|Year : 2020 | Volume
| Issue : 2 | Page : 73-78
Human T lymphotropic virus antibodies seroprevalence among healthy blood donors and high risk groups at Riyadh regional laboratory in Riyadh, Saudi Arabia
Fadel Hassan Al-Hababi1, Ibrahim Mohammed Al-Deailej2, Hussein Ali Al-Sulatan1, Yasser Abdullah Al-Ghamdi1, Kamel Mohammed Al-Dossari2
1 Department of Microbiology and Virology, Riyadh Regional Laboratory, Riyadh, KSA
2 Department of Microbiology and Virology, Riyadh Regional Blood Bank, Riyadh Regional Laboratory, Riyadh, KSA
|Date of Submission||15-Mar-2020|
|Date of Decision||29-Mar-2020|
|Date of Acceptance||29-Mar-2020|
|Date of Web Publication||1-Jul-2020|
Fadel Hassan Al-Hababi
Department of Microbiology and Virology, Riyadh Regional Laboratory, King Saud Medical Complex, P.O. Box 61734, Riyadh 11757
Source of Support: None, Conflict of Interest: None
Aims: Transmission of human T lymphotropic viruses (HTLV) testing performed as routine pretransfusion screening. In Riyadh city the prevalence of HTLV1/2 among healthy volunteers in Riyadh city more than two decades. In addition, no information available related to the HTLV1/2 infections in HIV/AIDS patients. This study first aims to determine the prevalence of HTLV1/2 infections among healthy volunteers in Riyadh city. Second, as HTLV1/2 transmission similar as HIV routes, we assess rates of HTLV1/2 coinfection among patients infected with HIV. Materials and Methods: A retrospective study depends on the data obtained from Riyadh Regional Laboratory (RRL) for 3 years, 2017–2019. The samples enrolled in study consist of 114638 healthy blood donors and 243 patient samples referred to RRL virology samples. In addition, 474 HIV-infected patients were included. All serum samples tested to detect infection with HTLV1/2 by commercial CMIA or enzyme-linked immunosorbent assay kits and any positive results confirmed and differentiated by western blot. Results: Among of 114638 blood donations were tested, only two confirmed HTLV1 positive found from two (0.002%) donors, one of them is Saudi female and the second donor was expatriates. None was positive for anti-HTLV2. The overall HTLV1 prevalence was 1.7/100,000 donations during the 3 years tested. In addition, none of the referred sample was positive for anti-HTLV1/2. In addition, a large number of HIV-positive individual population enrolled none tested positive for HTLV1/2. Conclusions: HTLV seroprevalence is very low among healthy blood donors population in Riyadh city, which reflects the situation in the general population. However, screening for HTLV1/2 blood donors for the first donation from endemic countries donors would keep safe blood donation in Saudi Arabia.
Keywords: HTLV, HTLV/HIV coninfection, seroprevalence
|How to cite this article:|
Al-Hababi FH, Al-Deailej IM, Al-Sulatan HA, Al-Ghamdi YA, Al-Dossari KM. Human T lymphotropic virus antibodies seroprevalence among healthy blood donors and high risk groups at Riyadh regional laboratory in Riyadh, Saudi Arabia. Saudi Crit Care J 2020;4:73-8
|How to cite this URL:|
Al-Hababi FH, Al-Deailej IM, Al-Sulatan HA, Al-Ghamdi YA, Al-Dossari KM. Human T lymphotropic virus antibodies seroprevalence among healthy blood donors and high risk groups at Riyadh regional laboratory in Riyadh, Saudi Arabia. Saudi Crit Care J [serial online] 2020 [cited 2021 Jun 25];4:73-8. Available from: https://www.sccj-sa.org/text.asp?2020/4/2/73/288727
| Introduction|| |
Human T-cell leukemia virus type 1 and type 2 (HTLV1 and HTLV2) was discovered in 1979 and it is belong to the family of Retroviridae from the genus of deltaretrovirus. HTLV1 is and associated with many aggressive diseases such as malignancy of T cells of adult T-cell leukemia/lymphoma (ATLL) and myelopathy/tropical spastic paraparesis (HAM/TSP)., In addition, responsible for predisposes patients to disseminate Strongyloidesstercoralis infection (strongyloidiasis). HTLV2 infection less common and associated with HAM/TSP and other neurological disorders.
