Allosteric Regulation of Switch-II Domain Controls KRAS Oncogenicity

RAS proteins are GTPases that regulate a wide range of cellular processes. RAS activity is dependent on its nucleotide-binding status, which is modulated by guanine nucleotide exchange factors (GEF) and GTPase-activating proteins (GAP). KRAS can be acetylated at lysine 104 (K104), and an acetylation-mimetic mutation of K104 to glutamine (K104Q) attenuates the in vitro-transforming capacity of oncogenic KRAS by interrupting GEF-induced nucleotide exchange. To assess the effect of this mutation in vivo, we used CRISPR-Cas9 to generate mouse models carrying the K104Q point mutation in wild-type and conditional KrasLSL-G12D alleles. Homozygous animals for K104Q were viable, fertile, and arose at the expected Mendelian frequency, indicating that K104Q is not a complete loss-of-function mutation. Consistent with our previous findings from in vitro studies, however, the oncogenic activity of KRASG12D was significantly attenuated by mutation at K104. Biochemical and structural analysis indicated that the G12D and K104Q mutations cooperate to suppress GEF-mediated nucleotide exchange, explaining the preferential effect of K104Q on oncogenic KRAS. Furthermore, K104 functioned in an allosteric network with M72, R73, and G75 on the α2 helix of the switch-II region. Intriguingly, point mutation of glycine 75 to alanine (G75A) also showed a strong negative regulatory effect on KRASG12D. These data demonstrate that lysine at position 104 is critical for the full oncogenic activity of mutant KRAS and suggest that modulating the sites in its allosteric network may provide a unique therapeutic approach in cancers expressing mutant KRAS.

SIGNIFICANCE

An allosteric network formed by interaction between lysine 104 and residues in the switch-II domain is required for KRAS oncogenicity, which could be exploited for developing inhibitors of the activated oncoprotein.

Allogeneic immunity clears latent virus following allogeneic stem cell transplantation in SIV-infected ART-suppressed macaques

Allogeneic hematopoietic stem cell transplantation (alloHSCT) from donors lacking C-C chemokine receptor 5 (CCR5Δ32/Δ32) can cure HIV, yet mechanisms remain speculative. To define how alloHSCT mediates HIV cure, we performed MHC-matched alloHSCT in SIV+, anti-retroviral therapy (ART)-suppressed Mauritian cynomolgus macaques (MCMs) and demonstrated that allogeneic immunity was the major driver of reservoir clearance, occurring first in peripheral blood, then peripheral lymph nodes, and finally in mesenteric lymph nodes draining the gastrointestinal tract. While allogeneic immunity could extirpate the latent viral reservoir and did so in two alloHSCT-recipient MCMs that remained aviremic >2.5 years after stopping ART, in other cases, it was insufficient without protection of engrafting cells afforded by CCR5-deficiency, as CCR5-tropic virus spread to donor CD4+ T cells despite full ART suppression. These data demonstrate the individual contributions of allogeneic immunity and CCR5 deficiency to HIV cure and support defining targets of alloimmunity for curative strategies independent of HSCT.

Therapeutic neutralizing monoclonal antibody administration protects against lethal yellow fever virus infection

Yellow fever virus (YFV) is a reemerging global health threat, driven by several factors, including increased spread of the mosquito vector and rapid urbanization. Although a prophylactic vaccine exists, vaccine hesitancy, supply deficits, and distribution difficulties leave specific populations at risk of severe YFV disease, as evidenced by recent outbreaks in South America. To establish a treatment for patients with severe YFV infection, we tested 37 YFV-specific monoclonal antibodies isolated from vaccinated humans and identified two capable of potently neutralizing multiple pathogenic primary YFV isolates. Using both hamster and nonhuman primate models of lethal YFV infection, we demonstrate that a single administration of either of these two potently neutralizing antibodies during acute infection fully controlled viremia and prevented severe disease and death in treated animals. Given the potential severity of YFV-induced disease, our results show that these antibodies could be effective in saving lives and fill a much-needed void in managing YFV cases during outbreaks.

Perceptions of Gender Equity by Urologic Subspecialty

OBJECTIVES

To evaluate how urologists in various subspecialties view the climate for female urologists, comparing perceptions of gender inequity based on characteristics including gender, subspecialty training, faculty status, parental status, and years in practice. Despite growth in female representation in urology, gender inequalities in career opportunities and compensation continue to exist.

