Blood screening is essential for blood safety. Traditional methods are not very effective in unknown pathogen testing. The blood metagenomic analysis with high-throughput sequencing as the main method is not limited to a particular microbe but detects all microbes in the sample (total genome), which has advantages that traditional methods cannot compare with. With the increasingly maturation of technology and the gradual reduction of cost, metagenomic sequencing has been applied more and more widely. In this paper, the concept and research procedures of metagenomics, the current status and future prospect of metagenomics sequencing technology in the field of blood screening are reviewed.

【Objective】 To investigate the CMV-IgG positive yeild among blood donors in Guangzhou and explore the differences in the efficacy of three test reagents, aimed at improving blood safety and service capacity of blood centers. 【Methods】 A total of 630 blood samples from eligible blood donors from July to October 2020 in our center were randomly selected and screened for CMV-IgG by one ELISA reagent.Among them, 180 samples were tested in parallel using three reagents (two ELISA reagents and one ECLIA reagent), and those tested negative were conducted quantitative CMV-DNA detection.The test results of different reagents were compared and analyzed. 【Results】 Out of the 630 samples, a total of 598 positive samples were screened out, including 180 samples yielded by three reagents, 171 and 175 by the two ELISA reagents, respectively, and 175 by ECLIA.The results given by three reagents were consistent (Kappa>0.4), and no significant difference in the positive yeild by three reagents was found.In the 180 samples, 11 were negative, among which 3, 2 and 6 samples were negative by all three reagents, two reagents and one reagent (ELISA), respectively.All the 11 samples were tested negative for CMV-DNA. 【Conclusion】 The yeild of positive CMV-IgG in blood donors was 94.9% (598/630), suggesting a high prevalence of CMV in Guangzhou. CMV serologically negative blood should be considered when providing blood products to immunocompromised patients to improve the safety of recipients.The detection results of ELISA reagents and ECLIA reagent for CMV- IgG are consistent, but ECLIA reagent has better detection efficacy.

[Objective] To analyze the prevalence of human T-lymphocyte leukemia virus (HTLV) among blood donors in Guangzhou from 2016 to 2021, and provide a basis for blood collection and supply management in this region. [Methods] A total of 2 116 951 voluntary blood donors were screened for anti-HTLV by enzyme-linked immunosorbent assay (ELISA) from March 2016 to December 2021 in Guangzhou, and the reactive cases were further confirmed by Western blotting (WB). Qualitative data were analyzed by χ2 with spss19 software. The trend of the total positive rate of HTLV confirmation test by WB from 2016 to 2021 was analyzed with the Joinpoint software, and the annual percent change (APC) was used to determine whether the trend changes were statistically significant. [Results] From March 2016 to December 2021, the total positive rate for anti-HTLV by ELISA among voluntary blood donors in Guangzhou was 0.019 7% (416/ 2116 951), and the WB confirmed positive rate was 0.001 1% (23/2 116 951). The total positive rate of HTLV among individual voluntary blood donors in the six main districts (0.002 12%, 19/895 301) was higher than that among group voluntary blood donors (0.000 32%, 3/951 947) (P<0.05). There was no significant difference in the total positive rate of HTLV confirmation between the six main districts (0.001 19%) and the three non-main districts (0.000 37%) (P>0.05). The trend of the total positive rate of HTLV infection in the six main districts and the Guangzhou area(including the six main districts and three non-main districts) showed no significant increase or decrease. [Conclusion] The prevalence of HTLV among blood donors in Guangzhou remains at a low level.

