Novel nutritional immune formula maintains host defense mechanisms

Military combat and training stress induce immune changes that increase the risk of infection and ultimately influence soldiers' performance and readiness. Strenuous military training/assessment provides a uniform stress and the opportunity to evaluate nutritional strategies to minimize stress-induced immune changes that predispose soldiers to infection. Immunological changes and effects of a novel nutritional immune formula (NNIF) were examined prospectively in a double-blind, controlled study of 200 soldiers attending Special Forces Assessment and Selection School. Immune function was measured by skin delayed-type hypersensitivity, lymphocyte phenotyping, mitogenic proliferative responses, and granulocyte function. Approximately 50% of soldiers completed the study (control, n = 57; NNIF, n = 50). Several stress-induced lymphocyte changes were observed (decreased mitogen-induced proliferation, T and total lymphocytes, and interferon-gamma-producing lymphocytes and increased percentage of neutrophils). NNIF modified several changes, including delayed-type hypersensitivity responses (NNIF, 78%; control, 59%; p < 0.05), increased proportions of helper T cells, activation of B cells, enhanced neutrophil phagocytosis, and attenuation of declines in certain functional subpopulations (i.e., cytotoxic/ suppressor lymphocytes). Soldiers who consumed NNIF experienced less stress-induced immune impairment, thereby lowering the risk of infection.

Effect of dietary ribonucleotides on infant immune status. Part 1: Humoral responses

The objective of this study was to further explore previously identified effects of supplemental ribonucleotides on infant immune status as measured by antibody responses to routine infant immunizations. Infants were randomized to a milk-based formula with (FN, n = 138) or without (F, n = 147) 72 mg ribonucleotides/L. A cohort of human milk-fed (HMF, n = 192) infants was also followed. Subjects were given Haemophilus influenzae type b (Hib), diphtheria tetanus acellular pertussis, and oral poliovirus vaccinations at 2, 4, and 6 mo of age, and specific antibody responses were assessed at 2, 6, 7, and 12 mo. Growth and safety data were also monitored. Using a two-group repeated measures analysis (RMA), FN-fed infants had significantly higher poliovirus type 1 neutralizing antibody (PV-VN1) responses than F-fed infants (p = 0.045). Using three-group RMA, PV-VN1 responses in HMF infants were not different from FN-fed infants, while HMF-fed infant PV-VN1 responses were significantly higher than F-fed infants at 6 (p = 0.0004) and 12 mo (p = 0.0001). FN-fed infants had responses to Hib Farr, diphtheria, tetanus toxoid, oral poliovirus-specific IgA, and PV-VN3 not significantly different from those of F and HMF infants. Growth, gastrointestinal tolerance, and adverse events were equivalent among the three groups. The FN-associated increase in PV-VN1 response and nonstatistically significant trends toward increased Hib and diphtheria antibody responses were consistent with observations from earlier studies, indicating immune benefits of nucleotide supplementation of infant formula.

Effect of dietary ribonucleotides on infant immune status. Part 2: Immune cell development

The objective of this study was to determine whether dietary ribonucleotides alter immune cell phenotypes or function in the first year of life. Newborn term infants in a double-blind, 12-mo, multicenter trial were randomized to cow milk formula groups with (FN, n = 138) or without (F, n = 147) 72 mg/L supplemental ribonucleotides. A nonrandomized HMF cohort (n = 192) was concurrently enrolled. Eighty-eight immune blood cell types were characterized by flow cytometry. Data were analyzed by multivariate ANOVA (MANOVA), ANOVA, and repeated measures analysis (RMA), with adjustments made for multiple comparisons. Ribonucleotide feeding changed subpopulations of T and natural killer (NK) cells. FN had higher numbers and percentages of memory/effector (M/E) cytotoxic/suppressor (CD45R0(+)CD8(+), RMA) T, Fas(+) M/E (CD45R0(+)CD95(+)CD3(+), 6 mo) T, and CD56(+)CD16(-) NK cells (CD56(+)CD16(-)CD3(-)CD8(-), 12 mo), and higher percentages of M/E helper (CD45R0(+)CD4(+), RMA) T, Tc1 (IFN gamma(+)CD4(-)CD3(+), RMA), total interferon (IFN)gamma T (IFN gamma(+)CD4(+/-)CD3(+), RMA), Th2 (IL-4(+)CD4(+)CD3(+), 7 mo), and CD57(+) NK-T cells (CD57(+)CD56(-)CD3(+), 6 mo, 7 mo) compared with F. Percentages of naive helper T (CD45RA(+)CD4(+), 12 mo) and numbers and percentages of CD56(+) NK-T cells (CD56(+)CD16(-)CD3(+)CD8(-), 2 mo, 6 mo) were lower in FN than F. Percentages of M/E cytotoxic/suppressor, Th2, and CD56(+)CD16(-) NK cells in FN were significantly higher than F but were not different from HMF, whereas F was significantly lower than HMF. Ribonucleotide supplementation of infant formula supported increased T-cell maturation and affected immunoregulatory NK cell subsets. These FN-associated immune cell profiles either did not differ from those infants fed HMF or tended to be more like those fed HMF than those fed F.

