Short Communication: Prevalence and Risk Factors for Human T Cell Lymphotropic Virus Infection in Southern Brazilian HIV-Positive Patients

Abstract

HIV/human T cell lymphotropic virus (HTLV) coinfection has a large range of prevalence in the different risk groups and geographic regions of the world. Most of the HTLV-infected people live in geographic areas where the virus is endemic, as it happens in Brazil. The aim of this study was to identify HTLV prevalence and risk factors in HIV-positive patients. A cross-sectional study was conducted with 580 HIV-positive patients (mean age of 40.6 years and 45.0% men) from a specialized HIV/AIDS diagnosis and treatment center in Southern Brazil. Sociodemographic data, HIV risk factors, and HTLV-1/2 antibodies were collected. HTLV proviral DNA was detected by polymerase chain reaction (PCR). A multivariate analysis was performed to identify risk factors for HTLV infection. HTLV antibodies were detected in 29 (5.0%) and HTLV provirus in 17 (2.9%) patients. HTLV-1 was identified in 11 (64.7%) patients and HTLV-2 in 6 (35.3%) patients. No significant differences were observed between mono and coinfected patients in clinical characteristics regarding HIV/AIDS (time since HIV diagnosis, HIV viral load, lymphocytes CD4⁺ count, and use of highly active antiretroviral therapy). Blood transfusion history was significantly associated with HIV/HTLV coinfection (p=0.039). Alcohol abuse was more prevalent in HTLV-positive (47.1%) than in HIV mono-infected patients (20.4%; p=0.008). Tattooing was the only risk factor independently associated with HIV/HTLV coinfection (p=0.035). This information contributes to an understanding of the epidemiology of HIV/HTLV coinfection in Brazil.

Human T cell lymphotropic virus type 1 (HTLV-1) and type 2 (HTLV-2) belong to the Retroviridae family and share biological and molecular properties.¹ HTLV infection shows a worldwide distribution and serological prevalence varies according to geographic region, ethnic and/or racial group, and the risk factors of the analyzed population.¹

HTLV-1 is endemic in Japan, Central Africa, the Caribbean, and in some regions of Latin America.² It is considered the etiologic agent of different clinical diseases, as a degenerative neurological disorder known as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), an adult T cell leukemia/lymphoma (ATLL), HTLV-associated uveitis (HAU), and dermatological and immunological abnormalities.^3,4 HTLV-2 is mainly present in Pygmies from Africa, Amerindian populations of the Americas, and among injecting drug users worldwide.⁵ Most individuals with HTLV-2 infection remain completely asymptomatic throughout life. Genetic and immunological host factors are primarily responsible for the onset of associated diseases.⁶

In the last years HIV/HTLV coinfection has been considered a public health issue, mainly in Africa and South America.⁷ In Brazil, HTLV-1/2 seroprevalence is relatively high in HIV-positive patients and according to the Brazilian region analyzed these rate ranges reach 20% in some studies.^8,9

HTLV and HIV are transmitted by the same routes: sexual contact, breastfeeding, blood transfusion, and injecting drug use.^10,11 Vertical and sexual transmission appears to be an important route in endemic populations; otherwise blood is considered an important vehicle of transmission of HTLV-1/2, mainly in injecting drug users with HIV-1.¹² Some epidemiological and experimental studies on the influence of HTLV infection in the progression of AIDS have suggested that coinfection may promote increased replication of HIV-1 and accelerate the development of the disease.^13
–15

This study aimed to estimate the prevalence of HTLV-1 and HTLV-2 in a Southern Brazilian HIV-1 population, and investigated the possible risk factors associated with the coinfection.

