The current results clarified the epidemiological characteristics and transmission cluster features of patients with HIV-1 CRF01_AE infection in Zhejiang, China.
HIV patients from different regions have been noted to display varied DRMs.19 In Ethiopia, K103N and K219Q were the predominant NNRTI and NRTI DRMs among pretreatment drug–resistant HIV patients over 2003–2018.20 In China, K103N was the most prevalent NNRTI DRM among HIV patients in 2017, followed by V179D and E138A.21 In the current study, the most frequent NNRTI DRM was V179D (3.95%, 6/152), followed by V179VD (1.32%, 2/152) and V106I (1.32%, 2/152). The most commonly observed NRTI DRM was S68G (3.95%,6/152). S68G, particularly prevalent among CRF01_AE strains, has been noted to be the most frequent natural polymorphism, typically followed by K65R; it can partially offset the replication impairment linked to K65R, another NRTI DRM.22,23 Nevertheless, in the current study, patients with S68G did not exhibit K65R. As such, further investigation on the relationship between S68G and K65R is warranted.
A study determined the strain lineage of HIV-1 CRF01_AE in China and noted the unique characteristics of each cluster.14 In the present study, we noted that most CRF01_AE strains in Zhejiang could be placed in Clusters 1, 4, and 5—with each strain exhibiting unique traits.
Cluster 4, the primary CRF01-AE strain in Zhejiang, may have originated from northern MSM populations and have become transmitted to Zhejiang. Thus, the CRF01_AE strains may be mainly transmitted via the MSM route in Zhejiang. Moreover, the patients in Cluster 4 were young or middle-aged men, most of whom were single and therefore may have had multiple sexual partners. The median CD4 + T-cell counts for Clusters 4a and 4b patients were 38 (24/111) and 30 (8/90), respectively. Moreover, the X4 tropism rates in Clusters 4a and 4b were high (13.2% and 20%, respectively). Studies have indicated that high X4 tropism is correlated with low CD4 + T-cell counts24 and that genetic clusters exhibiting the X4 phenotype reduce ART efficacy.18 Notably, DRM rates were more variable and higher in Cluster 4b than in Cluster 4a. Moreover, the predominant NNRTI DRM was V179D. However, Cluster 4b DRMs can lead to decreased susceptibility to efavirenz and nevirapine.25 As such, the use of these drugs in ART for patients with Cluster 4b infections should be restricted. In summary, Cluster 4, particularly Cluster 4b, may be a high-risk cluster in Zhejiang, with young men being the most affected population. Patients with Cluster 4 infections may require immune reconstitution over an extended period and may be relatively vulnerable to severe opportunistic infections. Careful consideration of the timing of ART and detection of opportunistic infections may improve the quality of life of these patients.
Cluster 5 was noted to share similarities with Cluster 4 in terms of its characteristics; however, it was associated with considerably higher CD4 + T-cell counts but without any X4 tropism. This result corroborates the findings of previous studies, indicating that Cluster 5 is stable.
A study indicated that Cluster 1 may have been transmitted to Zhejiang via heterosexual individuals and injection drug users in southern China. In the current study, Cluster 1 was mainly present in middle-aged and older married patients, with 35.3% of them being female, and the median CD4 + T-cell count associated with Cluster 1 was 15. A study reported that the likelihood of CD4 + T-cell count recovery and immune reconstruction is relatively low among Cluster 1 patients.26 As such, we propose that middle-aged and older married individuals, particularly women, should be considered the key target group for Cluster 1 infections. Furthermore, equal attention should be paid to marital harmony and well-being among this population.
In the present study, 48.03% (73/152) of individuals constituted the genetic transmission networks. HIV CRF_01AE transmission risk appears to be higher in Zhejiang than in the southwest border region of China (32.2%) or in Guangdong, China (25.8%).27,28
Our results also indicated that the prevalence of NNRTI DRMs was higher than that of NRTI DRMs. In the largest cluster, two patients shared a DRM (S68G), indicating the potential for transmission between them. Because a larger number of individuals from Cluster 4 were present in the genetic transmission networks, Cluster 4 may be a high-risk transmission cluster. Cluster 4b demonstrated more DRMs than Cluster 4a, suggesting that the mutual DRM transmission risk between Clusters 4a and 4b is high. Thus, to minimize the spread of Cluster 4 HIV-1 CRF01_AE strains and potentially prevent their evolution, drug resistance testing and dynamic transmission monitoring of these strains, particularly Cluster 4b strains, should be prioritized.
This study has a few limitations. First, our HIV patient sample was small and enrolled from a single centre; this may have led to sampling errors and limited the generalizability of our findings size. Consequently, further comprehensive analysis of the characteristics of patients with HIV-1 CRF01_AE infections in Zhejiang as a whole is warranted. Second, all the included HIV patients were hospitalized; thus, the higher proportion of DRMs among them could have been due to impairments in their immune function and infection status. Furthermore, before 2017, integrase strand transfer inhibitors (INSTIs) were rarely used as first-line treatment for HIV infection, and our study did not include sequencing for INSTIs. Nevertheless, INSTI resistance may be more prevalent in HIV-experienced patients than in HIV-naïve patients.29
In conclusion, our study revealed the presence of HIV-1 CRF01_AE Clusters 1, 4, and 5 in Zhejiang, China, with each cluster demonstrating distinct characteristics. Cluster 4 was noted to be the most significant in terms of both DRMs and transmission risks. To minimize the spread of HIV strains, effective targeted drug resistance testing and ongoing transmission dynamics surveillance are essential.