HTLV1 infects about 15–20 million people worldwide. This virus is endemic in the southwestern part of Japan, sub-Saharan Africa, South America, and the Caribbean and some foci in the Middle East such as (Iran) and Australia-Melanesia. The main modes of HTLV1 transmission include mainly from mother to child through breastfeeding, transfusion of blood products, intravenous drug use (IDU), sexual contact, and organ transplantation., While HTLV2 prevalence is limited in specific geographical and ethnic groups that occurs mainly in the Americas and among pygmy tribes in Africa, Native Americans in North, Central and South America showed a positive for HTLV2 with different rates (5%–30%).,
Although the methods for human-to-human transmission of both HTLV1 and HTLV2 are similar, including sexual contact, breastfeeding, and blood transfusion., Seroprevalence varies greatly because HTLV is transmitted mainly through blood products containing HTLV-infected lymphocytes, and therefore free viral particles cannot be found in infected blood plasma, lymphocytes without viruses are less contagious, as well as the life of HTLV1 particles is extremely short estimated 0.6 h at 37°C., HTLV1 transmission associated with blood transfusion requires at least 90,000 cells with HTLV1 infection to receive infection in the recipient. Thus, reducing leukocytes below this limit would reduce the occurrence of HTLV1 by blood transfusion.
There are few studies related to HTLV infection were done in some hospitals in Riyadh and all of them more than two decade ago, while other studies were done in other cities though the kingdom ranges from more a decade to few years ago. Therefore, we aimed first to determine the prevalence of HTLV1/2 among healthy volunteers in Riyadh city, as well as to justify the inclusion of HTLV antibody screening in blood transfusion safety protocols. This study appears to be the first of its kind in Riyadh city at the largest blood donation center and center for confirmatory HTLV screening cases for the all Riyadh region. In addition, many studies suggested that these HIV and HTLV coinfection could lead to increase morbidity. However, HTLV coinfection among HIV-infected patients did not studied before in Saudi Arabia. Thus, the second aim is to evaluate prevalence of HTLV1/HTLV2 among high-risk HIV infection patients.
| Materials and Methods|| |
Study design, participants, and sample collection
Data obtained from the main database of Riyadh Regional Laboratory and Blood Bank (RRL and BB) between the years 2017 and 2019 and reviewed retrospectively. In 114,638 blood donation records were evaluated and considered eligible for blood donation, age were between 18 and 60 years of and all of them were voluntary donors (for low-risk group). During the same 3-year period (February 2017 to February 2019), 243 blood serum/blood plasma samples were referred to the Virology-Microbiology Department, RRL, for confirmation diagnosis of HTLV infection. These samples were from all over the blood banks in the Riyadh region (except for RRL BB) and from a variety of clinical settings that were previously found reactive and referred for confirmation tests. Furthermore, samples from patients who considered at risk of HTLV infection such as HIV clinic patients and pre transplantation. In addition, 474 frozen serum samples from known HIV-positive patients (for high risk group) were tested.
The presence of anti-HTLV1/2 antibodies is primarily assessed using Abbott ARCHITECT rHTLV1/2 chemiluminescent assay (CLIA; Abbott Laboratories, IL). The results described as qualitative detection of HTLV-1 and HTLV-2 antibodies by measuring the individual absorbance of optical density of each sample after calculation signal-to-cutoff (S/CO ratio). Negative results are samples with S/CO ratio <1, which indicates that no HTLV antibodies detected. Positive results are samples with S/CO ratio >1. And when the S/CO ratio between 0.9 and 1.1 considered borderline.
Initially reactive (IR) samples were retested in duplicate and the samples that repeatedly reactive (RR) subjected to a high-risk donor group for an HTLV test on the diagnosis of MP HTLV1/2 enzyme-linked immunosorbent assay (ELISA) 4.0 examination (MP Biomedicals, Germany), then confirmed by line immunoassay (LIA) (MP Biomedicals, Germany) in the Department of Virology at RRL, Riyadh. Samples that were positive by confirmatory Western blot test considered positive samples infected with HTLV1. This test is highly specific based on the use of recombinant glycoproteins from HTLV1/2. In addition, it allows the distinction between the two types of virus by interacting with antibodies against recombinant versions of gp46-I and gp46-II. Samples results considered negative when there are no bands, and considered positive when two envelope glycoproteins (Gd21 and rgp46-I) and at least one band (p19 with or without p24) were detected. In case when the interactions are present on other bands but absent against gp46I and gp46II glycoprotein or existed against both, it was “untyped” diagnosed HTLV infection. It considered indeterminate in the presence of insufficient bands to diagnose the infection.
