Postnatally-transmitted HIV-1 Envelope variants have similar neutralization-sensitivity and function to that of nontransmitted breast milk variants

Abstract

BackgroundBreastfeeding is a leading cause of infant HIV-1 infection in the developing world, yet only a minority of infants exposed to HIV-1 via breastfeeding become infected. As a genetic bottleneck severely restricts the number of postnatally-transmitted variants, genetic or phenotypic properties of the virus Envelope (Env) could be important for the establishment of infant infection. We examined the efficiency of virologic functions required for initiation of infection in the gastrointestinal tract and the neutralization sensitivity of HIV-1 Env variants isolated from milk of three postnatally-transmitting mothers (n=13 viruses), five clinically-matched nontransmitting mothers (n=16 viruses), and seven postnatally-infected infants (n = 7 postnatally-transmitted/founder (T/F) viruses).ResultsThere was no difference in the efficiency of epithelial cell interactions between Env virus variants from the breast milk of transmitting and nontransmitting mothers. Moreover, there was similar efficiency of DC-mediated trans-infection, CCR5-usage, target cell fusion, and infectivity between HIV-1 Env-pseudoviruses from nontransmitting mothers and postnatal T/F viruses. Milk Env-pseudoviruses were generally sensitive to neutralization by autologous maternal plasma and resistant to breast milk neutralization. Infant T/F Env-pseudoviruses were equally sensitive to neutralization by broadly-neutralizing monoclonal and polyclonal antibodies as compared to nontransmitted breast milk Env variants.ConclusionPostnatally-T/F Env variants do not appear to possess a superior ability to interact with and cross a mucosal barrier or an exceptional resistance to neutralization that define their capability to initiate infection across the infant gastrointestinal tract in the setting of preexisting maternal antibodies.

Association of HIV-1 Envelope-Specific Breast Milk IgA Responses with Reduced Risk of Postnatal Mother-to-Child Transmission of HIV-1

“…1B and C) (23). The ID 50 neutralization titers against these isolates did not significantly differ between HIV-infected nontransmitting women and uninfected controls (B.MN, P ϭ 0.201; C.1209BMH5, P ϭ 0.092; Wilcoxon test).…”

“…Plasma and breast milk neutralization were measured against the tier 1 HIV-1 clade C isolate MW965 (GenBank accession number U08455). Breast milk samples were also tested for neutralization against tier 1 HIV-1 clade B isolate MN (GenBank number M17449) and a tier 2 postnatally transmitted isolate, 1209BMH5 (GenBank number HM070570) (23). Plasma was tested at a starting dilution of 1:20, and delipidized milk was tested at a starting dilution of 1:10.…”

“…CEM.NKR CCR5 cells (NIH AIDS Reagent Program, Division of AIDS, NIAID, NIH, from Alexandra Trkola [25]) were used as targets after being coated with recombinant gp120 from HIV-1 isolate 4403BMC5, representing a clade C postnatally transmitted virus (GenBank number HM070724) (23). Cryopreserved human peripheral blood mononuclear cells (PBMC) from an HIV-seronegative donor with the heterozygous 158F/V genotype for Fc-gamma receptor IIIa were used as the source of effector cells (26).…”

Optimized ReplicatingRenillaLuciferase Reporter HIV-1 Utilizing Novel Internal Ribosome Entry Site Elements for Native Nef Expression and Function

“…Previously we developed and described the replicationcompetent Env-IMC-LucR.T2A reporter virus technology 8 that has demonstrated widespread use in a variety of applications including HIV-1 transmission studies, 4,73 humanized mouse models, 16 and several immunological assays, 9,10,[12][13][14][15]17,18,20 including measurement of NAb activity in sera from vaccinees participating in the RV144 trial. 11 We also demonstrated the expression of Nef from the LucR.T2A-nef cassette comprised within LucR.T2A reporter virus after transfection of 293T cells with proviral DNA.…”

Phenotypic characterisation of Human Immunodeficiency Virus type 1 Envelope entry efficiency of transmitted/founder variants circulating in Mbeya, Tanzania

“…Pseudovirion stock generated by the transfection of the pSG3.1∆env backbone was used as a negative control, and the RLU reading of cells only was considered as background signal. A RLU reading of 2.5 times above background was considered a positive infection measurement based on the TCID50 methodology of Reed and Meunch (Fouda et al, 2013). …”