Investigation on HTLV Infection among Voluntary Blood Donors in Wuzhou City ()
Human T lymphotropic virus (HTLV) is closely related to leukemia and can cause other diseases; Due to the harmfulness of diseases caused by HTLV and the characteristics of blood transmission, many countries and regions pay more and more attention to the detection and confirmation of HTLV, and gradually carry out systematic investigation and research on the infection situation of HTLV. Transfusion of blood products containing HTLV infected lymphocytes is the most common mode of transmission of HTLV through blood; Therefore, the most direct and effective method to prevent HTLV transmission through blood transfusion is HTLV screening for unpaid blood donors; At present, in some developed countries and regions with high prevalence of HTLV, HTLV screening has been included in the routine items of blood screening for blood donors [ 1 , 2 ]. The research on HTLV in China is still in its infancy, and HTLV is not included in the routine screening of blood donors in the blood station technical operating procedures (2019 version). The purpose is to understand the HTLV infection of unpaid blood donors in Wuzhou City, and to provide data support for assessing the risk of HTLV transmission through blood transfusion. At the same time, it also provides the monitoring data of this outpost for the national health administration department, so as to provide a scientific basis for whether the country lists HTLV-I/II screening as a routine screening project for unpaid blood donation. According to the national monitoring requirements for HTLV infection in Guangxi, Wuzhou City, as one of the monitoring points, the laboratory of our station conducted HTLV-I/II serological screening on blood samples collected from unpaid blood donors in Wuzhou City from January 2018 to June 2018 and from December 2019 to August 2020. The test results are reported as follows.
2. Materials and Methods
2.1. Specimen Source
There are 20222 blood samples from unpaid blood donors in Wuzhou central blood station from January 2018 to June 2018 and from December 2019 to August 2020.
2.2. Instruments and Reagents
2.2.1. Instrument
Xantus44/OH-150 automatic sampler (Shenzhen Aikang Electronics Co., Ltd.), TECAN (Tecan) automatic enzyme immunoassay workstation FREEDOM EVOLYZER-2 200 (Swiss TECAN SCHWEIZ company), FAME24/20, FAME24/30 full Automatic enzyme immunoassay system (Hamilton, Switzerland), the above instruments and equipment are verified and calibrated every year.
2.2.2. ELISA Kit
Human T-lymphocytic leukemia virus antibody ELISA detection kit (Beijing Wantai Bio-Pharmaceutical Co., Ltd.), batch numbers T20170904B, T20191109B; the reagents have the manufacturer’s inspection report.
2.3. Methods
The domestic Wantai anti-HTLV-I/II ELISA detection reagent (double-antigen sandwich method) was used to detect 20, 222 human specimens. Operate in strict accordance with the instructions of the kit; The interpretation standard is that the samples with s/co value ≥1 detected for the first time need to use the same reagent for double hole retest; If the s/co value ≥1 in one hole of the retest is judged as HTLV screening reactivity; it shall be sent to the clinical testing center of the National Health Commission of China for virus nucleic acid and Western blot detection for confirmation.
2.4. Statistical Analysis
Use Excel statistical analysis to process data and draw corresponding charts.
3. Results
Among the 20, 222 samples of unpaid blood donors, 9 samples with anti-HTLV-I/II reaction were screened, and the screening positive rate was 0.04% (9/20222); The virus nucleic acid (PCR) and Western blotting (WB) of 9 samples with primary screening reactivity were further tested, and 2 were HTLV-1 positive and 7 were negative; The s/co value of the preliminary screening reactivity was between 1.12 - 2.50; After confirmation by viral nucleic acid and Western blotting, 2 were positive, including 1 male and 1 female, and 7 negative; The male-positive person has donated blood for the 8th time, and his native place is Cangwu County, Wuzhou City; the female-positive person has donated blood for the first time, and her native place is Cenxi, Wuzhou City. After investigation, the family members of the two positive blood donors have no history of leukemia, and they have been working and living in Wuzhou. The specific results are shown in Table 1 below.
4. Discussion
Human T-lymphotropic virus (HTLV) is the first RNA retrovirus found to be associated with cancer; A single positive-stranded RNA enveloped virus belonging to the Mammalian C type of the tumor virus subfamily of the Retroviridae family, which was first reported in 1980 [ 3 ]; American scholar Poiesz et al. [ 4 ] isolated the HTLV-1 virus from the skin T cells of a patient with cutaneous T-cell lymphoma. Since then, four HTLV subtypes have been isolated; Among them, HTLV-I promotes the occurrence of adult T-cell leukemia, related myelopathy, tropical spastic paraplegia and other diseases in infected patients by regulating the expression of HBZ, Tax protein and HMGB1 and co-regulates the transcription of virus and the proliferation of infected cells [ 5 , 6 ]; Although some current treatment methods such as CHOP, CHOPE and super CAVD classic chemotherapy, Mogamulizumab monoclonal antibody, alemtuzumab, antigen CD52 and other targeted drugs, new antiviral drugs, immunomodulatory agents, interleukins and interferons have certain clinical therapeutic effects [ 7 ]; However, due to the complex mechanism of HTLV infection and individual differences, effective therapeutic drugs and preventive vaccines have not been successfully developed; Well, HTLV-II is related to the occurrence of T-hairy cell/megaloblastic leukemia and other disease; In addition, HTLV is also associated with some neurological diseases, uveitis, chronic inflammatory joint disease, and the occurrence of infectious dermatitis. The main routes of transmission are blood transfusion, sexual contact and mother-to-child transmission. The prevalence of HTLV infection is regional, mainly concentrated in southern Japan, sub-Saharan Africa, the Caribbean, central and western Africa, central and southern South America, Papua New Guinea, and northern Australia. In order to prevent the transmission of HTLV through blood transfusion, countries and regions such as Japan, the
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Table 1. Information about anti-HTLV reactive blood donors in Wuzhou.
