- Demographics and HIV genotyping of study subjects
HIV pol sequences were obtained for 436 of the 510 study subjects, with a success rate of 85.5%. HIV 384 env sequences were obtained for 436 subjects with pol sequences successfully amplified. The median age of these subjects was 29 years (range, 16–75): 94.0% (410/436) were Han ethnicity, 74.3% (324/436) were permanent residents, and 41.5% (181/436) had obtained college degrees or higher. Of these subjects, 66.5% (290/436) were single and 20.4% (89/436) were divorced or widowed. Of these subjects, 56.9% (248/436), 27.8% (121/436), 7.3% (32/436), 4.1% (18/436), and 0.2% (1/436) were infected with HIV genotypes CRF01_AE, CRF07_BC, B, CRF55_01B, and CRF59_01B, respectively. Additionally, 16 unique recombinant form (URF) samples (3.7%, 16/436) were observed with different genotypic identification from the pol and env regions (Table 2 and Fig 1).
Table 2 Information on URF samples with different genotypic identification from pol and env regions
Sample ID
|
Year of diagnosis
|
Age (years)
|
Marriage
|
Ethnicity
|
Register
|
pol
genotype
|
env
genotype
|
16QR151
|
2016
|
22
|
unmarried
|
Han
|
Tianjin
|
01BC
|
CRF01_AE
|
16QR673
|
2016
|
17
|
unmarried
|
Han
|
Tianjin
|
01BC
|
CRF01_AE
|
16QR870
|
2016
|
24
|
unmarried
|
Han
|
other
|
CRF01_AE
|
CRF07_BC
|
16QRA20
|
2016
|
28
|
unmarried
|
Han
|
Tianjin
|
CRF01_AE
|
CRF07_BC
|
16QRB97
|
2016
|
38
|
unmarried
|
Han
|
Tianjin
|
01BC
|
CRF01_AE
|
17QR411
|
2017
|
46
|
Divorced/
Widowed
|
Han
|
Tianjin
|
01BC
|
CRF59_01B
|
17QR848
|
2017
|
27
|
unmarried
|
Han
|
other
|
01BC
|
CRF07_BC
|
17QR866
|
2017
|
45
|
Divorced/Widowed
|
Han
|
Tianjin
|
01BC
|
CRF07_BC
|
17QRA14
|
2017
|
27
|
unmarried
|
Han
|
other
|
01BC
|
CRF08_BC
|
TJ150049
|
2015
|
25
|
unmarried
|
other
|
Tianjin
|
01BC
|
CRF09_BC
|
18LS1505
|
2018
|
24
|
unmarried
|
Han
|
other
|
01BC
|
CRF10_BC
|
18LS1657
|
2018
|
23
|
unmarried
|
Han
|
other
|
01BC
|
CRF11_BC
|
18LS4856
|
2018
|
36
|
unmarried
|
Han
|
Tianjin
|
01BC
|
CRF12_BC
|
18LS5068
|
2018
|
22
|
unmarried
|
Han
|
Tianjin
|
01BC
|
CRF13_BC
|
18LS5311
|
2018
|
21
|
unmarried
|
Han
|
Tianjin
|
01BC
|
CRF14_BC
|
18LS5454
|
2018
|
24
|
unmarried
|
Han
|
Tianjin
|
0107
|
01BC
|
- Characteristics of transmission clustering
The pol sequences of 213 individuals were clustered in 42 clusters at 1.5% genetic distance by the TN93 model in HIV-Trace (Fig 1). Of the 213 pol sequences, 110 sequences in 34 clusters at bootstrap support values ≥90% in the neighbor-joining trees (Fig 2-A). Clustering performed based on partial pol was mostly sustained by the env sequences (Fig 2-B), except that two pol clusters were identified as 4 clusters because of two env clusters divided into two smaller clusters respectively. Thus, 36 robust clusters including 110 individuals (25.2%, 110/436) were identified according the clustering consistency analyzed and reference to relevant literature [14, 15]. Of the 110 clustered individuals in the 36 clusters, 78.2% (86/110) were in 32 small clusters (including 2–5 nodes) and 21.8% (24/110) were in four large clusters (including >5 nodes) (Fig 1 and Fig 2). The annual distribution of the individuals clustered showed an increasing trend from 2014 to 2016 followed by a decreasing trend (Table 3).
Table 3 Annual distribution of the individuals clustering and prevalence of DRMs
Year of diagnosis
|
Number of Infections
(%)a
|
Clustering*
(%)a, b
|
Prevalence of DRMs (%)a, c
|
2014
|
40 (100)
|
11 (27.5)
|
2 (5.0)
|
2015
|
57 (100)
|
16 (28.1)
|
2 (3.5)
|
2016
|
62 (100)
|
24 (38.7)
|
5 (8.1)
|
2017
|
158 (100)
|
35 (22.2)
|
14 (8.9)
|
2018
|
119 (100)
|
24 (20.2)
|
7 (5.9)
|
Total
|
436 (100)
|
110 (25.2)
|
30 (6.9)
|
a Numbers in parentheses indicate the proportion of HIV-1 cases as a percentage of each subgroup
b χ2 = 8.450, p = 0.075 calculated using Fisher’s exact method
c χ2 = 2.200, p = 0.697 calculated using Fisher’s exact method
Fig. 1 HIV transmission clusters of pol identified from newly diagnosed ART-naïve HIV infections in the MSM population in Tianjin, China (2014–2018) by HIV genetic transmission network using HIV-TRACE by a 1.5% genetic distance.