We used Excel to summarize the data collected for descriptive and analytical statistics. The prevalence of HTLV calculated per 100,000 blood donation (percentage (%) and 95% confidence interval [95% CI]), specificity and positive predictive value (PPV) calculated by for the assays were calculated based on confirmed HTLV samples by WB seropositive or seronegative using the following formulas. Where a is the number of true positives, b is the number of false positives, c is the number of false negatives, and d is the number of true negatives: % sensitivity = a/(a + c) ×100; % specificity = d/(b + d) ×100; and % PPV = a/(a + b) ×100. These analysis were performed with MedCalc statistical software (available online; https://www. medcalc. org). Cohen's kappa (κ) was calculated to assess agreement between Architect and MP Biomedicals HTLV1/2 ELISA 4.0. The Cohen's κ value was interpreted as κ value of 0.91–1.00 near-perfect agreement.
| Results|| |
Blood donors and referred samples
Among the total 114,638 samples tested from blood donations from 2017 to 2019 have been collected at Riyadh Regional Blood Bank. The age of the donors ranged from 18 to 60 years (mean age 34.8 ± 10.4). The majority of the donors were non-Saudi (54.4%), most of them were male 99.1 and 0.9 were female. Less than half of them are Saudi 46.6%. Of these the majority were male 96.6% and 3.4% were female. In addition, most of those donors (72.2%) were first time-donated blood and only (27.8%) had repeated donations. The demographic characteristics of blood donors summarized in [Table 1].
Of these 114,638 blood donors screened by HTLV1/2 ELISA. 114398/114638 (99.8%) were initially nonreactive and 242 individuals were IR. These IR samples then referred to Virology section for confirmatory testing which tested samples with the HTLV1/2 ELISA 4.0 assay and confirmed with LIA assay and identify the HTLV subtype. At virology section, all samples were retested using MP Biomedicals HTLV1/2 kit for screening to test two tubes for each donor referred. A tube from blood bag and a tube from the donor for quality assurance. On retesting, 220/242 (91.7% [overall 0.19%]) samples were showed negative screening results with the second kit. only 22/242 (9.1% (overall 0.02%)) individuals were found to be positive by HTLV1/2 ELISA. These positive samples then tested by LIAMP kit HTLV1/2 to confirm diagnosis. According to the LIAassay, 2/22 (0.83% [overall 0.002%]) samples were indeterminate; 18/22 (7.4% [overall 0.016%]) samples were negative and 2/22 (0.83% (overall 0.002%)) were positive for HTLV. Those two positive samples both found HTLV1 type. These positive samples related to an Indian nationality, male age 41 years old and second donor was Saudi female with 24 years old. No HTLV2 found [Table 2]. These results showed that HTLV1 prevalence among Riyadh region was 1.7/100,000 donations during the 3 years' period (95% CI: 88.6–108/100,000). These results of Architect giving a 100% sensitivity in detecting HTLV-positive samples and specificity of 99.8% (95% CI: 99.76% to 99.82%) with PPV 0.01% (95% CI 0.01% to 0.01%). The agreement with percentage showed almost perfect agreement between HTLV ½ Architect assay and MP Biomedicals HTLV1/2 results nearly 99.98% between the two kits and Cohen's kappa value equals 0.96. These results of screening kits showed the possibility to lead to false-positive results, indicating the need of WB for confirmation requirements. Of the 243 referred patients tested, 234 had a negative result of HTLV1/2 antibody. Nine of the remaining patients (3.7%) gave the result of the initial reaction, and these samples retested by several LIAHTLV1/2. Of these samples, 7/9 (77.8%, (2.88% overall) negative, and two indeterminate samples 2/9 (22.2%, (0.82% overall). No positive HTLV1/2 result observed among HIV patients [Table 2].
