Peripheral T follicular helper cells from H1N1/09 vaccine nonresponders fail to induce antigen-specific antibody production in vitro

Background

Mechanisms underlying poor Ab responses to vaccines in well controlled HIV infected patients are not fully understood. In this study we have examined the role of a novel subset, the peripheral T follicular helper cells (pTFH) in Ab production.

Methods

The study was conducted in cryopreserved cells of 16 HIV-infected, ART-treated individuals and 8 healthy donors (HD) who had been given a single dose of H1N1/09 influenza vaccine in 2009. Only 8 of the 16 patients and all HD had a flu-Ab response at 4 wks post vaccination. Vaccine responder (VR) and non responder (VNR) patients were equivalent in mean age, viral load, CD4 and CD8 T and B cells. B (CD20+) and TFH (CD3+ CD4+ CD45RA– CXCR5+) cells were purified by cell sorting on a FACS ARIA and co-cultured. IgG levels in culture supernatants were determined by ELISA. B and T cell phenotypic analysis was performed by multicolor flow cytometry. Differences between groups were analyzed by Student t-test or the 2-sample Wilcoxon rank-sum (Mann-Whitney) test.

Results

Frequency of pTFH was equivalent in HIV+ patients and HD before vaccination. pTFH cells underwent significant expansion at wk4 compared to baseline in VR patients (p= 0.003) and HD (p= 0.001) with increased frequency of Ki67+ cells. In VR, H1N1-specific IgG production was evident in CD4+ CXCR5+/B cell co-cultures but not in CD4+ CXCR5–/B cell co-cultures [HIV+ n = 3; p = 0.043] and [HD n=3; p = 0.014], concurrently with increase in frequencies of plasmablasts. These changes were not seen in vaccine nonresponders.

Conclusion

pTFH cells promote antigen-specific Ab production by B cells in vitro. Although their relationship to lymph node germinal center TFH has not been clarified, analysis of pTFH function represents a novel and easily accessible surrogate marker for vaccine responsiveness in stable HIV infected patients with equivalent CD4 T cells.