key: cord-0720525-5sss52fz authors: Haagmans, Bart L.; Noack, Danny; Okba, Nisreen M.A.; Li, Wentao; Wang, Chunyan; Bestebroer, Theo; de Vries, Rory; Herfst, Sander; de Meulder, Dennis; van Run, Peter; Lamers, Mart M.; Rijnders, Bart; Rokx, Casper; van Kuppeveld, Frank; Grosveld, Frank; Drabek, Dubravka; GeurtsvanKessel, Corine; Koopmans, Marion; Bosch, Berend Jan; Kuiken, Thijs; Rockx, Barry title: SARS-CoV-2 neutralizing human antibodies protect against lower respiratory tract disease in a hamster model date: 2020-08-24 journal: bioRxiv DOI: 10.1101/2020.08.24.264630 sha: daaca00dc450edc0960ee564c4dbcec04c96867f doc_id: 720525 cord_uid: 5sss52fz Effective clinical intervention strategies for COVID-19 are urgently needed. Although several clinical trials have evaluated the use of convalescent plasma containing virus-neutralizing antibodies, the effectiveness has not been proven. We show that hamsters treated with a high dose of human convalescent plasma or a monoclonal antibody were protected against weight loss showing reduced pneumonia and pulmonary virus replication compared to control animals. However, a ten-fold lower dose of convalescent plasma showed no protective effect. Thus, variable and relatively low levels of virus neutralizing antibodies in convalescent plasma may limit their use for effective antiviral therapy, favouring concentrated, purified (monoclonal) antibodies. On 31 December 2019, the World Health Organization (WHO) was informed of a cluster of 30 cases of pneumonia of unknown cause in Wuhan City, Hubei Province of China 1 . Subsequently 31 a novel coronavirus (SARS-CoV-2), was identified and as of August 11 th , WHO reported more 32 than 20 million cases of SARS-CoV-2 infection worldwide, with over 700,000 deaths. 33 SARS-CoV-2 infection is characterized by a range of symptoms, including fever, cough, dyspnea 34 and myalgia 2 . In severe cases, SARS-CoV-2 infection can be complicated by acute respiratory 35 distress syndrome leading to respiratory insufficiency and multi-organ failure 3 . 36 An effective treatment is a high priority as SARS-CoV-2 continues to circulate in many regions, 37 and there is a risk of additional future waves of infection. To date, WHO reported at least 166 38 vaccine candidates being in different stages of development while other efforts include the 39 development of neutralizing antibodies for prevention and/or treatment of SARS-CoV-2 40 infection. Early during the outbreak, the usefulness of convalescent plasma transfusion was 41 considered for treatment of severe cases 4 . Several large clinical trials have now been initiated 42 to evaluate the efficacy and safety of convalescent plasma treatment of SARS-CoV-2 patients 5 . 43 Data on the outcomes of these trials have been limited and to date, preliminary results from 44 only a few small cohorts and one randomized clinical trial have been published. Results from a 45 randomized clinical trial did not show a benefit 6,7 , while results from the small cohorts 46 suggested clinical benefit but lacked controls for proper interpretation [8] [9] [10] [11] . Although preclinical 47 research indicated a limited protective effect of hamster serum when given to hamsters 48 infected with SARS-CoV-2 early in the disease course 12,13 , effects of human plasma have not 49 been analyzed in this animal model. Importantly, data on the level of neutralizing antibodies 50 that are required to provide a clinically meaningful protective effect are not available. 51 Apart from convalescent plasma, different human monoclonal antibodies (MAb) against SARS- 52 CoV-2 have been identified and characterized, for prophylactic and therapeutic use. Most of 53 these studies have shown efficient neutralization of SARS-CoV-2 in vitro, but few antibodies 54 have been evaluated for their efficacy in vivo. We previously determined that MAb 47D11 55 efficiently neutralizes both SARS-CoV and SARS-CoV-2 in vitro 14 . In the present study, we used 56 this MAb and two doses of human convalescent plasma, differing almost ten-fold in neutralizing 57 antibody concentration, to evaluate the efficacy of prophylactic antibody treatment in a 58 hamster model of moderate to severe SARS-CoV-2 pneumonia. Characteristics of neutralizing antibodies 61 We pooled 6 convalescent plasma samples from PCR-confirmed COVID-19 patients. The In addition, we used human MAb 47D11 directed against SARS-CoV, which cross-reacts with 70 SARS-CoV-2 and targets a conserved epitope in the S1 domain, previously shown to neutralize 71 SARS-CoV-2 with an IC50 of 0.57 μg/ml 14 . At a concentration of 3mg/mL the human MAb 47D11 72 preparation had an equivalent neutralizing antibody titer of 1:5260. Table 2 ). There was no significant difference in SARS-CoV-2 162 specific IgG titers among treatment groups with IgG titers of 1:12.800. MAbs and convalescent plasma 389 We previously identified MAb 47D11 which efficiently neutralizes SARS-CoV-2 in vitro 14 . The 390 irrelevant isotype control antibody used in this study was characterized previously 32 . 391 Convalescent plasma was collected from donors who had a RT-PCR confirmed SARS-CoV-2 392 infection and were asymptomatic for at least 14 days 7 . Of all donors tested, only plasma with 393 neutralizing antibodies against SARS-CoV-2 confirmed by a SARS-CoV-2 plaque reduction 394 neutralization test (PRNT) and a PRNT50 titer of at least 1:1280 was used. Equal volumes of 395 plasma from 6 donors was pooled and used for prophylactic treatment in hamsters (High dose). 396 In addition, the pooled plasma was diluted 10-fold in PBS (Median dose). Normal human plasma 397 from a healthy donor was used as a control. 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Emerg Microbes 378 Infect H2020 grant agreement 874735-471 VEO to M.K., the Netherlands Organisation for Health Research and Development (ZONMW) 472 grant agreement 10150062010008 to B.H. and H2020 grant agreement The research was co-funded by the PPP Allowance (grant agreement LSHM19136) made 474 available by Health Holland, Top Sector Life Sciences & Health writing-review and editing, all authors; 481 funding acquisition 468 We thank J.M. Fentener van Vlissingen, Y. Kap, D. Akkermans, V. Vaes, for assistance with the 469 animal studies. This research is (partly) financed by the NWO Stevin Prize awarded to M.K. by 470 To test for SARS-CoV-2 antibodies, hamster serum samples were collected at days 4 and 22. 426 Serum samples were tested for SARS-CoV-2 antibodies using a spike S1 and nucleocapsid 427 protein (N) ELISAs 23 . Briefly, ELISA plates were coated overnight with SARS-CoV-2 S1. After