|Table 2: Summary of the results obtained from blood donors and referred serum samples analyzed for the presence of human T-lymphotropic viruses1/2 antibodies results screening and western blot tests|
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HIV patient results
An additional 474 samples from high-risk for STIs were tested. HIV infection defined as evidence of current exposure to HIV seropositive and detection of HIV RNA. Among of 474 HIV-infected patients evaluated in the study. The majority of participants were male 303 (79.1%) with a mean age of 35.4 ± 10.78 years (95% CI 35.25–36.64) [Table 3]. Among HIV-positive patients, only one sample was IR and RR reactive for anti-HTLV1/2antibodies [Table 3].
|Table 3: Summary of the results obtained from HIV positive samples analyzed for the presence of human T-lymphotropic viruses1/2 antibodies|
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| Discussion|| |
HTLV1/2 infection is associated with high mortality and poor outcome include ATLL, and HAM/TSP with no cure available yet. In endemic areas, HTLV is predominantly acquired through mother-to-child transmission, breastfeeding, and through sexual contact. Blood transfusion is an important source of HTLV infection. Therefore, blood screening programs of HTLV antibodies implemented in many countries including Saudi Arabia as mandatory blood donation protocol. In addition, tissue and stem cell donations currently routinely screened in a number of countries. In some countries, blood services perform screening of first-time donors or rely on leukodepletion as an HTLV risk-reduction measure.
Prevention is the best way to control the virus burden outcome. Therefore, to control the virus transmission, it is necessary to control the common transmission routes, which mainly include blood transfusion and sexual intercourses. The first strategy to prevent HTLV transmission different countries have introduced anti-HTLV blood screening to ensure the blood safety. However, different countries have followed different policies depends on increasing prevalence rates per donations in first-time donors and consequently the cost effectiveness. HTLV screening is mandatory for example in the United States and several European countries such as the UK, France, Demark, Greece, Portugal, Romania, and Sweden and recommended in others such as Ireland, Luxembourg, and Norway. Some Scandinavian countries only did it on first-time donors, while Norway and Finland stopped screening. On the other hand, Italy and Germany, HTLV1/2 blood screening not recommended., Seroprevalence of healthy blood donors infected with HTLV1 or HTLV2 among these countries ranges from 0.0006% (9) to 0.046% (10) in Europe. Romania showed an exception which reported rates of HTLV1 reach up to 0.053% in first-time blood donors. In the UK, a study between 2002 and 2006, showed that prevalence was higher among first time new donors 10-fold than repeat donation and they estimated the risk of potentially infectious donation at 0.11/million donations.
This country implemented both strategies, anti-HTLV screening and blood cell leukoreduction. However, cost-effectiveness is a key issue and frequently discussed in several countries, even in high income countries beside the limited resources countries. Therefore, the revision of these strategies were reviewed in frequently related to HTLV screening based on factors including virus prevalence, risk factors of transmission and cost-effectiveness. In this study, data of blood donations included first-time and repeat donors screened for anti-HTLV antibodies collected from the biggest blood donation center in RRL at Riyadh city. These first-time donors and repeat donors considered a low-risk as they negative for sexually transmitted disease (STI) including HIV. Additionally high-risk groups, which were seropositive for HIV, collected and tested. A total of 114638 donors were examined, of whom 46.4% were Saudi and 53.6 non-Saudi. Two men samples confirmed seropositive for HTLV1. The first sample related to Saudi citizen women while the second belong to non-Saudi (Indian) donor. The overall HTLV1/2 seroprevalence was 1.7 per 100,000. These results indicate the absence or very low prevalence of HTLV infection in the general population. This conclusion is strengthen by failing to find any positive case of HTLV infection among high risk STI HIV infection patients. The seroprevalence of HTLV1/2 infection is below 0.002% among blood donation in Riyadh. In addition, these blood centers have been implemented leukoreduction of blood components to preclude the transmission of infectious agents present in white blood cells. Taken these factors together proceed and to address universal screening for HTLV1/2 infection in blood donation centers and its cost effectiveness discussionable and considerable to our medical services authorities that consider the reassessment of risk HTLV transmission and then HTLV screening testing. However, HTLV1/2 screening should take highly consideration for blood donors coming from endemic areas.
