Protection of Newborn Macaques by Plant-Derived HIV Broadly Neutralizing Antibodies: a Model for Passive Immunotherapy during Breastfeeding

Preventing human immunodeficiency virus (HIV) infection in newborns by vertical transmission remains an important unmet medical need in resource-poor areas where antiretroviral therapy (ART) is not available and mothers and infants cannot be treated prepartum or during the breastfeeding period. In the present study, the protective efficacy of the potent HIV-neutralizing antibodies PGT121 and VRC07-523, both produced in plants, were assessed in a multiple-SHIV (simian-human immunodeficiency virus)-challenge breastfeeding macaque model. Newborn macaques received either six weekly subcutaneous injections with PGT121 alone or as a cocktail of PGT121-LS plus VRC07-523-LS injected three times every 2 weeks. Viral challenge with SHIVSF162P3 was twice weekly over 5.5 weeks using 11 exposures. Despite the transient presence of plasma viral RNA either immediately after the first challenge or as single-point blips, the antibodies prevented a productive infection in all babies with no sustained plasma viremia, compared to viral loads ranging from 103 to 5 × 108 virions/ml in four untreated controls. No virus was detected in peripheral blood mononuclear cells (PBMCs), and only 3 of 159 tissue samples were weakly positive in the treated babies. Newborn macaques proved to be immunocompetent, producing transient anti-Env antibodies and anti-drug antibody (ADA), which were maintained in the circulation after passive broadly neutralizing antibody clearance. ADA responses were directed to the IgG1 Fc CH2-CH3 domains, which has not been observed to date in adult monkeys passively treated with PGT121 or VRC01. In addition, high levels of VRC07-523 anti-idiotypic antibodies in the circulation of one newborn was concomitant with the rapid elimination of VRC07. Plant-expressed antibodies show promise as passive immunoprophylaxis in a breastfeeding model in newborns. IMPORTANCE Plant-produced human neutralizing antibody prophylaxis is highly effective in preventing infection in newborn monkeys during repeated oral exposure, modeling virus in breastmilk, and offers advantages in cost of production and safety. These findings raise the possibility that anti-Env antibodies may contribute to the control of viral replication in this newborn model and that the observed immune responsiveness may be driven by the long-lived presence of immune complexes.

Improved delivery of broadly neutralizing antibodies by nanocapsules suppresses SHIV infection in the CNS of infant rhesus macaques

Broadly neutralizing antibodies (bNAbs) directed to HIV-1 have shown promise at suppressing viremia in animal models. However, the use of bNAbs for the central nervous system (CNS) infection is confounded by poor penetration of the blood brain barrier (BBB). Typically, antibody concentrations in the CNS are extremely low; with levels in cerebrospinal fluid (CSF) only 0.1% of blood concentrations. Using a novel nanotechnology platform, which we term nanocapsules, we show effective transportation of the human bNAb PGT121 across the BBB in infant rhesus macaques upon systemic administration up to 1.6% of plasma concentration. We demonstrate that a single dose of PGT121 encased in nanocapsules when delivered at 48h post-infection delays early acute infection with SHIV_SF162P3 in infants, with one of four animals demonstrating viral clearance. Importantly, the nanocapsule delivery of PGT121 improves suppression of SHIV infection in the CNS relative to controls.

In patients where HIV-1 is fully suppressed by antiretroviral drugs, HIV-1 still persists in reservoirs. If antiretroviral drugs are stopped, the virus will emerge from these reservoirs and re-seeds systemically. The central nervous system (CNS) is proposed to be a tissue compartment that harbors other HIV-1 reservoirs. A key obstacle that constrains the treatment for the CNS infection is the blood–brain barrier (BBB), a highly restrictive barrier separating the circulating blood from the brain and extracellular fluid in the CNS, which impedes ~98% of the small molecule therapeutics and almost all macromolecules including broadly neutralizing antibodies (bNAbs) directed to HIV-1. Our “nanocapsule” strategy is based on a nanotechnology wherein bNAb molecules are encapsulated within nanocapsules of which the surface contains abundant choline and acetylcholine analogues. This design allows the nanocapsules to effectively cross the BBB to deliver bNAbs into the CNS upon systemic administration and show an impact of bNAb on CNS reservoirs in SHIV infected infant macaques.

