Effect of HIV-1 Subtype on Virologic and Immunologic Response to Starting Highly Active Antiretroviral Therapy

May 2009

Effect of HIV-1 Subtype on Virologic and Immunologic Response to Starting Highly Active Antiretroviral Therapy

Geretti AM, et al. Clin Infect Dis 2009;48:1296-1305. [PubMed Abstract]

Purpose: Most reports on virologic and immunologic response to HAART are based on studies in patients with subtype B infection. The purpose of this report was to determine response to HAART among patients with diverse non-B subtypes.

Methods: The authors use the UK Collaborative Group on HIV Drug Resistance and the UK Collaborative HIV Cohort Study databases to determine the number of patients who achieve a viral load of less than 50 c/ml, time to rebound and number with virologic failure. For immunologic response, they measured median CD4 cell count response at a median of 39 months. The results were restricted to patients who were treatment naïve and the databases showed 1550 subtype B infections and 436 non type B infections. Patients were also stratified by transmission category.

Results: The overall results showed that 1906 of 2116 (90%) of patients achieved undetectable viral load at 12 months and 335 (18%) subsequently had virologic failure. The number with virologic failure and odds ratio by HIV-1 subtype is summarized in the following table which also provides similar data by transmission category.

Virologic failure rates by HIV subtype and transmission category

Characteristics

No.

No. with viral failure

HIV-1 subtype

CRF_AG

Non-B

Transmission group

MSM

Heterosexual male

Heterosexual female

IDU

1381

255

118

1306

206

305

17%

20%

14%

19%

16%

17%

13%

22%

15%

1.0

1.4

1.0

0.7

1.0

1.2

1.0

1.2

1.0

With regard to CD4 cell count, the recovery occurred at similar rates for all subtypes with a median increase of 206 cells/mm³ at 1 year.

Conclusion: Patients with non-B subtypes showed rates of virologic suppression and failure, and rates of CD4 cell count recovery with HAART compared to those with subtype B infections.

Comment: This is one of the relatively few clinics that can do this work because of their heterogeneous patient population by HIV-1 subtype that is standardized in terms of HAART regimens and laboratory testing. The results are reassuring for those working in other geographic areas where non-B subtypes dominate and for those with large immigrant populations. This work cannot be done in the US due to the sparse number of non-B subtype infections reflecting immigration laws.