Luís Roberto Camargo Gonçalves

The COVID‐19 pandemic revealed reduced vaccine efficacy and worse outcomes in people with type 2 diabetes mellitus (T2DM). However, how T2DM, independent of obesity, alters immune responses and lymphoid organ architecture remains unclear. We evaluated antibody production and lymphoid organ morphology following SARS‐CoV‐2 antigen immunization in Goto‐Kakizaki (GK) rats, a non‐obese T2DM model, to evaluate the isolated effect of diabetes. Ten‐week‐old male Wistar and GK rats received three intramuscular injections of SARS‐CoV‐2 antigens at 15‐day intervals. Two antigen formulations were used: chemically inactivated whole SARS‐CoV‐2 containing aluminum hydroxide adjuvant and an inactivated Newcastle virus engineered to express the SARS‐CoV‐2 spike protein. Fifteen days after the final dose, anti‐Spike IgG titers were measured by ELISA, and histological and morphometric analyses of lymphoid tissues were performed. GK rats exhibited elevated anti‐Spike IgG responses compared with WT controls, regardless of the antigen formulation. Distinct morphological alterations in the lymphoid organs accompanied the enhanced IgG responses. Mesenteric lymph nodes from GK rats exhibited a morphology similar to that of WT rats. The thymus exhibited features of involution, including septal thickening, reduced corticomedullary distinction, diminished cortical cellularity, cortical thinning, and medullary expansion. The spleen showed white pulp remodeling, characterized by enlargement of germinal centers and periarteriolar lymphoid sheaths, along with a reduction in the marginal zone. We described herein the remodeling of the primary and secondary lymphoid organs in non‐obese diabetic GK rats, which may play a role in the antibody response to an immune challenge.

In recent years, extensive research has delved into the pathophysiology of local reactions triggered by Bothrops snake venoms. Even though antivenom works well at reducing death and systemic effects, it is still not very effective in treating local reactions because it cannot counteract damage that has already been triggered. This limitation might be attributed to certain molecules that amplify the venom-induced innate response. While evidence suggests endogenous mediators at the venom site play a role in this envenomation, in Brazil, the concurrent use of anti-inflammatory agents or other drugs alongside antivenom remains uncommon. This study evaluated the pharmacological mediation of alterations in leukocyte–endothelium interactions following the experimental envenomation of mice with Bothrops jararaca venom, the main culprit of snake-related accidents in Southeast Brazil. We treated envenomed mice with inhibitors of different pharmacological pathways and observed the cremaster muscle microcirculation with intravital microscopy. We found that eicosanoids related to cyclooxygenase pathways and nitric oxide significantly contributed to B. jararaca venom-induced alterations in leukocyte–endothelium interactions. Conversely, lipoxygenase-mediated eicosanoids, histamine, and serotonin had minimal participation. Notably, dexamethasone and antivenom treatment diminished B. jararaca venom–induced alterations in leukocyte–endothelium interactions. The limited efficacy of the antivenom in managing Bothrops venom-induced local reactions emphasizes the critical need for supplementary treatments to enhance therapeutic outcomes.

In recent years, extensive research has delved into the pathophysiology of local reactions triggered by Bothrops snake venoms. Even though antivenom works well at reducing death and systemic effects, it is still not very effective in treating local reactions because the venom works so quickly, and antivenom cannot fix injuries that have already been triggered. This might be attributed to certain molecules amplifying the venom-induced innate response. While evidence suggests endogenous mediators at the venom site play a role in this envenomation, in Brazil, concurrent use of anti-inflammatories or other drugs associated with the antivenom remains uncommon. The aim of this study was to determine how various inflammatory mediators affected the leukocyte-endothelium interaction (LEI) following a B. jararaca bite. According to our findings, nitric oxide and cyclooxygenase pathway eicosanoids significantly contribute to alteration of LEI induced by B. jararaca venom. Conversely, lipoxygenase-mediated eicosanoids, histamine, or serotonin had minimal participation. Markedly, treatment with dexamethasone alongside antivenom mitigated alterations of LEI induced by the B. jararaca snake venom. The limited efficacy of the antivenom in managing Bothrops venom-induced local reactions emphasizes the critical need for supplementary treatments to enhance therapeutic outcomes.

Snake venom metalloproteinases (SVMP) are involved in local inflammatory reactions observed after snakebites. Based on domain composition, they are classified as PI (pro-domain + proteolytic domain), PII (PI + disintegrin-like domains), or PIII (PII + cysteine-rich domains). Here, we studied the role of different SVMPs domains in inducing the expression of adhesion molecules at the microcirculation of the cremaster muscle of mice. We used Jararhagin (Jar)—a PIII SVMP with intense hemorrhagic activity, and Jar-C—a Jar devoid of the catalytic domain, with no hemorrhagic activity, both isolated from B. jararaca venom and BnP-1—a weakly hemorrhagic P1 SVMP from B. neuwiedi venom. Toxins (0.5 µg) or PBS (100 µL) were injected into the scrotum of mice, and 2, 4, or 24 h later, the protein and gene expression of CD54 and CD31 in the endothelium, and integrins (CD11a and CD11b), expressed in leukocytes were evaluated. Toxins induced significant increases in CD54, CD11a, and CD11b at the initial time and a time-related increase in CD31 expression. In conclusion, our results suggest that, despite differences in hemorrhagic activities and domain composition of the SVMPs used in this study, they behave similarly to the induction of expression of adhesion molecules that promote leukocyte recruitment.

