Demographic characteristics
From 2005 to 2015, blood samples were collected from 3418 MSM at diagnosis of HIV infection in Shenzhen, with genotype distribution as follows: 1446 (42.3%) CRF07_BC, 1169 (34.2%) CRF01_AE, 467 (13.7%) CRF55_01B, 249 (7.3%) subtype B, and 87 (2.5%) other subtypes (CRF_08BC, CRF_01B, C, and others) (Figure 1). Of note, we found that CRF55_01B had significantly expanded during the past years (P< 0.05), and had replaced subtype B as the third predominant strain since 2012 in Shenzhen, China. By excluding the other subtypes and the infections which were more than one year prior to sampling, there were 1792 recent infection for CRF07_BC, CRF01_AE, and CRF55_01B. Demographic characteristics of the 1792 MSM are shown in table 1.
CD4 T-cell count and plasma HIV RNA load
Among the 1792 samples for the three main subtypes, the mean genetic distance was 0.045±0.003 for CRF01_AE, 0.018±0.001 for CRF07_BC, and 0.022±0.002 for CRF55_01B. CRF55_01B-infected MSM showed a significantly lower median CD4 count than CRF07_BC-infected MSM at diagnosis of HIV infection (349.5 [IQR, 250.2~474.8] vs 370.0 [IQR, 278.0~501.0], P<0·05), as well as at initiation of cART (224.0 [IQR, 165.2~283.0] vs 265.0 [IQR, 198.0~348.0], P<0.01) (Figure 2). However, the median CD4 count of CRF55_01B-infected MSM was not significantly different from that of CRF01_AE-infected MSM at diagnosis of HIV infection (349.5 [IQR: 250.2~474.8] vs 335.0 [IQR: 237.0~464.0], P=0.352) and at initiation of cART (224.0 [IQR, 165.2~283.0] vs 203.0 [IQR, 130.5~287.0], P=0.154). In contrast, CRF55_01B-infected MSM was associated with a significantly higher median plasma HIV RNA load (5.4 log10 copies/ml; IQR, 5.0~5.9) than CRF01_AE-infected MSM (5.3 log10 copies/ml; IQR, 4.8~5.7, P<0.05) and CRF07_BC (5.0 log10 copies/ml; IQR, 4.5~5.5, P<0.01) at the initiation of cART (Figure 2). In addition, those infected with CRF55_01B showed significantly higher plasma HIV RNA load (4.7 log10 copies/ml; IQR, 4.1~5.3) than those infected with CRF07_BC (4.3 log10 copies/ml; IQR, 3.7~4.8, P<0.01) at diagnosis, although similar to those infected with CRF01_AE (4.6 log10 copies/ml; IQR, 4.1~ 5.1, P=0.695).
Change trend of CD4 T-cell count and plasma HIV RNA load
A total of 753 MSM were included for estimate and comparison of the declining rates of CD4 count by subtype, and 199 MSM were included for analysis of the increasing rates of plasma HIV RNA load by subtype. Demographic characteristics and time interval between the two measurements of CD4 count and viral load were presented in Supplementary table 1 and 2. Stratified analyses were conducted according to the initial CD4 count at diagnosis as different initial CD4 counts represent different status of disease progression of the patients. Table 2 showed the estimated declining rates of CD4 counts by subtype. Specifically, for the group with initial CD4 counts between 200 and 350 cells/μL, infection with CRF55_01B was associated with a significantly lower declining rate ([cells/μL]1/2/year) than with CRF01_AE (13.4 [95%CI, 8.2~18.6] vs 22.9 [95%CI, 15.8~30.0], P <0.05), while similar to CRF07_BC (13.4 [95%CI: 8.2~18.6] vs 10.8 [95%CI, 8.2~13.4], P =0.383). However, no significant difference was found for the other group with initial CD4 value above 350 cells/μL. Linear mixed effect model results also showed that the declining rate of CD4 count for CRF55_01B-infected MSM was 10.3 [cells/μL]¹/²/year (95%CI, 0.7~19.9, P<0.05) lower than that for CRF01_AE-infected MSM among the patients with CD4 counts of 200~350 cells/μL at HIV diagnosis, with adjustments for age at diagnosis, ethnicity, marital status, and year of HIV diagnosis.
In general, for all MSMS with initial CD4 count of 200 cells/μL or above, CRF55_01B infections caused a significantly higher increasing rate of plasma HIV RNA load than CRF07_BC infections (2.0 log10 copies/ml [95%CI, 1.1~2.9] vs 0.7 log10 copies/ml [95%CI, 0.5~0.9], P <0.01), while not significantly different from infection with CRF01_AE (1.4 log10 copies/ml [95%CI, 0.8~2.0], P=0.324) (Table 3). Furthermore, the model with random effect also showed CRF55_01B infections were 1.2 log10 copies/ml/year higher increasing rate of viral load than CRF07_BC infections after adjustment for age at diagnosis, ethnicity, marital status, and year of HIV diagnosis, although not significantly different for the group with initial CD4 count as 350cells/μL or above.