Polyfunctional Tier 2-Neutralizing Antibodies Cloned following HIV-1 Env Macaque Immunization Mirror Native Antibodies in a Human Donor

Vaccine efforts to combat HIV are challenged by the global diversity of viral strains and shielding of neutralization epitopes on the viral envelope glycoprotein trimer. Even so, the isolation of broadly neutralizing Abs from infected individuals suggests the potential for eliciting protective Abs through vaccination. This study reports a panel of 58 mAbs cloned from a rhesus macaque (Macaca mulatta) immunized with envelope glycoprotein immunogens curated from an HIV-1 clade C-infected volunteer. Twenty mAbs showed neutralizing activity, and the strongest neutralizer displayed 92% breadth with a median IC50 of 1.35 μg/ml against a 13-virus panel. Neutralizing mAbs predominantly targeted linear epitopes in the V3 region in the cradle orientation (V3C) with others targeting the V3 ladle orientation (V3L), the CD4 binding site (CD4bs), C1, C4, or gp41. Nonneutralizing mAbs bound C1, C5, or undetermined conformational epitopes. Neutralization potency strongly correlated with the magnitude of binding to infected primary macaque splenocytes and to the level of Ab-dependent cellular cytotoxicity, but did not predict the degree of Ab-dependent cellular phagocytosis. Using an individualized germline gene database, mAbs were traced to 23 of 72 functional IgHV alleles. Neutralizing V3C Abs displayed minimal nucleotide somatic hypermutation in the H chain V region (3.77%), indicating that relatively little affinity maturation was needed to achieve in-clade neutralization breadth. Overall, this study underscores the polyfunctional nature of vaccine-elicited tier 2-neutralizing V3 Abs and demonstrates partial reproduction of the human donor's humoral immune response through nonhuman primate vaccination.

Multimeric Epitope-Scaffold HIV Vaccines Target V1V2 and Differentially Tune Polyfunctional Antibody Responses

The V1V2 region of the HIV-1 envelope is the target of several broadly neutralizing antibodies (bNAbs). Antibodies to V1V2 elicited in the RV144 clinical trial correlated with a reduced risk of HIV infection, but these antibodies were without broad neutralizing activity. Antibodies targeting V1V2 also correlated with a reduced viral load in immunized macaques challenged with simian immunodeficiency virus (SIV) or simian/human immunodeficiency virus (SHIV). To focus immune responses on V1V2, we engrafted the native, glycosylated V1V2 domain onto five different multimeric scaffold proteins and conducted comparative immunogenicity studies in macaques. Vaccinated macaques developed high titers of plasma and mucosal antibodies that targeted structurally distinct V1V2 epitopes. Plasma antibodies displayed limited neutralizing activity but were functionally active for ADCC and phagocytosis, which was detectable 1-2 years after immunizations ended. This study demonstrates that multivalent, glycosylated V1V2-scaffold protein immunogens focus the antibody response on V1V2 and are differentially effective at inducing polyfunctional antibodies with characteristics associated with protection.

Enhanced Fc-mediated complement activity with broadly neutralizing antibody 10E8v4 does not improve viral outcomes following SHIV challenge in rhesus macaques

Fc modified broadly neutralizing antibodies (bNAbs) are being developed for both prophylactic and therapeutic treatment of HIV with some success in extending half-life, but in vivo benefits of enhanced FcγR interaction remain unclear. Here we sought to improve bNAb efficacy by increasing Fc-mediated complement activity. A panel of Fc variants was screened for complement enhancement of 10 bNAbs. Modified 10E8v4, which weakly neutralizes SHIVSF162p3 (IC80 30 mg/ml) and does not mediate ADCC, was selected for macaque studies. Compared to wildtype, the EFTAE modification resulted in greater affinity for multiple FcγRs, >2-fold enhanced complement deposition, viral lysis, and antibody-mediated complement dependent cytotoxicity, but reduced serum half-life. Subcutaneous infusion with a sub-protective 5 mg/kg dose of 10E8v4 followed by a single high dose intrarectal challenge with SHIVSF162p3 showed unmodified 10E8v4 treated animals displayed lower plasma viremia compared to the complement/FcgR dual knockout (LALA) and controls. Unexpectedly, the EFTAE group displayed higher plasma viremia than controls, and viral DNA was significantly enhanced in tissues at necropsy (9 wpi, p <0.0001). Viremia in EFTAE treated animals inversely correlated with plasma neutralization titer at time of challenge; however, elevated viremia was not seen in animals treated with 10 and 20 mg/kg Ab, suggesting that complement mediated enhanced infection was mitigated by greater neutralizing activity. These are the first in vivo results substantiating in vitro reports of complement dependent enhanced infection mediated by non-neutralizing HIV Abs and indicate that future studies modulating complement induction by therapeutic bNAbs are warranted.

Medical student suicide, 1989-1994

OBJECTIVE

Studies examining suicide rates for medical students have yielded conflicting data. This article addresses medical student suicide from August 1989 through May 1994.

METHOD

Telephone interviews were conducted with a representative from each U.S. medical school, generally the dean of student affairs. If a suicide had occurred, information regarding demographic characteristics, psychiatric or substance abuse history, means of suicide, month, and presence of a suicide note was obtained.

RESULTS

Responses were obtained from 101 (80%) of the 126 U.S. medical schools. Responding schools reported 15 suicides by medical students from August 1989 through May 1994. Fourteen were by men. Six suicides were committed during the third year of medical school, and four occurred during the fourth year. Six students left notes, and nine of 13 had psychiatric histories.

CONCLUSIONS

The results demonstrate a lower suicide rate than that found in previous studies and emphasize the need for standardized reporting methods.