Holly Melroe

Tracking human immunodeficiency virus-type 1 (HIV-1) infection at the cellular level in tissue reservoirs provides opportunities to better understand the pathogenesis of infection and to rationally design and monitor therapy. A quantitative technique was developed to determine viral burden in two important cellular compartments in lymphoid tissues. Image analysis and in situ hybridization were combined to show that in the presymptomatic stages of infection there is a large, relatively stable pool of virions on the surfaces of follicular dendritic cells and a smaller pool of productively infected cells. Despite evidence of constraints on HIV-1 replication in the infected cell population in lymphoid tissues, estimates of the numbers of these cells and the virus they could produce are consistent with the quantities of virus that have been detected in the bloodstream. The cellular sources of virus production and storage in lymphoid tissues can now be studied with this approach over the course of infection and treatment.

A quantitative technique was developed to determine HIV-1 viral burden in two important cellular compartments in lymphoid tissues (LT). Image analysis and in situ hybridization were combined to show that in the presymptomatic stages of infection there is a large pool of about 108 copies per gram of LT of viral RNA in virions on the surfaces of follicular dendritic cells, and a smaller pool of 103 to 105 (per gram) of infected cells with 20 to 200 copies of viral RNA. The concentration of viral RNA in these cells was found to be much less than in productively infected cells in culture, consistent with restriction of replication of HIV-1 in vivo by immune or other mechanisms. The agreement, however, between theoretical estimates of viral production in LT and clearance of virus from plasma suggest that sufficient virus could nonetheless be generated in LT to account for levels of virus detected in plasma, and that plasma assays may turn out to accurately mirror virus production in tissues. Tracking HIV-1 infection at the cellular level in tissue reservoirs provides opportunities to better understand the pathogenesis of infection and the impact of treatment. Science 274 (1996): 985-989.

OBJECTIVES: Our objective was to assess the feasibility of using tonsillar lymphoid biopsy specimens obtained on an outpatient basis to quantitate a patient's lymphoid human immunodeficiency virus (HIV) RNA titers. DESIGN: A pilot cohort study was performed. PATIENTS: We evaluated ten HIV-seropositive patients who ranged in age from 26 to 48 years and had CD4+ cell counts ranging from 110 to 833 at enrollment. MAIN OUTCOME MEASURES: The main outcome measures were tolerance and safety of outpatient tonsil biopsies and quantitation of HIV RNA titers in tonsillar lymphoid biopsy specimens, plasma, and peripheral blood mononuclear cells determined by a new method of HIV RNA signal amplification with branched DNA probes. RESULTS: Outpatient tonsil biopsies were well tolerated and were performed without complications. Nine of 10 tonsil biopsies from the HIV-seropositive patients examined were positive for significant concentrations of HIV RNA, ranging from 106 to 101 HIV RNA equivalents per gram of tissue. All of the HIV RNA-positive tonsillar lymphoid specimens had HIV RNA titers that were 101 to 104 times greater than those recovered from plasma (per milliliter) of the same patient obtained at the time of biopsy. CONCLUSIONS: Sufficient tonsillar tissue can be obtained in an outpatient clinic setting to quantitate lymphoid HIV titers by the new branched-DNA signal amplification method with relative ease and without complication. The biopsy method described here affords ready access to the lymphoreticular system, which may help to advance our understanding of the pathogenesis of myriad immune diseases without the need for excisional node biopsies.