Real world effectiveness of sotrovimab in preventing COVID-19-related hospitalisation or death in patients infected with Omicron BA.2

BACKGROUND

Laboratory-based evidence indicates that neutralization of the BA.2 (Omicron) variant by sotrovimab is reduced versus previous SARS-CoV-2 variants. Since there is a lack of real-world data, we investigated whether sotrovimab has reduced clinical efficacy against the BA.2 variant.

METHODS

We performed a prospective cohort study using real-world data from 1180 randomly-selected BA.2 variant-infected patients. Follow-up to study endpoints averaged 29 days. For mild cases (not requiring oxygen-supplementation), primary outcomes were requiring O2-supplementation, intensive care unit (ICU) admission or death. For moderate-to-severe COVID-19 cases (requiring oxygen-supplementation other than mechanical ventilation), the primary outcome was ICU admission or death.

RESULTS

Patients in the sotrovimab group (n = 569) and control patients (n = 611) were included. Sotrovimab-treated patients versus controls had reduced risk of death (0.4% vs 6.4%, p < 0.001), need for oxygen supplementation (3.5% vs 12.8%, p < 0.001) and ICU admission (0.2% vs 4.9%, p < 0.001). The adjusted-odds ratio for developing any of these outcomes was 0.090 (95% CI 0.049-0.165, p < 0.001). Subgroup analysis of moderate-to-severe sotrovimab-treated patients versus controls revealed reduced mortality (17.7% vs 37.2%, p = 0.006) and ICU admission (0.0% vs 37.2%, p < 0.001). Adjusted-hazards ratio for death or ICU admission was 0.256 (95% CI 0.111-0.593, p < 0.001).

CONCLUSION

Sotrovimab was effective in reducing COVID-19 progression risk in high-risk BA.2 variant-infected patients. This finding may alleviate concerns about its clinical efficacy.

Mitogenic stimulation of bovine peripheral blood mononuclear cells by Theileria sergenti antigen and inhibition by antibody from experimentally infected cattle

Stimulation with a lysate of Theileria sergenti-parasitized red blood cells (PRBC) resulted in marked proliferation of normal bovine peripheral blood mononuclear cells (PBMC) in vitro. Partial inhibition of the proliferation was demonstrated by the addition of immunoglobulin (Ig) obtained from experimentally infected cattle when they revealed high levels of parasitemia and antibody titres. A mouse monoclonal antibody recognizing a 32 kDa antigen also showed inhibitory activity against the in vitro proliferation of bovine PBMC, but complete inhibition could not be achieved.

Effective isolation of MPB64 from a large volume of culture filtrate of Mycobacterium bovis BCG Tokyo

MPB64, a secretory protein of Mycobacterium bovis BCG Tokyo, was isolated from a culture filtrate of the bacteria in Sauton synthetic medium harvested on day 8. The protein was isolated by five steps; (i) concentration of the culture filtrate by cutting the molecules smaller than 5 kDa with the Millipore Pellicon Cassette system, (ii) affinity separation by a Phenyl Sepharose CL-4B column, (iii) separation with a DEAE-Sepharose CL-6B column with 3 M urea, (iv) separation with a Sephacryl S200HR column, and (v) separation with a DEAE-Sepharose column without urea. MPB64 in each fraction was determined by comparing the band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with that of standard MPB64. The specificity of isolated MPB64 was tested by immunoblotting with anti-MPB64 antibody. The potency of isolated MPB64 in eliciting skin reaction in the BCG-sensitized guinea pigs was the same to that of standard MPB64. The method described herein is an improved one for isolating MPB64 from a large volume of culture filtrate of M. bovis BCG Tokyo. The technique should be applicable to isolation of other mycobacterial secretory proteins.

[Studies on the method to quantify PPD and its adsorption onto glass-surface]

