Sporotrichosis: startup develops a serological test for the diagnosis of the disease in cats and humans

It is difficult to estimate the real magnitude of the epidemic, since sporotrichosis is not a mandatory notification disease by public health agencies

Considered by the Pan American Health Organization (PAHO) as a zoonotic hyperendemic, the largest in the history of Mycology in the world, human and feline sporotrichosis caused by the new pathogen Sporothrix brasiliensis, discovered in 2007, is spreading in Brazil without any prospect of epidemiological control and lights up an alert with the increase in registered cases each year. As the disease is not of compulsory notification by public health agencies, it is difficult to estimate the real magnitude of this silent epidemic, since cases may be underreported, or not being correctly diagnosed, as there is still a lack of knowledge by part of doctors and veterinarians about the epizootic. The zoonotic species Sporothrix brasiliensis is responsible for more than 90% of these cases. In August 2019, PAHO issued an alert for the disease in South America.

Since 2000, the number of cases in humans and animals has grown exponentially and currently human sporotrichosis occurs in 22 states, which represent the main endemic areas while different clinical forms of the disease are reported. The increase in the number of cases is justified by the negligence of the competent authorities to contain the epidemic on early stages, leading to its unrestrained development, in addition to the absence of a program or control actions at the national level, lack of easily available free-of-charge medications for the treatment, both in humans and in animals, as well as the populations lack of knowledge about control measures. In the last five years, cases of the disease have been registered in both animals and humans in all regions of Brazil, with an increase of up to 600% in the number of patients notified.

The incapacity to carry out diagnoses in most of the affected municipalities is another obstacle. Aiming to develop a test for the diagnosis of sporotrichosis caused by Sporothrix brasiliensis, the startup BioInsumos e Diagnosticos (BiDiagnostics) developed, with support from the Innovative Research Program in Small Businesses (PIPE), of the Foundation for Research Support of the State of São Paulo ( FAPESP), a serological test called human and feline Sporothrix-ELISA. All the work was based on the studies carried out by Dr. Leila M. Lopes Bezerra, who has dedicated the last 20 years to studying and characterizing fungal cell wall antigens, glycoconjugates. From there, it was possible to identify a specific antigen for the serological diagnosis of human sporotrichosis. The new test, whose protocol was completely modernized, was clinically validated in patients treated by the Emílio Ribas Infecitous Diseases Institute, during the first PIPE project.

The new test, which was modified by BIDiagnostics, in addition to speeding up the diagnosis, can reduce hospitalization costs due to delays or misdiagnoses. Dr. Lopes-Bezerra explains that the Mycological test remains the gold standard due to the isolation of the fungus Sporothrix spp and its conversion into the yeast phase. However, as Sporothrix is a slow-growing fungus, this cultivation process, standard test, takes at least 15 days and can reach up to 1 month. “Furthermore, often, the culture contaminates or the collection is not positive. In this sense, the serological test for anti-Sporothrix antibodies (IgG) allows a quick response for the physician to start the treatment. The test takes less than 12 hours”, highlights the researcher. Also according to her, another advantage is to allow the differential diagnosis between diseases that can be clinically similar, such as cutaneous leishmaniasis (CL). “Our prototype proved to be effective in discriminating patients with sporotrichosis from the group of patients with CL, both of which are the gold standard”, she adds. Both diseases are now endemic in Brazil.

Asked about the false negative rate, the biochemist states that the human Sporothrix-ELISA test had a Positive Predictive Value of 82%, that is, only 18% of false negatives, for both the gold standard and the suspect groups confirmed by other methodologies. For this, in partnership with Dr. José Angelo Lindoso, from Emílio Ribas Infectious Diseases Institute, we carried out a double-blind study, in which all clinically suspected patients were tested serologically and by mycological test (confirmed by PCR),” she points out. So far, there is no product with this technology on the market. “Our test, besides being cheaper and accessible, uses national technology, with high quality and is effective in diagnosing patients infected with S. brasiliensis, S. globosa and S. schenckii. In other words, it identifies IgG antibodies against Sporothrix spp”, recalls the researcher, emphasizing that BIDiagnostics wants to reach the international market, to be recognized as the first 100% Brazilian company in the field of diagnostic tests for fungal infections, to be born in academia and putting academic knowledge at the service of society.

Regarding the expectation of large-scale production and so that they are available in health units throughout Brazil, Dr. Lopes-Bezerra explains that a partnership was established with Merck-Brazil and the forecast is that the industrial pre-scaling and prototyping stages of the human test will be completed in the first half of this year. After these steps, the product can be launched on the market, with industrial partners and certified by the National Health Surveillance Agency (Anvisa). Meanwhile, in accordance with current legislation, the Sporothrix-ELISA in house (“research use only”) test is available to physicians through a partnership with the Medical Research Laboratory (LIM 53) of the USP Medical School Clinics Hospital and the DASA Network.

Recently, BiDiagnostics developed, also with the support of FAPESPs PIPE, a new rapid test for the diagnosis of sporotrichosis transmitted by the species Sporothrix brasiliensis in cats. The immunochromatographic test (LFA), popularly known as the rapid test, is a screening test at the time of consultation, within the concept of Point of Care, which can be used without the need of laboratory structure in any region, even the most distant from the large cities. In a country like Brazil, with continental dimensions and places with difficult access to the health structure, this is a great advantage,” observes the researcher. With a minimally invasive method, the test ensures a faster and more accurate diagnosis of sporotrichosis and can be used directly in veterinary offices for diagnostic screening, speeding up treatment and improving the chances of a cure, since so far there are no diagnostic tools for feline sporotrichosis that can be directly used by the veterinarian in the office. The LFA test has not yet been clinically validated, however, the entire functional protocol was carried out for validation in the following phases of the project.

Researchers at the startup, incubated at the Center for Innovation and Entrepreneurship at the University of São Paulo (CIETEC/USP), have now started studies to validate the test for canine sporotrichosis. Dr. Lopes-Bezerra also reveals that the companys medium-term goal is the rapid test for human diagnosis. The World Health Organization (WHO) is studying the inclusion of sporotrichosis in the list of neglected fungal diseases. One of the challenges pointed out is the lack of an effective laboratory test for the prompt diagnosis of human sporotrichosis, which can distinguish it from other infections that present a similar clinical picture, in particular, Cutaneous Leishmaniasis. Another challenge raised is the diagnosis reaching patients who live in remote regions. Apparently, serological tests such as Sporothrix-ELISA and LFA would solve these problems.