【Objective】 To study the CD4 T cell epitopes in Core and NS3 protein of genotype 1(GT1) and 6(GT6) of hepatitis C virus(HCV). 【Methods】 A total of 298 overlapping peptides(16-mer) spanning Core and NS3 protein of GT1 and GT6 HCV were synthesized. Peripheral blood mononuclear cells(PBMCs) from 17 HCV+ and 7 healthy blood donors were stimulated by peptide pools, followed by evaluating T cell response by IFN-γ ELISPOT, by which 21 peptides with positive results were found. These peptides were further applied to individually stimulate 20 HCV+ and 18 healthy PBMCs. The differences of responsive frequencies to the 21 positive peptides between the two study groups were compared. 【Results】 Pooled and individual peptide stimulation tests showed that HCV+ PBMCs were responsive to the stimulation of 5 peptides(GT1 NS31273-1288 and NS31315-1330; GT6 NS31033-1048, NS31087-1102 and NS31351-1366), with a responsive frequency ranging 18.9%-27.0%. In contrast, healthy PBMCs were not or low responsive(0%-4.0%) to these five peptides. The responsive frequencies were statistically different between the two groups(P<0.05). No reported epitopes in IEDB were found identical with these 5 peptides via sequence alignment. 【Conclusion】 Our study identified novel CD4 T cell epitopes in NS3 protein of GT1 and GT6 HCV, which has potential application value for the research and development of HCV vaccine.

【Objective】 To investigate the correlation of peripheral myeloid-derived suppressor cells (MDSC) with hepatitis c virus (HCV) infection. 【Methods】 109 voluntary blood donors who donated blood during February 2018 to September 2020 at Guangzhou Blood Center were recruited in this study. They were assigned to chronic hepatitis c (CHC) group (n=48), spontaneous clearance (SC) group (n=29) and healthy donors (control) group (n=32) according to the results of anti-HCV and HCV RNA tests. Blood samples were drawn from the participants and peripheral blood mononuclear cells (PBMC) were freshly isolated, followed by staining with fluorescently-labeled antibody against cell surface markers of MDSC, which were then applied to the detection of monocytic- (M) and polymorphonuclear (PMN)-MDSC by flow cytometry. Parameters for liver function including alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyl transpeptidase (GGT), total bilirubin (TBIL) and direct bilirubin (DBIL) were also measured. One-way ANOVA tests were applied to compare the differences of M- and PMN-MDSC and liver function between three study groups. For pairwise comparisons, P values were adjusted for multiple comparisons by Bonferroni correction (Pc). 【Results】 The frequencies of M-MDSC (%) in CHC, SC and HC were 1.39±0.86, 0.85±0.63 and 0.57±0.23, respectively (P<0.01). Specifically, CHC presented significantly higher level of M-MDSC than SC (Pc<0.01) and control (Pc<0.05). There was no significant difference in the frequencies of PMN-MDSC among the three study groups (0.81±0.54 vs 0.65±0.40 vs 0.62±0.29, P>0.05). In addition, AST (34.4±19.2 vs 23.0±7.78 U/L) and GGT (40.8±31.4 vs 22.3±7.40 U/L) level were higher in CHC compared with control (Pc<0.05 and Pc<0.01, respectively). 【Conclusion】 The level of peripheral M-MDSC was significantly elevated in chronic HCV infected donors, which would related to the progression of chronicity after HCV infection.

【Objective】 To explore the composition of culturable bacteria in platelets through bacterial culturomics and verify the results of culturomics and metagenomics to improve the detection rate of bacteria in platelets. 【Methods】 Platelet samples from 6 healthy people were collected. Eight kinds of culture media were placed in aerobic conditions and 12 kinds of culture media were placed in anaerobic conditions for large-scale culture and isolation of bacteria in platelets. The isolated single colony was identified by 16S rRNA gene sequencing. The bacterial abundance of healthy human platelet microbiome was analyzed by metagenomic sequencing, and the cultivable bacterial species in platelets was confirmed based on metagenomic and culturomics results. 【Results】 A total of 90 strains of bacteria belonging to 3 phylums, 5 classes, 5 orders, 7 families, 9 genus and 23 species were isolated from 6 platelet samples by culturomics. Among them, the strains with more monoclonal clones at the species level were Brevundimonas aurantiaca (16.7%), Bacillus sp. Y1 (15.6%), Cutibacterium acnes (14.4%) and Brevibacillus brevis (13.3%). The platelet samples sequenced by mNGS showed that the abundance values of Proteobacteria, Firmicutes and Actinobacteria were high. The bacteria detected by both culturomics and metagenomic sequencing methods were as follows: Firmicutes: Bacillus sp. Y1, B. thuringiensis, B. cereus, B. mobilis, B. velezensis, Staphylococcus epidermidis, and Brevibacillus brevis; Actinobacteria: Cutibacterium acnes; Proteobacteria: Escherichia coli and Delftia tsuruhatensis. 【Conclusion】 The mutual validation of culturomics and metagenomics has identified some bacteria, proving that bacteria exist in platelets.