Black lines indicate the worst-based support (p) of the length between the two nodes <0.05
Red lines indicate the worst-based support (p) of the length between the two nodes ≥0.05
Fig 2 Phylogenetic tree analysis of partial pol (A) and env (B) region sequences from newly diagnosed ART-naïve HIV infections in the MSM population in Tianjin, China (2014–2018)
- Co-receptor tropism
Overall, of the 384 database-derived env V3 sequences, 117 (30.5%) were predicted as X4 tropisms and 267 (69.5%) as R5-tropic. As shown in Fig 3, The prevalence of X4 viruses in individuals infected with CRF55_01B (56.3%, 9/16) and CRF01_AE (46.2%, 102/221) was higher than in those infected with CRF07_BC (2.8%, 3/107), subtype B (8.3%, 2/24), and URFs (6.3%,1/16) (χ2 = 92.839, p = 0.000). The proportion of R5-tropic viruses in the clusters was slightly higher than in no-clustering (69/98 = 70.4% vs 198/286 = 69.2%), and that of the X4-tropic viruses displayed the opposite trend, without significant differences (χ2 = 0.048, p = 0.899).
Fig 3 X4 and R5 co-receptor tropism of HIV 384 env sequences were obtained for 436 subjects with pol sequences successfully amplified. A: Co-receptor usage based on different subtypes; B: Co-receptor usage based on clustering. CRF: circulating recombinant form; URFs: unique recombinant forms.
- Drug resistance (Table 3)
Among the 436 pol sequences in the ART-naïve population, 30 (6.9%) contained sequences harboring DRMs. The population prevalence rates of DRMs to NNRTI, NRTI, PI, and NNRTI+NRTI were 4.4% (19/436), 0.7% (3/436), 1.1% (5/436), and 0.7% (3/436), respectively. Furthermore, among the 19 sequences for resistance only to NNRTIs, 11 exhibited K101E mutations, four K103N mutations, one Y181C mutation, one Y188L mutation, and one V106M mutation, whereas one exhibited two mutations (K101E+K103N). The three sequences for resistance to NRTIs only exhibited the following mutation sites: D67N, K219E, and M184I. Among the 5 sequences for resistance to PIs, four sequences exhibited M46L and one I54T mutation. Of the three strains harboring multiple DRMs specific to both NRTIs and NNRTIs, one exhibited K70R + M184V + K103N + Y181C and two exhibited K219E+Y188C. The annual prevalence of DRM strains showed an increasing trend from 2014 to 2017 and then a decreasing trend from 2017 to 2018 (Table 2).
- Characterization of HIV molecular transmission networks
In the 32 small clusters (with 2–5 nodes), 56 nodes in 22 clusters were CRF01_AE subtypes, 12 nodes in three were CRF07_BC, eight nodes in three were 55_01B, eight nodes in three were URFs, and two nodes in one were B. Of the four large clusters, one including six nodes belonged to CRF07_BC, one cluster including six nodes belonged to CRF01_AE, and two clusters including six nodes belonged to B. For the different genotypes, the proportion of individuals involved in the networks exhibited significant differences (Table 4, χ2 = 62.667, p = 0.000). In the clusters with 2–5 nodes, the proportion of individuals infected with URFs (8/16 = 50%) was higher than in those infected with CRF55_01B (44.4%, 8/18), CRF01_AE (22.6%, 56/248), CRF07_BC (12/121 = 9.9%), subtype B (2/32 = 6.3%), and CRF59_01B (0/1 = 0.0%). In large clusters (with >5 nodes), the proportion of individuals infected with subtype B (12/24 = 50.0%) was higher than in those infected with CRF01_AE (6/24 = 25.0%), CRF07_BC (6/24 = 25.0%), CRF55_01B (0/24 = 0.0%), URFs (0/24 = 0.0%), and CRF55_01B (0/24 = 0.0%).
The demographic characteristics of transmission clustered individuals are shown in Table 4. The age distribution of individuals in the different clustering patterns showed significant differences (χ2 =10.790, p = 0.013). In the large clusters, the proportion of individuals in the 25–40 years age group (14/174, 8.0%) was higher than those in other age groups. In small clusters, the proportion of individuals in the <25 years age group (30/108, 27.8%) was higher than those in the other age groups. There was no difference in the marital status, nationality, residence characteristics, and education characteristics of individuals in the different clustering patterns (Table 4). Of the 36 transmission clusters in the network, 17 transmission clusters contained 23 individuals who were non-Tianjin (including eight cases were registered in Hebei province, four in Jilin, four in Heilongjiang, three in Anhui, two in Shandong, and one in Shanxi and Sichuan, respectively) (Fig 1).