A cross-sectional study was conducted in a population of 580 HIV-1-positive adult patients from the city of Canoas (located in the metropolitan region of Porto Alegre, Rio Grande do Sul state, Brazil) from July 2008 to January 2009. The target population was composed of adult patients, either receiving or not receiving HAART, and users of the referral services for patient care and antiretroviral drug supply in the city of Canoas. Sociodemographic and potential risk factors for HIV infection were obtained from a standardized individual questionnaire that was administered by a trained interviewer in a private room. Ethnicity was investigated as self-reported skin color and patients were classified as white or nonwhite. Clinical data of each patient, as well as the treatment, CD4⁺ T cell count, and viral loads, were obtained from treatment center medical records, using data from the most recent tests at the time of interview. The Alcohol Use Disorders Identification Test (AUDIT), validated in Brazilian Portuguese, was used to screen for alcohol use disorders by a score ≥8.¹⁶ The study was approved by the Research Ethics Committee of the Universidade Luterana do Brasil (process 139H/2007). All participants signed an informed consent form.

Blood samples were collected by venipuncture in 5-ml tubes, using ethylenediaminetetraacetic acid (EDTA) as anticoagulant, and afterward were centrifuged for plasma and cell separation. Plasma and buffy coat separation were divided into aliquots and stored at −20°C. The presence of antibodies to HTLV (anti-HTLV-1/2) was determined using an enzyme-linked immunosorbent assay (ELISA; Ab-Capture ELISA Test System, Ortho-Clinical Diagnostics, Raritan, NJ). HTLV-1/2-seropositive samples were subjected to polymerase chain reaction (PCR). Buffy coat samples were defrosted and processed together with positive and negative controls. The total DNA of each clinical sample was purified by a standard silica-based procedure.¹⁷ Detection of proviral DNA was performed by nested PCR using primers for the pol gene region and HTLV types were determined by restriction fragment length polymorphism (RFLP) analysis, as described previously.¹⁸

Double entry data was performed using the EPIDATA software, version 3.1. Data analysis was conducted with SPSS software, version 18.0. Quantitative variables were compared between groups using the Student's t-test or the nonparametric Mann–Whitney U test. Frequencies were compared between groups using Fisher's exact test or chi-square when indicated. Multivariate models were carried out using modified Poisson regression¹⁹ to test the independent associations of demographic, socioeconomic, clinical, and behavioral characteristics, including the use of illicit drugs, with the positive result for the HIV/HTLV coinfection. The prevalence ratio (PR) and their confidence intervals (95% CI) were computed, and the adjusted PR took into account the following factors: gender, age, education, and illicit drugs use. Associations that presented values of p between 0.05 and 0.15 were regarded as having borderline significance, and these variables were included in the modeling of confounding factors. All p values presented are two-tailed and the values of p<0.05 were considered statistically significant.

Sociodemographic, clinical, and behavioral characteristics of HIV patients included in the study are presented in Table 1. HTLV-1/2 antibodies were detected in 29 (5.0%) of 580 HIV-infected patients. HTLV-1/2 proviral DNA was detected in 17 (2.9%) samples. HIV/HTLV-coinfected patients showed lower educational levels (i.e., few years at school) than mono-infected patients (p=0.031). No other differences were observed between mono and coinfected patients with regard to sociodemographic characteristics (gender, household income, and race).

Table 1.

Distribution of Sociodemographic and Clinical Factors in HIV-Mono-Infected and HIV/Human T Cell Lymphotropic Virus-Coinfected Patients

