Neonatal pneumococcal conjugate vaccine immunization primes T cells for preferential Th2 cytokine expression: a randomized controlled trial in Papua New Guinea

Abstract

The effects of neonatal immunization with 7-valent pneumococcal conjugate vaccine (7vPCV) on development of T-cell memory and general immune maturation were studied in a cohort of Papua New Guinean newborns. Neonatal 7vPCV priming (followed by a dose at 1 and 2 months of age) was associated with enhanced Th2, but not Th1, cytokine responses to CRM(197) compared to 7vPCV at 1 and 2 months of age only. T cell responses to non-7vPCV vaccine antigens were similar in all groups, but TLR-mediated IL-6 and IL-10 responses were enhanced in 7vPCV vaccinated compared to controls. Neonatal 7vPCV vaccination primes T cell responses with a polarization towards Th2 with no bystander effects on other T cell responses.

Fig. 1

T cell responses to 7vPCV and concomitant vaccines. Peripheral blood mononuclear cells were cultured in vitro with medium only, or stimulated with the vaccine protein carrier CRM₁₉₇, the polyclonal phytohemagglutinin (PHA), and vaccine antigens including soluble Hepatitis B antigen (HbsAg), mycobacterium purified protein derivative (PPD) and tetanus toxoid (TT). Antigen-specific cytokine responses were calculated by subtracting background levels that were produced in cultures with medium only from responses measured in stimulated cell cultures (‘delta concentration’). Represented are the geometric means (GMs) and standard errors of geometric means (SEGMs) for children randomized to the neonatal (white bar), infant (grey bar) and control group (black bar). Significant differences between groups are indicated at the 0.001 (***), 0.01 (**) and 0.05 (*) level.

Fig. 2

Co-production of CRM₁₉₇-specific Th1 and Th2 responses in neonatal, infant and control groups. Children were considered to produce Th1 responses to the 7vPCV protein carrier CRM₁₉₇ when in vitro CRM₁₉₇-induced IFN-γ responses were at least four times the background level, and Th2 responses if CRM₁₉₇-induced IL-5 and/or IL-13 responses were at least four times the background. For each study group the proportion of children with no memory responses (hatched), Th2 without Th1 (light grey), mixed Th1/Th2 (dark grey) and Th1 without Th2 (black) is presented.

Fig. 3

TLR-mediated immune responses. PBMC of 3-month-old children in the neonatal (white bar), infant (grey bar) and control group (black bar) were stimulated in vitro with lipoteichoic acid (LTA) (neonatal n = 37; infant n = 39; control n = 33), polyinosinic–polycytidylic acid (Poly:IC) (neonatal n = 40; infant n = 38; control n = 34), lipopolysaccharide (LPS) (neonatal n = 42; infant n = 40, control n = 35) and oligonucleotide CpG (CpG) (neonatal n = 32; infant n = 34; control n = 27). Bars represent geometric means and standard errors of geometric means of ligand specific cytokine responses (minus background response).

Fig. 4

LPS-induced expression of inflammatory and cytotoxic mediators. PBMC of 3-month-old children in the neonatal 7vPCV (white bar), infant 7vPCV (grey bar) and control group (black bar) were stimulated in vitro with lipopolysaccharide (LPS). MRNA expression of IL-23, type-I interferon, Granzyme B and lymphotoxin-α were measured and normalized (ratio) for the expression of the housekeeping gene UBE2D2. Bars represent the geometric means and standard errors of geometric means of normalized mRNA expression in cells cultured in medium only (control) and LPS.