Low-frequency fluctuation characteristics in rhesus macaques with SIV infection: a resting-state fMRI study

Simian immunodeficiency virus (SIV)-infected macaque is a widely used model to study human immunodeficiency virus. The purpose of the study is to discover the amplitude of low-frequency fluctuation (ALFF) and fractional ALFF (fALFF) changes in SIV-infected macaques. Seven rhesus macaques were involved in the longitudinal MRI scans: (1) baseline (healthy state); (2) SIV infection stage (12 weeks after SIV inoculation). ALFF and fALFF were subsequently computed and compared to ascertain the changes caused by SIV infection. Whole-brain correlation analysis was further used to explore the possible associations between ALFF/fALFF values and immune status parameters (CD4+ T cell counts, CD4/CD8 ratio and virus load). Compared with the baseline, macaques in SIV infection stage displayed strengthened ALFF values in left precuneus, postcentral gyrus, and temporal gyrus, and weakened ALFF values in orbital gyrus and inferior temporal gyrus. Meanwhile, increased fALFF values were found in left superior frontal gyrus, right precentral gyrus, and superior temporal gyrus, while decreased fALFF values existed in left hippocampus, left caudate, and right inferior frontal gyrus. Furthermore, ALFF and fALFF values in several brain regions showed significant relationships with CD4+ T cell counts, CD4/CD8 ratio, and plasma virus load. Our findings could promote the understanding of neuroAIDS caused by HIV infection, which may provide supplementary evidences for the future therapy study in SIV model.