The proportion of individuals with sexually transmitted diseases (STDs) (8.9% and 24.7%) was higher than the proportion of individuals without STDs (3.8% and 17.2%) in both large and small clusters (Table 4, χ2 = 9.166, p = 0.010). The proportion of individuals with DRM (7/30, 23.3%) was higher than that of individuals without DRM (17/406, 4.2%) in the large clusters (Table 4, χ2 = 20.990, p = 0.003). Of the 11 clustered sequences with at least one DRM, eight clustered with at least one other shared the same DRM. One of the three strains harboring multiple DRMs to both NRTIs and NNRTIs (K70R + M184V + K103N + Y181C) was confirmed to be clustered in the genetic transmission networks.
Table 4. Characteristics of transmission clustered individuals
|
Total
N (%)a
|
Not clustered
N (%)a
|
clustered
|
χ2
|
P
|
≤5 nodes/cluster
N (%)a
|
>5 nodes/cluster
N (%)a
|
Total (%)
|
436 (100)
|
326 (74.8)
|
86 (19.7)
|
24 (5.5)
|
|
|
Age (years)
|
|
|
|
|
113.777
|
0.028 b
|
<25
|
108 (100)
|
73 (67.6)
|
30 (27.8)
|
5 (4.6)
|
|
|
25–34
|
174 (100)
|
124 (71.3)
|
36 (20.7)
|
14 (8.0)
|
|
|
35–44
|
70 (100)
|
59 (84.3)
|
10(14.3)
|
1(1.4)
|
|
|
>45
|
84 (100)
|
70 (83.3)
|
10 (11.9)
|
4 (4.8)
|
|
|
Marital status
|
|
|
|
|
3.476
|
0.17
|
Single
|
290 (100)
|
209 (72.1)
|
65 (22.4)
|
16 (5.5)
|
|
|
Married
|
57 (100)
|
47 (82.5)
|
8 (14.0)
|
2 (3.5)
|
|
|
Divorced/Widowed
|
89 (100)
|
70 (78.7)
|
13 (14.6)
|
6 (6.7)
|
|
|
Nationality
|
|
|
|
|
4.465
|
0.314
|
Han
|
410 (100.0)
|
305 (74.3)
|
81 (19.8)
|
24 (5.9)
|
|
|
Other
|
26 (100.0)
|
21 (80.8)
|
5 (19.2)
|
0 (0.0)
|
|
|
Education
|
|
|
|
|
2.564
|
0.635
|
Middle school and below
|
127 (100.0)
|
89 (70.1)
|
31 (24.4)
|
7 (5.5)
|
|
|
· High School
|
128 (100.0)
|
99 (77.3)
|
22 (17.2)
|
7 (5.5)
|
|
|
College and above
|
181 (100.0)
|
138 (76.2)
|
33 (18.2)
|
10 (5.5)
|
|
|
Permanent Register
|
|
|
|
|
1.610
|
0.447
|
Tianjin
|
324 (100.0)
|
237 (73.1)
|
68 (21.0)
|
19 (5.9)
|
|
|
Other
|
112(100.0)
|
89 (79.5)
|
18 (16.1)
|
5 (4.5)
|
|
|
STDs
|
|
|
|
|
9.166
|
0.010b
|
With
|
146 (100.0)
|
97 (66.4)
|
36 (24.7)
|
13 (8.9)
|
|
|
Without
|
290 (100.0)
|
229 (79.0)
|
50 (17.2)
|
11 (3.8)
|
|
|
Genotype
|
|
|
|
|
62.667
|
0.000b
|
CRF01_AE
|
248 (100.0)
|
186 (75.0)
|
56 (22.6)
|
6 (2.4)
|
|
|
CRF07_BC
|
121 (100.0)
|
103 (85.1)
|
12 (9.9)
|
6 (5.0)
|
|
|
B
|
32 (100.0)
|
18 (56.2)
|
2 (6.3)
|
12 (37.5)
|
|
|
CRF55_01B
|
18 (100.0)
|
10 (55.6)
|
8 (44.4)
|
0 (0.0)
|
|
|
URFs
|
16 (100.0)
|
8 (50.0)
|
8 (50.0)
|
0 (0.0)
|
|
|
CRF59_01B
|
1 (100.0)
|
1 (100.0)
|
0 (0.0)
|
0 (0.0)
|
|
|
DRM
|
|
|
|
|
20.990
|
0.003 b
|
With
|
30 (100.0)
|
19 (63.3)
|
4 (13.4)
|
7 (23.3)
|
|
|
Without
|
406 (100.0)
|
307 (75.6)
|
82 (20.2)
|
17 (4.2)
|
|
|
a Numbers in parentheses indicate the proportion of HIV-1 subtypes as a percentage of each subgroup
b p < 0.05 calculated using Fisher’s exact method