Variable	Total (n=580)	HIV mono-infected (n=563)	HIV/HTLV co-infected (n=17)	p
Male sex	261 (45.0)	250 (44.4)	11 (64.7)	0.098
Age (years) [mean (SD)]	40.6 (10.8)	40.5 (10.7)	44.8 (12.6)	0.138
Level of education^a				0.031
Complete primary education or less	411 (70.9)	395 (70.3)	16 (94.1)
Secondary or higher education	168 (29.0)	167 (29.7)	1 (5.9)
Per capita household income, by minimum wage [mean (25–75% quartiles)]	0.7 (0.2–0.9)	0.7 (0.2–0.9)	0.6 (0.2–1.1)	0.888
Race (white)	369 (64.0)	360 (64.3)	9 (52.9)	0.337
CD4⁺ count (cells/mm³) [mean (SD)]	458.1(310.5)	460.9 (312.5)	373.7 (235.5)	0.268
HIV viral load (log₁₀ copies/ml) [mean (SD)]	2.9 (1.3)	2.9 (1.3)	3.1 (1.6)	0.689
HAART use^a	380 (73.2)	368 (73.3)	12 (70.6)	0.804
Time since HIV diagnosis (years) [mean (SD)]	5.6 (3.8)	5.5 (3.8)	6.2 (4.2)	0.378
Sexual practice^a				0.074
Heterosexual	503 (86.7)	491 (88.0)	12 (70.6)
Homosexual	28 (4.8)	26 (4.7)	2 (11.8)
Bisexual	43 (7.4)	40 (7.2)	3 (17.6)
Age at first sexual intercourse [mean (SD)]	15.9 (4.5)	15.9 (4.5)	15.1 (3.6)	0.145
Number of sexual partners in the past 12 months [mean (25–75% quartiles)]	3.6 (1.0–2.0)	3.6 (1.0–2.0)	3.6 (1.0–3.0)	0.166
Possible forms of HIV infection^b				0.116
Sex	490 (84.5)	477 (84.7)	13 (76.5)
Blood transfusion	25 (4.3)	23 (4.2)	2 (6.9)
Cutting objects	20 (3.4)	20 (3.6)	0 (0)
Sharing needles	42 (7.2)	39 (6.9)	3 (17.6)
Injecting drug use	63 (10.9)	59 (10.5)	4 (23.5)	0.089
Smoking drug use	200 (34.5)	191 (33.9)	9 (52.9)	0.104
Snorting drug use^a	163 (28.2)	155 (27.5)	8 (47.1)	0.080
Alcohol use disorder	123 (21.2)	115 (20.4)	8 (47.1)	0.008
Blood transfusion history	121 (20.9)	114 (20.4)	7 (41.2)	0.039
Tattoo	158 (27.2)	149 (26.5)	9 (52.9)	0.016
Body piercing	47 (8.1)	45 (8.0)	2 (11.8)	0.575
Dental surgery history	524 (90.3)	511 (90.8)	13 (76.5)	0.050
Surgery history	350 (60.3)	340 (60.4)	10 (58.8)	0.897

Totals do not coincide due to lack of data from certain participants in the study.

Multiple response.

HAART, highly active antiretroviral therapy; HTLV, human T cell lymphotropic virus.

Sexual transmission was reported by patients as the most probable HIV infection route (84.5%). A higher frequency of patients stating homosexual or bisexual practice was observed in coinfected (29.4%) than in mono-infected (11.9%) patients (p=0.030). Blood transfusions were associated significantly with HIV/HTLV coinfection (p=0.039). No differences were observed in regard to surgery, dental surgery, or body piercings. Coinfected patients reported illicit drug use more frequently (64.7%) than mono-infected patients (44.2%), but differences did not reach significance (p=0.095). Alcohol misuse was also more prevalent in HTLV-positive (47.1%) than in HIV mono-infected patients (20.4%) (p=0.008). To determine which factors are independently associated with HIV/HTLV coinfection, a multivariate analysis was performed (Table 2). Statistical significance was observed only for tattooing (PR 2.61; 95% CI: 1.07–6.38; p=0.035).

Table 2.

Multivariate Analysis of Risk Factors in Human T Cell Lymphotropic Virus Infection in HIV-Positive Patients (n=580).

Variable	PR adjusted	CI (95%)	p-value
Male sex	1.16	0.34–3.98	0.814
Age >45 years old	2.19	0.92–5.20	0.075
Low schooling	6.17	0.73–51.84	0.094
Heterosexual preference	2.31	0.80–6.67	0.122
Sex debut <15 years old	1.10	0.35–3.44	0.866
Snorting drug use	1.19	0.42–3.40	0.741
Injecting drug use	0.98	0.24–4.12	0.982
Smoking drug use	0.92	0.37–2.36	0.878
Alcohol use disorder	2.30	0.81–6.53	0.118
Tattoo	2.61	1.07–6.38	0.035

HTLV-1 was identified in 11 (64.7%) and HTLV-2 in 6 (35.3%) patients. HTLV-1-infected patients were older (48.7±11.9 years) than those infected with HTLV-2 (37.7±11.2 years), but this difference did not reach statistical significance (p=0.070). HIV/AIDS clinical characteristics (time since HIV diagnosis, HIV viral load, lymphocytes CD4⁺ count, and HAART use) were not different between patients infected with HTLV-1 and 2.

