infected patients. HAM(+) exhibited higher CD4⁺ T-cell counts as compared to HIV+ mono-infected patients and lower HTLV-1 proviral load as compared to mono-infected HAM(-) patients. AS(+) exhibited higher levels of CysLT, CXCL8/IL-8 and lower levels of CCL5/RANTES as compared to AS(-). Increased levels of IL-6 and TNF with reduced levels of CXCL10/IP10 and CCL5/RANTES were observed in co-infected pHAM(+) as compared to mono-infected pHAM(-). HAM(+) patients revealed an increase in CXCL8/IL-8, CCL2/MCP-1, CXCL-10/IP-10, TNF and a decrease in IL-2 as compared to HAM(-) subgroup.

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.

STLV-1 as a model for studying HTLV-1 infection

Few years after HTLV-1 identification and isolation in humans, STLV-1, its simian counterpart, was discovered. It then became clear that STLV-1 is present almost in all simian species. Subsequent molecular epidemiology studies demonstrated that, apart from HTLV-1 subtype A, all human subtypes have a simian homolog. As HTLV-1, STLV-1 is the etiological agent of ATL, while no case of TSP/HAM has been described. Given its similarities with HTLV-1, STLV-1 represents a unique tool used for performing clinical studies, vaccine studies as well as basic science.

Health economic implications of testing blood donors in South Africa for HTLV 1 & 2 infection

BACKGROUND AND OBJECTIVES

Currently, HTLV screening is not performed in South Africa (SA). This report describes an economic assessment (budget impact and cost-effectiveness) of implementing different HTLV screening strategies.

METHODS

A modified version of the Alliance of Blood Operators risk-based decision-making framework was used to assess the risk and consequences of HTLV in the blood supply in SA. We developed a deterministic model of the cost and consequences of four screening strategies: none, universal, all donors once and first time donors only assuming a transfusion-transmission (TT) efficiency of 10% and a manifestation of clinical disease of 6%.

RESULTS

Unscreened blood results in 3·55 symptomatic TT-HTLV cases and a total healthcare cost of Rand (R)3 446 950 (US Dollars (USD)229 800) annually. Universal screening would cost R24 000 000 (USD1 600 000) per annum and prevent 3·54 (99·8%) symptomatic TT-HTLV cases in the first year and 0·55 (98·4%) symptomatic TT-HTLV cases in the second year at a cost per TT-HTLV prevented of R6 780 000 (USD450 000) in year one and R43 254 000 (USD2 890 000) in year two. Screening all donors once would cost R16,200,000 (USD1 080 000) or R4 600 000 (USD306 000) per symptomatic TT-HTLV infection prevented in year one. Total costs decrease to R5 100 000 (USD340 000) in year 2 but the cost per TT-HTLV prevented increases to R10 700 000 (USD713 333).

CONCLUSION

This analysis contributed to the decision not to implement HTLV screening as the healthcare budget and particularly the budget for blood transfusion in SA is insufficient to provide appropriate treatment. Arguably, available resources can be more efficiently utilized in other healthcare programs.

HTLV-1, the Other Pathogenic Yet Neglected Human Retrovirus: From Transmission to Therapeutic Treatment

Going back to their discovery in the early 1980s, both the Human T-cell Leukemia virus type-1 (HTLV-1) and the Human Immunodeficiency Virus type-1 (HIV-1) greatly fascinated the virology scene, not only because they were the first human retroviruses discovered, but also because they were associated with fatal diseases in the human population. In almost four decades of scientific research, both viruses have had different fates, HTLV-1 being often upstaged by HIV-1. However, although being very close in terms of genome organization, cellular tropism, and viral replication, HIV-1 and HTLV-1 are not completely commutable in terms of treatment, especially because of the opposite fate of the cells they infect: death versus immortalization, respectively. Nowadays, the antiretroviral therapies developed to treat HIV-1 infected individuals and to limit HIV-1 spread among the human population have a poor or no effect on HTLV-1 infected individuals, and thus, do not prevent the development of HTLV-1-associated diseases, which still lack highly efficient treatments. The present review mainly focuses on the course of HTLV-1 infection, from the initial infection of the host to diseases development and associated treatments, but also investigates HIV-1/HTLV-1 co-infection events and their impact on diseases development.

