Background: We recently described that HIV latent infection can be established in vitro following incubation of resting CD4+ T-cells with chemokines that bind to CCR7. The main aim of this study was to fully define the post-integration blocks to virus replication in this model of CCL19-induced HIV latency. Results: High levels of integrated HIV DNA but low production of reverse transcriptase (RT) was found in CCL19-treated CD4+ T-cells infected with either wild type (WT) NL4.3 or single round envelope deleted NL4.3 pseudotyped virus (NL4.3- Δenv). Supernatants from CCL19-treated cells infected with either WT NL4.3 or NL4.3- Δenv did not induce luciferase expression in TZM-bl cells, and there was no expression of intracellular p24. Following infection of CCL19-treated CD4+ T-cells with NL4.3 with enhanced green fluorescent protein (EGFP) inserted into the nef open reading frame (NL4.3- Δnef-EGFP), there was no EGFP expression detected. These data are consistent with non-productive latent infection of CCL19-treated infected CD4+ T-cells. Treatment of cells with phytohemagluttinin (PHA)/IL-2 or CCL19, prior to infection with WT NL4.3, resulted in a mean fold change in unspliced (US) RNA at day 4 compared to day 0 of 21.2 and 1.1 respectively (p = 0.01; n = 5), and the mean expression of multiply spliced (MS) RNA was 56,000, and 5,000 copies/million cells respectively (p = 0.01; n = 5). In CCL19-treated infected CD4+ T-cells, MS-RNA was detected in the nucleus and not in the cytoplasm; in contrast to PHA/IL-2 activated infected cells where MS RNA was detected in both. Virus could be recovered from CCL19-treated infected CD4+ T-cells following mitogen stimulation (with PHA and phorbyl myristate acetate (PMA)) as well as TNFα, IL-7, prostratin and vorinostat. Conclusions: In this model of CCL19-induced HIV latency, we demonstrate HIV integration without spontaneous production of infectious virus, detection of MS RNA in the nucleus only, and the induction of virus production with multiple activating stimuli. These data are consistent with ex vivo findings from latently infected CD4+ T-cells from patients on combination antiretroviral therapy, and therefore provide further support of this model as an excellent in vitro model of HIV latency.

RNA interference (RNAi) is now widely used for gene silencing in mammalian cells. The mechanism uses the RNA-induced silencing complex, in which Dicer, Ago2, and the human immunodeficiency virus type 1 (HIV-1) TAR RNA binding protein (TRBP) are the main components. TRBP is a protein that increases HIV-1 expression and replication by inhibition of the interferon-induced protein kinase PKR and by increasing translation of viral mRNA. After HIV infection, TRBP could restrict the viral RNA through its activity in RNAi or could contribute more to the enhancement of viral replication. To determine which function will be predominant in the virological context, we analyzed whether the inhibition of its expression could enhance or decrease HIV replication. We have generated small interfering RNAs (siRNAs) against TRBP and found that they decrease HIV-1 long terminal repeat (LTR) basal expression 2-fold, and the LTR Tat transactivated level up to 10-fold. In the context of HIV replication, siRNAs against TRBP decrease the expression of viral genes and inhibit viral production up to fivefold. The moderate increase in PKR expression and activation indicates that it contributes partially to viral gene inhibition. The moderate decrease in micro-RNA (miRNA) biogenesis by TRBP siRNAs suggests that in the context of HIV replication, TRBP functions other than RNAi are predominant. In addition, siRNAs against Dicer decrease viral production twofold and impede miRNA biogenesis. These results suggest that, in the context of HIV replication, TRBP contributes mainly to the enhancement of virus production and that Dicer does not mediate HIV restriction by RNAi.

Bovine colostrum (first milk) contains very high concentrations of IgG, and on average 1 kg (500 g/liter) of IgG can be harvested from each immunized cow immediately after calving. We used a modified vaccination strategy together with established production systems from the dairy food industry for the large-scale manufacture of broadly neutralizing HIV-1 IgG. This approach provides a low-cost mucosal HIV preventive agent potentially suitable for a topical microbicide. Four cows were vaccinated pre- and/or postconception with recombinant HIV-1 gp140 envelope (Env) oligomers of clade B or A, B, and C. Colostrum and purified colostrum IgG were assessed for cross-clade binding and neutralization against a panel of 27 Env-pseudotyped reporter viruses. Vaccination elicited high anti-gp140 IgG titers in serum and colostrum with reciprocal endpoint titers of up to 1 × 10⁵. While nonimmune colostrum showed some intrinsic neutralizing activity, colostrum from 2 cows receiving a longer-duration vaccination regimen demonstrated broad HIV-1-neutralizing activity. Colostrum-purified polyclonal IgG retained gp140 reactivity and neutralization activity and blocked the binding of the b12 monoclonal antibody to gp140, showing specificity for the CD4 binding site. Colostrum-derived anti-HIV antibodies offer a cost-effective option for preparing the substantial quantities of broadly neutralizing antibodies that would be needed in a low-cost topical combination HIV-1 microbicide.

We have previously reported induction of transcriptional gene silencing (TGS) of HIV-1 by short hairpin RNA (shRNA) expressed in MOLT-4 cells. The shRNA (termed shPromA) targets the highly conserve...

The global COVID-19 pandemic caused by SARS-CoV-2 has resulted in over 2.2 million deaths. Disease outcomes range from asymptomatic to severe with, so far, minimal genotypic change to the virus so understanding the host response is paramount. Transcriptomics has become incredibly important in understanding host-pathogen interactions; however, post-transcriptional regulation plays an important role in infection and immunity through translation and mRNA stability, allowing tight control over potent host responses by both the host and the invading virus. Here, we apply ribosome profiling to assess post-transcriptional regulation of host genes during SARS-CoV-2 infection of a human lung epithelial cell line (Calu-3). We have identified numerous transcription factors (JUN, ZBTB20, ATF3, HIVEP2 and EGR1) as well as select antiviral cytokine genes, namely IFNB1, IFNL1,2 and 3, IL-6 and CCL5, that are restricted at the post-transcriptional level by SARS-CoV-2 infection and discuss the impact this would have on the host response to infection. This early phase restriction of antiviral transcripts in the lungs may allow high viral load and consequent immune dysregulation typically seen in SARS-CoV-2 infection.