HIV/HTLV coinfection is growing worldwide, mainly in South America and Africa. Seroprevalence studies in the United States, Europe, and developing countries demonstrated a high frequency (5–15%) of patients coinfected with HTLV-1/2 and HIV-1.²⁰ To date, a variable prevalence of HIV/HTLV coinfections has been demonstrated in Brazil. In the Brazilian states of Bahia, Rio de Janeiro, and São Paulo HTLV-1/2 rates were 23, 11.1, and 13.6%, respectively.^8,21,22 A study conducted in the city of Porto Alegre (same geographic area as the present study) reported an HTLV prevalence of 2.4% in HIV patients.²³ In a study conducted in the state of Paraná, the HTLV prevalence was 6.4%.²⁴ Our study showed a similar rate (5.0%) of HIV/HTLV coinfection (p=0.257).

There are three usual transmission routes for HTLV: sexual (with exchange of body fluids), parenteral (through whole blood transfusion or needle sharing), and mother to infant (especially by breastfeeding). In Brazil, studies associated HIV/HTLV coinfection with risk factors that include previous blood transfusion, intravenous drug usage, and sexual contact with multiples partners.^11,24
–26 In the present study, we found that the only risk factor independently associated with HTLV infection in HIV-positive patients was tattooing (a parenteral route). In Brazil, tattooing was not regulated until recently and most of the tattooing occurred in irregular conditions before 2010.²⁷ Presumably, nonsterile equipment and/or nondisposable equipment were the main source of transmission. Tattoing has been previously associated with HTLV-2 transmission in intravenous drug users (IDUs).²⁸

HIV/AIDS clinical characteristics (time since HIV diagnosis, HIV viral load, lymphocytes CD4⁺ count, and HAART use) showed no significant differences between mono-infected and coinfected patients in our study. Turci et al.²⁹ demonstrated an association between coinfection, high CD4⁺/CD8⁺ load, and delayed progression to AIDS in patients who had received HAART therapy. The coinfection also has been linked to low levels of HIV RNA and a decrease in immune activation marker CD38 on CD8⁺ T cells.³⁰ Other Brazilian studies have shown that HAART introduction and HIV/HTLV coinfection were linked to decreased survival and increased risk for HAM/TSP and other neurological manifestations.¹

The type of study has limitations with regards to causality, as it has collected information about the exposure and outcome simultaneously. Another limitation of our study is the small number of coinfected individuals, which limits the statistical power of the results to detect differences. In addition, the aim of this study did not include measuring clinical data or virologic measures related to HTLV; such information could be gathered in future studies and analyzed to better define the clinical manifestations of HTLV-1 and 2 infection.

In conclusion, the presence of tattoos was the only risk factor independently associated with HIV/HTLV coinfection. Educational interventions on risk and prevention of blood-borne and sexually transmitted viral infections could be essential for reducing the prevalence of these infections.

Footnotes

Acknowledgments

The authors would like to thank the patients and staff of the Specialized Service (SAE) and Testing and Counseling Center (CTA) of Canoas, RS, for their collaboration in the development of this study. This research project was funded by the Brazilian Ministry of Health, Secretaria de Vigilância em Saúde (Department of Health Surveillance), Programa Nacional de Doenças Sexualmente Transmissíveis e Aids (MS/SVS/PN-DST/AIDS–Brazilian Program of Sexually Transmitted Diseases and AIDS–Cooperation Term 282/07) through the International Technical Cooperation Project AD/BRA/03/H34, established between the Brazilian government and the United Nations Office on Drugs and Crime (UNODC).

Author Disclosure Statement

No competing financial interests exist.

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