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Epidemiology

State of alert

Recombinant or potentially more aggressive subtypes of Aids virus advance in Brazil

A study carried out in the country with 366 persons who have recently been identified as HIV-positive and who have still not taken any medicine against Aids reveals a complex, multifaceted picture with regard to the genetic profile of the virus of the disease that is circulating today in Brazilian territory. The work shows an increase in some regions of the country of potentially more aggressive, rare or mutant forms of HIV-1, the type of Aids virus most common in Brazil (and the world) today.

“It is as if there were three epidemics of Aids in Brazil (from the point of view of the genetic diversity of the virus)”, comments infectologist Ricardo Diaz, director of the Retrovirology Laboratory of the Federal University of São Paulo (Unifesp), one of the coordinators of the work carried out by Revire, the Vigilance against Resistance Network (to anti-retrovirals, anti-Aids drugs), maintained by the Ministry of Health, which has gathered together seven of the country’s scientific institutions.

According to the study, the first one with national cover carried out by Revire, when one looks at Brazil as a whole, the epidemic aspects of the disease simply seem to obey the same molecular pattern that is found in the rest of America, Europe, Australia and Japan: the form that is still most amply dominant in Brazil is the B subtype of HIV-1, the first to enter here in the 80’s, or even before that. However, a more refined analysis, in which one seeks to map local specifics, as the authors of the research did, makes regional tendencies strike the eye, very often masked, or not very well delineated, by the national statistics.

Scenario No. 1
In the states of São Paulo and Rio de Janeiro, where a little less than three quarters of all the 230,000 officially recognized cases of the disease in Brazil are concentrated, and in the Northeast, the situation continues to be similar to what happens in the greatest part of the western world. That is to say, at least 80% of the people who took part in the study were carriers of the B subtype of the virus. The other individuals showed other forms of HIV-1, such as the F or C subtypes, or even recombinations of two of the three subtypes identified in these parts of the country. So far, there does not seem to be any great novelty regarding the situation of the disease in a good part of the western world. The surprises come from Brazil’s extremities.

Scenario No. 2
In the Center-West/North, although B still accounts for 70% of the cases, the rare F subtype, found in few parts of the planet, seems to be gaining ground and shaping up a second epidemic, from the point of view of molecular genetics. About 30% of the HIV-positivesfrom this large region of the country had a virus of the F subtype, in its pure form (24%) or recombined with the B subtype (6%).

Scenario No. 3
The study’s potentially most worrying data concerns the increase in the southern part of the country of the C subtype, a strain of HIV-1 described in international studies as more aggressive than B. In Rio Grande do Sul, almost 67% of the bearers analyzed in the study have the pure form of this subtype (45%) or the recombinant form (22%), a hybrid virus of C with B or C with F. This level of incidence makes subtype C the dominant one amongst those infected in the state, leaving B with about 30% and F with 3%. In Paraná, subtype C is also proving to be very present: it was found 32% of those infected, in their majority bearers of the non-recombinant form of this strain of the virus.

It was precisely in Rio Grande do Sul that this form of the virus was detected for the first time, before the end of the 80’s. “Subtype C seems to be expanding from the south, in the direction of the north of the country”, explains Diaz, who is also responsible for a FAPESP thematic project on the molecular characteristics of the Aids virus found in Santos (SP), one of the Brazilian cities with the highest infection occurrence. “What worries us is that this form of the virus has turned into the dominant one in the regions it has entered.” In India and South Africa, two countries that, together, have at least 8 million HIV-positives, the C subtype has today become responsible for the majority of the new cases of the disease. There are some indications from research abroad, not totally proven, that the C subtype is more easily transmitted between heterosexuals than between homosexuals. In Revire’s study, however, the researchers have not been able to establish any relationship between the subtypes in circulation in Brazil and the sexual options of their bearers.

Mutant forms
Another disturbing fact unveiled by the research: mutant or recombinant forms of HIV-1, where the virus’s genome is a hybrid of two or more subtypes, are already present in all the parts of the country. Until then, this genetic recombination of the disease’s virus was something found practically only in the southeast and south of the country. The dissemination in Brazil of various subtypes of HIV-1, pure or hybrid, may mean yet another obstacle to the prevention, diagnosis and, above all, treatment of Brazilian patients, since most of new drugs and potentia vaccines against Aids adopt as their standard the B subtype, more common in Europe and the United States, which are the major financiers of research. To avoid being dependent on these studies, which may not be totally useful for controlling the disease epidemic in its territory, India announced, last month, that it intends to develop a specific vaccine for the C subtype of HIV-1.