A comparative study of human T-cell lymphotropic virus-associated myelopathy in HIV-positive and HIV-negative patients in KwaZulu-Natal

Background

KwaZulu-Natal is an endemic area for HIV and human T-cell lymphotropic virus (HTLV) infection. The main neurological manifestation of HTLV is HTLV-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The effect of HIV co-infection in patients with HAM/TSP is not well documented.

Aims

To determine the prevalence of HIV seropositivity in patients with HAM/TSP and compare the clinical, laboratory and radiological features of patients mono-infected with HTLV and those dually infected with HTLV and HIV.

Methods

Adult patients referred to the Neurology Department at Inkosi Albert Luthuli Central Hospital in KwaZulu-Natal, South Africa, for the period 01 January 2004 to 31 December 2015 with a positive HTLV serology were identified from the National Health Laboratory Service database. A retrospective chart review was conducted to identify all patients who had a diagnosis of HAM/TSP and to record their HIV status. Clinical, laboratory and radiological data were compared for HIV-positive and HIV-negative patients.

Results

A total of 52 patients with HAM/TSP were identified. HIV results were available in 44 patients of whom 23 (52%) patients were HIV co-infected. Patients who were HIV-positive had a younger age of presentation compared to HIV-negative patients (median: 31 vs 50 years, p = 0.002). HIV-positive patients had a median duration of symptoms at presentation of 12 months compared to 16 months for HIV-negative patients, but the difference did not reach statistical significance (p = 0.082). The CD4 cell counts of HIV-positive patients were well preserved with a median count of 781 cells/µL.

Conclusions

HIV co-infection is commonly seen in the setting of HAM/TSP in KwaZulu-Natal. An interaction between the viruses may accelerate the development of HAM/TSP, leading to a younger age of presentation. Co-infection may have treatment implications because of CD4 counts being preserved in these patients.

Human T-lymphotropic Virus Co-infections in Adults Infected With Human Immunodeficiency Virus

INTRODUCTION

Human T-lymphotropic virus type 1 or 2 (HTLV-1/2) co-infection in patients infected with the human immunodeficiency virus (HIV) can lead to increased morbidity. Because HTLV-1/2 shares a similar transmission route with HIV, HTLV-1/2 infection may be more prevalent in HIV-infected individuals. However, rates of HTLV-1/2 co-infection among HIV-infected individuals have not been studied recently in the United States.

MATERIALS AND METHODS

We conducted a cross-sectional study using serum from 292 HIV-infected subjects from one clinic in Virginia. Serum samples were tested for co-infection with HTLV-1/2 by commercial ELISA; positive results were then confirmed via western blot, which also differentiated between HTLV-1 and -2.

RESULTS

Seven (2.4%) of the subjects were co-infected with HTLV-2. One subject (among the seven co-infected with HTLV-2) was co-infected with HTLV-1 (0.3%). The only demographic factor significantly associated with HTLV-2 infection was history of intravenous drug abuse (p=0.002).

CONCLUSIONS

While our results are limited to a single city, our low rates of co-infection do not support routine screening for HTLV-1/2 co-infection among HIV-infected individuals in the United States.

Molecular insights on analogs of HIV PR inhibitors toward HTLV-1 PR through QM/MM interactions and molecular dynamics studies: comparative structure analysis of wild and mutant HTLV-1 PR

Retroviruses HTLV-1 and HIV-1 are the primary causative agents of fatal adult T-cell leukemia and acquired immune deficiency syndrome (AIDS) disease. Both retroviruses are similar in characteristics mechanism, and it encodes for protease that mainly involved in the viral replication process. On the basis of the therapeutic success of HIV-1 PR inhibitors, the protease of HTLV-1 is mainly considered as a potential target for chemotherapy. At the same time, structural similarities in both enzymes that originate HIV PR inhibitors can also be an HTLV-1 PR inhibitor. But the expectations failed because of rejection of HIV PR inhibitors from the HTLV-1 PR binding pocket. In this present study, the reason for the HIV PR inhibitor rejection from the HTLV-1 binding site was identified through sequence analysis and molecular dynamics simulation method. Functional analysis of M37A mutation in HTLV PR clearly shows that the MET37 specificity and screening of potential inhibitors targeting MET37 is performed by using approved 90% similar HIV PR inhibitor compounds. From this approach, we report few compounds with a tendency to accept/donate electron specifically to an important site residue MET37 in HTLV-1 PR binding pocket.