United States, France, the Netherlands, Sweden, South Korea, Taiwan of China and other countries and regions have successively included it in the routine blood screening program [ 8 ]. The infection rate of HTLV in my country is low, and HTLV has not been used as one of the routine screening items for blood donors. However, in recent years, my country has successively carried out HTLV screening studies in more than 20 provinces, cities and municipalities directly under the central government, including ELISA primary screening, WB or NAT confirmation. It was found that there is a certain proportion of HTLV infection in the population in many places, and HTLV-I type is mainly prevalent. The confirmed positive rate of special populations is higher in Henan, Hubei, Fuzhou, Ningde and other places, 0.39%, 0.2%, 0.58%, 0.33% respectively [ 9 , 10 ]. The person with asymptomatic HTLV infection among voluntary blood donors has been reported in some areas, and the positive rate was slightly higher in the coastal areas of Ningde in Fujian, Xiamen, Putian, and Taizhou in Zhejiang, which were 0.34%, 0.13%, and 0.10%, 0.03%, respectively [ 11 - 14 ]; The positive rate was lower in inland Chengdu, Tianjin, Shijiazhuang, Lanzhou, Suzhou and coastal eastern Shenzhen, with 0.06%, 0.05%, 0.06%, 0.007%, 0.0039%, 0.0046% [ 15 - 20 ].
However, Chongqing, Zhengzhou, Luoyang, Shenyang, Beijing and other regions had a certain positive rate of HTLV serological screening, but no HTLV positive blood donors have been found after confirmation tests [ 21 - 24 ]. Among the 20222 blood donor samples screened in Wuzhou city, 9 samples showed reactivity, with a positive rate of 0.04%. Two samples were confirmed to be positive by PCR and western blotting, with a positive rate of 0.01%, which was similar to that in inland areas, indicating a low epidemic area. In addition, one of the confirmed positive patients had donated blood for the eighth time and had already donated blood successfully for seven times; The blood recipients were followed up by the clinical blood transfusion department, and no HTLV infection was found in the recipients who received the blood of the donor; Since HTLV-infected patients are mostly asymptomatic carriers, the incubation period after infection is 20 - 40 years [ 7 ]; and the follow-up time does not indicate that there is no infection, which suggests that when we carry out HTLV screening for first-time blood donors, the HTLV detection of repeated blood donors should not be ignored, otherwise such blood donors may further expand the risk of HTLV transmission.
Since 2015, the National Health Commission has allocated special funds for monitoring the prevalence of HTLV among blood donors in various regions of the country. Based on the HTLV screening and testing data of blood donors in various regions, the cost of blood donor testing and the harmfulness of HTLV will be assessed as the basis for whether HTLV needs to be included in the routine screening of national or local blood donors. The infection rate of HTLV in China is regional; the coastal areas of Ningde in Fujian, Xiamen, Putian, and Taizhou in Zhejiang have higher prevalence, so HTLV serological screening should be carried out for blood donors; the prevalence in inland areas is low, so whole blood can be treated with leucocyte filtration. At present, our station has not carried out routine HTLV test on blood donors. It can be seen from Table 1 that one of the blood donors confirmed to be positive by PCR and WB has donated blood for the eighth time and belongs to a fixed unpaid blood donor. Therefore, there is a risk of HTLV transmission through blood transfusion in local clinical blood transfusion. In order to ensure the safety of clinical blood transfusion, we have plan to take the following measures: 1) earnestly do a good job in pre donation consultation, and try to exclude blood donors with high risk factors of HTLV infection; 2) Purchase blood bags with leukocyte filters to filter the collected whole blood; HTLV is infected with cd4+t lymphocytes; After filtering, the risk of HTLV transmission through blood transfusion can be reduced; 3) Before routine HTLV screening of blood donors, it is recommended that clinical blood transfusion ≤ 14d should not be conducted as far as possible, so as to inactivate the possible HTLV virus and reduce the residual risk of infection; 4) Purchase virus inactivation equipment to inactivate fresh frozen plasma; HTLV virus was inactivated by chemical methods such as methylene blue light and riboflavin light by using virus inactivation technology to reduce the risk of HTLV transmission through plasma.
5. Conclusion
There is a certain positive rate of HTLV-1 among the voluntary blood donors in Wuzhou, which belongs to the low-endemic area, but it still poses a certain risk of HTLV infection to clinical blood transfusion in Wuzhou.
6. Limitations of the Study
Since the object of this study is not a sample of the whole year, the data obtained are limited, and it is impossible to reliably and accurately understand the HTLV infection status of blood donors in this city.
Acknowledgements
This research has been successfully completed, and we have received strong support from the functional departments of the unit and the help of colleagues. I would like to express my heartfelt thanks for their support and help! I wish them good health, smooth work and all the best!