In the same study in which they show the prevalence of HIV-1 subtypes in recent victims of the infection, the researchers from Revire supply another interesting fact – and in this case, for the time being, one that is tranquilizing – about the genetic profile of the virus in circulation in Brazil. Less than 7% of the 366 persons who took part in the study showed any resistance to one or more drugs in the cocktail normally used to control the symptoms of Aids, a percentage regarded as low. “That is why, for the time being, we are not recommending doing routine tests in the public network to measure possible resistance to drugs in the cocktail in HIV-positives who are starting the treatment against Aids”, says Amilcar Tanuri, from the Molecular Virology Laboratory of the Federal University of Rio de Janeiro (UFRJ), another coordinator of the work of the Ministry of Health network.

Methodology
To carry out the work, Revire’s researchers selected an initial sample of 535 individuals who, last year, had been given the news that they were HIV-positive after having been examined at 13 of the public network’s Anonymous Testing Centers from eight states in the country (Rio Grande do Sul, Paraná, São Paulo, Rio de Janeiro, Mato Grosso do Sul, Pará, Bahia and Ceará). As they did not know that they were carrying HIV-1 in their blood, these people, until then, had never taken any medicine against the disease and, potentially, represented a group of recently infected individuals. Due to difficulties in amplifying in the laboratory the DNA of the virus of a part of these individuals and to other snags, the final sample was reduced to 366 HIV-positives, 60% of which were male. On these people that scientists carried out their analyses.

They sequenced two regions of an important gene of the Aids virus called pol, which codifies a pair of the enzymes that are fundamental for the development of infection by HIV-1 in man, protease and reverse transcriptase. The role of these enzymes is so paramount in the progression of the infection of the human body that the final objective of the anti-Aids cocktail of drugs is precisely to inhibit their action. Produced by one of the genomic regions of the pol, protease breaks down two precursor proteins into smaller fragments, without which the virus loses its ability to grow, infect and replicate.

Reverse transcriptase, codified by another region of the gene, allows HIV-1 to integrate itself with the DNA of the cells of its host and victim, man. Having determined the sequencing of base pairs (the chemical units that codify the DNA) of the parts of the pol gene that produce these enzymes, the scientists are able to say to which subtype of the Aids virus these regions belong. Extrapolating, they are able to state which variety of HIV-1 is infecting the patient. “In the case of the hybrid forms of HIV-1, each one of these regions of the pol gene came from a different subtype of the Aids virus”, Ricardo Diaz observes.

Low resistance to drugs

Revire’s study found that the presence of strains of HIV-1 with high resistance to the cocktail of medicines used against Aids, a set of drugs known as anti-retroviral, is still very low in recent victims of infection by HIV-1 in Brazil. Of the 366 persons who comprised the nationwide sample analyzed in the work, only 23 individuals, less than 7% of the total, carried some type of the virus with significant tolerance to one of the drugs used in the treatment of the disease. Eight persons showed resistance to some medicine that acts as an inhibitor of protease, and 15 to some medicine classified as an inhibitor of reverse transcriptase – the main objective of the treatment was to annul the action of these two enzymes. In no case, however, did one and the same patient have a form of the virus that was resistant both to protease inhibitors and reverse transcriptase inhibitors.

The Brazilian level of resistance to anti-retrovirals is regarded as very low, compared with some developed nations like the United States and Spain, when the rate of tolerance to the medicines in the cocktails is three times more. “Some earlier works showed that the resistance to drugs in the cocktail has previously been lower in Brazil (about 2%), but, statistically, the numbers from the past are not very different from the current ones”, comments Amilcar Tanuri, from the Molecular Virology Laboratory of the Federal University of Rio de Janeiro (UFRJ), one of the coordinators of Revire’s research.

In practical terms, the results of the new study do not question – nor was this the purpose – the effectiveness of the national strategy of the free distribution of the medicines of the cocktail in the public network for 115,000 HIV-1 victims. Also, according to the authors of the work, there is not, for the time being, any need for systematic tests to be carried out on the patients to discover who shows tolerance to the medicines. “But we need to monitor this situation periodically, since there is apparently an international tendency for the levels of resistance to grow”, says Ricardo Diaz, of the Federal University of São Paulo (Unifesp), one of Revire’s coordinators. “This has also now been seen in some Brazilian cities”.

In another study, done in the ambit of a FAPESP thematic project and carried out in Santos, one of the Brazilian cities hardest hit by the epidemic of Aids, Diaz’s team found that 20% of those recently infected by HIV-1 – people who had caught the virus up to three months ago at the most – showed total resistance to 3TC, one of the inhibitors of reverse transcriptase that there are on the market, and partial resistance to AZT, the oldest medicine used against the disease.

Among the patients who had contracted HIV-1 the longest time ago, the rate of resistance was only 5%, an indication that the current strains of HIV-1 that are in circulation in the city show mutations that make them more tolerant to the cocktail. It is logical that one cannot compare the situation in one municipality with that of the whole country, but neither is it prudent to close one’s eyes to what is happening in the famous São Paulo seaside resort, one of the first places in Brazil to adopt more effective methods for the control of Aids.

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