Evaluating the antibody response elicited by diverse HIV envelope immunogens in the African green monkey (Vervet) model.

African Green (Vervet) monkeys have been extensively studied to understand the pathogenesis of infectious diseases. Using vervet monkeys as pre-clinical models may be an attractive option for low-resourced areas as they are found abundantly and their maintenance is more cost-effective than bigger primates such as rhesus macaques. We assessed the feasibility of using vervet monkeys as animal models to examine the immunogenicity of HIV envelope trimer immunogens in pre-clinical testing. Three groups of vervet monkeys were subcutaneously immunized with either the BG505 SOSIP.664 trimer, a novel subtype C SOSIP.664 trimer, CAP255, or a combination of BG505, CAP255 and CAP256.SU SOSIP.664 trimers. All groups of vervet monkeys developed robust binding antibodies by the second immunization with the peak antibody response occurring after the third immunization. Similar to binding, antibody dependent cellular phagocytosis was also observed in all the monkeys. While all animals developed potent, heterologous Tier 1 neutralizing antibody responses, autologous neutralization was limited with only half of the animals in each group developing responses to their vaccine-matched pseudovirus. These data suggest that the vervet monkey model may yield distinct antibody responses compared to other models. Further study is required to further determine the utility of this model in HIV immunization studies.

Faecal glucocorticoid metabolite monitoring as a measure of physiological stress in captive and wild vervet monkeys.

The development of non-invasive techniques to analyse physiological stress in mammalian species has revolutionised field-based endocrinology. However, careful validation of the methods used to determine faecal glucocorticoid metabolite (fGCM) and other hormone concentrations are required on a species- and sex-specific basis. In this study, we performed an adrenocorticotropic hormone (ACTH) stimulation test on four (two male and two female) captive vervet monkeys (Chlorocebus pygerythrus) to determine the most appropriate enzyme immunoassay (EIA) from a suite of available EIAs. Furthermore, we took advantage of a potentially stressful event in our wild vervet population from Samara Private Game Reserve, South Africa, to examine if an alpha-beta female rank reversal increases the physiological stress of those individuals directly involved, as well as other group members. Both our physiological and biological validation studies revealed that a cortisol assay was the most appropriate EIA for monitoring fGCM alterations in vervet monkeys. In addition, we found that the observed rank-reversal had no significant effect on the physiological stress levels of uninvolved group members. Our study highlights that physiological validation is imperative and, where possible, should be conducted in parallel with a carefully considered biologically-relevant test under natural conditions. Overall, our results provide a necessary step for future studies to examine physiological stress of vervet monkeys via fGCM monitoring by validating a suitable EIA for this species. This paves the way for future research into the health and welfare of both captive and wild vervet monkeys, and will allow researchers to assess the behavioural, social and ecological correlates of physiological stress levels of this species.

The effect of housing and environmental enrichment on stereotyped behavior of adult vervet monkeys (Chlorocebus aethiops).

Little information is available on the response of vervet monkeys to different housing conditions or on the suitability of enrichment devices or methods for vervet monkeys. In this study, the authors evaluated the occurrence of stereotyped behavior in adult vervet monkeys under various conditions of housing and enrichment. The variables included cage size, cage level (upper or lower), enrichment with a foraging log, enrichment with an exercise cage and presence of a mate. The authors first determined the incidence of stereotyped behavior in captive-bred, singly housed adult female and male vervet monkeys. They then exposed monkeys to different housing and enrichment situations and compared the incidence of stereotyped behavior among the monkeys. The authors found that more females than males engaged in stereotyped behavior and that females, on average, engaged in such behavior for longer periods of time than males. Stereotyped behavior was most often associated with a small, single cage. The average amount of observed stereotyped activity in monkeys housed in a small cage was significantly lower when the monkeys had access to either a foraging log or an exercise cage. Stereotyped behavior was also lower in female monkeys that were housed (either with a male or without a male) in a larger cage. The least amount of abnormal behavior was associated with the largest, most complex and enriched housing situation. Males and females housed in cages on the lower level of two-level housing engaged in more stereotyped behavior than did monkeys housed in the upper level, regardless of the presence or type of enrichment provided.