A study in Riyadh university hospital, 1998, screened 34,541 blood donors for HTLV1/2, 60.8% of them were Saudi. And only three non-Saudis found to be positive on initial screening but diagnosed as indeterminate by western blot. In Al-Hofuf, Al-Hasa, during 1997–2003, screened 47426 blood donors for HTLV1/2 antibodies. They found only three 3 (0.006%) donors showed confirmed detected HTLV, two of them were expatriates (Indian) and one was native Saudi donor. In Eastern Saudi Arabia region, 13,443 blood samples from blood donors in between 1998 and 2001 screened. They found only eight HTLV positive cases for (0.060%), five of them (0.056%) belonged to Saudi and three (0.113%) to non-Saudi donors and (6/8) positive were for patients without history of known risk factor for HTLV1/2 transmission. In more recent studies, such as in Majmaah from August 2015 to March 2017, they screened 3028 blood samples from blood donors and they found only 6 (0.20%) positive to HTLV. Collectively, all these studies conclude that the very low prevalence of HTLV1/2 among Saudi donors does not support routine screening, and screening could be performed for other nationalities where HTLV1/2 is endemic. This conclusion were proposed from a large study conducted in Jeddah In large study conducted in Jeddah from donor-testing results from main Blood donation center at KAUH by reviewing 10-year donation data, from 2006 to 2015. They screened 107,419 donors and the Saudis compromised 47.6%. They found only 95 (0.088%) donors showed positive to HTLV screening tests and they did not find positive by Western blot. They conclude that screening of HTLV in native Saudi blood donors is not cost effective. In this study they estimate that the average cost of testing US$ 171 870/year. Moreover, they propose to change the policy from mandatory testing for all donors to be replaced with screening donors coming from endemic area. This accompanied by universal leukodepletion performance, which could lead to a reduction of testing cost and keeping safety blood.
HIV and HTLV coinfection documented because they share similar transmission modes mainly sexual contact, breastfeeding, blood transfusion, and IDU and they shared the tropism for T-lymphocytes. While T-CD4+ for HTLV1 infection and HTLV2 preferentially infect CD8+ cells. This coinfection may worsen clinical related outcomes,, includes progress with higher CD4+ T cell counts and higher levels of activation markers which account for a faster progression to AIDS., However, rates of HTLV ½ coinfection among HIV-infected individuals have not been studied in Saudi Arabia. All studies among blood donation as well as this study showed very low prevalence in Saudi Arabia general population. No study included people with a known risk for blood-borne diseases. This study is could be the first in test HTLV1/2 in HIV1 infected individuals in Saudi Arabia. Here, we performed screening tests for HTLV1/2 antibodies in 474 HIV confirmed positive cases identified by detected RNA and INNO-LIA tests at RRL virology section. We did not find positive of these HIV-positive patients showed positive with HTLV1 or 2 infection among this study population. However, most of studies related to HIV and HTLV1/2 coinfection was contributed the high risk significantly associated more frequently with history of IDUs from people who inject drugs (PWID).,
Saudi Arabia has become a land of work immigration from several countries in African, Central and Eastern Asia in recent decades as results of socio-economic factors. Some of these countries areas with an intermediate or high HTLV endemicity such as India, Philippine. In this study, the prevalence of blood donors seropositive for HTLV1 was 1.7 per 100,000 donations. Here, it is important to mention that most of the blood donors are non-Saudi, around 60% of blood donation and highly needed. Therefore, it should take the maximum effort to keep blood as safe as possible. Thus, to keep this country at low level of prevalence of HTLV infection, the continued screening of HTLV1/2 for blood donors especially in the first donation from the affected countries, will contribute to maintain blood donation safety and save public health.
