Phylogenetic Analysis of SIV and STLV Type I in Mandrills (Mandrillus sphinx): Indications That Intracolony Transmissions Are Predominantly the Result of Male-to-Male Aggressive Contacts

Abstract

Natural SIVmnd and STLVmnd infections of mandrills in a colony at the Centre International de Recherches Médicales de Franceville (CIRMF) in Gabon were investigated by genetic analysis to determine the extent of intracolony transmission. SIVmnd pol sequence analysis indicates that the six strains present in the colony belong to the SIVmnd lentivirus subgroup previously defined according to the only available prototype sequence (SIVmndGB1), which originated from the same colony. The intraanimal nucleotide diversity (1.1-3.1%) was similar in range to that reported in individuals infected by other HIV/SIVs. The interanimal diversity (0.5-4.3%) was not significantly different from that observed in each individual mandrill, indicating an epidemiological link among the SIVmnd isolates of distinct animals within the colony. Phylogenetic analysis of these isolates, together with seroepidemiological and behavior surveillance within the colony, indicates a predominant male-to-male transmission of SIVmnd that probably occurred during bouts of interanimal aggression. Moreover, our results suggest one case of vertical transmission of SIVmnd from a naturally infected founder female to one of her six offspring. The first genetic analysis of STLV isolates from mandrills is also reported here. Partial tax/rex sequences were used to evaluate the diversity between seven STLVmnd isolates and their phylogenetic relationships with other known strains of human and nonhuman primate T cell leukemia virus, types I and II (PTLV-I/II). They all belong to the PTLV-I subtype, but two genetically distinct STLVmnd groups were evidenced within the mandrill colony. The phylogenetic analyses of the STLVmnd isolates, together with seroepidemiological and behavior surveillance of the mandrills, indicate that intracolony transmissions of STLVmnd are also predominantly the result of male-to-male aggressive contacts.

Paucity of CD4 + CCR5 + T Cells May Prevent Transmission of Simian Immunodeficiency Virus in Natural Nonhuman Primate Hosts by Breast-Feeding

“…First, in this colony, no sexual transmission was found after 16 years of follow-up (9,14,18,38), which is different from what has been seen with wild mandrills from central Gabon, where cases of SIVmnd-1 infection could be diagnosed in both sexes (63). Two of the founders of the CIRMF colony had been infected with two different virus types (SIVmnd-1 and SIVmnd-2) (63,66).…”

Two Novel Simian Arteriviruses in Captive and Wild Baboons (Papio spp.)

“…Additionally, our data show that the prevalence of MYBV-1 is greater in adult male yellow baboons than juvenile or subadult males of the same social groups. Although only samples from Mikumi male baboons were available for testing, this observation may be relevant to the mode of simian arterivirus transmission, as aggressive encounters between male primates is a common mode of transmission for other bloodborne viruses (28). A prolonged duration of infection could also potentially explain the higher prevalence of infection in adult baboons.…”

Understanding the benign nature of SIV infection in natural hosts

“…A direct evolutionary pressure is certainly easy to imagine if the "ancestral" SIV infection of natural hosts manifested a tempo of disease similar to that observed in SIV-infected macaques (with progression to AIDS observed in most cases within 1-2 years of primary infection). It should be noted, however, that if the original and putatively pathogenic infections of African monkeys had a course of disease similar to that observed today in HIV-infected individuals (i.e., taking an average of 10 years to proceed from infection to death), it is hard to fathom a strong evolutionary pressure in animals with a 15-20 year lifespan in the wild that usually acquire infection as adults (75)(76)(77)(78). In this perspective, it is possible to imagine that the original epidemics of SIV infection in African NHPs generated strong evolutionary pressure to avoid vertical transmission from mother to offspring, particularly if one considers (a) the likely deleterious effect of moving the "clock" of the infection back 4-5 years and (b) the fact that primate lentiviral infections appear to be more severe in newborns compared with adults (79,80).…”