Immunoglobulins and measles antibody in sera of newborn cynomolgus monkeys and in milk of their mothers

Essentials for starting a pediatric clinical study (3): Dynamic changes in early development of immune system in macaque monkeys--the significance from standpoint of preclinical toxicity test using nonhuman primates

Macaque monkeys are essential laboratory animals in preclinical safety assessment for human-specific biological products including humanized antibody drug. In most case, investigators are leaving their ages out of consideration, and young individuals aged around 3 years are mainly used because of their small individual differences in biological responses to various stimulations. Since the immune system starts to develop just after birth and remarkable phenotypic and functional changes occur in various kinds of immunocompetent cells during the first few years of life in macaque monkeys, their actual immunological condition must be carefully considered in case of safety assessment of novel drugs which modulate human immune function. The early development of major immune functions of macaque monkeys is summarized as follows. These findings suggest that immunocompetent cells drastically differentiate into activated ones during early development. 1) The serum immunoglobulin contents gradually rise with increasing age up to sexual maturity. 2) The blood group-associated antibodies, anti-A and anti-B antibody, are detected around 40-days of age and antibody levels rapidly increase after one year old. 3) Infant cynomolgus monkeys obviously produce the significant levels of IgG antibody against Campylobacter jejuni within 4 weeks after infection when maternal antibody becomes undetectable (8 weeks of age). 4) The frequency of lymphocyte subpopulations expressing the resting surface phenotypes is much higher than that having activated phenotypes in neonates, and the relative population of lymphocyte subsets with resting phenotype decrease with increasing age, while the subpopulation associated with activation gradually increase with age.

Nonhuman primate models of intrauterine cytomegalovirus infection

Congenital human cytomegalovirus (HCMV) infection has long been recognized as a threat to the developing fetus, even though studies have shown that only a subset of congenital infections results in clinical signs of disease. Among the estimated 8000 children who develop sequelae from congenital CMV infection each year in the United States alone, most suffer permanent developmental defects within the central nervous system. Because there is currently no approved vaccine for HCMV, and anti-HCMV drugs are not administered to gravid women with congenital infection because of potential toxicity to the fetus, there is a clear clinical need for effective strategies that minimize infection in the mother, transplacental transmission of the virus, and/or fetal disease. Animal models provide a method to understand the mechanisms of HCMV persistence and pathogenesis, and allow for testing of novel strategies that limit prenatal infection and disease. The rhesus macaque model is especially well suited for these tasks because monkeys and humans share strong developmental, immunological, anatomical, and biochemical similarities due to their close phylogenetic relationship. This nonhuman primate model provides an invaluable system to accelerate the clinical development of promising new therapies for the treatment of human disease. This review addresses salient findings with the macaque model as they relate to HCMV infection and potential avenues of discovery, including studies of intrauterine CMV infection. The complexity of the natural history of HCMV is discussed, along with the ethical and logistical issues associated with studies during pregnancy, the recent contributions of animal research in this field of study, and future prospects for increasing our understanding of immunity against HCMV disease.

Longitudinal characterization of CD4, CD8 T-cell subsets and of haematological parameters in healthy newborns of cynomolgus monkeys

A longitudinal characterization of immune cell subpopulations (lymphocytes, CD4+ and CD8+ cells), of routine haematological parameters and of immunoglobulin serum levels was carried out in newborn Macaca fascicularis starting from 1 week up to 1 year of life. In neonates, the percentage of CD4+ lymphocytes is almost double, while the percentage of CD8+ cells is lower than that found in adult monkeys (> 5-years old). An inverted trend in the percentage of the two T-lymphocyte subpopulations was observed during the weeks following birth, with a progressive increase of circulating CD8+, paralleled by a decrease of CD4+ cell number. Consequently, the CD4/CD8 ratio slowly decreases, even if, at 12 months of life, it is still higher than that found in adult animals. Several differences were also noted between young and adult monkeys with regard to the total number of circulating CD4+ and CD8+ cells. Haematological parameters did not show consistent differences with respect to adult values. The plasma IgG level is high at birth, then decreases until 6 months of life, while the IgM and IgA values are very low during the first weeks of life but increase in the following period. Our data showed that variations of immunological (CD4+, CD8+ cells) patterns and of some haematological parameters in M. fascicularis are dependent on age. These variations should be therefore considered whenever young animals are used in experimental protocols.

Serum kappa and lambda light immunoglobulin chains in cynomolgus macaques (Macaca fascicularis) during the first twenty months of age

Growth is coupled to physiological modifications of the immune system which reaches the functional capabilities according to age-related milestones. Few data are available on the circulating immunoglobulin levels and no data exist on total immunoglobulin light chains in infant macaques. Therefore we studied by a nephelometric assay, the age-dependent variations of kappa and lambda serum light chains in the experimental animal model Macaca fascicularis during the first 20 months of age. Both kappa and lambda showed a marked increase in their concentrations during the first 7-8 months of life. Infants' light chain levels were anyhow significantly lower than those of the nursing dams and of the control group, never attaining, even at the 20th month, the same concentration as the adult, although the value of the kappa/lambda ratio was apparently the same.

Humoral immunity factors in cynomolgus macaques (Macaca fascicularis) serum: immunoglobulins and total light chains in nursing dams

This study was aimed at the identification of variations in humoral immunity parameters during the lactation period in macaque females, a recognized model in reproductive physiology and pathology. The importance of such evaluation is evidenced in particular by the central role played by the maternally transferred immunity to the progeny. The trends of serum immunoglobulins and light chains were characterized by immunonephelometry during the 6-months of lactation. The levels attained by nursing females were evaluated against a control group. The main modifications induced by lactation were in the IgM class, whose levels remained constantly lower than in the control group; the other Igs, even if showing different trends, returned to levels comparable to the control group by the end of the sixth month. Light chains quantification evidenced a significant decrease in Kappa levels; Lambda chains showed a similar trend. The variation of the Kappa/Lambda ratio was therefore minimal.

Development of lymphocyte subsets in pigtailed macaques

The early development of eight lymphocyte subsets was determined for pigtailed macaque infants from 0 to 800 days of age using two-color flow cytometry and fluorescein- and R-phycoerythrin-conjugated monoclonal antibodies specific for human leukocyte antigens. Four major lymphocyte subsets in monkeys (B, CD4+ T, CD8+ T, and NK cells) could be further divided using two-color analysis. In neonates, the frequency of lymphocyte subpopulations having surface phenotypes found principally on dense, resting cells (IgD+ B cells, Lp220+ CD4+ T cells, and CD18dull CD8+ T cells) was much higher than subpopulations having phenotypes present principally on buoyant, activated cells (IgD- B cells, Lp220- CD4+ T cells, CD18bri CD8+ T cells). There was a complete absence of two CD18bri CD8+ subsets (CD8dull and CD8bri) during the first 300 days of life. The relative proportion of lymphocyte subsets with resting phenotype decreased with increasing age, while the subpopulations associated with activation gradually increased with age. These findings suggest that during early development immunocompetent cells gradually differentiate into activated lymphocytes.