Serotyping of Hiv-1 subtypes in Hiv-infected individuals at Chulalongkorn hospital and its clinical correlation

Abstract

Studies of HIV-1 subtypes in Thai patients were carries out using 2 different techniques, namely serotyping with specific peptides and genotyping with nested PCR by using selective primer for each subtype. It was found that serotyping was highly specific (100% specificity) but was less sensitive than genotyping (70% sensitivity). Therefore, serotyping would be better suited as a screening test, while genotyping is more applicable in nontypable cases or dual reactive cases by serotyping. If a sample remains untypable after serotyping and genotyping, DNA sequencing analysis is eventually required. A cohort of HIV-1 infected individuals who had been followed at the Immune Clinic of Chulalongkorn Hospital between 1989-1994 was analysed to study the correlation between HIV-1 subtypes and natural history of the infection. Those patients with the initial staging of asymptomatic or PGL, a baseline CD4 cell count equal of greater than 200 cells/cu.mm. (n=94) were included. The patients were classified according to their risk factor into heterosexuals, IVDUs and homo/bisexuals, HIV-1 subtyping were done by the serotyping method from stored sera. The Natural history was determined by the clinical progression from asymptomatic or PGL staging to ARC or AIDS, and by the annual rate of CD4 decline. The baseline CD4 cell count in heterosexual group (n=64) was found to be significantly (p<0.05) lower than the non-heterosexual group (n=30), but there was no significant difference between the patients with HIV-1 subtype E and non-E (p>0.05). The rates of disease progression and CD4 decline was similar among all risk groups. When the heterosexual group, which was the major risk group, was analysed, the individuals carrying subtype E had a significantly higher rate of disease progression than those with subtype non-E in the third year of follow-up (p<0.05). This observations suggests E patients are more likely to progress faster than subtype non-E patients. Interestingly, our results also confirm the previous observed segregation in Thai patients of the HIV-1 subtypes by modes of transmission, i.e., subtype E being present in the majority of heterosexuals, and subtype BThai in the majority of IVDUs. In addition, this is the first time that subtype BMN not subtype BThai was found to be the most common HIV variant in Thai homo/bisexuals. This study has provided further understanding of the HIV-1 molecular epidemiology and the correlation between HIV-1 subtypes and the clinical course of Thai HIV patients. This will lead to the future development of better therapeutic modalities and HIV-1 vaccine.