The lack of PBMC cells is the main limitation in this study. These cells were required for performing the molecular confirmatory assay to identify true reactivity in samples with positive and indeterminate blot results by detection of HTLV1/2 pro-viral DNA. However, LIA assays efficient in confirming HTLV-1 seropositivity by showing a low incidence of indeterminate results with high agreement with PCR and sensitivities reach to 97.2%., In addition, in HIV patients, the risk-associated factors such as PWID were not identified.
| Conclusions|| |
This study data show very low rate of HTLV1/2 infection among Riyadh city blood donors. Also, very low rate among the citizen population and non-Saudi residents in regular donors and high-risk STI population. This country is attracting populations from Asian and Middle Eastern countries to stay for work in Saudi Arabia. While some of these countries are endemic for HTLV1/2, periodic surveillance will be useful to monitor new emerging and re-emerging diseases would be required. Absence or very low rate of HIV and HTLV coinfection do not support routine testing for HTLV among HIV infected patients. Finally, the consideration of implementing technologies such as leukodepletion appears necessary for the safety of blood supply in Saudi Arabia.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Orland JR, Engstrom J, Fridey J, Sacher RA, Smith JW, Nass C, et al
. Prevalence and clinical features of HTLV neurologic disease in the HTLV outcomes study. Neurology 2003;61:1588-94.
Futsch N, Mahieux R, Dutartre H. HTLV 1, the other pathogenic yet neglected human retrovirus: From transmission to therapeutic treatment. Viruses. 2017;10:1.
Salvador F, Sulleiro E, Piron M, Sánchez-Montalvá A, Sauleda S, Molina I. Seroprevalence of Strongyloides stercoralis infection among HTLV-I infected blood donors in Barcelona, Spain: A cross-sectional study. Acta Trop 2017;176:412-4.
Biswas HH, Engstrom JW, Kaidarova Z, Garratty G, Gibble JW, Newman BH, et al
. Neurologic abnormalities in HTLV-I-and HTLV-II-infected individuals without overt myelopathy. Neurology 2009;73:781-9.
Armstrong MJ, Corbett C, Rowe IA, Taylor GP, Neuberger JM. HTLV-1 in solid-organ transplantation: Current challenges and future management strategies. Transplantation 2012;94:1075-84.
Gessain A, Cassar O. Epidemiological aspects and world distribution of HTLV-1 infection. Front Microbiol 2012;3:388.
Willems L, Hasegawa H, Accolla R, Bangham C, Bazarbachi A, Bertazzoni U, et al
. Reducing the global burden of HTLV-1 infection: An agenda for research and action. Antiviral Res 2017;137:41-8.
Alessio L, Minichini C, Starace M, Occhiello L, Caroprese M, Di Caprio G, et al
. Low prevalence of HTLV1/2 infection in a population of immigrants living in southern Italy. PLoS Negl Trop Dis 2018;12:e0006601.
Fujino T, Nagata Y. HTLV-I transmission from mother to child. J Reprod Immunol 2000;47:197-206.
Stuver SO, Tachibana N, Okayama A, Shioiri S, Tsunetoshi Y, Tsuda K, et al
. Heterosexual transmission of human T cell leukemia/lymphoma virus type I among married couples in Southwestern Japan: An initial report from the Miyazaki Cohort Study. J Infect Dis 1993;167:57-65.
Pasquier A, Alais S, Roux L, Thoulouze MI, Alvarez K, Journo C, et al
. How to control HTLV-1-associated diseases: Preventing de novo
cellular infection using antiviral therapy. Front Microbiol 2018;9:278.
Sobata R, Matsumoto C, Uchida S, Suzuki Y, Satake M, Tadokoro K. Estimation of the infectious viral load required for transfusion-transmitted human T-lymphotropic virus type 1 infection (TT-HTLV-1) and of the effectiveness of leukocyte reduction in preventing TT-HTLV-1. Vox Sang 2015;109:122-8.
Marcon CE, Campos KR, Silva GB, Schuelter-Trevisol F, Schlindwein AD, Trevisol DJ, et al.
The first survey of human T-cell lymphotropic viruses (HTLV) in HIV/AIDS patients in Santa Catarina State, Brazil. Rev Inst Med Trop Sao Paulo 2019;61:e53.
Ireland G, Croxford S, Tosswill J, Raghu R, Davison K, Hewitt P, et al
. Human T-lymphotropic viruses (HTLV) in England and Wales, 2004 to 2013: testing and diagnoses. Euro Surveill, 2017;22:30539.
Laperche S, Worms B, Pillonel J, European Network of Transfusion Medecine Societies, Steering Committee. Blood safety strategies for human T-cell lymphotropic virus in Europe. Vox Sang 2009;96:104-10.
Ruggieri M, Berini C, Ducasa N, Malkovsky M, Fisch P, Biglione M. Molecular detection of human T-lymphotropic virus type 1 infection among oncology patients in Germany: A retrospective view. PLoS One 2019;14:e0217560.