【Objective】 To explore the correlation between serological screening of human T-lymphotropic virus antibodies (anti HTLV) and Western blot(WB) confirmatory tests among blood donors, so as to explore the infection status of HTLV Ⅰ/Ⅱ in Guangzhou. 【Methods】 The anti HTLV Ⅰ/Ⅱ enzyme-linked immunosorbent assay(ELISA) kit was used to screen voluntary blood donors from Guangzhou Blood Center from July 2016 to August 2022. WB was used to confirm 395 reactive blood samples by ELISA. The correlation between the S/CO values of anti HTLV Ⅰ/Ⅱ ELISA reagents and the confirmatory test was analyzed using ROC curves. 【Results】 The results showed that 25 out of 395 initially screened reactive blood donor samples were confirmed as HTLV positive by WB, while 16 were uncertain. ROC curve analysis showed a correlation between the S/CO values by ELISA and the confirmatory test results: the S/CO value at the highest Youden index was 3.789, which was the optimal threshold. The S/CO value had a certain correlation with the predicted positive rate of confirmatory results (P<0.05): the larger the S/CO value, the higher the predicted positive value. The overall prevalence of HTLV in Guangzhou is relatively low. 【Conclusion】 The prevalence of HTLV among blood donors in Guangzhou is low.Since the false positive rate of HTLV Ⅰ/Ⅱ antibody by ELISA serological screening is high, the confirmatory testing is particularly important.

【Objective】 HLA-DRB1 * 11:01, as a class HLA-Ⅱ gene, was reported to be associated with spontaneous clearance of HCV in Han and Li population. Our study was to investigate the effects of viral selection pressure and CD4+T cell epitope on the natural outcome of HCV infection in HLA-DRB1 * 11:01 positive infected patients. 【Methods】 The positive selection sites and population growth of E1E2 and NS3 genes of common HCV 6a in HLA-DRB1 * 11:01 positive and negative groups in Guangdong were respectively analyzed. The peptide library covering the conserved regions of common HCV genotypes was used to stimulate HCV spontaneous clearance group and chronic infection group using ELISPOT method. Reactive peptides were obtained according to the number of spot-forming cells per well and the frequency of occurrence in different groups. 【Results】 The positive selection sites (PSSs) of E1E2 and NS3 of common HCV 6a in HLA-DRB1 * 11:01 negative group were greater than those in HLA-DRB1 * 11:01 positive group. Furthermore, the number of PPSs in CD4+T cell peptide in HLA-DRB1 * 11:01 negative group were also greater than those in HLA-DRB1 * 11:01 positive group; Both groups of HCV 6a had a population growth in Guangdong, and the expansion trend of HLA-DRB1 * 11:01 negative group was significantly higher than that of HLA-DRB1 * 11 :01 positive group. Compared to HCV chronic infection group, the response rate of HCV spontaneous clearance group to five peptides (C-52 E2691-707, C-119 NS31545-1560, C-134 NS4A1669-1684, C-154 NS4B1912-1927, C-159 NS4B1929-1944) was higher. However, the HCV chronic infection group showed a higher response rate to two of the peptides(C-111 NS31497-1512, C-130 NS31650-1665). When HLA-DRB1 * 11:01 typing was considered, there was no significant difference in HCV-specific immune response generated by PBMCs between HLA-DRB1 * 11:01 positive and HLA-DRB1 * 11:01 negative groups. 【Conclusion】 This study revealed the relationship between viral selection pressure of HLA-DRB1 * 11:01 HCV infected persons and CD4+T cell antigen epitopes. At the same time, CD4+ T cell antigen epitopes of HCV pan-genotype were obtained, providing basic data for the development of T cell vaccine suitable for HCV pan-genotype.