Inhibition of HIV type 1 replication by human T lymphotropic virus types 1 and 2 Tax proteins in vitro

Patients with HIV-1 and human T-lymphotropic virus type 2 (HTLV-2) coinfections often exhibit a clinical course similar to that seen in HIV-1-infected individuals who are long-term nonprogressors. These findings have been attributed in part to the ability of HTLV-2 to activate production of antiviral chemokines and to downregulate the CCR5 coreceptor on lymphocytes. To further investigate these observations, we tested the ability of recombinant Tax1 and Tax2 proteins to suppress HIV-1 viral replication in vitro. R5-tropic HIV-1 (NLAD8)-infected peripheral blood mononuclear cells (PBMCs) were treated daily with recombinant Tax1 and Tax2 proteins (dosage range 1-100 pM). Culture supernatants were collected at intervals from days 1 to 22 postinfection and assayed for levels of HIV-1 p24 antigen by ELISA. Treatment of PBMCs with Tax2 protein resulted in a significant reduction in HIV-1 p24 antigen levels (p<0.05) at days 10, 14, and 18 postinfection compared to HIV-1-infected or mock-treated PBMCs. This was preceded by the detection of increased levels of CC-chemokines MIP-1α/CCL3, MIP-1β/CCL4, and RANTES/CCL5 on days 1-7 of infection. Similar, but less robust inhibition was observed in Tax1-treated PBMCs. These results support the contention that Tax1 and Tax2 play a role in generating antiviral responses against HIV-1 in vivo and in vitro.

Laboratory diagnosis of CNS infections by molecular amplification techniques

The initial presentation of symptoms and clinical manifestations of CNS infectious diseases often makes a specific diagnosis difficult and uncertain, and the emergence of polymerase chain reaction-led molecular techniques have been used in improving organism-specific diagnosis. These techniques have not only provided rapid, non-invasive detection of microorganisms causing CNS infections, but also demonstrated several neurologic disorders linked to infectious pathogens. Molecular methods performed on cerebrospinal fluid are recognized as the new 'gold standard' for some of these infections caused by microorganisms that are difficult to detect and identify. Although molecular techniques are predicted to be widely used in diagnosing and monitoring CNS infections, the limitations as well as strengths of these techniques must be clearly understood by both clinicians and laboratory personnel.

Antiretroviral therapy promotes an inflammatory-like pattern of human T-cell lymphotropic virus type 1 (HTLV-1) replication in human immunodeficiency virus type 1/HTLV-1 co-infected individuals

Upon antiretroviral therapy (ART) human immunodeficiency virus (HIV)/human T-cell lymphotropic virus type 1 (HTLV-1) co-infected individuals frequently develop neurological disorders through hitherto unknown mechanisms. Here, we show that effective anti-HIV ART increases HTLV-1 proviral load through a polyclonal integration pattern of HTLV-1 in both CD4(+) and CD8(+) T-cell subsets that is reminiscent of that typically associated with HTLV-1-related inflammatory conditions. These data indicate that preventing ART-triggered clonal expansion of HTLV-1-infected cells in co-infected individuals deserves investigation.

Neurological manifestations of coinfection with HIV and human T-lymphotropic virus type 1

HIV-individuals are at risk for human T-lymphotropic virus (HTLV) coinfection and neurological diseases. Little is known about the impact of HAART among coinfected patients. In this study, 47 out of 428 HIV individuals were coinfected with HTLV (10.9%). Coinfection was an independent variable associated with neurological outcome (odds ratio 8.73). Coinfection was associated with myelopathy [chi square (X(2)) = 93, P < 0.001], peripheral neuropathy (X(2) = 6.5, P = 0.01), and hepatitis C virus infection (X(2) = 36.5, P < 0.001). HAART did not appear to protect against neurological diseases and had no impact on HTLV proviral load.