Davison KL, Dow B, Barbara JA, Hewitt PE, Eglin R. The introduction of anti-HTLV testing of blood donations and the risk of transfusion-transmitted HTLV, UK: 2002-2006. Transfus Med 2009;19:24-34.
Arif M, Ramia S. Seroprevalence of human T-lymphotropic virus type I (HTLV-I) in Saudi Arabia. Ann Trop Med Parasitol 1998;92:305-9.
Ul-Hassan Z, Al-Bahrani AT, Panhotra BR. Prevalence of human T-lymphotropic virus type I and type II antibody among blood donors in Eastern Saudi Arabia. Saudi Med J 2004;25:1419-22.
Fawaz NA, Tamim H, Almawi WY. Low prevalence of antibodies to human T-lymphotropic virus-I/II among blood donors in Eastern Saudi Arabia. Am J Infect Control 2005;33:189-91.
Alaidarous M, Choudhary RK, Waly MI, Mir S, Bin Dukhyil A, Banawas SS, et al
. The prevalence of transfusion-transmitted infections and nucleic acid testing among blood donors in Majmaah, Saudi Arabia. J Infect Public Health 2018;11:702-6.
Hindawi S, Badawi M, Fouda F, Mallah B, Mallah B, Rajab H, et al
. Testing for HTLV 1 and HTLV 2 among blood donors in Western Saudi Arabia: Prevalence and cost considerations. Transfus Med 2018;28:60-4.
Beilke MA. Retroviral coinfections: HIV and HTLV: Taking stock of more than a quarter century of research. AIDS Res Hum Retroviruses 2012;28:139-47.
Caterino-de-Araujo A, Magri MC, Sato NS, Morimoto HK, Brigido LF, Morimoto AA. Inability to detect human T cell lymphotropic virus type 2-specific antibodies in a patient coinfected with HIV-1, human T cell lymphotropic virus type 1, human T cell lymphotropic virus type 2, and hepatitis C virus. AIDS Res Hum Retroviruses 2014;30:97-101.
Bahia F, Novais V, Evans J, Le Marchand C, Netto E, Page K, et al
. The impact of human T-cell lymphotropic virus I infection on clinical and immunologic outcomes in patients coinfected with HIV and hepatitis C virus. J Acquir Immune Defic Syndr 2011;57 Suppl 3:S202-7.
Gudo ES, Bhatt NB, Bila DR, Abreu CM, Tanuri A, Savino W, et al
., Co-infection by human immunodeficiency virus type 1 (HIV-1) and human T cell leukemia virus type 1 (HTLV-1): Does immune activation lead to a faster progression to AIDS? BMC Infect Dis 2009;9:211.
Bhatt NB, Gudo ES, Semá C, Bila D, Di Mattei P, Augusto O, et al
. Loss of correlation between HIV viral load and CD4+T-cell counts in HIV/HTLV-1 co-infection in treatment naive Mozambican patients. Int J STD AIDS 2009;20:863-8.
Abad M, Dronda F, Dominguez E, Moreno S, Vallejo A. HTLV-2b among HIV type 1-coinfected injecting drug users in Spain. AIDS Res Hum Retroviruses 2011;27:579-83.
Jõgeda EL, Avi R, Pauskar M, Kallas E, Karki T, Des Jarlais D, et al
. Human T-lymphotropic virus types 1 and 2 are rare among intravenous drug users in Eastern Europe. Infect Genet Evol 2016;43:83-5.
Umeki K, Umekita K, Hashikura Y, Yamamoto I, Kubo K, Nagatomo Y, et al
. Evaluation of line immunoassay to detect HTLV-1 infection in an endemic area, Southwestern Japan; comparison with polymerase chain reaction and Western Blot. Clin Lab 2017;63:227-33.
Campos KR, Gonçalves MG, Costa NA, Caterino-de-Araujo A. Comparative performances of serologic and molecular assays for detecting human T lymphotropic virus type 1 and type 2 (HTLV-1 and HTLV-2) in patients infected with human immunodeficiency virus type 1 (HIV-1). Braz J Infect Dis 2017;21:297-305.
[Table 1], [Table 2], [Table 3]