Sites of vulnerability in SARS-CoV-2: Antibodies that neutralize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) could be an important tool in treating coronavirus disease 2019 (COVID-19). Brouwer et al. isolated 403 monoclonal antibodies from three convalescent COVID-19 patients. They show that the patients had strong immune responses against the viral spike protein, a complex that binds to receptors on the host cell. A subset of antibodies was able to neutralize the virus. Competition and electron microscopy studies showed that these antibodies target diverse epitopes on the spike, with the two most potent targeting the domain that binds the host receptor. Science , this issue p. 643

Age-associated comorbidities (cardiovascular and renal disease) were more prevalent among HIV-positive compared with HIV-uninfected patients. Comorbidity was associated with cardiovascular risk factors, but also with HIV infection, immunodeficiency, and, to a lesser extent, systemic inflammation and prior high-dose ritonavir use. Background. Human immunodeficiency virus (HIV)-infected individuals may be at increased risk of age-associated noncommunicable comorbidities (AANCCs). Methods. Cross-sectional analyses of AANCC prevalence (including cardiovascular, metabolic, pulmonary, renal, bone, and malignant disease) and risk factors in a prospective cohort study of HIV type 1–infected individuals and HIV-uninfected controls, who were aged ≥45 years and comparable regarding most lifestyle and demographic factors. Results. HIV-infected participants (n = 540) had a significantly higher mean number of AANCCs than controls (n = 524) (1.3 [SD, 1.14] vs 1.0 [SD, 0.95]; P < .001), with significantly more HIV-infected participants having ≥1 AANCC (69.4% vs 61.8%; P = .009). Hypertension, myocardial infarction, peripheral arterial disease, and impaired renal function were significantly more prevalent among HIV-infected participants. Risk of AANCC by ordinal logistic regression was independently associated with age, smoking, positive family history for cardiovascular/metabolic disease, and higher waist-to-hip ratio, but also with HIV infection (odds ratio, 1.58 [95% confidence interval, 1.23–2.03]; P < .001). In those with HIV, longer exposure to CD4 counts <200 cells/µL, and, to a lesser extent, higher levels of high-sensitivity C-reactive protein and soluble CD14, and longer prior use of high-dose ritonavir (≥400 mg/24 hours) were each also associated with a higher risk of AANCCs. Conclusions. All AANCCs were numerically more prevalent, with peripheral arterial, cardiovascular disease, and impaired renal function significantly so, among HIV-infected participants compared with HIV-uninfected controls. Besides recognized cardiovascular risk factors, HIV infection and longer time spent with severe immunodeficiency increased the risk of a higher composite AANCC burden. There was a less pronounced contribution from residual inflammation, immune activation, and prior high-dose ritonavir use.

Key Points: Human and mouse macrophages share partially conserved gene and protein expression programs in the resting or M2 activated state. TGM2 is a novel M2 marker consistently induced in human and mouse M2 macrophages.

A single sugar makes all the difference: Antibodies are divided into several classes based on their nonvariable tail (Fc) domains. These regions interact with disparate immune cell receptors and complement proteins to help instruct distinct immune responses. The Fc domain of immunoglobulin G (IgG) antibodies contains a conserved N-linked glycan at position 297. However, the particular glycan used at this position is highly variable. IgG lacking core fucosylation at this position initiates enhanced antibody-dependent cellular cytotoxicity by increased affinity to the Fc receptor FcRIIIa. Larsen et al. report that COVID-19 patients with severe symptoms have increased levels of anti–severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG afucosylation compared with patients with mild disease. These findings suggest that treatment of COVID-19 patients with fucosylated anti–SARS-CoV-2 antibodies may circumvent pathologies associated with severe COVID-19. Science , this issue p. eabc8378

Macrophage-tropic, non-syncytium-inducing, HIV-1 variants predominate in the asymptomatic phase of infection and may be responsible for establishing infection in an individual exposed to the mixture of HIV-1 variants. Here, genotypical and phenotypical characteristics of virus populations, present in sexual, parenteral, or vertical donor-recipient pairs, were studied. Sequence analysis of the V3 domain confirmed the presence of a homogeneous virus population in recently infected individuals. Biological HIV-1 clones were further characterized for syncytium inducing capacity on the MT2 cell line and for macrophage tropism as defined by the appearance of proviral DNA upon inoculation of monocyte-derived macrophages. Both sexual and parenteral transmission cases revealed a selective outgrowth in the recipient of the most macrophage-tropic variant(s) present in the donor. In three out of five vertical transmission cases, more than one highly macrophage-tropic virus variant was present in the child shortly after birth, suggestive of transmission of multiple variants. In three primary infection cases, homogeneous virus populations of macrophage-tropic, non-syncytium-inducing variants were present prior to seroconversion, thus excluding humoral immunity as the selective pressure in favour of macrophage-tropic variants. These observations may have important implications for vaccine development.