Longitudinal study of intracellular T cell cytokine production in infants compared to adults

Intracellular cytokine production in lymphocytes obtained longitudinally from 325 healthy infants aged 2-12 months was compared with adult lymphocytes using four-colour flow cytometry. Peripheral blood samples (180 microlitres) were stimulated with phorbol 12-myristate 13-acetate, ionomycin and brefeldin A to induce production and intracellular accumulation of cytokines. The method was validated by assessing reproducibility, repeatibility, ruggedness (i.e. fresh versus day-old blood samples), precision, linearity and sensitivity. Among infants, the number and percentage of T lymphocytes (helper/inducer T cell subsets and cytotoxic/suppressor T cell subsets) producing IFN-gamma (type 1) and IL4 (type 2) increased over the first year of life but remained significantly lower than levels found in adults. In both infants and adults more CD4- T cells than CD4+ T cells were induced to make IFN-gamma. Infant Th1/Th2 ratios revealed modest Th1-skewed (predominant) profiles compared to adults, which were 5-10 times higher. Infant Tc1/Tc2 ratios revealed Tc1-skewed responses which were equal to adult ratios by age 12 months. At 12 months infant Th2 responses were closer to adult levels than were Th1 cells. Intracellular cytokine detection by flow cytometry is a rapid, sensitive, rugged and precise method to characterize immune status changes over time.

Immune status of infants fed soy-based formulas with or without added nucleotides for 1 year: part 1: vaccine responses, and morbidity

BACKGROUND

Immunologic development of soy-fed infants has not been extensively studied. Early studies of soy flour-based formulas showed decreased immunoglobulin production when soy protein intake was limited. However, there were no significant differences in rotavirus vaccine responses between breast-fed and soy protein isolate-based formula-fed infants. Nucleotides added to milk-based formula benefit infant immune status, but reports of the immunologic effects of adding nucleotides to soy-based formula are not available. This study evaluated immune status and morbidity of infants fed soy protein isolate formulas with and without added nucleotides for 1 year.

METHODS

Newborn, term infants enrolled in a masked 12-month feeding trial were assigned randomly to groups fed soy formula with or without added nucleotides (n = 94, n = 92). A nonrandomized human milk/formula cohort (n = 81) was concurrently enrolled. Recommended immunizations were administered at 2, 4, and 6 months. Immune status was determined from antibody responses to Haemophilus influenzae type b, tetanus, diphtheria, and poliovirus vaccines at 6, 7, and 12 months. Parents and physicians reported morbidity data.

RESULTS

All vaccine responses were within normal ranges. No response differences were observed between infants fed soy formula and those fed nucleotide-supplemented soy. However, antibody to H. influenzae type b at 7 and 12 months was higher in infants fed nucleotide-supplemented soy than in infants fed human milk/formula ( P = 0.007, P = 0.008, respectively). Human milk/formula-fed infants had higher poliovirus neutralizing antibody at 12 months than did soy-fed infants ( P = 0.016). Morbidity analyses showed that only physician-reported diarrhea was different among groups (groups fed human milk/formula had less diarrhea than did soy groups, P = 0.011).

CONCLUSIONS

Term infants fed soy protein isolate-based formulas have normal immune development as measured by antibody responses to childhood immunizations.

Immune status of infants fed soy-based formulas with or without added nucleotides for 1 year: part 2: immune cell populations

BACKGROUND

Infants fed a soy protein isolate-based formula have immunization responses similar to breast-fed infants. However, cellular aspects of the immunologic development of soy-fed infants have not been studied extensively. Nucleotides added to milk-based formula benefit infant immune status, but reports of the immunologic effects of adding nucleotides to soy-based formula are not available. This study examines immune cell populations of infants fed soy protein isolate formulas with and without added nucleotides for 1 year.

