The Changing Molecular Epidemiology of HIV in the Philippines: Major Shift from Subtype B to CRF01_AE
The Philippines is one of only nine countries globally with rapidly increasing rates of HIV infection. Annual reported cases have increased 37-fold in the last decade. Sexual transmission still accounts for over 95% of cases, and a major shift from a heterosexual to men who have sex with men (MSM) transmission has occurred. Reasons for this remain unclear, but may include increased testing among MSMs, increased local transmission, and more aggressive strains of HIV. This study seeks to determine whether local molecular subtypes of HIV have changed over the last decade.
Following institutional review board approval and individual informed consent, 81 newly-diagnosed, treatment-naive HIV-positive patients at the Philippine General Hospital were interviewed and underwent genotyping of HIV RT and PR genes using WHO approved-protocols for HIV genotyping. Generated sequences were analyzed using the Stanford Drug Resistance Database. Demographics, sexual habits and CD4 counts at presentation were collected.
The cohort had an average age of 29 years (range 19-51 years), CD4 count of 254 cells/mm3 (2-744 cells), and self-reported acquisition time of 2.42 years (0.17-8.17 years). All were male, and 79 were MSM. Genotype distribution was CRF01_AE (75%), B (22%), C (1%) and CRF01_AE/K (1%).
Pooled analysis of published data from samples collected from 1985-2000 showed that the majority of Philippine HIV infections were previously caused by subtype B (71%, N=100), followed by subtype CRF01_AE (20%). Comparison with our cohort shows a highly significant shift in subtype (p<0.001 by Chi-square)
Comparison of CD4 counts at presentation between CRF01_AE and B showed a significantly lower count (233 cells/mm3 versus 350 cells/mm3, p=0.03 by T-test) despite no difference in age (p=0.15), and self-reported time to acquisition (p=0.66). This is consistent with previous reports that CRF01_AE is more aggressive, with faster progression to AIDS. While no viral loads were available for this cohort, CRF01_AE has been reported to have a higher rate of transmission. These two factors may partly explain the explosive increase in the number of new infections.
The molecular epidemiology of HIV in the Philippines has changed, with the more aggressive CRF01_AE now being the predominant subtype.
P. Ching, None
S. Ganchua, None
M. Alejandria, None
J. Lim, None
R. Destura, None
E. M. Salvana, None