Cytomegalovirus Infection in Gambian Infants Leads to Profound CD8 T-Cell Differentiation

Abstract

Cytomegalovirus (CMV) infection is endemic in Gambian infants, with 62% infected by 3 months and 85%by 12 months of age. We studied the CD8 T-cell responses of infants to CMV following primary infection. CMV-specific CD8 T cells, identified with tetramers, showed a fully differentiated phenotype (CD28. Strikingly, the overall CD8 T-cell population developed a similar phenotype following CMV infection, which persisted for at least 12 months. In contrast, primary infection was accompanied by up-regulation of markers of activation (CD45R0 and HLA-D) on both CMV-specific cells and the overall CD8 T-cell population and division (Ki-67) of specific cells, but neither pattern persisted. At 12 months of age, the CD8 T-cell population of CMV-infected infants was more differentiated than that of uninfected infants. Although the subpopulation of CMV-specific cells remained constant, the CMV peptidespecific gamma interferon response was lower in younger infants and increased with age. As the CD8 T-cell phenotype induced by CMV is indicative of immune dysfunction in the elderly, the existence of a similar phenotype in large numbers of Gambian infants raises the question of whether CMV induces a similarly deleterious effect.

Analysis of flow cytometry data using an automatic processing tool

“…In the case of multiple regions in Figure 1C, the final step in Figure 1D is to automatically identify the lymphocyte population, in this case by size. In one study (11), this approach was used for 1,511 infant peripheral blood samples that had been processed as whole blood and so contained all leukocyte populations, and only failed to find the lymphocyte population six times. In these cases, there was a large high-frequency event region either in the ''neutrophil region'' or at the origin of the forward side scatter plot.…”

“…The 95% confidence interval for the break point coordinates was (220-261), indicating that the breakpoint regression is robust. Two hundred and sixty-two data files from the CMV-infected infants (11) were processed to estimate the CD45RA bright CD45R0 2 cutoff, and each was validated manually by an ''expert.'' Five percent of the break points were queried after manual expert scrutiny and the majority of these had low event counts.…”

“…We used clustering to identify the differentiation status of infant CD8 T-cells, which lose CD28 first and then CD27 and so may be classified as naive or early differentiated (CD27 1 CD28 1 ), intermediate (CD27 2 CD28 1 ), and late differentiated (CD27 2 CD28 2 ) (14) as shown in Figure 3A with data from (11). Figure 3A has 20,027 event locations and the output from the Gath-Geva clustering algorithm is a 3 by 20,027 matrix giving the cluster membership probabilities for each event location.…”

“…For example, we have already used the APT to identify peptide-specific CD8 Tcells stained with tetramers (11), and the identification of the sparse FOXP3 1 population is a process essentially similar to that of identifying cytokine-producing cells following stimulation with specific antigens (22). All data so far analyzed using the APT employed hardware compensation and no data transformations were used.…”

The immunological underpinnings of vaccinations to prevent cytomegalovirus disease

“…This area is sketchy even though response parameters have been documented. [64][65][66][67][68][69][70] Fetal immunity late in gestation or in the newborn occurs at times when susceptibility to congenital disease declines, although more needs to be learned from studies that consider the contribution of overall development relative to immunological development for this to decline. Transmission takes place throughout pregnancy, with the highest frequency occurring during the third trimester, 22 which is coincident with the development of fetal immunocompetence.…”