Local replication of simian immunodeficiency virus in the breast milk compartment of chronically-infected, lactating rhesus monkeys

Breast milk transmission remains a major mode of infant HIV acquisition, yet anatomic and immunologic forces shaping virus quasispecies in milk are not well characterized. In this study, phylogenic analysis of envelope sequences of milk SIV variants revealed groups of nearly identical viruses, indicating local virus production. However, comparison of the patterns and rates of CTL escape of blood and milk virus demonstrated only subtle differences between the compartments. These findings suggest that a substantial fraction of milk viruses are produced by locally-infected cells, but are shaped by cellular immune pressures similar to that in the blood

The Magnitude and Kinetics of the Mucosal HIV-Specific CD8+ T Lymphocyte Response and Virus RNA Load in Breast Milk

BACKGROUND: The risk of postnatal HIV transmission is associated with the magnitude of the milk virus load. While HIV-specific cellular immune responses control systemic virus load and are detectable in milk, the contribution of these responses to the control of virus load in milk is unknown. METHODS: We assessed the magnitude of the immunodominant GagRY11 and subdominant EnvKY9-specific CD8+ T lymphocyte response in blood and milk of 10 A*3002+, HIV-infected Malawian women throughout the period of lactation and correlated this response to milk virus RNA load and markers of breast inflammation. RESULTS: The magnitude and kinetics of the HIV-specific CD8+ T lymphocyte responses were discordant in blood and milk of the right and left breast, indicating independent regulation of these responses in each breast. However, there was no correlation between the magnitude of the HIV-specific CD8+ T lymphocyte response and the milk virus RNA load. Further, there was no correlation between the magnitude of this response and markers of breast inflammation. CONCLUSIONS: The magnitude of the HIV-specific CD8+ T lymphocyte response in milk does not appear to be solely determined by the milk virus RNA load and is likely only one of the factors contributing to maintenance of low virus load in milk

HIV-Specific Antibodies Capable of ADCC Are Common in Breastmilk and Are Associated with Reduced Risk of Transmission in Women with High Viral Loads

There are limited data describing the functional characteristics of HIV-1 specific antibodies in breast milk (BM) and their role in breastfeeding transmission. The ability of BM antibodies to bind HIV-1 envelope, neutralize heterologous and autologous viruses and direct antibody-dependent cell cytotoxicity (ADCC) were analyzed in BM and plasma obtained soon after delivery from 10 non-transmitting and 9 transmitting women with high systemic viral loads and plasma neutralizing antibodies (NAbs). Because subtype A is the dominant subtype in this cohort, a subtype A envelope variant that was sensitive to plasma NAbs was used to assess the different antibody activities. We found that NAbs against the subtype A heterologous virus and/or the woman's autologous viruses were rare in IgG and IgA purified from breast milk supernatant (BMS) – only 4 of 19 women had any detectable NAb activity against either virus. Detected NAbs were of low potency (median IC50 value of 10 versus 647 for the corresponding plasma) and were not associated with infant infection (p = 0.58). The low NAb activity in BMS versus plasma was reflected in binding antibody levels: HIV-1 envelope specific IgG titers were 2.2 log10 lower (compared to 0.59 log10 lower for IgA) in BMS versus plasma. In contrast, antibodies capable of ADCC were common and could be detected in the BMS from all 19 women. BMS envelope-specific IgG titers were associated with both detection of IgG NAbs (p = 0.0001)and BMS ADCC activity (p = 0.014). Importantly, BMS ADCC capacity was inversely associated with infant infection risk (p = 0.039). Our findings indicate that BMS has low levels of envelope specific IgG and IgA with limited neutralizing activity. However, this small study of women with high plasma viral loads suggests that breastmilk ADCC activity is a correlate of transmission that may impact infant infection risk

Multiple antibiotic susceptibility associated with inactivation of the prc gene.

A Tn5 insertion which led to increased susceptibility to multiple drugs, including tetracycline, chloramphenicol, nalidixic acid, erythromycin, spectinomycin, norfloxacin, and novobiocin, was identified in Escherichia coli. Cloning and sequence studies showed that the insertion was in the previously identified prc gene at min 40.4. The prc product is known to function as a protease linked to processing of penicillin-binding protein 3 and lambda repressor and when absent to allow some leakage of periplasmic constituents. Complementation studies with the prc gene on plasmids showed complete recovery of parental levels of susceptibility to all drugs except chloramphenicol, with which only partial reversion to wild-type levels was observed