In South America, accidental contact with Lepidoptera larvae can produce a diversity of reactions that vary from dermatological problems to severe hemorrhagic syndromes, such as those caused by contact with caterpillars of the genus Lonomia (Saturniidae). Lonomia venom can alter the hemostatic system and lead to renal failure, internal and brain bleeding, and in severe cases, death. The only specific treatment available for these envenomations is the Lonomia Antivenom (LAV) produced by the Butantan Institute, in Brazil, using an extract of Lonomia obliqua scoli as the antigen. LAV has been used to treat exposure to other Lonomia species across South America. However, no experimental studies have been performed to test the efficacy of LAV in neutralizing the venom of species other than L. obliqua found in Southern Brazil. In this study, we tested the effectiveness of LAV in reversing the hemostatic disturbances induced by injecting Lonomia casanarensis (Lca) and Lonomia orientoandensis (Lor) scolus extracts into rats and compared the effects to the case of L. obliqua (Lob) scolus extract-induced envenomation. Lca and Lor caterpillars were collected in Colombia, and some of them were reared to adults for identification. The Minimum Defibrinating Doses (MDD) of Lca and Lor were estimated. Rats were injected (i.d.) with a dose of 3 MDD per rat of each scolus extract and treated (i.v.) with 1.5 mL of LAV or 1.5 mL of saline. Twenty-four hours after the treatment, the fibrinogen levels and platelet counts had recovered to the hemostatic levels in the groups treated with LAV. The groups treated with the saline solution had fibrinogen levels and platelet counts at non-hemostatic levels. Thromboelastometric analyses confirmed these results. In conclusion, the results showed that LAV is effective at neutralizing the envenomation induced by Lca and Lor spine extracts in rats and restoring hemostasis. A specific antivenom therapy is recommended for treating envenomation caused by venomous animals, such as snakes, spiders, scorpions, and Lonomia caterpillars. Studies with snake bites have shown that antivenoms are effective for treating the envenomation caused by snakes of the same genus, even when the antigen composition used to generate the antivenom did not include the specific venom. The Lonomia antivenom produced by the Butantan Institute to treat envenomations caused by contact with Lonomia caterpillars only uses the extract of Lonomia obliqua scoli as the antigen. However, there are reports of other species of Lonomia in South America that demonstrate biological activities that are different from those observed in response to L. obliqua venom, but which cause similar symptoms in human envenomation. No information is available regarding the neutralizing capacity of the Lonomia antivenom in these other species. This study showed that the Lonomia antivenom efficiently reversed the hemostatic disorders induced in rats by injection of extracts of the scoli of L. casanarensis and L. orientoandensis from Colombia. These results support the possibility of using this antivenom for treating envenomations caused by other Lonomia species in humans.

Sea urchins are animals commonly found on the Brazilian shoreline, being Echinometra lucunter the most abundant species. Accidents caused by E. lucunter have been reported as one of the most frequent in Brazil, and are characterized by intense pain and inflammation, consequence of spine puncture in the skin. In order to characterize such toxic effects, we isolated one molecule that caused inflammatory and nociceptive effects. E. lucunter specimens were collected without gender distinction. Spines were removed and molecules were extracted, fractionated by RP-HPLC and assayed for inflammatory and nociceptive activity, in a biological-driven fractionation way, until the obtainment of one active molecule and its subsequent analysis by mass spectrometry (MS and MS/MS). For inflammation, intravital microscopy was performed on the mouse cremaster muscle, in order to evaluate rolled, adherent and migrating leukocytes. Paw edema was also evaluated. For the nociceptive activity, the paw pressure test was performed in rats. One molecule could be isolated and related to the inflammatory and nociceptive activity. Regarding inflammation, increase in adherent and migrating cells was observed in the cremaster muscle after the administration of the molecule. Corroborating the inflammatory response, paw edema was also observed, although only in 20% of controls and 20 min after injection. Additionally, this molecule was able to decrease significantly the pain threshold, characterizing hyperalgesia. This molecule was analyzed by mass spectrometry, and according to the exact molecular mass, isotopic distribution and fragmentation profile, it was possible to propose the molecular formula C29H48N3O10. One isolated molecule from the spine extract of E. lucunter is able to elicit inflammation and hypernociception in animal models, which is in agreement with the effects observed in sea urchin accidents.