Pathogen-specific antibodies: codependent no longer

B Cell Compartmentalization in Blood and Cerebrospinal Fluid of HIV-Infected Ugandans with Cryptococcal Meningitis

Activated B cells modulate infection by differentiating into pathogen-specific antibody-producing effector plasmablasts/plasma cells, memory cells, and immune regulatory B cells. In this context, the B cell phenotypes that infiltrate the central nervous system during human immunodeficiency virus (HIV) and cryptococcal meningitis coinfection are ill defined. We characterized clinical parameters, mortality, and B cell phenotypes in blood and cerebrospinal fluid (CSF) by flow cytometry in HIV-infected adults with cryptococcal (n = 31) and noncryptococcal (n = 12) meningitis and in heathy control subjects with neither infection (n = 10). Activation of circulating B cells (CD21low) was significantly higher in the blood of subjects with HIV infection than in that of healthy controls and greater yet in matched CSF B cells (P < 0.001). Among B cell subsets, elevated frequencies of memory and plasmablasts/plasma cells most clearly distinguished the CSF from blood compartments. With cryptococcal meningitis, lower frequencies of expression of the regulatory protein programmed death-1 (PD-1) on plasmablasts/plasma cells in blood (median, 7%) at presentation were associated with significantly decreased 28-day survival (29% [4/14 subjects]), whereas higher PD-1 expression (median, 46%) characterized subjects with higher survival (88% [14/16 subjects]). With HIV infection, B cell differentiation and regulatory markers are discrete elements of the circulating and CSF compartments with clinical implications for cryptococcal disease outcome, potentially due to their effects on the fungus and other local immune cells.

Paucity of initial cerebrospinal fluid inflammation in cryptococcal meningitis is associated with subsequent immune reconstitution inflammatory syndrome

BACKGROUND

Cryptococcal meningitis (CM)-related immune reconstitution inflammatory syndrome (IRIS) complicates antiretroviral therapy (ART) in 20%-40% of ART-naive persons with AIDS and prior CM. Pathogenesis is unknown.

METHODS

We compared initial cerebrospinal fluid (CSF) cultures, inflammatory markers, and cytokine profiles in ART-naive patients with AIDS who did or did not subsequently develop IRIS after starting ART. We also compared results obtained at IRIS events or CM relapse.

RESULTS

Of 85 subjects with CM, 33 (39%) developed CM-related IRIS and 5 (6%) developed culture-positive CM relapse. At CM diagnosis, subjects subsequently developing IRIS had less inflammation, with decreased CSF leukocytes, protein, interferon-gamma, interleukin-6, interleukin-8, and tumor necrosis factor-alpha, compared with subjects not developing IRIS (P<.05, for each). Initial CSF white blood cell counts < or =25 cells/microL and protein levels < or =50 mg/dL were associated with development of IRIS (odds ratio, 7.2 [95% confidence interval, 2.7-18.7]; P<.001). Compared with baseline levels, we identified CSF elevations of interferon-gamma, tumor necrosis factor-alpha, granulocyte colony-stimulating factor, vascular-endothelial growth factor, and eotaxin (CCL11) (P<.05, for each) at the time of IRIS but minimal inflammatory changes in those with CM relapse.

CONCLUSIONS

Patients who subsequently develop CM-related IRIS exhibit less initial CSF inflammation at the time of CM diagnosis, compared with those who do not develop IRIS. The inflammatory CSF cytokine profiles observed at time of IRIS can distinguish IRIS from CM relapse.