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

Ivona Pandrea,^1,3 Richard Onanga,¹ Sandrine Souquiere,¹ Augustin Mouinga-Ondéme,¹ Olivier Bourry,² Maria Makuwa,¹ Pierre Rouquet,² Guido Silvestri,⁵ François Simon,^1,6 Pierre Roques,^1,7, and Cristian Apetrei^1,4,*

Departement de Virologie,¹ Centre de Primatologie, Centre International de Recherches Medicales, Franceville, Gabon,² Divisions of Comparative Pathology,³ Microbiology, Tulane National Primate Research Center, Tulane University Health Science Center, Covington, Louisiana,⁴ Department of Pathology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19107,⁵ Laboratoire de Virologie, Hopital St. Louis, Paris, France,⁶ Service d'Immuno-Virologie Université Paris XI, Commisariat à l'Energie Atomique, Fontenay aux Roses, France⁷

Received 29 November 2007/ Accepted 20 March 2008

Simian immunodeficiency virus (SIV) persistence in wild populations of African nonhuman primates (NHPs) may occur through horizontal and vertical transmission. However, the mechanism(s) and timing of the latter type of transmission have not been investigated to date. Here we present the first study of SIV transmissibility by breast-feeding in an African NHP host. Six mandrill dames were infected with plasma containing 300 50% tissue culture infective doses of SIVmnd-1 on the day after delivery. All female mandrills became infected, as demonstrated by both plasma viral loads (VLs) and anti-SIVmnd-1 seroconversion. Neither fever nor lymphadenopathy was observed. At the peak of SIVmnd-1 viral replication (days 7 to 10 postinoculation), plasma VLs were high (8 x 10⁶ to 8 x 10⁸ RNA copies/ml) and paralleled the high VLs in milk (4.7 x 10⁴ to 5.6 x 10⁵ RNA/ml). However, at the end of the breast-feeding period, after 6 months of follow-up, no sign of infection was observed for the offspring. Later on, during a 4-year follow-up examination, two of the offspring showed virological evidence of SIVmnd-1 infection. Both animals seroconverted at least 6 months after the interruption of lactation. In conclusion, despite extensive viral replication in mandrill mothers and high levels of free virus in milk, no SIVmnd-1 transmission was detectable at the time of breast-feeding or during the following months. Since we observed a markedly lower expression of CCR5 on the CD4⁺ T cells of young mandrills and African green monkeys than on those of adults, we propose that low levels of this viral coreceptor on CD4⁺ T cells may be involved in the lack of breast-feeding transmission in natural hosts of SIVs.

Published ahead of print on 2 April 2008.

C.A. and P.R. contributed equally to this work.