The potency of PPD is very stable when kept as a lyophilized preparation or as a solution of high concentrations, but, as is well known, when diluted to the practical concentrations such as used in skin-testing for human, its potency diminishes rather rapidly. It has been considered that such decrease in potency is not due to denaturation of PPD, but due to its adsorption onto the surface of glass- or plastic-container. The adsorption of PPD had been studied by several authors with radiolabeled PPD or by the potency test in experimental animals or human. However, either method is not satisfactory because they are not quantitative and reproducible. Consequently, we developed a new method basing on ELISA to measure such low concentrations of PPD as used in skin-testing in human. Using this new method, we analyzed the adsorption of PPD onto glass-surface. The major characteristics of the PPD adsorption revealed by the present studies are as follows; (1) The adsorption of PPD takes place very rapidly immediately after the distribution of PPD solution to a new container and then proceeds in slower rates. (2). The rate of adsorption is influenced by both temperature and concentration of PPD solution. The rates of adsorption are almost the same at -80 degrees C and at 6 degrees C, much higher at 22 degrees C and further higher at 37 degrees C at any concentration tested. At -80 degrees C and 6 degrees C, there is no difference among the adsorption rates at three different concentrations, but at 22 degrees C and 37 degrees C, the rate of adsorption at the lowest concentration (0.25 microgram/ml) is much higher than those at higher concentrations. (3) The amounts of PPD adsorbed are determined by the surface area of glass in contact with PPD solution. (4) The larger the volume of PPD solution distributed, the bigger the absolute amount of PPD adsorbed, but the smaller the rate of adsorption. (5) So-called "volume effects" are evidenced. Commercially available Japanese PPD preparations have been produced and adjusted their potency taking such adsorption phenomena into consideration. But, if undue adsorption is induced by unappropriate handling and/or usage, the potency might be diminished. Especially, the single-dose preparation may be affected most strongly by so-called "volume-effects". Standard handling and usage recommended by the manufacturer are strictly required.

Distribution of antibody titres against phenolic glycolipids from Mycobacterium tuberculosis in the sera from tuberculosis patients and healthy controls

Sera from tuberculosis (TB) patients and healthy controls were tested by ELISA for their antibody titres against the two major phenolic glycolipids (PGLs) of Mycobacterium tuberculosis, PGL-tbO (a 1:3 mixture of PGL-tb1 and its analogue whose phthiocerol moiety is phenolphthiotriol A) and PGL-tbK. Both PGL-tbs were shown to be specific to M. tuberculosis, and the profiles of serum anti-PGL-tbK titres revealed that PGL-tbK, like PGL-tb1, was fairly widely distributed among strains of M. tuberculosis. Even when these two PGL-tbs were used, however, the rate of ELISA-positives was not very high among TB patients, which is probably explained by the nature of the disease. Moreover, a considerable number of sera from healthy controls, especially from younger age groups, had high anti-PGL-tb titres, which implies that environmental exposure to M. tuberculosis is much higher than has been estimated from the actual TB cases. The ELISA system using these species-specific PGL-tb antigens may be useful for the survey of TB infection, since it gives more direct information on TB infection than the PPD skin test.

Analyses of antigenic and genetic diversities of Theileria sergenti piroplasm surface proteins

Monoclonal antibodies (MoAbs) against Theileria sergenti Fukushima stock, an intraerythrocytic protozoan parasite of cattle, were produced. The MoAbs reacted with 32 kDa or 23 kDa piroplasm surface protein (p32 or p23) in Western blot analysis. Using a panel of the MoAbs, antigenic analysis of the stocks and field isolates distributed in Japan was carried out. The results revealed antigenic diversity of T. sergenti isolates, but diversity did not appear to be correlated with the geographical region of the isolates. N-terminal amino acids sequences analysis revealed substitutions of a few amino acids between the p23 of two T. sergenti stocks. The sequences couldn't be found in amino acid sequence of the p32 deduced from cDNA, which indicated that the p23 is not a proteolytic product of the p32. Genetic diversity of T. sergenti isolates was also observed by Southern blot analysis using a cDNA of the p32 as a probe.

Incorporation of [3H]hypoxanthine by short-term cultured Theileria sergenti and its inhibition by drugs

Red blood cells parasitized with Theileria sergenti were cultured in vitro for a short period in microplate wells. Addition of [3H]hypoxanthine to cultures enabled us to titrate the intraerythrocytic parasite growth because a significant amount of [3H]hypoxanthine was incorporated into the parasitized red blood cells (PRBC) in proportion to the number of PRBC. The incorporation of [3H]hypoxanthine was almost completed in an early phase of incubation. Bovine peripheral blood leukocytes incubated with lysate of PRBC did not incorporate [3H]hypoxanthine, indicating that contaminating leukocytes were not involved in the incorporation in the PRBC culture. The incorporation of [3H]hypoxanthine was decreased markedly by the addition of certain anti-parasitic drugs such as chloroquine, quinine, and pyrimethamine. This inhibition test was performed quantitatively with high sensitivity. Based on these results, this short-term culture seemed to be useful for drug screening or studying the mechanisms of theilerial infection. However, anti-T. sergenti antibodies failed to inhibit the [3H]hypoxanthine incorporation.