【Objective】 To detect the anti-SARS-CoV-2 antibody levels in blood donors in Guangzhou, so as to provide laboratory data support for the collection and clinical use of convalescent plasma. 【Methods】 Anti-SARS-CoV-2 antibodies were measured by ELISA in qualified donors. Among them, 326 donors who gave blood in February 2023 were tested for IgG antibodies, 444 donors were tested for neutralizing antibodies. In July 2023, 398 donors were tested for IgG and IgM. 【Results】 399 of 724 blood samples diluted with normal saline (1∶160) were IgG reactive, with a reactive rate of 55.11%. Chi-square test showed that there was a significant difference in the reactive rate of IgG among samples collected at different times (25.46% in February vs 79.40% in July, χ²=210.74, P<0.01, 95%CI: 7.97, 15.98), but there was no significant difference in the reactive rate between different genders and different age groups. IgM was detected in 5 of 398 blood samples, with a reactive rate of 1.26%. The IgG test results of these five blood donors were all reactive, whereas the nucleic acid test results were negative. Neutralizing antibody was detected in 440 of 444 blood samples, with a reactive rate of 99.10%, and 71.59% of the reactive donors had a neutralizing antibody level of 10 μg/mL or more. 【Conclusion】 Blood donors in Guangzhou have a high level of SARS-CoV-2 antibody, which is sufficient to provide convalescent plasma for clinical treatment.

【Objective】 To learn the situation of the evolution process of HCV virus population and the selection pressure of HCV NS5B in intravenous drug users (IDUs) in Guangdong. 【Methods】 141 blood samples from hepatitis C virus (HCV) RNA-positive blood donors and 58 from HCV patients in Guangdong were randomly collected for HCV NS5B sequence amplification, combined with HCV NS5B sequences from blood donors and IDUs obtained by sequencing previously(between 2009 and 2011). Homology analysis was performed by Molecular Evolutionary Genetics Analysis (MEGA) software, evolutionary analysis were performed by Bayesian Evolutionary Analysis Sampling Trees (BEAST) software package. Selection pressure analysis was performed on sequences isolated from IDUs by Datamonkey online software package with Mixed Effects Model Evolution (MEME) method, and the population expansion of species were analyzed using Tajima and Fu neutrality test by Arlequin software. 【Results】 The comparison results of internal homology among different subtypes of IDUs in this group were as follows : HCV-3b had the highest homology (97%), followed by HCV-3a (96%), HCV-6a (95%) and HCV-1b (94%); HCV evolution rate analysis showed that HCV-1b had the fastest evolution rate [2.17E-03 substitutions/site/year (y/y/y)], followed by HCV-3b (2.12E-0 y/y/y), HCV-3a (1.58E-03 y/y/y) and HCV-6a (1.28E-03 y/y/y). The analysis on effective population of HCV: 1980~1990 was rapid growth period for HCV-6a, 1990~1995 period for HCV-1b, and 2000~2007 period for HCV-3a. HCV population genetic characteristics was as follows: HCV-1b, 3a, 3b and 6a experienced population expansion, among which 3a and 3b were the most obvious. As to the analysis of HCV selection pressure, two positive selection sites (235 and 243)were found in the 339 nucleotide fragment of the NS5B sequence in injecting drug users, but mutation only occurred at position 316 [mutation rate 1.24% (14/1 130)] among 5 direct antiviral drug (DAA) sites in this gene. 【Conclusion】 The evolution of HCV-3b in Guangdong has showed an obvious trend of population expansion, with a high proportion and homology especially in the local IDUs. HCV-3b should be the focus of HCV prevention and control in this region. Given that the positively selected sites of the HCV NS5B gene region of IDUs in Guangdong are non-DAA binding sites, DAA is expected to demonstrate a good effect on these patients.