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Maintaining high rates of CD4 cells (>500/mm3) is a main objective of the treatment of HIV infections. Maraviroc blocks the entry of CCR5-tropic viruses, which play a major role in HIV transmission and predominate throughout infection. Viruses using CXCR4 co-receptor emerge later and are associated with disease worsening. Maraviroc showed a rapid and high immune response, partly due to its capacity to diffuse in sanctuary areas. Viraltropism appears very useful to predict both disease progression and CCR5- antagonist efficacy. Based on the V3 loop of HIV-envelope gp120, genotypic tests show an acceptable concordance with plasma-derived phenotypic tests and, when performed at blood cellular levels, a slightly higher prevalence of archived X4 variants. They also seem to be predictive of the virological response to treatment. The perspective of an accurate prediction of viral tropism in blood cell reservoirs could lead to discuss the use of CCR5-antagonists in patients with undetectable viral load.

Objective: To investigate factors related to early virological response among a cohort of 224 patients who started a protease inhibitor (PI) for the first time. To determine which factors are associated with persistent response among patients with early response., Patients and Methods: Early complete response was defined as an undetectable plasma viral load 2 to 3 months after treatment onset (< 400 copies/ml, Quantiplex HIV 2.0 Chiron diagnostics), incomplete response as at least 1 log reduction of viral load. In patients with an undetectable plasma viral load at 2 or 3 months, we also assessed the persistence of the response on the same regimen. Virology failure was defined by two consecutive viral load levels above the detection limit., Results: In the total cohort, 66% of the patients had an early complete response, 11% a partial response and 23% no response. Complete virological response was significantly more frequent in naive (89%) than in pretreated (59%) patients (p < 0.001). Multivariate analysis of factors predictive of early response in pretreated patients (n = 169) showed that viral load (p = 0.001), the number of nucleoside analogs previously received (p = 0.06) and a full or partial treatment switch (p = 0.10) were associated with complete response. Analysis of later response in the 45 naive patients with prolonged follow-up showed that 22% had treatment failure after 3 to 16 months. None of the baseline variables (viral load, CD4+ cell count or nature of the PI) were associated with duration of response. The only factor associated with persistent response in pretreated patients was a low number of antiretroviral drugs previously received (log-rank test, p = 0.04)., Conclusions: The absence of previous antiretroviral treatment as the main factor associated with an early complete virological response. In patients pretreated with nucleoside analogs who presented early virological success, the number of drugs previously received, often associated with full or partial switch of nucleoside analog, significantly influence the persistence of response to a given triple-drug regimen.

As many factors may be involved in therapeutic response to triple therapy with protease inhibitor (PI), the aim of this study was to determine the influence of epidemiological factors (sex, risk factors), clinical status (previous number of AIDS defining events), immunological status (baseline CD4 T cells count), virological factor (baseline viral load), previous antiretroviral therapy and duration of AZT therapy (> or < 6 months), number of prescribed reverse transcriptase inhibitors (RTI), therapeutic strategy (switch to different RTI or only addition of PI) and compliance, on early virological response (M2-M3) after initiation of triple therapy with PI. These results concerned 167 patients treated with triple therapy including PI. A viral load response was defined in three types: complete response (undetectable: < 500 copies/ml) for 100 patients; partial response (significant decrease: > 0.5 log from baseline) for 30 patients and no response for 37 patients. Only two parameters were associated of good virological response: no previous antiretroviral therapy (p < 0.001) and good compliance (p < 0.001). No significant difference was observed between patients with no prior therapy and pretreated patients, in terms of median baseline CD4 count and observance. The baseline median viral load was higher in naive patients despite a better response. In pretreated patients, the type of response appeared to be dependent on the duration of AZT treatment (p = 0.06) and good compliance (p = 0.06). Among the 100 patients with initial complete response, only 23/81 were still undetectable after a median of 13 months of therapy.

Summer's discovery in 1978 of a DNA virus, very close to human Hepatitis B virus in a woodchuck population in the U.S.A. (Pennsylvania) was a confirmation of the first description made by Snyder at Penrose Research Laboratory (Philadelphia). It was the first animal model of human B hepatitis infection. The comparative study of morphological, ecological and ethological characteristics of the marmot (Marmota marmota) and the woodchuck (Marmota monax) enables an easy distinction between these two species. The natural infection of M. monax by the WHV shows that the woodchuck is a good model for human B hepatitis and should be extended to M. marmota. A sample of 24 marmots caught in the Alpes of Haute-Provence has not revealed any spontaneous infection in these animals by the woodchuck virus. The failure of experimental inoculation of the marmot (24 animals) with the WHV confirms the refractory status of this species (no viremia and very low and short serological response with or without an immunosuppressive treatment). These preliminary results require a confirmation in other animals of different age and geographical region and also by using more specific tests such as molecular hybridization, research on DNA polymerase and direct transfection trials.

Blackleg (Clostridium chauvoei) infection in Charollais cattle appears to have undergone some etiological and pathogenic changes which are reflected in the apparent failure of vaccination. Two methods have been used to determine the quality of the vaccines in order to meet the different requirements specified by pharmacopeias. The two methods differ in the vaccination schedules of the guinea pigs and the test strain used which may be either a virulent culture or a suspension of spore in calcium chloride. Both methods appear to be efficient in selecting vaccines which provide good protection. It follows, therefore, that the vaccination failures would appear to be the result of intensive selection of beef cattle with reduced immunological response. If this is the case, the remedy for these vaccination failures might lie in an adaptation of the vaccination schedule to the early developing breeds of cattle obtained by intensive selective breeding.

The antiviral activity of bromovinyldeoxyuridine has been studied on the wild type of pseudorabies virus. A heterogenicity of viral populations has been observed. A resistant clone presented special characteristics both in vitro (large syncytia, round cells) and in vivo (reduced pathogenicity and immunogenic power).

Live (diluted) and inactivated rabies vaccines of low antigen content induce early and enhanced death in mice, inoculated before vaccination with a wild type of rabies virus. Such vaccines, which neither induce interferon nor protect, produce a low level of antibodies which appear later than with vaccines of higher antigenicity. It is recommended to examine rabies vaccines not only by the usual (pre-exposure) potency test-NIH test or modified NIH test (one vaccination), but also by a post-exposure potency test.