A population-based study of Kaposi Sarcoma-associated herpesvirus seropositivity in Uganda using principal components analysis

Kaposi Sarcoma-Associated Herpesvirus in a Rural Ugandan Cohort, 1992-2008

Background

The prevalence and titers of antibodies against Kaposi sarcoma-associated herpesvirus (KSHV) in rural Africa are not completely understood, nor are their trends over time in populations in which human immunodeficiency virus (HIV) is also endemic. We examined prevalence, titers, temporal trends, and determinants of anti-KSHV antibodies in each of 3 time periods (1990-1991, 1999-2000, and 2007-2008) within a long-standing, rural population-based cohort in southwestern Uganda.

Methods

For each period, we measured antibodies to the K8.1 and ORF73 KSHV antigens in approximately 3000 people of all ages (1:1 sex ratio).

Results

In all periods, KSHV prevalence increased rapidly through childhood to approximately 90% by age 15 years, plateauing at approximately 95% thereafter. Similarly, antibody titers, particularly against the lytic antigen K8.1, were among the highest seen and increased significantly with age, suggesting sustained viral replication in this population. Male sex was also independently associated with higher prevalence, whereas HIV coinfection was not. A modest reduction in prevalence among children was noted in the most recent period.

Conclusions

KSHV seroprevalence and antibodies titers in this rural Ugandan population are the highest yet reported, perhaps reflecting frequent viral reactivation and persistently elevated transmission.

Use of principal components analysis and protein microarray to explore the association of HIV-1-specific IgG responses with disease progression

The role of HIV-1-specific antibody responses in HIV disease progression is complex and would benefit from analysis techniques that examine clusterings of responses. Protein microarray platforms facilitate the simultaneous evaluation of numerous protein-specific antibody responses, though excessive data are cumbersome in analyses. Principal components analysis (PCA) reduces data dimensionality by generating fewer composite variables that maximally account for variance in a dataset. To identify clusters of antibody responses involved in disease control, we investigated the association of HIV-1-specific antibody responses by protein microarray, and assessed their association with disease progression using PCA in a nested cohort design. Associations observed among collections of antibody responses paralleled protein-specific responses. At baseline, greater antibody responses to the transmembrane glycoprotein (TM) and reverse transcriptase (RT) were associated with higher viral loads, while responses to the surface glycoprotein (SU), capsid (CA), matrix (MA), and integrase (IN) proteins were associated with lower viral loads. Over 12 months greater antibody responses were associated with smaller decreases in CD4 count (CA, MA, IN), and reduced likelihood of disease progression (CA, IN). PCA and protein microarray analyses highlighted a collection of HIV-specific antibody responses that together were associated with reduced disease progression, and may not have been identified by examining individual antibody responses. This technique may be useful to explore multifaceted host-disease interactions, such as HIV coinfections.