TLR7/8 adjuvant overcomes newborn hyporesponsiveness to pneumococcal conjugate vaccine at birth.

Infection is the most common cause of mortality in early life, and immunization is the most promising biomedical intervention to reduce this burden. However, newborns fail to respond optimally to most vaccines. Adjuvantation is a key approach to enhancing vaccine immunogenicity, but responses of human newborn leukocytes to most candidate adjuvants, including most TLR agonists, are functionally distinct. Herein, we demonstrate that 3M-052 is a locally acting lipidated imidazoquinoline TLR7/8 agonist adjuvant in mice, which, when properly formulated, can induce robust Th1 cytokine production by human newborn leukocytes in vitro, both alone and in synergy with the alum-adjuvanted pneumococcal conjugate vaccine 13 (PCV13). When admixed with PCV13 and administered i.m. on the first day of life to rhesus macaques, 3M-052 dramatically enhanced generation of Th1 CRM-197-specific neonatal CD4+ cells, activation of newborn and infant Streptococcus pneumoniae polysaccharide-specific (PnPS-specific) B cells as well as serotype-specific antibody titers, and opsonophagocytic killing. Remarkably, a single dose at birth of PCV13 plus 0.1 mg/kg 3M-052 induced PnPS-specific IgG responses that were approximately 10-100 times greater than a single birth dose of PCV13 alone, rapidly exceeding the serologic correlate of protection, as early as 28 days of life. This potent immunization strategy, potentially effective with one birth dose, could represent a new paradigm in early life vaccine development.

Viral and immunological factors associated with breast milk transmission of SIV in rhesus macaques.

BACKGROUND: The viral and host factors involved in transmission of HIV through breastfeeding are largely unknown, and intervention strategies are urgently needed to protect at-risk populations. To evaluate the viral and immunological factors directly related to milk transmission of virus, we have evaluated the disease course of Simian Immunodeficiency Virus (SIV) in lactating rhesus macaques (Macaca mulatta) as a model of natural breast milk transmission of HIV. RESULTS: Fourteen lactating macaques were infected intravenously with SIV/DeltaB670, a pathogenic isolate of SIV and were pair-housed with their suckling infants throughout the disease course. Transmission was observed in 10 mother-infant pairs over a one-year period. Two mothers transmitted virus during the period of initial viremia 14-21 days post inoculation (p.i.) and were classified as early transmitters. Peak viral loads in milk and plasma of early transmitters were similar to other animals, however the early transmitters subsequently displayed a rapid progressor phenotype and failed to control virus expression as well as other animals at 56 days p.i. Eight mothers were classified as late transmitters, with infant infection detected at time points in the chronic stage of the maternal SIV disease course (81 to 360 days). Plasma viral loads, CD4+ T cell counts and SIV-specific antibody titers were similar in late transmitters and non-transmitters. Late breast milk transmission, however, was correlated with higher average milk viral loads and more persistent viral expression in milk 12 to 46 weeks p.i. as compared to non-transmitters. Four mothers failed to transmit virus, despite disease progression and continuous lactation. CONCLUSION: These studies validate the SIV-infected rhesus macaque as a model for breast milk transmission of HIV. As observed in studies of HIV-infected women, transmission occurred at time points throughout the period of lactation. Transmission during the chronic stage of SIV-infection correlated with a threshold level of virus expression as well as more persistent shedding in milk. This model will be a valuable resource for deciphering viral and host factors responsible for transmission of HIV through breastfeeding.

The replicative capacity of rhesus macaque peripheral blood mononuclear cells for simian immunodeficiency virus in vitro is predictive of the rate of progression to AIDS in vivo.

Survival of rhesus macaques (Macaca mulatta) experimentally infected with simian immunodeficiency virus (SIV) varies significantly from animal to animal. Some animals die within 2 months while others survive for more than 5 years, even when identical inocula are used. This diversity in survival creates a significant problem in the design of therapeutic and vaccine trials using the SIV-macaque model because the use of small numbers of animals may provide results that are misleading. Identifying an in vitro assay that could determine the survival of monkeys prior to infection would prove extremely useful for stratifying experimental groups. Analysis of the survival of a cohort of 59 control animals obtained from over a decade of vaccine and therapeutic trials has demonstrated that the ability of peripheral blood mononuclear cells (PBMC) from a naïve animal to produce virus in vitro was highly predictive of disease progression in vivo following experimental inoculation. Animals classified in vitro as high producers of virus progressed to disease significantly more rapidly than animals classified as either low (P=0.002) or intermediate (P=0.013) producers of virus. The hierarchy of high and low virus production was maintained in purified CD4(+) T cell cultures, indicating that this phenotype is an intrinsic property of the CD4(+) T cell itself. These findings should significantly aid in the design of vaccine and therapeutic trials using the SIV-macaque model. Furthermore, since these studies suggest that the rate of virus replication is controlled by innate characteristics of the individual, they provide new insight into the pathogenesis of AIDS.