METHODS

An IRB approved survey was sent out to the following list-serves: Society of Urological Oncology (SUO), Society of Endourology (ENDO), Genitourinary Reconstructive Surgeons (GURS), Society of Pediatric Urology (SPU), Society of Urodynamics, Female Pelvic Medicine and Urogenital Reconstruction (SUFU), and American Urogynecologic Society (AUGS). A validated study, the Culture Conducive to Women's Academic Success (CCWAS) was used, and scores analyzed using Wilcoxon Rank-Sum and Kruskal-Wallace tests.

RESULTS

There were 430 survey responses (35.3% female, 64.7% male). There was a statistically significant difference in CCWAS score for gender, parental status, and society. On multiple regression analysis controlling for gender, parental status and society were not statistically significant. Years in practice and practice type were not significant. Male urologists perceived practice culture toward women as more equitable than their female colleagues, (median [interquartile range] CCWAS score, 203.5 [184.25, 225.0] vs 162.5 [130.75, 188.0]; P < .0001). This discrepancy in perception between genders was consistent across all subcategories; equal access, work-life balance, freedom of gender bias, and leadership support.

CONCLUSIONS

This study suggests that there are gender-based differences in how gender inequities are perceived and experienced in urology. Acknowledgment of these differences is the first step in identifying opportunities for improvement.

Perceptions and Experiences of Gender Equity Among Endourologists

Introduction: Only 9.9% of practicing urologists in the United States are women. This percentage is even smaller in leadership positions and high-ranking appointments. Endourology is one of the least reported fellowships completed by women urologists. We sought to evaluate how endourologists perceived the climate for women physicians and compare perceptions and experiences of gender equity. Materials and Methods: An IRB approved and validated survey, Culture Conducive to Women's Academic Success (CCWAS) questionnaire was sent out to the Endourological Society listserve. Subcategories of equal access, work-life balance, freedom of gender bias, and leadership support were analyzed. An open comment section was provided for respondents to include their own experiences. Wilcoxon rank-sum and Kruskal-Wallis tests were used to compare CCWAS scores between groups. Results: A total of 104 completed surveys were received. Response rate was 7% (104/1492), 26.9% of which were female. There was a statistically significant difference between male and female respondent CCWAS scores; p < 0.05. The male CCWAS score median was 196.0 (interquartile range [IQR] 176.75-214.0) vs female CCWAS score median of 166.5 (IQR 127.5-210.0). There was no significant difference in CCWAS scores based on years in practice, parental status, or academic vs private practice. Discussion: In this study, male endourologists' perceptions of gender equity were incongruent with the reported experiences of their female colleagues. This indicates that male respondents perceive the culture in their department toward women more positively than their female colleagues. This is suggestive that there are gender-based differences in how gender inequities are perceived and potentially experienced.

Suppression of human and simian immunodeficiency virus replication with the CCR5-specific antibody Leronlimab in two species

The CCR5-specific antibody Leronlimab is being investigated as a novel immunotherapy that can suppress HIV replication with minimal side effects. Here we studied the virological and immunological consequences of Leronlimab in chronically CCR5-tropic HIV-1 infected humans (n = 5) on suppressive antiretroviral therapy (ART) and in ART-naïve acutely CCR5-tropic SHIV infected rhesus macaques (n = 4). All five human participants transitioned from daily combination ART to self-administered weekly subcutaneous (SC) injections of 350 mg or 700 mg Leronlimab and to date all participants have sustained virologic suppression for over seven years. In all participants, Leronlimab fully occupied CCR5 receptors on peripheral blood CD4+ T cells and monocytes. In ART-naïve rhesus macaques acutely infected with CCR5-tropic SHIV, weekly SC injections of 50 mg/kg Leronlimab fully suppressed plasma viremia in half of the macaques. CCR5 receptor occupancy by Leronlimab occurred concomitant with rebound of CD4+ CCR5+ T-cells in peripheral blood, and full CCR5 receptor occupancy was found in multiple anatomical compartments. Our results demonstrate that weekly, self-administered Leronlimab was safe, well-tolerated, and efficacious for long-term virologic suppression and should be included in the arsenal of safe, easily administered, longer-acting antiretroviral treatments for people living with HIV-1.

Trial Registration: ClinicalTrials.gov Identifiers: NCT02175680 and NCT02355184.