METHODS

Newborn, term infants studied in a masked 12-month feeding trial were assigned randomly to soy formula groups with and without added nucleotides (n = 94, n = 92). A nonrandomized human milk/formula-fed cohort (n = 81), was concurrently enrolled. Blood samples were collected at 6, 7, and 12 months. Thirty-two immune cell populations were characterized using three-color flow cytometry. Cellular markers were chosen to assess general pediatric immune status, emphasizing maturation and activation of B, T, and NK lymphocytes.

RESULTS

All cell populations, number and percentages, were within age-related normal ranges. The only significant difference found between soy formula and human milk/formula-fed infants was the percentage of CD57 + NK T cells at 12 months (human milk/formula > soy formula, P = 0.034). There were significant differences at some time points between human milk/formula-fed and nucleotide-supplemented soy formula-fed infants in populations of lymphocytes, eosinophils, total T, helper T, naive helper, memory/effector helper, CD57 - T, and CD11b + CD8 + NK cells. None of the cell populations differed between infants fed soy formula versus soy plus nucleotides.

CONCLUSIONS

Infants fed this commercial soy formula demonstrated immune cell status similar to human milk/formula-fed infants, consistent with normal immune system development. The addition of nucleotides to soy formula did not significantly change specific individual immune cell populations but tended to increase numbers and percentages of T cells and decreased numbers and percentages of NK cells.

Modulation of the immune system by human milk and infant formula containing nucleotides

OBJECTIVE

To determine whether human milk and nucleotides added to infant formula at levels present in human milk enhance development of the immune system during infancy.

METHODS

A 12-month, controlled, randomized and blinded, multisite feeding trial was conducted on two infant formulas: iron-fortified, milk-based control formula (Control) or the same formula fortified with nucleotides (Nucleotide). The level (72 mg/L) and ratio of individual nucleotides selected were patterned after those available in human milk. A third group fed human milk exclusively for 2 months and then human milk or Similac with iron until 12 months of age also was studied. Response to immunizations was chosen to assess development of the immune system. Infants followed the immunization schedule recommended by the American Academy of Pediatrics in 1991.

OUTCOME VARIABLES

Antibody responses were determined at 6, 7, and 12 months of age to Haemophilus influenzae type b polysaccharide (Hib), to diphtheria and tetanus toxoids, and to oral polio virus (OPV) immunizations.

RESULTS

Of 370 full-term, healthy infants enrolled, 311 completed the study (107 Control, 101 Nucleotide, 103 human milk/Similac with iron). Intake, tolerance, and growth of infants were similar in all three groups. Compared with the Control group 1 month after the third immunization (7 months of age), the Nucleotide group had a significantly higher Hib antibody concentration (geometric mean concentrations of 7.24 vs 4.05 micrograms/mL, respectively), and a significantly higher diphtheria antibody concentration (geometric mean of 1.77 vs 1.38 U/mL). The significantly higher Hib antibody response in the Nucleotide group persisted at 12 months. The antibody responses to tetanus and OPV were not enhanced by nucleotide fortification. There also was an effect of breastfeeding on immune response. Infants who breastfed had significantly higher neutralizing antibody titers to polio virus than either formula-fed group (1:346 vs 1:169 and 1:192 in the Control and Nucleotide groups, respectively) at 6 months of age.

CONCLUSION

Infant formula fortified with nucleotides enhanced H influenzae type b and diphtheria humoral antibody responses. Feeding human milk enhanced antibody responses to OPV. Dietary factors play a role in the antibody response of infants to immunization.

Prevention of human rotavirus-induced diarrhea in gnotobiotic piglets using bovine antibody

The efficacy of passively administered bovine antibody for preventing human rotavirus (HRV)-induced diarrhea was investigated using a gnotobiotic pig model. Cows were immunized with inactivated HRV serotypes 1 (Wa) and 2 (S2) and simian rotavirus serotype 3 (SA11), and immune colostrum and milk were collected. Antibody concentrates derived from these materials were fed to germ-free piglets that were subsequently inoculated with HRV Wa. Both viral shedding and diarrhea were effectively reduced or eliminated in a dose-dependent manner as a result of HRV immune antibody feeding. A quantitative virus-neutralizing (VN) antibody method permitted assessment of the functional antibody dose required to achieve a 50% reduction of disease (PD50). PD50 dose levels of 15.8 and 19.5 x 10(6) VN antibody units were determined for inhibition of diarrhea and viral shedding, respectively. Studies reported here provide new information on the quantitative relationship between protective antibody dose and diarrheal disease response.

