Julio C. Ruiz

Experimental Zika Virus Infection of Neotropical Primates

The establishment of a sylvatic reservoir of Zika virus (ZIKV) in the Americas is dependent on the susceptibility of primates of sufficient population density, the duration and magnitude of viremia, and their exposure to the human mosquito-borne transmission cycle. To assess the susceptibility of squirrel (Saimiri sp.) and owl monkeys (Aotus sp.) to infection, we inoculated four animals of each species with ZIKV from the current epidemic. Viremia in the absence of detectible disease was observed in both species and seroconversion occurred by day 28. ZIKV was detected in the spleen of three owl monkeys: one at 7 days postinoculation (dpi) and two at 14 dpi. This study confirms the susceptibility to ZIKV infection of two Neotropical primate species that live in close proximity to humans in South America, suggesting that they could support a widespread sylvatic ZIKV cycle there. Collectively, establishment of a ZIKV sylvatic transmission cycle in South America would imperil eradication efforts and could provide a mechanism for continued exposure of humans to ZIKV infection and disease.

Phenotypic and Functional Characterization of Lymphocytes from Different Age Groups of Bolivian Squirrel Monkeys (Saimiri boliviensis boliviensis)

Due to many physiological and genetic characteristic similarities to humans, squirrel monkeys provide an ideal animal model specifically for studying malaria, and transmissible spongiform encephalopathies (Creutzfeldt-Jacob disease). While squirrel monkeys three years and older are generally considered adult subjects suitable for use in medical research studies, little is known about the functional properties of lymphocytes in relation to the age of these animals, which could significantly impact the quality and quantity of innate and adaptive immune responses. In this study, we investigated differences in the phenotype and function of lymphocytes subsets of young (3–4 years), adult (8–10 years) and aged (16–19 years) squirrel monkeys. In general, animals in all three age groups exhibited comparable numbers of different lymphocyte subsets except for CD20+ B cells that were significantly lower in aged relative to young animals and T cells subsets expressing both CD4 and CD8 (double positive) were significantly higher in aged relative to young animals. With increasing age, phenotypic differences in central and effector memory T cells subsets were observed, that were more pronounced for the CD8+ T cells. Despite equal proportions of CD3+ T cells among the three age groups, responses of peripheral blood mononuclear cells to T cell mitogens PHA and Con A showed lower IFN-γ producing cells in the aged group than that in the young group. Furthermore, aged animals showed significantly higher plasma levels of inflammatory cytokines IL-6, IFN-γ, TNF-α, IL-10 and IL-12. These findings suggest that while the squirrel monkeys in general share phenotypic and functional similarities of lymphocyte subsets with humans in relation to age, specific differences exist in immune function of lymphocytes between young and old animals that could potentially impact experimental outcomes for which the measurement of immunologic endpoints are critical.

Randomized trial of cesarean vs vaginal delivery for effects on the pelvic floor in squirrel monkeys

BACKGROUND Vaginal delivery is a risk factor in pelvic floor disorders. We previously described changes in the pelvic floor associated with pregnancy and parturition in the squirrel monkey, a species with a humanlike pattern of spontaneous age- and parity-associated pelvic organ prolapse. OBJECTIVE The potential to prevent or diminish these changes with scheduled cesarean delivery (CD) has not been evaluated. In a randomized, controlled trial, we compared female squirrel monkeys undergoing spontaneous vaginal delivery with those undergoing scheduled primary CD for pelvic floor muscle volumes, muscle contrast changes, and dynamic effects on bladder neck position. STUDY DESIGN Levator ani, obturator internus, and coccygeus (COC) muscle volumes and contrast uptake were assessed by magnetic resonance imaging in 20 nulliparous females examined prior to pregnancy, a few days after delivery, and 3 months postpartum. The position of bladder neck relative to bony reference line also was assessed with abdominal pressure using dynamic magnetic resonance imaging. RESULTS Baseline measurements of 10 females randomly assigned to scheduled primary CD were not different from those of 10 females assigned to spontaneous vaginal delivery. Levator ani and obturator internus muscle volumes did not differ between groups, while volumes were reduced (P < .05) in the observation immediately after pregnancy. The COC muscles increased (P < .05) immediately after delivery for females in the spontaneous vaginal delivery group, but not for females in the scheduled CD group. Position of the bladder neck descended (P < .05) by 3 months postpartum in both groups. CONCLUSION Scheduled CD diminishes changes in COC muscle volume and contrast reported to be associated with spontaneous vaginal delivery in squirrel monkeys. However, pelvic support of the bladder was not protected by this intervention suggesting that effects of pregnancy and delivery are not uniformly prevented by this procedure.

Aortic aneurysm in a Cebus apella monkey with experimentally induced atherosclerosis

The sudden death of a Cebus apella female (>19 years old) on an experimental hyperlipidic diet during three years is described. The gross lesions were hemothorax, atherosclerotic plaques in the aortic curve, and an aneurysm in the ascending aorta.

Functional morphology of the tubular genital organs in the female owl monkey (Aotus spp.)

Studies on reproductive morphology are important to understand the reproductive cycle of non‐human primates.