Retroviral coinfections: HIV and HTLV: taking stock of more than a quarter century of research

Retroviral coinfections with HIV-1 and HTLV-1 or with HIV-1 and HTLV-2 occur with variable frequencies throughout the world with the highest prevalence in large metropolitan areas in the Americas, Europe, and Africa. The recognition that retroviral coinfections exist dates back to the discovery of HIV-1 over 25 years ago. Despite the large body of published information regarding the biological and clinical significance of retroviral coinfections, controversy throughout several decades of research was fueled by several flawed epidemiologic studies and anecdotal reports that were not always supported with ample statistical and scientific evidence. However, the growing consensus obtained from recent systematic and well-devised research provides support for at least three conclusions: (1) HIV-1 and HTLV-1 coinfections are often seen in the context of patients with high CD4(+) T cell counts presenting with lymphoma or neurological complications; (2) HIV-1 and HTLV-2 coinfections have been linked in some cases to a "long term nonprogressor" phenotype; and (3) differential function and/or overexpression of the HTLV-1 and HTLV-2 Tax proteins likely play a pivotal role in the clinical and immunologic manifestations of HIV/HTLV-1 and -2 coinfections. This review will recount the chronology of work regarding retroviral coinfections from 1983 through the present.

Relationship between Human T Lymphotropic Virus (HTLV) Type 1/2 Viral Burden and Clinical and Treatment Parameters among Patients with HIV Type 1 and HTLV-1/2 Coinfection

BACKGROUND

Human T lymphotropic virus types 1 (HTLV-1) and 2 (HTLV-2) are frequent copathogens among individuals infected with human immunodeficiency virus type 1 (HIV-1). The long-term effects of coinfection are unknown, and little information exists regarding how levels of HTLV-1/2 viral burden are affected by antiretroviral medications.

METHODS

Factors associated with HTLV-1/2 viral burden were examined in patients with HIV-HTLV-1/2 coinfection. A total of 72 subjects were evaluated. The variables analyzed included HTLV-1/2 proviral load, HTLV-1/2 tax/rex mRNA expression, HIV load, HTLV-1/2 viral antigen detection in peripheral blood mononuclear cell (PBMC) cultures, T cell subsets, demographic variables (age, race, sex, and reported use of injection drugs), and administration of highly active antiretroviral therapy.

RESULTS

An HTLV-1/2 proviral DNA copy number >20,000 copies/10(6) PBMCs was significantly associated with the following variables: (1) a positive HTLV-1 Western blot test result, (2) a positive HTLV-1/2 PBMC culture result, (3) a positive tax/rex mRNA result, (4) an HIV load <10,000 copies/mL, and (5) higher CD4 cell counts among subjects with HIV-HTLV-1 coinfection. There was no correlation between HTLV-1/2 proviral copy number or HTLV-1/2 tax/rex mRNA detection and administration of antiretroviral therapy.

CONCLUSIONS

HTLV-1/2 proviral burden was significantly higher among patients with HIV-HTLV-1 coinfection than among patients with HIV-HTLV-2 coinfection. Highly active antiretroviral therapy may be of limited value in controlling virus expression of HTLV-1/2 in patients with HIV-HTLV-1/2 coinfection.

The HTLV-1 neurological complex

Human T-cell lymphotropic virus type 1 (HTLV-1) is a retrovirus that infects about 20 million people worldwide and causes immune-mediated diseases of the nervous system. The classic neurological presentation of HTLV-1 infection is a myelopathy called HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). However, HAM/TSP is not the only neurological outcome that can result from HTLV-1 infection. In this Personal View, we show that HTLV-1 has a broader neurological spectrum than the names HAM/TSP suggest and that people infected with this virus can present with various isolated or assorted syndromes.