With approximately 37 million people living with HIV, stopping the HIV epidemic remains a top global health priority. While daily oral antiretroviral therapy limits HIV replication, its use is a lifelong requirement and increases the likelihood for the development of drug-resistant variants. Indeed, the global prevalence of HIV drug resistance has exponentially increased in recent years, leading to a need for new drug targets. CCR5 is an ideal drug target as HIV uses this molecule to gain entry into target cells. As an example of the importance of CCR5, individuals that lack CCR5 expression due to a natural genetic mutation are naturally resistant to HIV infection. Here, we report that weekly injections of Leronlimab, an anti-CCR5 antibody that blocks the binding of HIV to CCR5, suppressed HIV replication in five HIV+ participants for over seven years. When used to treat acutely infected rhesus macaques, we found that the average amount of virus in the blood of Leronlimab-treated macaques was 10,000 times lower than in untreated macaques. These data suggest that Leronlimab is a safe and effective anti-HIV therapeutic drug.

Phagocytosis by an HIV antibody is associated with reduced viremia irrespective of enhanced complement lysis

Increasingly, antibodies are being used to treat and prevent viral infections. In the context of HIV, efficacy is primarily attributed to dose-dependent neutralization potency and to a lesser extent Fc-mediated effector functions. It remains unclear whether augmenting effector functions of broadly neutralizing antibodies (bNAbs) may improve their clinical potential. Here, we use bNAb 10E8v4 targeting the membrane external proximal region (MPER) to examine the role of antibody-mediated effector and complement (C’) activity when administered prophylactically against SHIV challenge in rhesus macaques. With sub-protective dosing, we find a 78–88% reduction in post-acute viremia that is associated with 10E8v4-mediated phagocytosis acting at the time of challenge. Neither plasma nor tissue viremic outcomes in vivo is improved with an Fc-modified variant of 10E8v4 enhanced for C’ functions as determined in vitro. These results suggest that effector functions inherent to unmodified 10E8v4 contribute to efficacy against SHIV_SF162P3 in the absence of plasma neutralizing titers, while C’ functions are dispensable in this setting, informing design of bNAb modifications for improving protective efficacy.

While antibodies neutralize HIV via Fab recognition of viral surface antigens, antibody Fc domains mediate effector functions, including antibody-dependent cellular phagocytosis (ADCP) and cytotoxicity (ADCC), and complement (C') activity. Here, Spencer et al. modify bNAb 10E8v4 to enhance C'-mediated potency in SHIV challenged rhesus macaques to probe its function in protection, showing that in the absence of neutralization, enhancing C' activities in vitro adds no value toward reducing viremia in either blood or tissue.

Women are underrepresented in prestigious recognition awards in the American Urological Association

OBJECTIVES

To determine the proportion of women who received awards from the American Urological Association (AUA) and evaluate whether this has changed over time as the proportion of practicing female urologists has increased.

METHODS

A retrospective review of award recipients from the AUA website was performed. Gender of award recipient, type of award and year received were collected and the trend over time was compared with the AUA census.

RESULTS

Of the 622 award recipients, 43 (6.9%) were women. There was a larger proportion of women who received early career awards (15/65; 23.1%) compared to women who received more prestigious mid (1/44; 2.3%) or senior (27/513; 5.3%) career awards. Additionally, 17/43 (39.5%) of female award recipients were not clinical urologists, compared to only 33/579 (5.7%) of male award recipients.

CONCLUSIONS

Despite increased representation by women in the field of urology, women remain underrepresented in awards given by the AUA. Although the proportion of women receiving awards over time has increased, it remains less than expected given the increased proportion of practicing female urologists. Strategic initiatives should be employed to help advance women in academic urology.

Antibody-based CCR5 blockade protects Macaques from mucosal SHIV transmission

In the absence of a prophylactic vaccine, the use of antiretroviral therapy (ART) as pre-exposure prophylaxis (PrEP) to prevent HIV acquisition by uninfected individuals is a promising approach to slowing the epidemic, but its efficacy is hampered by incomplete patient adherence and ART-resistant variants. Here, we report that competitive inhibition of HIV Env-CCR5 binding via the CCR5-specific antibody Leronlimab protects rhesus macaques against infection following repeated intrarectal challenges of CCR5-tropic SHIVSF162P3. Injection of Leronlimab weekly at 10 mg/kg provides significant but partial protection, while biweekly 50 mg/kg provides complete protection from SHIV acquisition. Tissue biopsies from protected macaques post challenge show complete CCR5 receptor occupancy and an absence of viral nucleic acids. After Leronlimab washout, protected macaques remain aviremic, and adoptive transfer of hematologic cells into naïve macaques does not transmit viral infection. These data identify CCR5 blockade with Leronlimab as a promising approach to HIV prophylaxis and support initiation of clinical trials.