Distinctive characteristics of crude interferon from virus-infected guinea-pig embryo fibroblasts

Crude interferon preparations from primary guinea-pig embryo cells infected with vesicular stomatitis virus strain T1026R1 were shown to be more sensitive to heat (37 degrees C), pH 2.0, and SDS than crude mouse interferon. Since the proportion of antiviral activity lost after each treatment was nearly the same, the existence of a single fraction of antiviral activity sensitive to all three treatments was suggested. Support for this possibility was given by the finding that subjecting this guinea-pig interferon to any one of the treatments rendered it insensitive to the effects of the other two.

Improved conditions for the production and detection of interferon from guinea pig embryo cells

Primary guinea pig embryo (GPE) fibroblasts were assessed as potential sources of guinea pig interferon (IFN). GPE cells proved to be excellent in vitro producers of guinea pig IFN, although the actual amounts produced were only detectable when sample irradiation under ultraviolet light (to inactivate inducing viruses) was substituted for overnight sample treatment at pH 2. Thus, the rapid spontaneous inactivation of large proportion of the antiviral activity after overnight exposure to 4 degrees C, regardless of pH, was avoided. IFN was induced using Newcastle disease virus (NDV), Sindbis virus, and a genetic variant of vesicular stomatitis virus, VSV T1026R1. Each virus exhibited different dose response kinetics, with VSV T1026R1 proving the most efficient inducer of the three. Optimal IFN production depended largely on virus multiplicity and cell age. All the antiviral activity produced by GPE fibroblasts had the classical properties of species specificity, susceptibility to trypsin, and a broad range of antiviral activity.

Host restriction property of a vesicular stomatitis virus mutant isolated from carrier cultures

Carrier cultures of L cells infected with wild-type vesicular stomatitis virus (VSV0) were initiated without the use of defective-interfering particles or homologous interferon. The cloned viruses recovered from such carrier cultures after passage 21 were characterized as temperature-sensitive. Furthermore, these clones of the mutant showed restricted replication at permissive temperature in HEp-2 cell cultures as compared to the wild-type VSV0. This restrictive replication of the mutant in HEp-2 cells was not due to a defect in the expression of virion-associated primary transcriptase activity in vivo, but due to the marked reduction in virus-specific characterized may govern the synthesis of mutant virus-specific amplified RNA in HEp-2 cells.

A sensitive method for quantification of vesicular stomatitis virus defective interfering particles: focus forming assay

A focus-forming assay for the quantification of defective interfering (DI) particles of vesicular stomatitis virus (VSV) is described. This assay is based on the procedures described for lymphocytic choriomeningitis (LCM) virus by Popescu et al. (1976). Under appropriate conditions this focus-forming assay can quantify fewer than 100 DI particles/ml in a preparation containing a large number of infectious particles.

Interferon induction by viruses. VI. Reovirus: virion genome dsRNA as the interferon inducer in aged chick embryo cells

The interferon-inducing particle (IFP) activity of avian and human reoviruses in aged chick embryo cells was determined by analyzing dose (multiplicity)-response (interferon yield) curves. These curves fit best a model in which each cell infected with greater than or equal to 1 IFP produces a quantum yield of interferon. Avian reovirus stocks contained as many as 60 times more IFP than plaque-forming particles (PFP). Upon UV-irradiation the ratio of IFP:PFP became 197, suggesting that virtually every physical particle of avian reovirus could function as an interferon-inducing particle. Thus, about one-third of the non-infectious particles were intrinsically IFP and the other two-thirds could be converted to IFP status at an optimal dose of UV radiation, the equivalent of 9.4 lethal hits, i.e., 8000 ergs/mm2. UV-irradiated avian reovirus induced about twice the usual yield of interferon on a per cell basis. Wildtype human reovirus (type 3) and mutants ts201(A,RNA+) and ts447(C,RNA-) were excellent inducers of interferon, but only about 1 in 3 infectious particles functioned as an interferon-inducing particle, meaning that virtually all physical particles failed to function as IFP, UV-irradiation of human reoviruses resulted in a slight loss of IFP activity. Our data support the hypothesis that virion genome dsRNA constitutes the interferon inducer moiety of avian reoviruses and that in its permissive host cell the processing of genome dsRNA from most particles to a putative recognition site in the cytoplasm occurs naturally with a high probability. For human reovirus this is a much rarer event which may be intrinsic only to infectious virus, and may require limited transcription for expression. The sensitivity of the avian reovirus-aged chick embryo cell system recommends it for further study on the mechanism of interferon induction by virions containing pre-existing dsRNA.